Dictionary


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in vitro

This type of experiment is performed in a laboratory. Specific types of cancer cells are placed in a Petri dish, treated with the compound of interest, and the results are observed. In vitro (literally means 'in glass') studies are usually the first step in experimentation because they do not have the possibility of hurting animals or humans. Positive results in these kinds of tests show potential of working in humans. These results do not necessarily translate to what would happen inside the environment of the human body or inform researchers of side effects.

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acetylation

The addition of a small carbon compound, an acetyl group(COCH3), to target molecules, usually proteins. Acetylation of proteins changes their activity. The acetylation of histone proteins in our chromosomes is associated with an increase in the activity of the genes in that region. The removal of the acetyl groups is termed deacetylation and has the opposite effect.

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ADCC

Antibody Dependent Cellular Cytotoxicity. This is a type of immune mediated cellular killing in which the target cell is coated with antibodies, labeling it for destruction by specific cells in the immune system.

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adenovirus

A DNA virus associated with human and animal disease. Adenoviruses cause one type of the common cold.
Adenoviruses are currently being explored for their potential use as gene-delivery devices for gene therapy.

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alkylating agent

A chemical that is able to transfer small hydrocarbons to other molecules. These agents are often mutagenic due to their ability to modify the nucleotides in DNA. Several different chemotherapy agents are known to be alkylating agents. They hinder tumor cell growth by damaging the DNA of the tumor cells. For examples, see the treatment section of the site.

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allele

alternate versions of the same gene. As an example, the gene that control whether you can roll your tongue has more than one version. This is why some people can roll their tongues and some people can not. Defective versions (alleles) of genes are associated with diseases such as cystic fibrosis. Note that since we have two copies of each chromosome, one from each parent, that we have two copies of each of our 30,000 or so genes. These two versions can be the same (same allele) or they can be different. Shown below is a pair of chromosomes with 'genes' marked in different colors. The chromosomes are shown as they would appear during cell division. If you compare bands (genes) at the same location on the two chromosomes (male and female) you4ll see that some of the bands are the same, indicating that the two alleles are the same, and that some bands are slightly different, indicating two different versions, or alleles.

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amino acid

A monomer building block used to build proteins. Of the many different known amino acids, twenty of them make up the bulk of our protein content. All amino acids are composed of three different components. They share two common components; a carboxyl (COOH) group and an amino (NH2) group. They also contain a variable portion, the R group, that differs. It is the nature of the R group that determines the functional capabilities of any given amino acid. As an example, the amino acid valine has an R group that is comprised entirely of carbon and hydrogen. This makes this portion of the molecule hydrophobic. For this reason, valine is found in regions of proteins that are not exposed to water.

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amplification

also: gene amplification. This refers to an abnormal process in which many copies of the same chromosome region are produced via DNA replication. The result can be a small 'microsatellite' chromosome or a region of DNA within a chromosome with many copies of a small set of genes.

This process occurs often in cancer cells. The genes involved are often oncogenes or genes that promote chemotherapy drug resistance.

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aneuploidy

Genetic imbalance caused by the loss or gain of one or a few chromosomes. Cancer cells are very often aneuploid. The abnormal numbers of chromosomes means that gene expression and the regulation of cellular functions is severely deranged.

One of the most familiar aneuploid conditions in a non-cancerous disorder is Down syndrome. In this disorder, the child inherits three copies of chromosome 21 instead of the normal two copies. The extra genetic information leads to developmental and neurologic abnormalities.

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angiogenesis

The formation of blood vessels. This process is required for a tumor to grow past a small size since the blood delivers nutrients to the cells in the mass. Much work has been done to find agents that can block the development of blood vessels in tumors. The blockade should lead to the 'starvation' of the tumor cells and tumor regression.

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antibodies

Also: Immunoglobulins. Antibodies are proteins produced by a type of white blood cell (B-cells or B-lymphocytes). These proteins bind to foreign materials (antigens)in our body and aid in their elimination. Cancer cells may sometimes express proteins on their surface that may be targets for antibodies. Our bodies contain thousands of different antibodies, produced by different groups of B-cells.
Monoclonal antibodies are those that are all derived from a single type of B cell. Monoclonal antibodies are currently being used as anti-cancer drugs. An example of a monoclonal antibody used for the treatment of cancer is Herceptin.. This antibody is directed against a protein that is present at very high levels on the surface of some cancers, including some breast and ovarian cancers.
The attachment of drugs to monoclonal antibodies allows for the specific delivery of the drugs to the cells bearing the correct receptor. This is a way of delivering drugs specifically to tumor cells. The modified antibodies are called conjugated monoclonal antibodies

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antibody

See antibodies.

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antigen

Any substance that is capable of being recognized by the immune system. Recognition of such a substance leads to the generation of an immune response. If the antigen is located on a bacteria, the immune system will work to eliminate the infection. Antigens are usually made of protein but can also contain carbohydrates or even lipids.

With regard to cancer, antigens play two key roles:
1) If an antigen or group of antigens on the surface of a cancer cell can induce an immune response, the cancer cells may be eliminated. Since cancer cells are abnormal, they often display unusual proteins on their surface and may induce an immune response.
2) Antigens may be introduced to the body via vaccination. This is an attempt to 'wake up' the immune system and get it to recognize similar antigens on the surface of cancer cells.

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antimetabolites

Drugs that interfere with the formation of key biomolecules within the cell. They often work by blocking the activity of enzymes These drugs often prevent the normal replication of DNA and therefore cell division. Other antimetabolites may interfere with the creation of RNA or other cellular processes.

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apoptosis

Also called programmed cell death. The death of the cells is a carefully controlled process that does not generate any inflammation. Apoptosis is a natural process that occurs throughout the lives of almost all plants and animals. It is a way to balance the production of new cells and to remove damaged cells.

Some examples of apoptosis include the loss of a tadpole's tale and the loss of leaves from trees in the Fall.

In cancer, induction of apoptosis is beneficial if the process causes the death of the abnormal cells. Many cancer drugs are designed to induce apoptosis. Successful tumors have acquired the ability to avoid at least some triggers of apoptosis.

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autosomal dominant

A way in which traits are passed down through families. An autosomal dominant trait only requires one abnormal copy of the gene in order to inherit the trait or syndrome.

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bacteria

Singular: bacterium.
Single-celled organisms that lack many of the organelles and structures found in our cells.
Bacteria do not contain a membrane-enclosed nucleus and are therefore called prokaryotes. Organisms whose cells contain a nucleus, including humans, are termed eukaryotes.
Examples of bacteria include the gut organism, E. coli and the disease causing Strep. pneumoniae.

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basal lamina

Also: basement membrane.
A layer of proteins and glycoproteins that surrounds our tissues.
Cancer cells that are in the process of metastasizing must cross the basal lamina to enter blood vessels or other areas of the body.

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basement membrane

See basal lamina.

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bcl-2

An protein that works to inhibit apoptosis (cell death). The gene was intially described in a B-cell lymphoma, from which it got its name.
There have been several proteins identified that are similar in structure and function to bcl-2 and an entirely different set of proteins whose function seems to be exactly the opposite. The life of a cell apparently hangs in the balance as these two sets of protein work against each other. A change in the cell that tips the scales towards the bcl-2 proteins will allow the cell to live.

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benign

A growth that does not leave its site of origin or invade surrounding tissue. While not generally as dangerous as malignant tumors, benign growths can get large and are capable of causing illness or even death, depending on the location of the growth.

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beta-catenin

A multi-functional protein that interacts with the cytoskeleton, aiding in the ability of the cell to react to extracellular signals and interactions. The protein also acts in the nucleus as a transcription factor, turning on genes that drive cell division.

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Bexxar.

Also: Tositumomab. A monoclonal antibody currently being evaluated for the treatment of non-Hodgkin's B-cell lymphoma. This antibody is different from others in that a radioactive molecule, I-131 has been attached to the antibody. The binding of the antibody the target cells acts to deliver the radioactive material, leading to DNA damage and ultimately, the death of the cell.

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biological response modifier

Also called BRM, these are agents that can potentiate the body's own response to an infection or a cancerous growth. Very often these agents are proteins that are produced naturally by our bodies. The proteins can be made in the laboratory and then injected back into the patient. Examples of these types of agents include alpha-interferon, gamma-interferon and interleukin 2 (IL-2). The goal of all of these therapies is to allow the patient's immune system to work at its best to eliminate the foreign invader or tumor.

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biomarker

A biological measurement used as an indicator for the status of a disease or process (for example, the level of a protein in the blood)

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biopsy

An invasive medical procedure in which a sample of tissue is removed for examination. Biopsies can be done in several ways, ranging from a small sample drawn into a needle to samples taken during more invasive surgery. The samples are then examined for evidence of disease.

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blood brain barrier

The tight connections between the cells lining blood vessels and capillaries in the brain block the passage of most substances from the blood into the fluid area surrounding the brain and the brain itself. This blockage creates a challenge for the delivery of anticancer drugs to tumors located in the brain.

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Breast Conserving Treatment (BCT)

Also: 'lumpectomy'. A surgical procedure in which a growth is removed from a breast with as little additional breast tissue as possible.

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c-myc

A transcription factor that controls the expression of several genes involved in cell division. The mutant form of this gene acts as an oncogene and is found in cancers of several types including neuroblastoma.

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CA-125

A glycoprotein secreted by some ovarian cancer tumors into the bloodstream. The protein can be detected in the blood and is used to monitor the progression of those cancers.

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carbohydrate

A sugar monomer, dimer or polymer. Sugars are comprised of carbon, hydrogen and oxygen. Carbohydrates are used for energy and for building structures such as the cell walls of plants. Carbohydrates are often added to other biomolecules such as proteins and lipids to form complex mixtures. The sticky nature of carbohydrates is utilized to allow different molecules to adhere to each other.

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carcinogenic

An agent that is able to cause cancer. Many of these are chemicals that cause changes (mutations)in DNA. Radiation is another type of carcinogen.

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carcinoma

Cancer of epithelial cells. This is the most common form of cancer, accounting for up to 90% of all cancers.

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catalyst

A substance that is able to speed up a reaction without undergoing any chemical changes itself. The most common type of catalyst in biological systems are made of protein and are termed enzymes.

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cellulose

A carbohydrate molecule composed of many linked molecules of the monomer sugar glucose. Cellulose is the primary building blocks of plant cells and a major component of wood. Cellulose is not digestible by humans and makes up the bulk of the dietary component often called fiber, bulk or roughage.

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centriole

A cylindrical array of microtubules located in the cytoplasm of animal cells. Centrioles are found in pairs, with the cylinders essentially perpendicular to each other. They are surrounded by a network of microtubules to form a larger complex termed a centrosome. Centrioles may function in the organization of the spindle fibers during cell division.

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centrosome

A subcellular structure that includes a pair of centrioles. The centrosomes at the ends of a dividing cell are at least partially responsible for the organization of the microtubules in the spindle. The spindle helps to separate the chromosomes and divide the cell.

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chemotherapy

Treatment of cancer patients with anticancer drugs. Commonly called chemo. These drugs are often very toxic, with severe side-effects such as nausea and vomiting. These drugs all work by attacking cell growth or division. Many of these agents are only effective at specific times during the cell division process. Often these agents are used in combination to take advantage of their different modes of attack on cell division.

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cholesterol

A type of lipid, cholesterol is part of a group of molecules called steroids. Testosterone and estrogen are other steroids that are very similar to cholesterol in structure but not function. Cholesterol is essential for the structure and function of our cellular membranes. Contrary to the entirely negative reputation cholesterol has in the popular press, it is required for normal life processes. Cholesterol can be obtained in the diet or produced from precursors in our bodies.

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chromatin

A combination of DNA and proteins. Our chromosomes are composed of DNA that is twisted around proteins much like thread on a spool. In addition to structural roles, the proteins also aid in the replication and cell division processes. Some of these proteins, the topoisomerases, are targets of chemotherapy drugs such as etoposide (VP16) and topotecan. See also, 'nucleic acid'.

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chromosome

A long DNA molecule containing genetic information (genes). Humans have 46 chromosomes. One set of 23 is inherited from each parent. The DNA molecules are extremely long and contain millions to hundreds of millions of nucleotides strung together. Our chromosomes reside in the nucleus within each of our cells. See also, 'nucleic acid'.

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chronic lymphocytic leukemia

Also: CLL. A cancer of B-lymphocytes (B-cells)in which the number of cells in the bone marrow, blood and tissues increases gradually with time.

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clinical trials

Please see the Clinical Trials section.

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codon

A string of three nucleotides along a messenger RNA (mRNA) molecule that encodes a single amino acid. Ribosomes are able to 'read' the encoded message in an mRNA and synthesize proteins from amino acids present in the cell.
As an example the codon AUG in an mRNA leads to the incorporation of the amino acid methionine into the growing polypeptide (protein). Some codons are used for 'punctuation', so that the codon UAA leads to the termination of the protein chain.

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colostomy

A surgical procedure that creates a way to drain waste from the large intestine. Colostomies can be permanent or may be reversed. A colostomy may be necessary after surgery to remove colorectal or anal cancer.

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conjugated monoclonal antibody

See the entry for antibodies.

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contraceptives

A device used to prevent pregnancy. Oral contraceptives used by women contain different mixtures of hormones such as estradiol and progesterone.

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CT scan

Computed Tomography. A non-invasive, X-ray based technique for imaging internal structures and identifying disease. May involve the use of an injected 'contrast' agent such as iodine. The images are analyzed by computer and can produce many 'slices' through the target organ or tissue.

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cyclin-dependent kinase inhibitors (CKI)

Naturally occuring proteins or synthetic drugs that block the activity of cyclin-dependent kinases.
These kinases (enzymes that attach phosphate groups to targets)are critical in the progression through the cell cycle. Inhibition of these enzymes would be expected to inhibit cell division and therefore, in the case of cancer, tumor growth.

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cytokinesis

The actual division of a cell into two daughter cells. This is a normal process and leads to cells that allow for growth of organs/tissues or replacement of dead cells. The two resultant cells are genetically identical to the parent cell.

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cytoplasm

The portion of a cell that is located outside the nucleus. This includes many organelles such as ribosomes and mitochondria. The cytoplasm also contains many fibers of the cytoskeleton. Compare to cytosol.

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cytoskeleton

The dense network of wire-like proteins that crisscrosses the cytoplasm of a cell. The cytoskeleton is responsible for giving a cell shape, anchoring organelles and allowing cellular movement and attachment. A wide range of proteins form the cytoskeleton, including actin and tubulin. Tubulin is used to form microtubules, targets of some chemotherapy agents.

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cytosol

The semi-liquid portion of the cell outside the nucleus, excluding the organelles. Compare to cytoplasm.

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cytotoxic

Having the ability to kill a cell. Many of the chemotherapy drugs are cytotoxic, as is radiation. Cells of our immune system also have the ability to recognize and kill certain cells, such as virally infected cells or cancer cells.

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de novo

again

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denature

The unfolding of a protein. A protein's function is exquisitely tied to its proper shape. Denaturing of proteins can be accomplished by heat, chemicals or biological(enzymatic) means. An example of denaturing proteins is a cooking egg. The clear part of the egg becomes white as the proteins denature from the heat.

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differentiation

The maturation of a stem cell into a fully functional cell. In many tissues, only a small set of immature cells are capable of cell division. The products of the divisions may go through a series of changes that alter the cell shape a functions. An example would be the maturation of a single type of precursor cell into several different type of blood cell.
The mature cells often have very different appearances and functions in the body despite the fact that they are derived from the same type of precursor or stem cell.
Fully differentiated cells often are incapable of cell division and many cancers are thought to arise via alterations in stem cells.
The cells in cancerous states also tend to become more like their precursor stem cells through a process of de-differentiation. Some anti-cancer drugs are designed to force cells to differentiate, reducing their ability to reproduce.

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disulfide bonds

The only covalent bond between the amino acids of a protein. Disulfide bonds (S-S), between the sulfhydryl groups of two cysteines are very strong and help to give proteins their structures

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DM1

A semi-synthethic drug (a maytansinoid derivative) that works to kill cancer cells by inhibiting microtubule function.
Current trials with this drug involve the attachment of DM1 to monoclonal antibodiesto allow for delivery specifically to tumor cells.
The products are being developed by several companies, including
ImmunoGen, Inc.

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DNA

Abbreviation for deoxyribonucleic acid. Composed of very long strings of nucleotide monomers. This is the storage form of our genetic material. All of the instructions for the production of our proteins is encoded in our DNA. Genes are comprised of short stretches of DNA. Our DNA is arranged into chromosomes. There are about 6 billion nucleotide pairs in the DNA of a single cell. Changes to the nucleotide sequence of the DNA are called mutations. Many chemotherapy agents work by altering the structure of DNA. These changes disable the cells and prevent them from dividing.

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dysplasia

An abnormal condition in which cells may have altered morphology (shape) or may divide in a manner that alters the appearance of the tissue or organ. This often occurs in rapidly dividing cells and may be a precursor to cancerous growth.

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ectodomain

The portion of a membrane protein that is exposed to the extracellular space.

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endometrial

Refers to the endometrium, the inner lining of the uterus. The endometrium is a common site of cancer.

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endoplasmic reticulum (ER)

A membranous hollow subcellular organelle. The ER is actually an extension of the outer nuclear membrane.
The ER has two structurally and functionally different regions,1) the rough ER, responsible for the modification and export of proteins, and 2) the smooth ER, which among other things, detoxifies drugs, manufactures steroid hormones and helps to build cell membrane components.

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enzyme

A protein that speeds up the process of chemical reactions in the body. The proteins act as catalysts; they speed up the reactions without getting altered in the process. Almost every biological process is driven by the activity of enzymes. Without them, the complex reactions that we need to build and breakdown cell parts would not happen at a rate that is compatible with life. Enzyme names usually describe the reaction that is being catalyzed and all of them end in -ase.

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epigenetic

In addition to actual alterations in DNA sequence, gene expression can be altered by changes to the DNA and chromatin that do not change the DNA sequence. Since these changes do not alter the sequence of the DNA in the genes, they are termed epigenetic changes. Two types are epigenetic changes are described below.

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epithelial

Also called epithelium. A type of tissue that covers our exposed surfaces, such as our skin. Also lines our hollow or tube-like organs/tissues such as our digestive tract. Since these tissues are often exposed to environmental insults such as chemicals and radiation from the sun, and are often rapidly dividing to replace lost cells, many cancers arise in epithelial tissues.

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ER

Also: endoplamic reticulum. A subcellular structure that is part of a large network of membranes within the cell. The ER membrane is an extension of the outer nuclear membrane. The ER has two structurally and functionally distinct regions.

Proteins produced by the RER and SER can be packaged into vesicles and sent to other locations in the cell or to the outside of the cell. Many vesicles are sent from the RER to the golgi apparatus, where the contents of the vesicles are processed.

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erbB2

See HER2/neu.

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estrogen

A steroid sex hormone. Estrogen has a structure that is closely related to cholesterol. Produced by the ovaries, estrogen has effects on the reproductive, cardiovascular and skeletal systems. Estrogen is also a growth factor for some types of cells, including breast cells. Inhibitors of estrogen function such as tamoxifen are used to block the growth effects of estrogen. See also, estrogen receptor.

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estrogen receptor

Abbreviated as ER. A protein located within cells that binds estrogen. The protein:estrogen complex then binds to DNA to increase the transcription of certain genes. The estrogen receptor therefore is a type of transcription factor. The estrogen receptor is the target of the anticancer drug tamoxifen. By binding to the ER, tamoxifen blocks the growth promoting effects of the hormone.

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eukaryote

A cell containing membrane bound organelles and a membrane enclosed nucleus. This is in contrast to bacteria, which are microbes that do not contain a nucleus. Humans are eukaryotic organisms. A typical eukaryotic cell is shown below.

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extracellular matrix

A complex of proteins and glycoproteins that surrounds the cells in our tissues and organs. The extracellular matrix is used for attachment and to help organize the cells.
Cells can attach to the extracellular matrix via proteins on their surfaces.

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familial adenomatous polyposis

Also: FAP. An inherited form of colon cancer characterized by the development of hundreds to thousands of colonic polys. Most of these growths are harmless but some eventually progress to malignant growths.
Another inherited form of colon cancer, HNPCC, does not present with polyps.
FAP is often diagnosed via colonoscopy.

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Fc region

For 'fraction crystallizable'. The constant region of an antibody. Antibodies are composed of two functionally different parts. The variable portion is responsible for binding to the target antigen and the constant portion is often recognized by cells of the immune system.
In ADCC, the Fc region of the antibodies bound to the target cell are recognized by cells of the immune system, leading to the death of the target cell.

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G1 and G2

These refer to two the stages of the cell division cycle. During these phases, the cells are growing and preparing to undergo the changes necessary for cell division. The cell cycle is divided into four stages. The remaining two are the S phase which is the time of DNA duplication and the M phase during which the cell actually splits into two daughter cells. The daughter cells have the exact same genetic information as the parent cell.

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gamete

A cell involved in reproduction; sperm and eggs. Gametes contain only half the genetic information of a typical cell. When two cells of this type fuse via the process of fertilization, the offspring formed has the full complement of genetic information. In the case of humans, each gamete contains 23 chromosomes and the embryo has 46 chromsomes.

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gene

A stretch of DNA that leads to the production of an RNA. The RNA is produced during the process of transcription. This RNA can be used to guide the formation of a protein via translation or can be used directly in the cell.

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gene chip

An advanced and relatively new method for monitoring gene expression. The differences between normal cells and cancer cells can be analyzed by examining the activity of thousands of genes simultaneously.
Gene chip analysis is being investigated for its potential in the diagnosis and treatment protocol design for several cancer types.

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gene expression

The act of transcription and, if needed, translation of a gene. Regulation of gene expression is tightly regulated. Genes must only be expressed in the correct cells, at the right time and in the correct amount. Abnormal gene expression is always found in cancer.

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genome

The full set of genes in an organism. Humans have an estimated 30,000 genes in their genome.

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genotoxic

Refers to agents that either directly or indirectly cause damage to cellular DNA. Some cancer causing agents, such as benzo-a-pyrene, found in cigarette smoke are genotoxic. These agents cause mutations and can lead to changes in proto-oncogenes and tumor suppressor genes.

A large number of chemotherapy drugs are also genotoxic. Examples include cisplatin, carboplatin and doxorubicin. These agents kill cancer cells by damaging their DNA, preventing cell division. The side effects seen with many cancer treatments are a result of their genotoxic effects on normal cells in the body.

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glial cells

A group of cells located in the brain and nervous system. Glial cells do not conduct nerve impulses but they support the neurons that do serve this function. Glial cells are very numerous and far outnumber neurons.

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glucocorticoids

A group of steroid hormones derived from cholesterol and produced in the adrenal gland. The majority of the activity related to glucocoricoids in humans is due to cortisol (also called hydrocortisone). This hormone is elevated in response to stress and has effects on many different aspects of human physiology including the ability to suppress the immune system.

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glycogen

A carbohydrate molecule composed of a long string of glucose subunits. Found in the liver and muscles of mammals; glycogen is the stored form of carbohydrates within the body.

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glycolipid

A lipid with a carbohydrate molecule or molecules attached to it. The phospholipids that make up our cell membrane are sometimes modified by the addition of carbohydrates.

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glycoprotein

A protein that has been modified by the addition of one or more carbohydrates. Many proteins are modified in this way. The addition of the sugar molecules alters the properties of the protein and often aid in the function of the protein. Many proteins that are located on the outside of our cell membranes are glycoproteins. The blood tests used to detect cancer often are actually detecting small amounts of glycoproteins that are produced by the particular cancer cells. For instance, both the prostate specific antigen (PSA) test used to detect prostate cancer and the CA125 test used to track ovarian cancer growth are actually monitoring the abundance of different glycoproteins that are released by the tumor (and sometimes normal) cells.

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golgi apparatus

A series of sac-like, membrane enclosed areas of the cytosol. The golgi apparatus is responsible for the processing of proteins secreted from the ER and shipment of those proteins to their final destinations. Vesicles leaving the golgi can go to other organelles or may fuse with the plasma membrane, releasing the contents into the space around the cell(the extracellular space).

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growth factor

A substance that stimulates cell division. Growth factors are usually small proteins or steroid hormones. They may be secreted by the same cells on which they act or by cells that may reside in a different part of the body than the target cells.
Some examples of growth factors include estrogen, a growth factor for breast cells and VEGF, a growth factor that causes the development of blood vessels.
Several different anti-cancer treatments are designed to inhibit the activity of growth factors.

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HER2/neu

Also: erbB-2. A transmembrane growth-factor receptor. This protein is found at very high levels on some breast and ovarian cancers and may be a prognostic factor in these types of cancer.
The cancer treatment Herceptin. (is a monoclonal antibody selected to attack cells that express high levels of this protein on their surface.)

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heterozygous

The state of having two different forms of any particular gene. Humans have two full sets of genes, one obtained from each parent. Although the each set has the same genes, they may not be exactly the same forms for each gene. Variations in the genes give us a wide range of different characteristics. Examples would be genes involved in the production of pigments. Variations in these genes give us black, brown, blonde or red hair and all the colors in between. When the versions of a gene received from both parents are the same, the genes are said to by homozygous. When they are different then the genes are heterozygous. Homo- and hetero- refer to same and different, respectively and -zygous refers to the formation of a zygote or embryo.

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HGF

Hepatocyte growth factor; a glycoprotein produced by cells in the bone marrow that promotes adhesion of cells to the matrix and may regulate cell migration

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histones

A group of proteins that combine to make a 'bead' around which our DNA is wrapped. The bead consisting of DNA and histones is called a nucleosome.

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HNPCC

Hereditary Non-polyposis Colorectal Cancer. A hereditary form of colon cancer. This colon cancer is not associated with the development of colonic polyps. Another familial form of colon cancer, FAP (familial adenomatous polyposis), is characterized by the development of hundreds or thousands of polyps in the large intestine. While most of these growths are benign, some inevitably progress to a malignant cancerous state.
Both of these disorders may be detected via colonoscopy.

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hormone

A chemical produced by cells that alters the activity of other cells. The chemicals may be lipids, such as testosterone and estrogen or proteins like insulin. Hormones may act at locations far from their site of origin. Estrogen, for example, is produced primarily by cells in the ovaries but acts on cells in the breast and elsewhere.

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hydrophilic

Describes molecules which readily interact with water or other polar molecules. From hydro-water and philic-loving. Our blood, body fluids and the insides of our cells are all composed mostly of water.

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hydrophobic

Describes molecules which do not interact with water or other polar molecules. From hydro-water and phobos-fearing The lipid hormones and fat are examples of hydrophobic molecules.

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IGF-1

Insulin-like growth factor type 1. A potent growth factor. Elevated levels of IGF-1 have been found in the blood of patients with certain types of cancer, including breast cancer.

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Immunological memory

Refers to the fact that once our immune system has encountered a particular substance (antigen) that causes the generation of an immune response, any subsequent response to that antigen is much more rapid and more rigorous.
Immunological memory is the basis for vaccinations, in which a small dose of an antigen is given so that a future exposure to a disease causing organism will result in rapid removal of the invader from the body.
In cancer, vaccinations are given to boost the response of the body against antigens present on cancer cells.

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immunotherapy

A treatment for a disease (including cancer) that involves the modulation of the immune system. Treatments include the administration of cytokines ( proteins produced by cells of the immune system), vaccination and even treatment with antibodies such as the breast cancer treatment, Herceptin..

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in situ

From the Latin; in place. Often written in italics. Refers to the detection of a process or molecule which is examined in its original location. This is in contrast to in vitro, which refers to processes or molecules examined in testtubes.
As an example, the production of a particular protein can be detected by looking into the cell while it is still whole (in situ) or after breaking the cell open and separating its parts (in vitro).

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inflammation

A reaction to cellular damage or tissue invasion. Small blood vessels become leaky, leading to redness, swelling and the infiltration of the area with cells of the immune system.

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insulin

A protein hormone secreted by the pancreas. Insulin controls glucose levels in the body by increasing uptake of glucose into cells of the body. Insulin also has stimulates the formation of glycogen and alters fat and protein metabolism.

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interferon

One of a group of protein messengers produced by cells of the immune system and some other cells. Interferons can help cells to defend themselves against viral infection and are currently being evaluated for their ability to increase the body's ability to eliminate cancer cells.

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isotypes

Types of antibody (immunoglobulin) molecules. While all antibodies have a similar basic structure and function, there are several different sub-types with different capabilities. For example, some antibodies are able to be recognized by cells of the immune system so that coated targets can be destroyed and other antibodies lack this property.
The main isotypes are IgG, IgM, IgA, IgE and IgD.

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kinase

An enzyme that adds phosphate groups to another molecule. Many of the key regulatory proteins in the control of gene expression are targets of kinases. The addition of a phosphate group to a protein by a kinase can alter the activity of the protein and are often used as molecular on/off switches. For example, the retinoblastoma tumor suppressor gene is 'off' when phosphate groups are added to the protein at specific locations. Removal of the phosphate groups turns the protein 'on'. Enzymes that remove phosphate groups are known as phosphatases. Note that all enzymes, regardless of function, end in ASE

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lesion

This is a broadly used term in pathology and refers to any defined (localized) structural abnormality or injury. The word 'lesion' does not imply that something (i.e. a tumor) is necessarily serious or advanced.

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leukemia

A cancer affecting the cells that develop into white or red blood cells. From leuko- white and -emia referring to blood. Both of these cell types originate in bone marrow. Red blood cells function to carry oxygen to our tissues and the white cells (leukocytes) are part of our immune system. The cancerous cells often accumulate in the blood.

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lipid

A class of biomolecule. Lipids all share a common feature in their hydrophobic nature. Lipids are one of four classes of biomolecules that make up the majority of the materials in our cells. The others are proteins, carbohydrates and nucleic acids.

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lumpectomy

A surgical procedure in which a tumor is removed with as little surrounding tissue as possible.

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lymph nodes

A grape-like cluster of rounded lymphatic tissue. Lymph nodes (or lymph glands) filter the lymph fluid that flows through the lymphatic system.
Lymph nodes collect fluid from discrete regions of the body and are often examined for the presence of metastasizing cancer cells.
See also
lymphatic system

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lymphatic system

The lymphatic system is a large network of vessels that carry fluid and cells of the immune system around the body. Lymph nodes are regional collection centers in the lymphatic system. Fluid from the areas surrounding the lymph nodes drains into the lymph nodes just like smaller streams fuse to form a larger river. Cells from tumors may break off the primary tumor and get carried to a nearby lymph node. The lymphatic system is a primary mechanism for tumors to move, or metastasize, to other parts of the body.

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lymphocyte

A immune cell that resides primarily in the lymphatic system. The lymphocytes include
1) T-cells: Cells involved in the control of immune responses and cellular cytotoxicity
2) B-cells: Cells that produce antibodies (immunoglobulins).

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lymphoma

A cancer arising in the lymphatic system. The white cells affected are part of the body's immune system. The lymphatic system is a large network of vessels that carry fluid and cells of the immune system around the body. Lymph nodes are regional collection centers in the lymphatic system. See also, 'lymphatic system'.

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lysosome

A subcellular organelle responsible for the digestion of intracellular debris such as defective or unneeded proteins, lipids and carbohydrates. Ingested cellular debris from dying cells is also digested by lysosomes. These small sac-like structures contain numerous destructive enzymes that rapidly break large molecules down to their components. The released components can then be re-cycled in the cell.

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Mabthera

Also: Rituximab, Rituxan.. A monoclonal antibody used to treat non-Hodgkin's lymphoma.
Learn more about Rituximab from Genentech.

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malignant

A tumor that is likely to invade neighboring tissue and metastasize.

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mammogram

A diagnostic procedure that involves taking an X-ray of the breasts. Changes due to cancer growth can often be seen in the images produced. More on ths topic can be found in the pages on breast cancer detection.

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matrix metalloproteases

A group of secreted enzymes that are able to degrade the basal lamina and allow for cancer cell migration. These enzymes are capable of degrading a wide range of extracellular proteins, such as collagen. The enzymes derive their name from the fact that they are secreted into the extracellular matrix and they have a requirement for metal ions in order to function properly.
Matrix metalloproteases (MMP) are key to cancer metastasis as they enable the moving cells to cross barriers such as the basal lamina

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membrane

1. cell membrane-A very thin barrier between the cytoplasm and the extracellular space. Cell membranes are composed mainly of lipids and proteins. A hallmark of cellular membranes is their selective permeability to certain ions and other molecules. 2. tissue membrane- a thin layer of cells or protein matrix that separates adjacent portions of organs or tissues. In order for tumors to metastasize, they usually have to encounter and break through a membrane, such as the cells of blood vessels.

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metabolism

The sum of all reactions in a cell or animal. The processes that lead to the creation of biomolecules such as proteins and nucleic acids are termed anabolic pathways. The processes in which biomolecules are broken down, such as the digestion of foods, are termed catabolic. Metabolism is a term that encompasses both of those sets of processes.

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metastases

Tumor growths located at a location distinct from the initial site of cancer development. Also: see the animation at ' metastasize '.

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metastasize

The movement of a cancer to a location outside its site of origin. The distant growths are termed metastases

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metastatic

The term for a cancer that has spread beyond its point of origin. Metastatic disease is reponsible for the majority of cancer deaths.
See also: the animation at ' metastasize '.

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microbe

Organisms that are too small to be seen with the naked eye. Microbes include bacteria, viruses and some fungi.
Infection with microbes poses a serious threat to patients with cancer.

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microtubule

A cable-like structure that is part of the cytoskeleton. Microtubules are composed of long chains of the protein tubulin. They serve to give a cell shape, aid in cellular motility and are very important in cell division. Microtubules are dynamic and grow and shrink depending on the needs of the cell. (see animation below.)
The anticancer drugs taxol, vincristine and vinblastine (and their derivatives) all work by interfering with the function of microtubules.

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mitochondria

Subcellular organelles. Mitochondria are responsible for extracting the bulk of the energy we use from the food we eat. As a byproduct of this activity, oxygen radicals (reactive chemicals) are produced that may contribute to cancer formation by damaging DNA. A cut-away view of a mitochondrion (the singular version of the word) is shown below, revealing the inner membranes of the organelle.


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mitosis

The portion of the cell-cycle during which the the cell divides into two daughter cells.

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monoclonal

Derived from a single source. In the context of cancer, the term is used in two ways. 1. To refer to the fact that tumors arise from a single damaged cell. 2. To describe the antibodies used in the treatment of cancer.

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monomer

A molecule or subunit that functions alone or combines with other similar molecules to form a polymer. All of the biomolecules that make up our cells are made up of strings of monomers. For example, proteins are made up of strings of amino acids and nucleic acids are strings of nucleotides.

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MRI

Also: nuclear magnetic resonance imaging (NMR). Magnetic Resonance Imaging is a non-invasive imaging procedure that utilizes strong magnets and radio waves to visualize tissues in a patient. Subtle differences in the ways that the tissues and organs absorb and reflect the waves enable the detection of many different disorders.

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mRNA

Messenger RNA, an RNA molecule that is used in the production of a protein. Messenger RNA is produced in the nucleus via the process of transcription and is exported through holes or pores in the nuclear envelope into the cytoplasm. The message then attaches to a ribosome and the encoded message is read to produce a protein in the process termed translation.

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Multiple Drug Resistance Protein

Also: MDR, P-glycoprotein and drug efflux pump. A transmembrane protein that is able to prevent the entry of some anti-cancer drugs into cells and to eject drugs from the cell after they have entered.
Increased expression of the protein is a leading cause of chemotherapy failure.

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multiple myeloma

Also: malignant plasmocytoma. A cancer of the bone marrow in which plasma cells overgrow the normal cells. Plasma cells are B-cells that are fully differentiated and are producing antibodies.

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mutagen

An agent that can cause alterations to DNA. If the alterations are not repaired exactly, changes in the nucleotide sequence can lead to altered gene expression or gene products (RNA). Many mutagens are also carcinogens, agents that can cause cancer. Since cancer results from mutations in key genes, an agent that can cause changes has the potential to cause the changes that lead to cancer. Ironically, radiation and many of the chemotherapy agents used to treat cancer also have the potential to cause mutations and lead to cancer themselves.

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mutagenic

See mutagen

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myelosuppression

The decreased activity of the blood cell precursors located in the bone marrow. The red blood cells and white blood cells in our bloodstream originate from stem cells located in our bones. These cells are often short-lived and must be replaced constantly. To do this, the precursor stem cells divide very rapidly. Chemotherapy agents, radiation and many other cancer treatments are designed to attack rapidly dividing cells and often inhibit the activity of these normal bone marrow cells.

Several side effects of cancer treatment, such as anemia and a decreased ability to fight infections (immunosuppression) are due to the effects of these treatments on bone marrow cells.

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nanoprobe

A complex in which a sphere containing iron oxide particles is linked to an anti-tumor antibody. This complex will rotate and produce heat when an alternating magnetic frequency is applied.

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NF-kappa B

A transcription factor that controls the activity of several genes involved in the regulation of cell division.

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nuclear envelope

The double membrane that surrounds the genetic material (chromosomes) in eukaryotic organisms. The nuclear envelope contains numerous pores to allow the export of RNA and the importation of many materials needed for proper cell function. The nuclear envelope is broken down during cell division and re-formed in the daughter cells. See the illustration at 'nucleus'.

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nuclear pore

A large protein complex that allows the movement of materials into and out of the nucleus. As an example, any proteins used in the nucleus, such as the histones and polymerases need to be imported. Any products that leave the nucleus, such as mRNA, must also pass through the pores.

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nucleic acid

One of the four basic biomolecules. Nucleic acids are the information carriers in the cell. There are two forms of nucleic acid, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). DNA can be thought of as the storage form of our genetic material. Our chromosomes are composed of DNA and protein and our genes are stretches of DNA. RNA is the working form of the information. RNA is produced through the process of transcription in which an RNA copy of a particular stretch of DNA (gene) is produced. The relationship between a cell, nucleus, chromosome, gene and DNA is shown below.


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nucleosomes

A functional unit of organization of our chromosomes. Nucleosomes are composed of a mixture of histone proteins around which the double-stranded DNA is wrapped.

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nucleotide

A monomer building block of the nucleic acids DNA and RNA. There are approximately 3,000,000,000 nucleotides in the entire human genome. Each chromosome contains from about 50-250 million nucleotides. The four nucleotides that are used to form DNA are abbreviated as A, C, G and T. RNA contains four nucleotides as well, but uses U instead of T, so that RNA contains A, C, G and U. Some chemotherapy agents, like 5-Fluorouracil ( 5-FU) and ARA-C are chemically very similar to one of the nucleotides and exert their effect by interfering with DNA function or leading to alterations in the nucleotide sequence of the affected DNA.

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nucleus

Plural, nuclei. A subcellular organelle that contains the chromosomes (chromatin). Present in eukaryotic cells. The nucleus is surrounded by the nuclear envelope. Within the nucleus is a region called the nucleolus in which the parts of ribosomes are constructed. The nuclear pores allow for the import and export of materials. Depicted below.

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oncogene

A defective gene that is involved in triggering cancer cell growth. Oncogenes are altered forms of genes that normally are involved stimulating cell division. These normal genes are mutated and function in an inappropriate manner in cancer cells. A reasonable analogy would be that a broken oncogene is akin to a gas pedal on a car that is always stuck in the on position. One or more oncogenes is mutant in all forms of cancer. Some examples of oncogenes that are altered in many cancers are myc, ras and Her-2/neu. Contrast with 'tumor suppressor'.

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organelle

A subcellular collection of biomolecules that performs a particular function in the cell. Like our liver or lungs, the organelles have specific jobs. For example, our nucleus acts like a brain for the cell, issuing commands and controlling cellular activities.

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osteosarcoma

Cancer of the bone. Osteosarcomas are derived from osteoblasts, cell that line the outside of bones. It is most common among children and young adults and affects males more than females.

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overexpression

A term used to desribe the abnormal regulation of a gene. When the tight controls on gene expression (transcription) break down, the gene may be turned off inappropriately, or it may be transcribed at high rates. High levels of transcription lead to the production of large amounts of mRNA and large amounts of the protein product.
If the protein in question is important in regulating cell division or some other key process, then too much protein can lead to unregulated cell division. An example is the overexpression of the Her2/neu protein on the surface of some breast and ovarian cancers. The presence of large amounts of this protein enhances the abnormal cell division seen in these diseases.

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p21

Also: CIP1, WAF1, CDKN1A. A gene that produces a potent cell cycle regulatory molecule. The p21 protein acts to inhibit kinases that control the progression of the cell cyle.
The p21 protein is thought to be the major effector molecule in the regulation of the cell cycle by the tumor suppressor, p53, and the p21 gene is activated by the p53 protein.

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p53

A tumor suppressor gene that is found to be mutated in over 50% of cancers of all types. The protein encoded by this gene is a transcription factor that controls entry into the cell division cycle. Many signals about the health of a cell are relayed to the p53 protein. This results in a decision by the cell as to whether or not cell division should occur. If the cell is damaged and can not be repaired, the p53 protein is involved in triggering a chain of events that causes the cell to kill itself in a process termed apoptosis. Cells defective for p53 do not have these controls and tend to divide even when conditions are not favorable. Like all tumor suppressors, the p53 gene is normally involved in slowing or monitoring cell division.

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Panorex.

Also: Edrecolomab. A monoclonal antibody used to treat coloretal cancer.

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peer-reviewed journal

Peer-reviewed journals are the most credible source of information on scientific experiments of any kind. When a scientist performs an investigation, they must write a detailed description of what they did, how they did it, and what they observed. Once this report is written, it is scrutinized by panel of experts (a group of peers) to determine if the procedure was as objective as possible. The analysis of the results must also be logical and statistically sound/significant. If the experiment passes these rigorous standards, it is published in a peer reviewed journal for the entire community to view. Although these reports are under stringent conditions, one paper does not mean that a whole line of scientific thinking will change. One fundamental aspect of these experiments is that they can be replicated. If anyone else who would use the same protocol, the same results ought to be observed.

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peptide

A small protein. Peptides, like larger proteins are made of strings of amino acids. There is no difference in structure between a peptide and a protein. The term is one of convenience to designate a protein that is composed of only a few to a few dozen amino acids. An typical protein would contain several hundred amino acids.

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phagocyte

Phago-eat cyte-cell. A cell of the immune system that consumes extracellular debris and foreign particles, including bacteria and viruses. Macrophages (big eaters) are a very good example of a type of cell that consumes large amounts of debris and foreign matter.
The process by which a cell takes in solid material is called phagocytosis

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phosphorylation

The addition of a phosphate group to a metabolic intermediate or to a protein. The addition or removal (dephosphorylation) of phosphate groups acts as a biological on/off switch for many processes. Addition or removal of a phosphate group can activate/inactivate an enzyme and control processes such as cell division.
Enyzmes that add phosphate groups are termed kinases and those that remove phosphate groups are called phosphatases.

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plasma membrane

The thin lipid bilayer surrounding a cell. The plasma membrane gives definition to a cell by enclosing all of the organelles and cellular material. Proper funtioning of the plasma membrane is essential to the integrity of the cell. Proteins located in the plasma membrane control the movement of nutrients and other material into and out of the cell. Proteins located on the surface of the plasma membrane enable the cell to receive signals from neighboring cells and the extracellular matrix as well as giving the cell the ability to adhere to the surrounding material.

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point mutation

A genetic change that involves the alteration of only one or a few nucleotides. The effects on the resulting RNA and protein may be profound. For more details, see the section on Types of Genetic Change.

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polyamines

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polyclonal antibodies

A mixture of antibodies. When presented with a foreign object that elicits an immune response (an antigen), many different B-cells are activated to produce antibodies. The result is a mixture of antibodies that would all recognize different parts of the antigen.

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polymer

A molecule formed from the joining of monomers. The biomolecules; proteins, carbohydrates and nucleic acids are all polymers. Like stringing together the 26 letters of our alphabet in different combinations can produce an enormous variety of words, the joining of the monomers of biomolecules can produce a virtually limitless collection of different polymers. Just like different combinations of the same letters can produce different words with different meanings, the different polymers can have very different properties and capabilities. The amino acids that build the protein in hair are the same as those that are in muscle yet they have obviously different properties.

The enzymes that string together the monomer building blocks to make long biomolecules are called polymerases. Examples include the enzymes that form DNA, DNA polymerase and RNA, RNA polymerase.

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polyp

A small growth that extends from the lining of the bowel. Many polyps appear as a small round mass on top of a small stalk. Most polyps do not become cancerous but they may cause anemia if they become damaged and bleed.

One hereditary colon cancer, familial adenomatous polyposis (FAP), is characterized by the growth of hundreds or thousands of polyps, some of which inevitably become cancerous.

Pictured below is a large cancerous polyp of the colon. The berry-like "head" of the polyp is the neoplastic portion; the long stalk is composed of normal cells and contains the blood supply.

(Image courtesy of: C. Whitaker Sewell, MD - Professor of Pathology, Emory University School of Medicine)

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polypeptide

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polyphenol

A naturally occurring chemical in plants which has antioxidant properties. The main groups of polyphenols are flavonoids, phenolic acids, phenolic alcohols, stilbenes and lignans.

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positron

an elementary particle with mass equal to that of the electron and with a positive charge equal to the magnitude of the electron's negative charge.

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primary tumor

The initial tumor mass formed by the abnormal growth of a cell. The primary tumor determines the type of cancer. When the initial tumor spreads to other locations, the metastatic growths retain the characteristics of the initial, primary, tumor.
As an example, if the initial site of cancer development is in the breast, then a metastatic growth in the brain would still be considered breast cancer, NOT brain cancer.

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proliferation

Refers to cell division. The proliferation rate is an indicator of how quickly a tumor is growing. The value may be represented as a percentage, showing what fraction of the cells are actively involved in the division process.

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proliferation rate

A measure of how quickly a group of cells are dividing. Tumors with a high proliferation rate have the potential to grow quickly.

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promoter

The portion of a gene that controls when and how much that particular gene will be expressed (transcribed). Promoters are like the on/off switch that determines the activity of a gene. Since genes are a sequence of nucleotides, promoters are also composed of DNA. Promoters do not control gene activity themselves. They work by binding to proteins called transcription factors. The transcription factors act as flags to wave-down the enzymes (RNA polymerases) that make RNA copies of the genes. Changes (mutations) in the promoter portion of a gene can lead to disruptions in the regulation of gene expression. These changes are often seen in cancer.

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prophase

A component of the M phase of the cell division cycle. During prophase, the chromosomes condense, revealing the familiar X shape of the replicated molecules. In preparation for cell division, the nuclear membrane breaks down and spindle fibers form in the cytoplasm.

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prophylactic mastectomy

The elective surgical removal of a healthy breast. This procedure is chosen by individuals who have a high risk for breast cancer due to either genetic factors, family history or their own medical history.

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prophylactic oophorectomy

The elective sugical removal of the ovaries. The removal of normal ovaries is done to lower risk of breast and ovarian cancers in individuals at high risk for the disease. The ovaries are the source of the steroid hormone estrogen, a growth factor for breast and ovarian cells. Removal of the ovaries reduces estrogene levels and sends the patient into menopause.

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protease

An enzyme that cleaves other proteins. A variety of proteases found in our digestive system break down the proteins we eat into sizes that can be absorbed. Proteases secreted by or associated with cancer cells allow them to digest their way through the tissues that contain them and allow them to spread or metastasize.

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protein

One of the four basic types of biomolecule. Proteins are polymers made up of strings of amino acids. Proteins serve many functions in organisms including transport of molecules, structure, cell adhesion and as signaling molecules such as hormones. Many transcription factors, including p53 and Rb are proteins.

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proto-oncogene

A gene that has functions to promote cell division. When these genes are mutated they may produce products that promote cell division in an abnormal fashion. See the section on Tumor Suppressors and Oncogenes for more details.
Examples of oncogenes include HER2/neu, ras, and src.

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radiation

In cancer biology: A cancer treatment in which high energy beams are used to kill cancer cells.
Radiation can also be the cause of genetic damage that can lead to cancer. As an example, skin cancer is believed to be greatly increased by exposure to ultraviolet (UV) radiation from the sun.

For more information, see the pages on
Radiation in the Cancer Treatments section.

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radioactive

Some elements (atoms) are not stable. The breakdown of these elements leads to the release of energy that is called radiation. The form of the energy (radiation) may differ between different unstable elements. The radiation from the breakdown of radioactive elements is damaging to cells and their genes. Cancer cells do not respond in a normal fashion to DNA damage and may be sensitive to killing by the radiation emitted from radioactive elements.

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raloxifene

Also: Evista.. A selective estrogen receptor modulator, or SERM. This drug interferes with some of the activities of estrogen and mimics other estrogen actions. It has been shown to be useful in preventing osteoporosis by replacing the bone-density enhancing function of estrogen in post-menopausal woment.
Raloxifene is currently being studied for a possible role in the prevention/treatment of breast cancer. A drug with a similar mode of action, tamoxifen, has long been used to treat breast cancer. It is hoped that Raloxifene will be as effective as tamoxifen with less negative effects.

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ras

A proto-oncogene that is found to be mutated in many different kinds of cancer. The ras protein is involved in transmitting signals through the cell that drive the cell into the division process.

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Rb

A tumor suppressor . The Rb gene is mutated in many different cancers but was initially described due to its role in the development of an eye cancer, retinoblastoma. The disease usually strikes young children. The protein product of the gene is a transcription factor that controls the expression of genes important in driving cells into the division process.
For more information on Rb and others, see the pages on
Tumor Suppressors.

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recombinant DNA

Refers to the creation of hybrid DNA molecules containing pieces of DNA from more than one source. This term is often used inappropriately in the popular press to refer to a wide range of molecular biological techniques.
Recombinant DNA is often created to allow the study of gene function and regulation.

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recombination

1. The generation of new combinations of genes in gametes by the random segregation of chromosomes into gametes. 2. The generation of new DNA sequences via the exchange of nucleotides between two different DNA sequences. An example,using single stranded DNA, would be: AAAAA + TTTTT => AAATT and TTTAA

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remission

A period of time in which the symptoms and signs of cancer are decreased or absent. Remission can be spontaneous or brought about by treatments. They may be of varying duration and do not necessarily indicate that a patient is cured.

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replication

The process by which DNA is duplicated. DNA replication occurs during the S phase of the cell cycle. Many of the chemotherapy drugs have their action during the process of DNA replication. Some are incorporated into the new DNA but cause problems and others interfere with enzymes necessary for DNA replication. See also, topoisomerase.

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retinoblastoma

A cancer of the retina. Found most often in small children, this disease has been linked to the inheritance of mutated copies of the Rb tumor suppressor gene. For more information, see the dictionary entry on Rb. and the pages on Rb in the Tumor Suppressor pages.

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retrovirus

A virus that has RNA as its genetic material. Since the most common genetic material for organisms is DNA, these viruses are sort of backwards, hence the name retro-virus. These viruses, upon infection of a cell, may on rare occasions, take some cellular DNA with them when they leave. Some of the first oncogenes were actually discovered because they were carried by retroviruses. These viruses were found to cause cancer and it was later shown to be due to the presence of the altered oncogene in the virus.

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ribosome

The organelle that is responsible for the production of protein. Ribosomes are comprised of two subunits that are synthesized in the nucleus at the nucleolus. Ribosomes bind to mRNA and use the information encoded in the RNA to synthesize a protein. Since the mRNA is copied from the gene in the DNA, it is really the DNA that encodes the information.

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Rituxan.

Also: Rituximab, MabThera.. A monoclonal antibody used to treat non-Hodgkin's lymphoma.
Produced by a joint venture of
Genentech and IDEC Pharmaceuticals Corporation . Distributed in the European Union countries by F. Hoffman-LaRoche

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RNA

Also: ribonucleic acid. A type of nucleic acid, RNA is a polymer comprised of the nucleotides A, C, G and U. RNA is the working form of our genetic information. RNA is produced via the process of transcription. Some RNA is used to help build ribosomes (rRNA) and some (mRNA) are used to guide the formation of proteins. Other forms of RNA are used to perform specialized functions in the nucleus.

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RNA polymerase

The enzyme that produces RNA during the process of transcription.

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sarcoma

A malignant cancer that originates bone, muscle or connective tissues.

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senescence

Outside of cell biology, this term refers to the aging process. In the context of cell division, the term refers to the aging and death of a culture of cells. All normal cells (aside from stem cells) have a limited ability to divide. Cancer cells do not undergo senescence, instead, they are capable of dividing indefinitely. Cells which can divide indefinitely are termed immortal.

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serous histology

An examination of the membrane that lines a body cavity. Serous mebranes secrete fluids into the cavities they contain. An example of a serous membrane is the peritoneum.

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somatic mutation

A mutation that occurs in a typical body cell such as those that make up our skin or organs. These mutations are not transmitted to offspring. Somatic mutations can be contrasted with germ line mutations that occur in the cells destined to become our gametes, sperm or egg. Mutations in germ cells may be transmitted to offspring.
Hereditary forms of cancer are passed to the offspring via gametes and sporadic forms of caner arise via somatic mutations. It is possible that the same cancer type can have both forms.

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spindle fiber

One of the microtubules that forms during cell division. The spindle fibers push the two newly forming cells apart and help separate the chromosomes into the daughter cells.

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spindle poison

Chemicals that block the formation or function of spindle fibers. By interfering with spindle fiber formation, these drugs block cell division. Examples include taxol, colchicine, vinblastine and their derivative.

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starch

A carbohydrate molecule composed of many linked glucose subunits. Starch is the storage form of energy in plants.

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stem cell

Precursor cells which are capable of developing into more than one cell type. All of the cells in a human body come from the division and differentiation of a single cell, formed from the fusion of an egg and sperm. This original cell has the capability to form any other cell type and is called totipotent. Over time, as tissues develop, the cells lose the ability to form all other tissues, they become 'committed' to forming only one or a few cell types. These stem cells are called pluripotent. An example of a type of pluripotent stem cell would be the cells in our bone marrow, that form many different kinds of blood cells.
Many of our fully
differentiated cells are not capable of cell division and are replaced, when they die, by the division of stem cells in that tissue.
Many forms of cancer are thought to be the result of abnormal division of stem cells.

Stem cell replacement procedures allow for the pluripotent stem cells in bone marrow to be replaced after high doses of chemotherapy.

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steroid

A type of lipid. Steroids are composed of four carbon rings fused to form one flat (planar) molecule. Examples of steroids include cholesterol, testosterone and estrogen.

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steroid hormone

A hormone derived from the precursor steroid cholesterol. Hormones are signal molecules that cause changes in cell behavior. Hormones are often produced in very small quantities and may affect cells that are located in distant parts of the body.
For example, the steroid hormone testosterone is made in the testes but acts on many different cell types in the body. The female sex hormone estrogen is manufactured primarily in the ovaries but also works on cells throughout the body.

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T cell factors (Tcf)

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tamoxifen

Also tamoxifen citrate, Nolvadex.. A selective estrogen receptor modulator, or SERM. This drug interferes with some of the activities of estrogen and mimics other estrogen actions. Tamoxifen is used to treat some breast and ovarian cancers. Currently, tamoxifent is being compared with another SERM,raloxifene for its ability to reduce occurance of breast cancer in those at risk.

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taxane

A derivative of the yew tree. The basis for several related chemotherapy drugs that work by inhibiting the function of microtubules.
See also Taxol. and Taxotere. and the sub-section dedicated to these drugs under Cancer Treatments.

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Taxol

Also: paclitaxel. An anticancer drug that works by interfering with the formation/function of microtubules (spindle fibers). Cells can not divide without correctly functioning spindle fibers. Several different derivatives exist and work by the same mechanism. See also TaxotereCBCB..
More Information on TaxolCBCB..

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Taxotere.

Also: docetaxel. An anticancer drug that works by interfering with the formation/function of microtubules (spindle fibers). Cells can not divide without correctly functioning spindle fibers. Several different derivatives exist and work by the same mechanism. See also, Taxol.
More information on TaxotereB..

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telomerase

An enzyme that functions to replace the ends of chromosomes. During NORMAL DNA replication, the ends of the chromosomes are shortened by a small amount. Telomerase is turned off in most adult tissues, a process that limits the number of cell divisions that can be completed by those cells. In cancer cells, telomerase is often reactivated, allowing the cells to divide indefinitely.

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testosterone

A steroid hormone. Testosterone is the main sex hormone in males and is responsible for the generation of the secondary sex characteristics. The hormone is produced in the testes of males and is found to a much lesser extent in females.

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thalidomide

Also: Thalomid.,. A drug that is currently being used to treat cancer and leprosy. Thalidomide was first used in the 1950s as a sedative. It was given to pregant women and had the terrible side-effect of causing severe birth defects.
Thalidomide is now being investigated or used on a limited basis for the treatment of several types of cancer including myeloma, breast and brain.

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topoisomerase

An enzyme that cuts double stranded DNA to reduce tension caused by twists in the DNA that result from the local unwinding of the helix. Topoisomerases are closely associated with the DNA in our chromosomes. Some chemotherapy drugs act by inhibiting the proper function of these enzymes. Examples include topotecan and etoposide (VP-16).

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Tositumomab

See Bexxar..

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transcription

The production of an RNA molecule from a DNA template. An RNA copy of a gene is produced by an enzyme, RNA polymerase. The RNA produced can either be used directly in the cell or can be used to direct the production of a protein through the process of translation. Many of the genes that are altered in cancer cells have potent effects on the process of transcription. See also, 'transcription factor'.

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transcription factor

A molecule, usually a protein, that binds to DNA at the start of a gene and enables that gene to be copied or transcribed to form an RNA molecule. Transcription factors bind to specific parts of genes called promoters. They are called that because they promote transcription. Binding of transcription factors to genes is required for the gene to be transcribed and is critical for the regulation of the process. Since transcription factors ultimately control what genes are turned 'on' at any given time in a cell, they are essential for the proper functioning of the cell and organism. A wide range of transcription factors are known to be associated with cancer. Changes, mutations, in these genes leads to a deregulation of the whole process. Some key transcription factors are the p53 and Rb proteins. See the animation above.

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transformation

The process by which a normal cell is converted to a cell that has the characteristics of cancer cells. The event that causes the change can be an alteration in an oncogene or infection with an oncogenic virus.

Transformed cells demonstrate several characteristic differences from normal cells including:

  • Density independent growth
  • Anchorage independent growth
  • Lack of dependence on growth factors.

For more information, see the Tumor Biology section of the site

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translation

The formation of protein by a ribosome reading a messenger RNA (mRNA). The RNA is produced in the nucleus via the process of transcription and shipped to the cytoplasm via the nuclear pores. The RNA is bound by ribosomes and the catalytic activity of the ribosomes allows the reading of the RNA and the formation of a protein based on the information encoded in the mRNA.

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transmembrane protein

A protein that spans the entire thickness of a membrane and has portions exposed on both sides. Often, transmembrane proteins located in the plasma membrane are involved in communicating messages from outside the cell to the inside, allowing the cell to change its behavior. Examples would include growth factor receptors and proteins involved in cell:cell adhesion.

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triacylglycerol

A type of lipid. Commonly called fat. Triacylglycerol or triglycerides are composed of three long hydrocarbons attached to the three carbon alcohol, glycerol. The fats are used for energy in our cells.

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truncated

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tubal ligation

A surgical procedure in which the fallopian tubes are sealed. The procedure prevents the delivery of an egg to the uterus and prevents pregnancy.

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tumor suppressor

A gene that functions in the control of cell division. These genes work to limit cell division and may be contrasted with oncogenes.
For more information, please see the
Genes of Cancer section.

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tyrosine kinase

An enzyme that adds phosphate groups to target molecules. Often the targets of these enzymes are proteins that control the cell division process, so the enzymes play a key role in cell division.
See also, kinase.

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ubiquitin

A small, 76 amino acid, protein that is added to other proteins that have been targeted for destruction by proteasomes. Ubiquitin is one of the most highly conserved proteins known and is found in all animals. The ubiquitin-proteasome system is key to cell survival and division. More information on proteasomes can be found in the Proteasome Inhibitor pages.

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VEGF

Vascular endothelial growth factor; a growth factor secreted by cells in the bone marrow that promotes the development of blood vessels (angiogenesis), leading to the growth of tumors

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vesicle

A bag-like, membrane-enclosed area in the cytoplasm of cells. Vesicles are used for storage and transport of many different biomolecules. As an example, proteins that are being released from a cell move from the ER to the surface of the cell in vesicles.

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vinblastine

An anticancer drug. Vinblastine and its derivatives work by blocking the formation/function of microtubules. Microtubules are essential to the division of cells.

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virus

The smallest type of organism known. A single virus particle is called a virion. Viruses are much smaller than cells and reproduce by invading cells and taking over. Viruses force the cells to make progeny virions.
Some virus types are associated with specific cancers and are able to convert normal cells into cancer cells. Examples of some viruses associated with cancer are:

  • papillomavirus-cervical cancer
  • hepatitis virus-liver cancer
  • Epstein-Barr virus-Burkitt's lymphoma

Virus induced transformation of cells was one of the very first model systems for the study of cancer. Viruses have also been a key tool in the identification of many oncogenes.

Because of their great ability to enter target cells viruses such as adenoviruses are being examined for their ability to deliver genes to cancer cells.

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xenografts

The transplantation of tissue from one species to another. An example would be the implantation of a pig heart valve into a human to correct heart defects.

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zymogen

An enzyme that is produced in an inactive form. They are often activated by enzymes that snip off small parts of the protein. Zymogens often function to break down other biomolecules, so their proper control is essential to prevent damage to the cells or tissues involved. An example of a zymogen is chymotrypsinogen, which is activated to form chymotrypsin, a digestive enzyme in our intestines.

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