This page presents a collection of graphics to explain key differences between normal and cancer cells. Most of the ideas shown below are explained in more detail on other pages. On this page we use only a few words and let the graphics provide the explanations.
Every case of cancer, in every patient, is unique. No two breast cancers or prostate cancers are identical. This variation is one of the things that makes cancer hard to treat.
Even with all the differences, all cancers DO share a set of common features. In 2000, Robert Weinberg and Douglas Hanahan published a paper that lists and described some of the most important things that cancers have in common - the 'Hallmarks of Cancer'.1 The cartoons below are based on this work and observations that have some since.
Note that additional details on ideas illustrated below can be found in: What is cancer?
In-depth descriptions of these and other topics are presented in the Cancer Biology section of the site.
How are cancer cells different from normal cells?
Normal cells only reproduce when they are given 'orders' to do so. They stop when those signals are removed.
When the man is not stepping on the button, the signal stops and normal cells stop dividing.
Cancer cells are able to reproduce without normal signals. They are stuck in the 'on' position.
Normal cells will stop reproducing when they are told to do so. This prevents cells from crowding each other or piling up.
Cancer cells ignore 'stop' signals and continue to reproduce. This leads to crowding and cells piling up on each other.
Normal cells have a built-in number of times that they are able to reproduce
Cancer cells are able to reproduce an unlimited number of times.
Normal cells will commit cellular suicide (apoptosis) when they become damaged.
Cancer cells can defend themselves and survive even when they're damaged.
Blood vessels provide nutrients and oxygen to cells. They are frequently built and repaired. The process is very organized and efficient. Examples include wound healing and the menstrual cycle.
Tumors need blood vessels to survive, but the blood vessels are abnormal, twisted and leaky. This can lead to treatment resistance and the spread of cancer.
Normal cells (other than those in the blood) stay in place. Cancer spread (metastasis) involves the movement of cancer cells from a tumor to distant places in the body.
Cancer cells can use the defective blood vessels found in tumors to travel to places in the body far from the original location.
When the genes (DNA) of normal cells gets damaged, it is repaired. The result is that all of the cells are genetically the same.
Cancer cells do not repair their DNA well. They gain changes over time. The cancer cells in a tumor are similar, but not exactly the same.
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