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CancerQuest > Introduction to Patient Information > Defining Cancer > Characteristics of Cancer Cells > Hallmarks of Cancer: Avoidance of Cell Death

Hallmarks of Cancer: Avoidance of Cell Death

In normal tissue there is a balance between the generation of new cells via cell division and the loss of cells through cell death. Old cells become damaged over time and are eliminated by a process termed programmed cell death or apoptosis. Apoptosis is a very orderly process during which the genome of the cell is broken down, the cell is fragmented into smaller pieces and the debris is consumed by nearby phagocytic cells that clean up the cell fragments.⁽¹⁾ This process is a normal and necessary means of maintaining ourselves. There are safeguards built into the cell cycle that allow for the identification and elimination of cells that are dividing in an aberrant manner. These safeguards are responsible for preventing the development of cancer. Cancer cells that get past this have acquired the ability to avoid the cell death signals triggered by their abnormal behavior. Avoidance of cell death, coupled with continued cell division leads to the growth of the tumor. Many of the chemotherapy drugs discussed in the Cancer Treatments section work by forcing the cancer cells to undergo apoptosis.

The process of apoptosis, including nuclear fragmentation and the formation of many small cell fragments is shown in the animation below.

The image below shows human lymphoma cells treated with the chemotherapy agent camptothecin. The cells that are undergoing apoptosis appear yellow and show the characteristic membrane blebbing (bubble formation) seen in cells dying via apoptosis.

The image above is used with the permission of the copyright owner, Molecular Probes..

References for this page:

1. Hengartner MO. "The biochemistry of apoptosis." Nature. 2000 Oct 12;407(6805):770-6. [PUBMED]