Defects in death receptor signaling are associated with some cancers. For example, mutations in the FasR gene for the Fas receptor increase the frequency of Hodgkin s lymphoma. As mentioned, p53 is a tumor suppressor. Cells mutant for p53 no longer undergo apoptosis or cell cycle arrest in response to cellular damage. This makes these cells susceptible to accumulating genetic defects that could result in cancerous proliferation.
Many cancer therapies depend on induction of apoptosis by causing cellular damage.
For example, radiation therapy causes damage to cells and dividing cells are the most sensitive. The idea is that actively dividing cancer cells will be induced to undergo apoptosis. Many other therapeutic agents work by similar means. However, some tumors become insensitive to therapy because of defects in the apoptotic machinery. One of the most common examples is defects in p53.