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Why do cancer cells fail to die when healthy cells normally would?
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cancer
View through an endoscope of a polyp, a benign precancerous growth projecting from the inner lining of the colon.
Cancer cells fail to die because they develop mechanisms to escape apoptosis, the body’s natural process of programmed cell death used to eliminate damaged or unnecessary cells. In healthy cells, apoptosis acts as a critical safeguard, triggered by severe genetic damage or cellular dysfunction to prevent the propagation of errors.1234
Cancer cells bypass this "suicide" program primarily through specific genetic mutations:
- Inactivation of p53: The p53 gene normally monitors DNA integrity. When it detects massive damage, it triggers apoptosis. In about half of all cancers, p53 is mutated or disabled, allowing cells with damaged DNA to survive and divide instead of self-destructing.135
- Overexpression of BCL-2: The BCL-2 gene produces a protein that blocks apoptosis. Mutations can cause this gene to remain in a permanent "on" position, producing excessive amounts of the protein that prevents the cell from initiating its death program.12
- Bypassing Senescence: Some cancer cells acquire mutations that prevent the shortening of telomeres, effectively granting them immortality by avoiding the natural end of their functional life span.5
By disabling these regulatory systems, cancer cells gain a survival advantage, allowing them to proliferate despite significant genetic instability.15