Outside of cancer biology, normal, well-behaved cells undergo a finite number of cell divisions. This is thought to be a general anti-cancer mechanism, since tired, older cells with metabolic dysfunction and increased exposure to environmental toxins- if they were to divide- are more likely to accumulate, and pass on mutations that cold promote the development of cancer. Because senescent cells have permanently exited the cell cycle, they are no longer at risk for passing along potentially harmful DNA mutations to daughter cells, potentially reducing cancer risk. [1]