Thus receptor mediated signaling can activate apoptosis independent of the mitochondrial pathway. TNF and other death signals can have very different effects on different cell types. TNF can signal division in some cells, differentiation in other cells, and apoptosis in yet other cell types. The response of a given cell depends on what other proteins are expressed by that cell. This is because of the failsafe mechanisms which allow cells to sense inappropriate proliferation and eliminate themselves.
Several factors contribute to the rarity of cancers.
One of these is the tight linkage between the cell cycle and apoptosis. Factors that promote cell division also promote apoptosis. Factors that inhibit apoptosis also inhibit cell division. There is a particularly tight relationship between the control of cell cycle checkpoints and apoptosis. Cell damage induces p53.