Figure 1.

Protective mechanisms against cancer. The survival and proliferation of altered cells can be prevented by three main mechanisms. Cell competition (left panel) is a tissue intrinsic mechanism, where unfit cells can be actively eliminated by fitter surrounding cells; cell senescence (central panel) is a cell intrinsic mechanism, where altered cells enter a permanent state of mitotic block; immune surveillance (right panel) represents an important tissue extrinsic mechanism for the elimination of senescent or otherwise altered cells.