Human cells have a built-in limitation on the number of times they can divide The cell division is cotrolled not only by extracellular mitogens but also by intracellular mechanisms that can limit cell proliferation Cell-cycle arrest excessive Myc production or apoptosis induced by ARF p excessive Mdm2 stimulation of mitogenic stable active p53 pathways 53 DEGRADATION cell-cycle OR apoptosis arrestHuman cells have a built-in limitation on the number of times they can divide The cell division is cotrolled not only by extracellular mitogens but also by intracellular mechanisms that can limit cell proliferation. Cell-cycle arrest or apoptosis induced by excessive stimulation of mitogenic pathways