Growth factors as survival factors: regulation of apoptosis.

Apoptosis is now widely recognized as a common form of cell death and represents a mechanism of cell clearance in many physiological situations where deletion of cells is required. Peptide growth factors, initially characterised as stimulators of cell proliferation, have now been shown to inhibit death in many cell types. Deprivation of growth factors leads to the induction of apoptosis, i.e. condensation of chromatin and degradation in oligonucleosome-sized fragments, formation of plasma and nuclear membrane blebs and cell fragmentation into apoptotic bodies which can be taken up by neighbouring cells. Here we discuss the mechanism(s) by which growth factors may inhibit apoptosis.