Signal transduction pathways in mitogenesis.

Quiescent cells arrested in the Go phase of the cell cycle can be stimulated to divide by polypeptide growth factors, pharmacological agents and neuropeptides which exhibit potent synergistic effects. Bombesin-like peptides are providing valuable model mitogens to elucidate the signalling pathways leading to mitogenesis. These peptides stimulate rapid increases in ionic fluxes, inositol polyphosphate formation, activation of protein kinases and expression of proto-oncogenes. A comparison of these early molecular events with those evoked by other growth factors indicate the existence of multiple signal-transduction pathways. We propose that stimulation of cell proliferation by single or multiple factors results from the activation of separate signal-transduction pathways that cooperate to elicit the complete set of molecular events leading to mitogenesis.