Cellular Basis Of Action Of Gastrointestinal Peptides/Growth factors

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During the year we have written a number of invited reviews and critical analyses which are partially based on our studies of the cellular basis of action of various gastrointestinal peptides (bombesin receptor family, VIP-PACAP peptide family, endothelin receptor family, neurotensin. These include papers reporting the effects of activation of a number of these receptors on cancer growth through the transactivation of the EGF receptor family as well as reviews of the possible therapeutic roles of PACAP/VIP and bombesin receptor families in various human diseases and CNS cancers, respectively. Recent studies show that in both normal and neoplastic tissues, gastrointestinal hormones (GI) and GI growth factors (GF) may cause cell growth by stimulating multiple intracellular tyrosine/serine/threonine phosphorylation (TyrP) signaling cascades as well as by transactivation of growth factor receptors. However, at present little is known about the ability of many gastrointestinal hormones/growth factors to activate these cascades. In a study this year we report that the neuropeptide, PACAP in lung cancer cells stimulates growth of these tumors while signaling principally by transactivation of a number of EGFR family members including EGFR, HER2 and HER3. In these cells PACAP stimulated the formation of EGFR/HER3 and HER2/HER3 dimers resulting in proliferation. Recent studies, including ours have demonstrated that in different cells the mechanisms of the ability of these peptides to stimulate tyrosine phosphorylation and receptor tyrosine kinases involves a number of different mechanisms, and this was reviewed in detail for PACAP-VIP, Bombesin, endothelin and neurotensin in an invited review this year. The novel abilities of these GPCRs to activate these tyrosine kinase cascades are demonstrating the importance of these receptors in numerous physiological/pathological processes, particular growth cascades of both normal and cancer tissues, opening new therapeutic approaches.