Figure 1.

Simplified representation of SSTs signaling: Somatostatin and SSAs binding to SSTs activate G proteins and inhibit AC activity, inhibit Na⁺/H⁺ exchanger, activate inwardly rectifying K⁺ channels and Ca²⁺ channels. These pathways modulate the antitumor activity of native somatostatin and SSAs through inhibition in secretion of several hormones and proangiogenic factors, induction of apoptosis and cell cycle arrest. GFR, growth factor receptor; PLC, phospholipase C; AC, adenylyl cyclase; cAMP, cyclic adenosine monophosphate; VEGF, vascular endothelial growth factor; PTP, phosphotyrosine phosphatase; MAPK, mitogen-activated protein kinase and Akt protein kinase B.