EGF Prevents the Neuroendocrine Differentiation of LNCaP Cells Induced By Serum Deprivation: The Modulator Role of P13K/Akt 1

The primary focus of this investigation was to study the relationship between neuroendocrine (NE) differentiation, epidermal growth factor (EGF) because both have been implicated in the progression of prostate cancer. For this purpose, we used gefitinib, trastuzumab, which are inhibitors of EGF receptor (EGFR), ErbB2, respectively. EGF prevents NE differentiation induced by androgen depletion. This effect is prevented by gefitinib, which blocks the activation of EGFR, ErbB2, stimulation of mitogen-activated protein kinase (MAPK), cell proliferation induced by EGF. Conversely, trastuzumab does not inhibit the effect of EGF on EGFR phosphorylation, MAPK activity, cell proliferation, NE differentiation, although it reduces ErbB2 levels specifically, suggesting that ErbB2 is not necessary to inhibit NE differentiation. Prevention of NE differentiation by EGF is mediated by a MAPK-dependent mechanism, requires constitutive Akt activation. The abrogation of the PI3K/Akt pathway changes the role of EGF from inhibitor to inductor of NE differentiation. We show that EGFR tyrosine kinase, MAPK, PI3K inhibitors inhibit the cell proliferation stimulated by EGF but induce the acquisition of NE phenotype. Altogether, the present data should be borne in mind when designing new clinical schedules for the treatment of prostate cancer, including the use of ErbB receptors, associated signaling pathway inhibitors.