Functional upregulation of the H2S/Cav3.2 channel pathway accelerates secretory function in neuroendocrine-differentiated human prostate cancer cells

Neuroendocrine-differentiated prostate cancer cells may contribute to androgen-independent proliferation of surrounding cells through Ca2+-dependent secretion of mitogenic factors. Human prostate cancer LNCaP cells, when neuroendocrine-differentiated, overexpress Ca(v)3.2 T-type Ca2+ channels that contribute to Ca2+-dependent secretion. Given evidence for the acceleration of Ca(v)3.2 activity by hydrogen sulfide (H2S), we examined the roles of the H2S/Ca(v)3.2 pathway and then analyzed the molecular mechanisms of the Ca(v)3.2 overexpression in neuroendocrine-differentiated LNCaP cells. LNCaP cells were differentiated by dibutyryl cyclic AMP. Protein levels and T-type Ca2+ channeldependent currents (T-currents) were measured by immunoblotting and whole-cell pacth-clamp technique, respectively. Spontaneous release of prostatic acid phosphatase (PAP) was monitored to evaluate secretory function. The differentiated LNCaP cells exhibited neurite outgrowth, androgenindependent proliferation and upregulation of mitogenic factors, and also showed elevation of Ca(v)3.2 expression or T-currents. Expression of cystathionine-gamma-Iyase (CSE) and cystathionine-beta-synthase (CBS), H2S-forming enzymes, and spontaneous secretion of PAP increased following the differentiation. The augmented T-currents were enhanced by H2S donors and suppressed by inhibitors of CSE, but not CBS. The PAP secretion was reduced by inhibition of CSE or T-type Ca2+ channels. During differentiation, Egr-1 and REST, positive and negative transcriptional regulators for Ca(v)3.2, were upregulated and downregulated, respectively, and Egr-1 knockdown prevented the Ca(v)3.2 overexpression. Our data suggest that, in neuroendocrine-differentiated LNCaP cells, H2S formed by the upregulated CSE promotes the activity of the upregulated Ca(v)3.2, leading to the elevated secretory functions. The overexpression of Ca(v)3.2 appears to involve upregulation of Egr-1 and downregulation of REST. (C) 2015 Elsevier Inc. All rights reserved.