CACNA1D overexpression and voltage-gated calcium channels in prostate cancer during androgen deprivation

Abstract

Prostate cancer is often treated by perturbing androgen receptor signalling. CACNA1D, encoding Ca _V1.3 ion channels is upregulated in prostate cancer. Here we show how hormone therapy affects CACNA1D expression and Ca _V1.3 function. Human prostate cells (LNCaP, VCaP, C4-2B, normal RWPE-1) and a tissue microarray were used. Cells were treated with anti-androgen drug, Enzalutamide (ENZ) or androgen-removal from media, mimicking androgen-deprivation therapy (ADT). Proliferation assays, qPCR, Western blot, immunofluorescence, Ca ²⁺-imaging and patch-clamp electrophysiology were performed. Nifedipine, Bay K 8644 (Ca _V1.3 inhibitor, activator), mibefradil, Ni ²⁺ (Ca _V3.2 inhibitors) and high K ⁺ depolarising solution were employed. CACNA1D and Ca _V1.3 protein are overexpressed in prostate tumours and CACNA1D was overexpressed in androgen-sensitive prostate cancer cells. In LNCaP, ADT or ENZ increased CACNA1D time-dependently whereas total protein showed little change. Untreated LNCaP were unresponsive to depolarising high K ⁺/Bay K (to activate Ca _V1.3); moreover, currents were rarely detected. ADT or ENZ-treated LNCaP exhibited nifedipine-sensitive Ca ²⁺-transients; ADT-treated LNCaP exhibited mibefradil-sensitive or, occasionally, nifedipine-sensitive inward currents. CACNA1D knockdown reduced the subpopulation of treated-LNCaP with Ca _V1.3 activity. VCaP displayed nifedipine-sensitive high K ⁺/Bay K transients (responding subpopulation was increased by ENZ), and Ni ²⁺-sensitive currents. Hormone therapy enables depolarization/Bay K-evoked Ca ²⁺-transients and detection of Ca _V1.3 and Ca _V3.2 currents. Physiological and genomic CACNA1D/Ca _V1.3 mechanisms are likely active during hormone therapy—their modulation may offer therapeutic advantage.