Abstract 2330: CaV1.3 calcium channel expression in prostate cancer cells during androgen-deprivation conditions

Background Prostate cancer (PCa) remains one of the most frequently diagnosed cancers in males in the western world. Despite efforts to reduce tumour burden through treatments including androgen-deprivation therapy (ADT), patients often relapse 2 years post-therapy due to emergence of castration-resistant disease. The importance of ion channels including calcium channels in cancer biology is increasingly recognized. CACNA1D encodes the calcium channel, CaV1.3, which is overexpressed in PCa biopsies. In addition to canonical ion transport, the c-terminal region of CaV1.3 may modulate gene expression. The purpose of this study was to elucidate the expression of CaV1.3 during PCa progression and explore the effects of calcium channel blockers. Methods A cell line panel comprising normal prostate epithelium (RWPE-1), androgen-sensitive PCa (LNCaP, VCaP) and castration-resistant PCa (C4-2B, DU145 and PC3) were used. LNCaP were cultured in charcoal-stripped serum-containing media to mimic ADT or with the anti-androgen enzalutamide (10μM) for 4-14 days. qPCR, Western blotting and immunofluorescence imaging were performed. Cell viability assays were performed in the absence/presence of ADT, enzalutamide and the CaV1.3 blocker nifedipine (1μM). Apoptosis was measured with flow cytometry in cells stained with Annexin V/Propidium Iodide (AV/PI). Results CACNA1D mRNA had higher expression in LNCaP, VCaP and C4-2B vs. RWPE-1 (p≤0.05; N=3). Western blotting/densitometry showed higher protein expression of CaV1.3 in LNCaP, VCaP and C4-2B relative to RWPE-1 (P≤0.05; N=3). Immunofluorescence indicated cytoplasmic and perinuclear localisation of CaV1.3 in the majority of cell lines and diffuse cytoplasmic staining in VCaP (N=2). ADT and enzalutamide-treated LNCaP displayed time-dependent increased CACNA1D expression over 14 days however, CaV1.3 protein expression peaked at 4 days (N=3). Cell viability assays of LNCaP treated with ADT or enzalutamide (4 days) showed significant reduction in viability when nifedipine was combined with the treatment (N=3; P≤0.05). Similarly, increased % of apoptotic LNCaP cells were observed when nifedipine was added to treated LNCaP vs. ADT or enzalutamide alone (N=2). Conclusion CaV1.3 expression is differentially expressed in cells lines modelling PCa progression and enhanced during ADT. Blockade of CaV1.3 in combination with ADT treatments further reduced cell viability and increased the apoptotic population. Citation Format: Niamh McKerr,