CaV1.3 enhanced store operated calcium promotes resistance to androgen deprivation in prostate cancer

Abstract

Androgen deprivation therapy (ADT) is the main treatment for advanced prostate cancer (PCa) but resistance results in progression to terminal castrate resistant PCa (CRPC), where there is an unmet therapeutic need. Aberrant intracellular calcium (Ca_i²⁺) is known to promote neoplastic transformation and treatment resistance. There is growing evidence that voltage gated calcium channel (VGCC) expression is increased in cancer, particularly CACNA1D/CaV1.3 in CRPC. The aim of this study was to investigate if increased CaV1.3 drives resistance to ADT and determine its associated impact on Ca_i²⁺ and cancer biology. Bioinformatic analysis revealed that CACNA1D gene expression is increased in ADT treated PCa patients. This was corroborated in both in vivo LNCaP xenograft mouse and in vitro PCa cell line models, which demonstrated a significant increase in CaV1.3 protein expression following ADT with bicalutamide. Expression was found to be of a shortened 170kDa CaV1.3 isoform associated with plasma and intracellular membranes, which failed to induce calcium influx following membrane depolarisation. Instead, under ADT CaV1.3 mediated a rise in basal cytosolic calcium and an increase in store operated calcium entry (SOCE). This mechanism was found to promote the proliferation and survival of ADT resistant CRPC cells. Overall, this study demonstrates for the first time in PCa that under ADT specific CaV1.3 isoforms promote an upregulation of SOCE which contributes to treatment resistance and CRPC biology. Thus, this novel oncochannel represents a target for therapeutic development to improve PCa patient outcomes.

Keywords: Abbreviations; Aberrant Intracellular Calcium; Androgen Deprivation Therapy; Androgen Deprivation Therapy (ADT); Androgen Receptor (AR); CACNA1D; CaV1.3; Calcium (Ca2+); Calcium Channel Blocker (CCB); Castrate Resistant Prostate Cancer (CRPC); Cellular Invasion and Migration (CIM); Colony Formation Assay (CFA); Cytosolic Calcium (Cac2+); Glyceraldehyde 3-phosphate dehydrogenase (GAPDH); Immunofluorescence (IF); Intracellular Calcium (Cai2+); Log2 fold-change (LogFC); Multiple Comparison Test (MCT); Principal Components Analysis (PCA); Prostate Cancer; Prostate Cancer (PCa); Quality Control (QC); Short Tandem Array (STR); SiRNA Control (sictr); Store Operated Calcium Entry (SOCE); Store Operated Current (SOC); Store operated calcium entry; Thapsigargin (Tg); Tumour Microarrays (TMA); Voltage Gated Calcium Channels (VGCC); siRNA CaV1.3 (SiCaV1.3).