Abstract 3561: Functional expression of BK channel subunits in LNCaP prostate cancer cells under androgen-deprivation conditions
Authors: Evans Bailey , Breen Conor , McKerr Niamh , Kennedy Richard , McCloskey Karen D. 
Published: August 2018

Introduction: Prostate cancer (PCa) is the most commonly diagnosed cancer in men. Treatment for PCa includes androgen deprivation therapy (ADT) which while initially effective in reducing tumour growth and volume, resistance develops and relapse typically occurs within 24 months. Ion channel proteins are differentially expressed in normal prostate epithelium and PCa cells. We have previously reported differences in expression of the BK channel subunits BKα and BKγ, in a panel of PCa cell lines representing early androgen-sensitive disease compared with late castration-resistance. Here, we hypothesised that BK subunit expression was sensitive to ADT conditions and aimed to elucidate the functional expression of BK subunits in androgen-sensitive LNCaP cells under ADT. Methods: qPCR, Western blot, immunofluorescence and patch-clamp assays were performed. The BK channel blocker paxilline (300nM), enzalutamide (10 µM) and dihydrotestosterone (DHT, 100nM) were used (vehicle DMSO/ethanol &lt;0.1%). ADT conditions were mimicked by substituting normal media with charcoal stripped, phenol-red free media for up to 10 days. Data are expressed as mean±SEM; ANOVA/paired Student's t-tests were performed; P≤0.05 considered as significant. Results: LNCaP cells were observed to have an epithelial morphology that became distinctly neuronal during ADT (N=3). Western blots showed decreased androgen receptor (AR) and increased neuron-specific enolase (NSE) protein expression, consistent with a neuroendocrine phenotype. BKα (KCNMA1) gene expression was decreased in LNCaP during ADT (n=3, P≤0.05) although protein expression was similar. BKγ (LRRC26) gene expression was reduced during ADT (N=4, P≤0.05). LNCaP had paxilline-sensitive BK currents, where current density was significantly reduced during ADT (N=9, N=7 respectively; P≤0.05). DHT treatment over 48hrs (following a 24hr serum starvation) increased KCNMA1 expression (N=2); this effect was attenuated with co-treatment of enzalutamide (10 µM) indicating that KCNMA1 in LNCaP may be partly modulated by DHT and the AR pathway. Interestingly, reintroduction of 10% FBS-containing media for 48hrs after the 24hr serum starvation period increased KCNMA1 expression. Conclusion

The findings suggest that BKα and BKγ gene expression in LNCaP cells is sensitive to ADT. The canonical role of BK channels to facilitate potassium ion transport was diminished during ADT, evidenced by reduced BK currents in ADT-treated cells. Modulation of BK subunit gene expression by DHT indicates regulation by the AR.

Citation Format: Bailey Evans, Conor Breen, Niamh McKerr, Richard Kennedy, Karen D. McCloskey. Functional expression of BK channel subunits in LNCaP prostate cancer cells under androgen-deprivation conditions [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3561.