TRPV6 calcium channel is a recognized oncochannel over-expressed in a number of epithelial cancers (e.g. breast, ovarian, prostate). TRPV6, a member of one of seven subfamilies of TRP channels, plays an important role in Ca2+ absorption from the intestinal lumen. TRPV6 over-expression is associated with a poor prognosis particularly with breast and prostate cancers. Although some TRPV6 mechanistic work is available and indicates that NFAT is involved, there is a need to better understand pathways involved in its mechanism of action (MOA). These data could allow the identification of clinically relevant biomarkers and identify potential for synergy of TRPV6-targeting therapies with other anti-cancer treatments. To determine which key pathways TRPV6 influences in prostate cancer, two TRPV6 knockouts (KO) were produced in a castration-resistant prostate cancer cell line (PC-3) using the CRISPR-Cas9 approach with two different gRNAs. In addition, knockdowns (KD) were produced by transfecting PC-3 cells with two TRPV6 siRNA targeting different regions of TRPV6 mRNA. The mRNA expression of 184 genes was analyzed using an RT-qPCR TaqMan array. The panel consisted of genes involved in cancer calcium signalling, genes that have been associated with the MOA of TRPV6 and genes directly or indirectly involved in NFAT signalling. Gene profiling results were generally consistent between the TRPV6 KD and KO cells. Results showed a dramatic reduction in expression of TRPV6 mRNA in the KO/KD cells (14 to 166-fold). TRPV6 KO/KD affected multiple genes involved in cancer cell proliferation (e.g. ESR1, CDH1), metastasis (e.g. SNAI1, MUC1/16), resistance to apoptosis (e.g. Bcl-2-type proteins, Fos) and angiogenesis (e.g. VEGFA/B, FLT4), as well as genes involved in the M2 immune tumor microenvironment (e.g. IL6 and VEGFA). The TRPV6 KO/KD data confirm the basic MOA of TRPV6, activating NFAT by increasing cytosolic calcium and provide information on the downstream pathways involved (e.g. NF-kB, estrogen and MAPK). The data allow for the identification of clinical efficacy biomarkers for TRPV6 inhibitors (e.g. a panel of CXCL12, FLT4, MUC16 and IL-6). Furthermore, results indicate TRPV6 inhibitors have the potential to modify the immune composition of the tumor microenvironment from a tumor promoting to a tumor control response, and thus may help trigger an anti-cancer immune defence. This study demonstrates a central role of TRPV6 and calcium signalling in cancer development.

Citation Format: Tyler Lutes, Michelle Davey, Christopher Rice, Tyson MacCormack, John M. Stewart, Dominique Dugourd. Molecular profiling of hormone-resistant prostate cancer cells with TRPV6 oncochannel knockout/knockdown [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 2891.