Androgens regulate CALCA gene expression in the prostate by methylation of CALCA Promoter

Abstract

Expression of calcitonin (CT) and its receptor (CTR) is frequently elevated in prostate cancer (PC), and activation of CT–CTR axis in non-invasive PC cells induces an invasive phenotype. However, the regulation of CT gene (CALCA) expression in the prostate has not been investigated. We investigated the regulation of CALCA gene expression in multiple PC cell lines and primary PC specimens. The results show that androgen-activated androgen receptor (AR) represses CALCA gene expression, and this can be abolished either by the knock-out of AR or the treatment with AR antagonists. Chromatin immunoprecipitation assay identified that AR induces methylation of CpG64 region of distal CALCA gene promoter, and this was prevented by knock-out of AR. This region was examined in multiple PC cell lines and primary PC specimens. PC cells that lacked CT mRNA abundance displayed methylated CpG64 region, and this methylation was partially reversed either with the knock-out of AR or incubation with AR antagonist. Primary prostate tissue specimens from normal or benign prostatic hyperplasia displayed methylated CALCA gene promoter. In contrast, those from advanced PCs displayed at least partially demethylated CALCA gene promoter. These results explain our earlier results that CALCA gene expression in the prostate is silent in benign prostate epithelium but is active in malignant prostate epithelium, and high level of CALCA gene expression in advanced PC. These results raise a possibility that elevated CALCA gene expression in malignant prostate may indicate progressive loss of AR expression and/or AR signaling.