GPRC6A and prostate cancer: Fourth, genetic ablation of GPRC6A attenuates prostate cancer progression in the TRansgenic Adenocarcinoma of the Mouse Prostate (TRAMP) model [12], Fifth, high serum levels of osteocalcin is a biomarker of prostate cancer [24], and the autocrine/paracrine release of osteocalcin may stimulate prostate cancer growth and progression through activation of GPRC6A [25].