Liu et al. (2013) found that REG4 down-regulation also resulted in the hypoexpression of p21 and p27, which negatively regulated cyclin D1 and blocked the G1/S transition of prostate cancer cells. Wang et al. (2016) showed that transforming growth factor (TGF)-α stimulated specificity protein 1 (SP1) to transcriptionally promote REG4 expression, while G protein-coupled receptor 37 (GPR37) complexed with REG4, which mediated EGFR signal transduction by REG4 and promoted peritoneal metastasis of gastric cancer cells. Here, GPR37 is linked to prostate cancer.