Involvement of the glutamine RF-amide peptide (QRFP) and its cognate receptor GPR103 in prostate cancer

Abstract

Glutamine RF-amide peptide (QRFP) belongs to the RFamide neuropeptide family, which is involved in a wide spectrum of biological activities, ranging from food intake and cardiovascular functioning to analgesia, aldosterone secretion, locomotor activity and reproduction. Recently, QRFP has been shown to exert its effects by activating the G protein coupled receptor GPR103. QRFP is expressed in the brain and peripherally in the adipose tissue, bladder, colon, testis, parathyroid and thyroid gland, as well as in the prostate gland. Following lung cancer, prostate cancer constitutes the second most frequently diagnosed cancer among men, whilst obesity appears to be a contributing factor for aggressive prostate cancer. In the present study we sought to investigate the role of QRFP in prostate cancer, using two androgen-independent human prostate cancer cells lines (PC3 and DU145) as in vitro experimental models and clinical human prostate cancer samples. Expression of both QRFP and GPR103 at gene and protein level was higher in human prostate cancer tissue samples compared to control and benign prostatic hyperplasia (BHP) samples. Furthermore, in both prostate cancer cell lines used in our study, QRFP treatment induced the phosphorylation of ERK1/2, p38, JNK and Akt. In addition, QRFP also increased cell migration and invasion in these in vitro models, with increased MMP2 expression. Moreover, we demonstrated that the pleiotropic adipokine leptin can increase the expression of QRFP and GPR103 in PC3 prostate cancer cells via a PI3K- and MAPK-dependent mechanism, suggesting a potential new link between adiposity and prostate cancer. Our present findings expand the existing evidence and provide novel insight into the implication of QRFP in prostate cancer.