Down-regulation of GPR137 expression inhibits proliferation of colon cancer cells.

G protein-coupled receptors (GPRs) are highly related to oncogenesis and cancer metastasis. G protein-coupled receptor 137 (GPR137) was initially reported as a novel orphan GPR about 10 years ago. Some orphan GPRs have been implicated in human cancers. The aim of this study is to investigate the role of GPR137 in human colon cancer. Expression levels of GRP137 were analyzed in different colon cancer cell lines by quantitative polymerase chain reaction and western blot analysis. Lentivirus-mediated short hairpin RNA was specifically designed to knock down GPR137 expression in colon cancer cells. Cell viability was measured by methylthiazoletetrazolium and colony formation assays. In addition, cell cycle characteristic was investigated by flow cytometry. GRP137 expression was observed in all seven colon cancer cell lines at different levels. The mRNA and protein levels of GPR137 were down-regulated in both HCT116 and RKO cells after lentivirus infection. Lentivirus-mediated silencing of GPR137 reduced the proliferation rate and colonies numbers. Knockdown of GPR137 in both cell lines led to cell cycle arrest in the G0/G1 phase. These results indicated that GPR137 plays an important role in colon cancer cell proliferation. A better understanding of GPR137's effects on signal transduction pathways in colon cancer cells may provide insights into the novel gene therapy of colon cancer.