OBJECTIVETo investigate the expression and clinical significance of G protein-coupled receptor 31 (GPR31) in colorectal cancer tissue.

METHODSCancer tissues and adjacent normal tissues of 321 cases with colorectal cancer confirmed by pathology and undergoing resection in the First Affiliated Hospital of Sun Yat-sen University from January 1996 to December 2008 were collected. The expression of GPR31 was examined by immunohistochemical staining. According to the expression level of GPR31 (A value=0.051), all the patients were divided into low GPR31 expression group and high GPR31 expression group. Clinicopathology and prognosis between the two groups were compared. Risk factors affecting prognosis were investigated.

RESULTSGPR31 expression was significantly higher in colorectal cancer tissues compared to adjacent normal tissues (mean A, 0.063±0.014 vs. 0.045±0.020, P<0.001). A total of 197 cancer tissue samples were defined as low expression and 124 as high expression. Significant difference was observed in the number of patient in pM classification between the two groups (P=0.007). High expression group had obviously higher distant metastasis rate than low expression group [12.1% (15/124) vs. 4.1% (8/197), P=0.007]. The 5-year survival rate and tumor-free survival rate were 84.3% and 82.2% in the low expression group, and both 59.7% in high expression group (all P<0.05). Multivariate analysis revealed elderly, abnormal CEA, lymphatic metastasis, distant metastasis and up-regulated GPR31 expression were independent risk factors of overall survival and disease-free survival in colorectal cancer patients (all P<0.05).

CONCLUSIONSGPR31 expression is significantly up-regulated in colorectal cancer tissues. High GPR31expression indicates poor prognosis of colorectal cancer, and may be used as a predictive marker.