Increased GPR35 expression in human colorectal and pancreatic cancer samples: A preliminary clinical validation of a new biomarker

Background. G protein-coupled receptor 35 (GPR35) is involved in carcinogenesis; however, limited experimental data are available on its actual expression in patients with colorectal cancer (CRC) and pancreatic adenocarcinoma (PDAC). Objectives. We aimed to measure the relative expression of GPR35 in samples from patients with CRC or PDAC. Materials and methods. Using real-time polymerase chain reaction (RT-PCR), we have examined GPR35 expression in surgery samples from 40 CRC and 17 PDAC patients, and performed analysis of the results. Results. The analysis of GPR35 expression in patients with CRC revealed correlations between relative GPR35 mRNA expression and several tumor characteristics, with statistical significance for higher American Joint Committee on Cancer (AJCC) stages, T stages and histological grades. GPR35 expression was significantly higher in tumor samples compared to the paired healthy samples collected from the same patient. Similar, although not statistically significant trends were found in PDAC tumor samples for sex (lower expression in women) and for samples with no nodal involvement (lower expression). Samples with higher tumor T stages and higher histological grades or considered inoperable had higher GPR35 expression. Conclusions. We have identified correlations which confirm our expectation of high GPR35 expression in CRC and PDAC. Our findings suggest the prognostic value of GPR35 testing in patients with an increased risk of CRC or PDAC development, and warrant further clinical confirmation.