Pathological significance of abnormal recepteur d'origine nantais and programmed death ligand 1 expression in colorectal cancer

BACKGROUND Programmed death ligand 1(PD-L1) immunotherapy remains poorly efficacious in colorectal cancer(CRC). The recepteur d'origine nantais(RON) receptor tyrosine kinase plays an important role in regulating tumor immunity.AIM To identify the patterns of RON and PD-L1 expression and explore their clinical significance in CRC.METHODS Gene expression data from the Gene Expression Omnibus database(GEO;n = 290) and patients at the First Affiliated Hospital, Zhejiang University School of Medicine(FAHZUSM;n = 381) were analyzed to determine the prognostic value of RON and PD-L1 expression within the tumor microenvironment of CRC. HT29 cell line was treated with BMS-777607 to explore the relationship between RON activity and PD-L1 expression. Signaling pathways and protein expression perturbed by RON inhibition were evaluated by cellular immunofluorescence and Western blot.RESULTS In the GEO patient cohort, cut-off values for RON and PD-L1 expression were determined to be 7.70 and 4.3, respectively. Stratification of patients based on these cutoffs demonstrated that high expression of RON and PD-L1 was associated with a poor prognosis. In the FAHZUSM cohort, rates of high expression of RON in tumor cells, high PD-L1 expression in tumor cells and tumor infiltrating monocytes, and both high RON and high PD-L1 expression in the tumor microenvironment were 121(32%), 43(11%), 91(24%), and 51(13.4%), respectively. High expression of RON was significantly correlated with high expression of PD-L1 in the tumor cell compartment(P < 0.001). High expression of RON and that of PD-L1 were independent prognostic factors for poorer overall survival. Concurrent high expression of both RON and PD-L1 in the tumor microenvironment was significantly associated with a poor prognosis. In vitro, BMS-777607 inhibited the phosphorylation of RON, inhibited PD-L1 expression, and attenuated activation of the ERK1/2 and AKT signaling pathways in CRC cells.CONCLUSION RON, PD-L1, and their crosstalk are significant in predicting the prognostic value of CRC. Moreover, phosphorylation of RON upregulates PD-L1 expression, which provides a novel approach to immunotherapy in CRC.