FGFR2 Promotes Expression Of PD-L1 In Colorectal Cancer Via The JAK-STAT3 Signaling Pathway

Objective To verify the expression of FGFR2 in colorectal cancer and its effect on invasion and metastasis.To explore the effect of Fibroblast growth factor receptor 2(FGFR2)signaling pathway on the expression of PD-L1,and the related molecular mechanisms in colorectal cancer.Methods The expressions of FGFR2 and PD-L1 in tumor tissues and corresponding adjacent normal tissues of 90 colorectal cancer patients were detected by immunohistochemistry,and the immunohistochemical staining of FGFR2 and PD-L1 was scored by H-Score.Combined with follow-up information,the correlation between the two proteins and clinicopathological features was analyzed.The correlation between the expression level of FGFR2 and PD-L1 in tumor tissues was analyzed.The gene expression information and clinical information of 434 CRC patients from The Cancer Genome Atlas(TCGA)were obtained,and the correlation between the gene expression level of FGFR2 and PD-L1 was analyzed.Four kinds of colorectal cancer cell lines were cultured,and the expression level of FGFR2 and PD-L1 in each cell line was detected by Western Blot.The FGFR2 high expression cell line(NCI-H716),and the FGFR2 low expression cell line(SW480)were selected for our study.The former kind of Cell line was transduced with lentiviruses to knock down FGFR2,and the latter one was transduced with lentiviruses to overexpress FGFR2.Cell scratch assay was used to analyze the migration of tumor cells,and Transwell assay was used to analyze the invasion of tumor cells.After lentiviruses transduction,PD-L1 expression level was detected by RT-PCR and Western Blot.The colorectal cancer cell line was cultured in medium with FGF7(10 ng/ml)to activate FGFR2 signaling pathway.The expression of FGFR2,P-FGFR,PD-L1,STAT3,P-STAT3,JAK2 and P-JAK2 were detected by Western Blot.The cells were cultured in a medium containing FGF7(10 ng/ml)for 24 hours,followed by culturing in the medium containing different concentrations of pathway inhibitors for 24 hours,and then the expression level of PD-L1 was detected.SW480-Vector,SW480-FGFR2 and SW480-FGFR2 cells pretreated with AG490 for 24 h were co-cultured with Jurkat cells for 24 hours,and apoptosis of Jurkat cells was determined by flow cytometry.The tumor model of colorectal cancer was established by subcutaneous injection of human CRC cells in nude mice,which were divided into SW480-Vector group,SW480-FGFR2 group,and SW480-FGFR2 treated with pathway inhibitor(AG490)treatment group.Tumor volumes were measure every two days.The mice were sacrificed on the 21 st day,and the expression of FGFR2 and PD-L1 of tissues of each group was detected by immunohistochemistry.Results The expression level of FGFR2 in cancer tissues was significantly higher than that in adjacent normal tissues(P < 0.001).A high expression level of FGFR2 was associated with lymph node metastasis(P = 0.032)and clinical stage(P = 0.033).Patients with high FGFR2 expression showed a high risk of lymph node metastasis and late clinical stage.Kaplan-Meier survival analysis showed that the overall survival(OS)of patients with high FGFR2 expression was poorer than those with low FGFR2 expression(P = 0.011).PD-L1 is overexpressed in human colorectal cancer and positively correlated with FGFR2 expression(r = 0.261,p = 0.013).The TCGA cohort showed that PD-L1 gene expression was positively correlated with FGFR2 gene expression(r = 0.111,P = 0.021).High expression of FGFR2 in tumor cells promotes tumor cell migration and invasion,and leading to tumor progression.FGFR2 promotes PD-L1 expression via the JAK-STAT3 pathway in vivo and vitro.FGFR2-induced upregulation of PD-L1 in human colorectal cancer cells promoted the apoptosis of T cells.Conclusion The expression of FGFR2 and PD-L1 protein was increased in colorectal cancer tissues,and both of them were positively correlated in protein and gene expression levels.High expression of FGFR2 promote tumor progression.In colorectal tumors,FGFR2 up-regulates PD-L1 expression through the JAK-STAT3 signaling pathway,which induces T cell apoptosis and leads to tumor immunosuppression.