DDR1 functions as an immune negative factor in colorectal cancer by regulating tumor-infiltrating T cells through IL-18.

Immunotherapies represented by programmed cell death protein 1/programmed cell death ligand 1 (PD-1/PD-L1) immune checkpoint inhibitors have made great progress in the field of anticancer treatment, but most colorectal cancer patients do not benefit from immunotherapy. Discoidin domain receptor 1 (DDR1), a tyrosine kinase receptor, is activated by collagen binding and overexpressed in various malignancies. However, the role of DDR1 in colorectal cancer and immunoregulation remains unclear. In this study, we found DDR1 is highly expressed in colorectal cancer tissues and negatively associated with patient survival. We demonstrated that DDR1 promotes colorectal tumor growth only in vivo. Mechanistically, DDR1 is a negative immunomodulator in colorectal cancer and is involved in low infiltration of CD4 and CD8 T cells by inhibiting IL-18 synthesis. We also reported that DDR1 enhances the expression of PD-L1 through activating the c-Jun amino terminal kinase (JNK) signaling pathway. In conclusion, our findings elucidate the immunosuppressive role of DDR1 in colorectal cancer, which may represent a novel target to enhance the efficacy of immunotherapy in colorectal cancer.