found that radiotherapy accentuated the immune suppression of head and neck cancer patients via changing regulatory T cells and CTLA4 and PD‐1 expression on CD4 cells in the peripheral blood, and expression of the FXDR, SESN1, GADD45, DDB2, and MDM2 were altered in the peripheral blood cells of patients after radiotherapy.50 Here, DDB2 is linked to head and neck cancer.