Immunohistochemistry was performed for tumor and skin tissues according to the standard procedure using the following primary antibodies: XRCC6 (ab92450; Abcam), LIG4 (ab193353; Abcam), PARP1 (ab191217; Abcam), DNA-PK (#38168; Cell Signaling) and XRCC5 (WH0007520M2; Sigma-Aldrich). Here, PRKDC is linked to neoplasm.