As there is interplay between the DNA repair pathways and the fact that mounting evidence, including this study, suggests the DNA-PK complex plays a role in protecting against tumorigenesis and cancer progression, we recommend adding the canonical NHEJ factors, in particular XRCC6 (Ku70), XRCC5 (Ku80) and PRKDC (DNA-PKcs), to the sequencing studies examining mutations of DDR proteins in carcinogenesis (22,49). Here, XRCC5 is linked to cancer.