To elucidate the physiological significance of the novel ARM domain-binding site in DNA-PKcs, CRISPR/Cas12a was used to create a mutant strain of HC116 cells (derived from human colon cancer) where the Phe3640 residue in DNA-PKcs was replaced with an Ala residue (Fig. 4D). The gene discussed is PRKDC; the disease is malignant colon neoplasm.