LIG1 and cancer: Ruptures of dsDNA cause a high percentage of malignant tumors, chromosome instability, and abnormal rearrangements of V (D) J genes; a recombination of class switches and/or somatic hypermutations (the ATM gene in A-T, the NBN gene in NBS, the DCLRE1C gene in severe combined deficiency immunodeficiency with sensitivity to ionizing radiation and Omenn syndrome, the LIG4 gene in the LIG4 syndrome, and the LIG1 gene in DNA ligase 1 deficiency) cause complex immunodeficiencies and malignant neoplasms, most often lymphomas [114,115].