This study initially used siRNA and CRISPR knockdown of BCL3 in human colorectal cancer cell lines to demonstrate sensitization to gamma irradiation via increased double stranded breaks, as indicated by increased phospho-Chk2 and gamma-H2Ax staining foci and a reduction in homologous recombination resulting in reduced RAD51 foci and increased sensitivity to PARP inhibition. This evidence concerns the gene BCL3 and colorectal cancer.