NHEJ1 and colonic neoplasm: Although, PAXX and XLF perform overlapping functions and XLF can efficiently compensate for PAXX deficiency in colon cancer cells (Tadi et al., 2016), however, another study demonstrated that one protein between PAXX and XLF is essential for NHEJ repair, and PAXX also promotes Ku accumulation at DSBs (Liu et al., 2017).