Numerous studies have shown that HDACi treatment across various cancer cell lines also results in the transcriptional downregulation of genes involved in homologous recombination and nonhomologous end-joining (Ku70, Ku86, DNA-PKcs, RAD51, BRCA1, and BRCA2), which are critical for DSB repair (26, 53, 63). This evidence concerns the gene XRCC5 and cancer.