XRCC6 and osteosarcoma: This further emphasizes that this new deregulation of DNA repair may be a common molecular alteration in chemoresistant cancer cells, as supported by the higher basal level of phospho-Ku70 in cancer cell lines resistant to DNA damage such as human glioma, osteosarcoma, hepatocellular carcinoma cell lines or cells derived from cancer of pancreas with a deficiency in homologous recombination repair (Supplementary Figure S4C).