Proteomic analysis of tissues from rectal cancer patients treated with neoadjuvant chemoradiotherapy revealed the upregulation of RAB5C and X-ray repair cross-complementing proteins 5 and 6 (XRCC5 and XRCC6, also known as Ku70 and Ku80), confirmed also in an in vitro model using irradiated cells. This evidence concerns the gene XRCC5 and rectal cancer.