In addition, activation of the EGFR signaling pathway can induce resistance to chemo-radiation in cancers by promoting DNA repair via multiple mechanisms, such as activating DNA dependent protein kinase, promoting the transcription of DNA repair genes (RAD51, ATM, and XRCC1) and phosphorylating proliferating cell nuclear antigen (PCNA) [22]. The gene discussed is PCNA; the disease is cancer.