RPA 3 is a potential marker of prognosis and radioresistance for nasopharyngeal carcinoma

Radioresistance‐induced residual and recurrent tumours are the main cause of treatment failure in nasopharyngeal carcinoma ( NPC ). Thus, the mechanisms of NPC radioresistance and predictive markers of NPC prognosis and radioresistance need to be investigated and identified. In this study, we identified RPA 3 as a candidate radioresistance marker using RNA ‐seq of NPC samples. In vitro studies further confirmed that RPA 3 affected the radiosensitivity of NPC cells. Specifically, the overexpression of RPA 3 enhanced radioresistance and the capacity for DNA repair of NPC cells, whereas inhibiting RPA 3 expression sensitized NPC cells to irradiation and decreased the DNA repair capacity. Furthermore, the overexpression of RPA 3 enhanced RAD 51 foci formation in NPC cells after irradiation. Immunohistochemical assays in 104 NPC specimens and 21 normal epithelium specimens indicated that RPA 3 was significantly up‐regulated in NPC tissues, and a log‐rank test suggested that in patients with NPC , high RPA 3 expression was associated with shorter overall survival (OS) and a higher recurrence rate compared with low expression (5‐year OS rates: 67.2% versus 86.2%; 5‐year recurrence rates: 14.8% versus 2.3%). Moreover, TCGA data also indicated that high RPA 3 expression correlated with poor OS and a high recurrence rate in patients with head and neck squamous cell carcinoma ( HNSC ) after radiotherapy. Taken together, the results of our study demonstrated that RPA 3 regulated the radiosensitivity and DNA repair capacity of NPC cells. Thus, RPA 3 may serve as a new predictive biomarker for NPC prognosis and radioresistance to help guide the diagnosis and individualized treatment of patients with NPC .