H2AX and head and neck squamous cell carcinoma: In addition, the evaluation of links between HR repair protein gene expression and the clinicopathological parameters indicated that LIG1, RPA2, ATM, BRCA2, NBN, and RAD50 showed significant differences across the T stages, while H2AX, MRE11, RPA1, MDC1, NBN, BRIP1, and RPA2 were differentially expressed across the N stages of HNSCC (Figures S1 and S2).