SOX2 and lip and oral cavity carcinoma: We observed that RAD51 protein was related to resistance to chemotherapy and radiotherapy We also observed that tumorsphere formation, a hallmark of cancer cell stemness, was increased in oral cancer cells overexpressing RAD51, while the expression of stemness markers, including CD44, CD133, Nanog, Oct4, and SOX2, was not changed by RAD51 expression.