PPIA and neoplasm: To assess the expression of the oxidative stress markers Keap1, Nrf2, and antioxidants PPIA, Prdx6, as well as CD147 in human OSCCs, we stained the tumor sections from human tissue arrays for OSCC (n = 43) with antibodies for Keap1, Nrf2, PPIA, Prdx6 and CD147 compared them with oral epithelial dysplasia (n = 67) and normal oral mucosa samples (n = 17).