APEX1 and cancer: Interestingly, elevated levels of APE1 protein in sera of different tumors, such as HCC and NSCLC, have been described (28, 29) and extracellular APE1 contribution in promoting chemoresistance, by affecting cell sensitivity to chemotherapy, was suggested (28, 58), allowing to hypothesize that sAPE1 could be considered as a prognostic and predictive biomarker in cancer.