KRAS and cancer: Given that APE1 is often overexpressed in multiple types of cancers including PDAC (47), and our current observation that APE1 regulates G4 DNA formation and promotes KRAS expression, we determined the levels of APE1 and G4 DNA in 23 PDAC patients’ tissue samples and 2 normal control pancreas tissues using IHC analysis with APE1 and G4 structure-specific antibodies.