**2.1 Base excision repair (BER) pathway**

Base excision repair (BER) is a repair mechanism responsible for repairing single-strand DNA breaks (SSBs) or different types of damages including oxidization, deamination, and alkylation on a single base that do not induce significant distortion to the DNA helix [15]. Among several proteins that are involved in this pathway, APE1/Ref-1 and Poly (ADP-ribose) polymerase (PARP) are considered as the most important players in cancer progression and drug resistance [16–19].
