Here we demonstrate in breast cancer cell lines that elevated expression of NEIL2, a bifunctional glycosylase normally involved in oxidative base excision repair (Chakraborty et al., 2015; Das et al., 2006; Hazra et al., 2002; Wiederhold et al., 2004), facilitates A3B-mediated mutations during U/G mismatch repair and induces double-strand breaks (DSBs) in genomic DNA. Here, NEIL2 is linked to breast carcinoma.