PARP12 and breast cancer: By combining i) our findings showing apoptosis induction in ER + breast cancer cells upon PARP12 knock-down and ii) increased PARP12 gene expression levels observed in patients unable to respond to chemotherapy or to endocrine therapies, we inferred a role of PARP12 in driving resistance, thus proposing this enzyme as a novel potential drug-target to sensitize resistant tumors to current endocrine or combinatorial therapies.