PARP1 and breast cancer: Indeed there are emerging preclinical data demonstrating enhanced antitumor activity with the combination of PARP and PI3K pathway inhibitors and PI3K inhibitors were found to have in vivo synergy with PARP inhibitors for the treatment of an endogenous mouse model for BRCA1-related breast cancers and patient derived xenograft models of TNBC without BRCA mutations39,40.