Abstract B12: Co-targeting PTEN-defined TNBC with p110beta-isoform specific inhibitor and PARP inhibitor BMN 673: A predictive context to sensitize PARP inhibitors in TNBC

Background: TNBC is a highly aggressive form of BRCA-associated BC subtype for which chemotherapy still remains a major form of treatment to which patients initially respond yet a majority of them inevitably relapse. PARP1 has been identified as a target in BRCA-defined cancers and inhibitors of PARP1 has been recently approved by FDA as targeted agents in BRCA-defined cancers. The loss of PTEN is the most common "first event" associated with basal-like subtype (Martins et al., 2012) and this PI3K-pathway activating event (deletion/mutation/loss of PTEN) occurs more frequently (35%) than PIK3CA mutations in this subtype of BC (Ellis & Perou, 2013). In the cytoplasm, PTEN-loss mediated upregulation of PI3K/AKT signal is known to depend on the PI3Kbeta-isoform. In contrast nuclear PTEN controls DNA repair (Bassi et al., 2013). A failure to repair the damaged DNA upon inhibition of PARP causes accumulation of DNA double-strand breaks and leads to apoptosis of cancer cells. Thus we hypothesized that a combination of p110beta-isoform specific inhibitor and PARP inhibitor will sensitize PARP inhibitors in PTEN-null TNBC model. Methods: Five PARP inhibitors, Talazoparib (BMN673, B), Niraparib (N), Olaparib (O), Rucaparib (R) and Veliparib (V) were tested in four PTEN-null TNBC cell lines, MDA-MB468, HCC70 (p.F90fs*9), BT549 (p.V275fs*1) and SUM149 cell lines in combination with p110beta specific inhibitor, AZD6482. Proliferative, apoptotic and PARylation signals following drug c...
Source: Molecular Cancer Research - Category: Cancer & Oncology Authors: Tags: Targeted Therapies: Poster Presentations - Proffered Abstracts Source Type: research