Abstract 2230: Preclinical activity of INK128, a TORC1/2 inhibitor, in triple negative breast cancer: A combination of PARP inhibitor with PI3K-mTOR pathway-targeted inhibitor

Abstract

Abstract Introduction: Recent understanding of the biology of Triple Negative (TN) tumor cells has resulted in the recognition of following molecular targets for the development of novel therapeutics, (1) cell surface receptor tyrosine kinases (RTKs, e.g. EGFR, IGFR, c-MET, FGFR), (2) intracellular signaling pathway(s) (PI3K-AKT-mTOR, RAS-MAPK-ERK), and (3) DNA-damage (chemo- or radiotherapy) repair pathway. INK128 is an orally bioavailable, potent and selective ATP site kinase inhibitor of mTOR complexes TORC1 and TORC2 that together play a crucial role in regulating tumor cell growth, metabolism and motility. INK128 is structurally and mechanistically distinct from allosteric rapamycin-based mTOR inhibitors such as RAD001. Methods: We tested effects of INK128 (alone or in combination with carboplatin and ABT888) on, (a) cell survival/proliferation, (b) cell signaling marker(s) of proliferation, (c) fibronectin-mediated migration, (d) fibronectin-directed matrigel-invasion, and (e) clonogenic survival (3D-ON-TOP assay) in different TNBT cell lines with high expression of EGFR (MDA-MB468, SUM149), BRCA mutations (HCC1937, SUM149) no expression of PTEN protein (HCC70, HCC1937, MDA-MB468, SUM149), PIK3CA mutation (BT20) and RAS/RAF mutation (MDA-MB231). Results: Data showed that, (1) although the range of EC50s for INK128 varied from 50 nM-500 nM in different TNBT cells, the PTEN-null cells exhibited favorable EC50s compared to the rest of the cell lines (with exception to HCC1937), (2) inhibition of phosphorylation of AKT (S473), S6RP, and 4EBP1 was observed following INK128 treatment (100 nM and 200 nM) as early as 6 hours, (3) treatment with 200 nM INK128 for 24 hours differentially blocked pERK in PTEN-null MDA-MB468 as compared to MDA-MB231 cells, (4) INK128 treatment (100 nM) inhibited migration of different TNBT cells (as compared to 2 uM RAD001, allosteric, partial TORC1 inhibitor)) and the inhibition was differentially pronounced in PTEN-null TNBT cells lines, (5) INK128 treatment (100 nM) also blocked invasion of MDA-MB468 cells, and (6) INK128 dose-dependently blocked clonogenic growth of TNBT cells. This effect was potentiated in the presence of ABT888 (10uM; small molecule PARP inhibitor) plus carboplatin (10uM; chemotherapeutic agent). Conclusion: INK128 (alone or in combination with carboplatin and ABT888) has anti-proliferative effect on TNBT cells. INK128 has anti-migratory and anti-invasive effects on TNBT cells. Interestingly, the anti-migratory effect of INK128 was most prominent in PTEN-null TNBT cells. We are currently pursuing studies to test the effect of INK128 on the endothelial cells, the results of which will be presented in the meeting. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2230. doi:1538-7445.AM2012-2230