Abstract C196: Co-treatment with NVP-BEZ235 and heat shock protein (hsp) 90 or pan-deacetylase (DAC) inhibitor is synergistically active against non-small cell lung cancer (NSCLC) cells with mutant RAS and LKB1

Abstract

Abstract Inactivating somatic mutation of LKB1 is found in approximately 30% of NSCLC and is often coincident with activating K-RAS mutation. In a mutant K-RAS-driven model of mouse lung cancer, strong cooperation and aggressive phenotype was seen with hemizygous inactivation of LKB1. Loss of LKB1 results in activation of mTOR pathway while somatic activating mutation in K-RAS results in activation of PI3K/AKT and RAS/RAF/ERK. Therefore therapeutic stratagies which target these pathways may have significant affect on the outcome of these cancers. NVP-BEZ235 is a dual PI3K and mTOR inhibitor and panobinostat (PS) (Novartis Pharmaceuticals Inc) is a pan-histone deacetylase (HDAC) inhibitor, which has been shown to induce proteasomal degradation and depletion of the levels of hsp90 client proteins, including AKT and c-RAF. Here, we determined the effects of BEZ235 and/or PS or AUY922 (an hsp90 inhibitor) on NSCLC A549 and H460 cells with LKB1 and K-RAS mutations (A549 and H460). Treatment with BEZ235 (200 to 1000 nM), PS (25 to 50 nM) or AUY922 (25 to 100 nM) dose-dependently increased % of cells in G2/M and decreased % of cells in S phase of cell cycle, as well as induced apoptosis of the NSCLC cells. Co-treatment with AUY922 or PS increased BEZ235 mediated depletion of p-AKT, p-4EBP1 and p-p70S6K levels, as well as synergistically induced apoptosis of A549 and H460 cells (combination indices < 1.0). Combined therapy with BEZ235 (25 mg/Kg) and PS (10 mg/Kg) or AUY922 (20 mg/Kg) resulted in significantly more tumor growth delay than treatment with each of the agents alone of A549 cell xenografts in nude mice (p < 05). We also determined the activity of BEZ235 and/or PS in the NSCLC H368 cells with mutant K-RAS and either wild-type (H358 cells) or stable knock down of LKB1 expression (H358/LKB1-KD cells), achieved by shRNA against LKB1, mimicking the presence of mutant LKB1. As compared to each agent alone, co-treatment with BEZ235 and PS exhibited a higher level of antitumor synergy against H358/LKB1-KD versus H358 cells. These pre-clinical in vitro and in vivo studies demonstrate that combined treatment with the dual PI3K/mTOR inhibitor BEZ235 and PS or AUY922 could potentially be a promising targeted therapy for NSCLC that harbors K-ras and LKB1 mutations. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):C196.