Abstract B90: HSP90 inhibitor NVP-AUY922 sensitizes intrinsic MEK inhibitor Trametinib-resistant NSCLC cells harboring KRAS mutation

Introduction: Mutant KRAS is feature of more than 25% of non-small cell lung cancers (NSCLC) and exemplifies one of the most popular oncogenic drivers. Ras-driven tumors are often hard to cure with conventional therapies and are necessary novel treatment strategies. Experiment: Using the HSP90 inhibitor NVP-AUY922, we investigated the potential of HSP90 inhibition to overcome the resistance to Trametinib, MEK inhibitor, in lung cancers harboring K-RAS mutant cell lines (H23, H358, H647, H1944, and A549). The synergistic effect of AUY-922 and trametinib was determined by analysis of the combination index (CI). After performing western blotting, we underwent following xenograft study with 6-week-old Balb/c-nu/nu female using H649 and H1944 cell lines. The mice were randomized into groups of 5, and NVP-AUY922 (5 mg/kg) was administered 3 days/week and GSK1120212 (300 μg/kg) was administered 5 days/week for up to 21 days in total. Result: NSCLC cells harboring G13D KRAS mutation showed intrinsic MEK inhibitor resistance via PI3K activation by highly expressed AKT as a bypass pathway. And then, HSP90 inhibitor AUY-922 suppresses both PI3K-AKT-mTOR and RAF-MEK-ERK reactivated by MEK inhibitor GSK1120212 and finally AUY-922 renders intrinsic MEK inhibitor resistant NSCLC cells sensitive to GSK1120212 with significant synergy. Furthermore, we showed this synergistic effect is occurred on sub-effective dose of either drug. Conclusion: The dual inhibition of HSP90 and MEK signaling pathways on sub-effective dose may constitute a potent therapeutic strategy to treat intrinsic MEK inhibitor resistant G13DKRAS mutant NSCLCs for resolving toxicity problem of dual inhibition of AKT and MEK in clinical trials. Citation Format: Dae Ho Lee, Kang-Seo Park, Bora Oh, Mi-Hee Lee, Hannah Yang. HSP90 inhibitor NVP-AUY922 sensitizes intrinsic MEK inhibitor Trametinib-resistant NSCLC cells harboring KRAS mutation. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr B90.