Abstract 4097: Src-met signaling confers apoptosis resistance to the combination of BKM120 and erlotinib in head and neck cancer

Abstract

Abstract Purpose: Molecularly targeted agents will play a major role in the next generation of personalized cancer therapies. However, intrinsic and acquired resistance to targeted agents poses challenges to the success of such treatments. The purpose of the current study was to investigate the intrinsic resistance of head and neck cancer (HNC) cell lines to apoptosis induced by the combination of EGFR inhibitor erlotinib and PI3K inhibitor BKM120. Methods: In a panel of 10 malignant and 1 premalignant HN cell lines, we evaluated cell growth inhibition (by SRB assay), IC50, combination index, dose reduction index (by CalcuSyn Software), and apoptosis (by Annexin-V staining). Protein expression levels were measured by Western blotting. Small molecule chemical inhibitors and siRNA-mediated knockdown strategies were used to inactivate and shut down the expression of the relevant proteins, respectively. Results: Single targeting of EGFR with erlotinib or PI3K with BKM120 (pan-PI3K inhibitor) suppressed cellular growth without inducing significant apoptosis. Co-targeting EGFR and PI3K demonstrated in vitro synergy in all except one cell line (based on combination index and dose reduction index) and more effectively inhibited HNC xenograft growth in vivo. The combination of erlotinib and BKM120 induced variable apoptosis: some cell lines were very sensitive (Tu686, 686LN, 93-VU-147T), some moderately (Fadu, SqCCy1, 1483, UMSSC90) and others were resistant (UD-SCC2, MSK-LEUK1, JHU022) to apoptosis induction. JHU022 and 1483 cell lines expressed very high levels of p-cMet. Targeting cMet with the small molecule inhibitor crizotinib or siRNA rendered these cell lines highly sensitive to erlotinib and BKM120 induced apoptosis. Moreover, inhibition of Src family kinases with the small molecule inhibitor dasatinib or with c-Src-specific siRNA inhibited p-cMet. In addition, inhibition of SFK in these cell lines conferred sensitivity to erlotinib and BKM120 induced apoptosis. Conclusions: Our results strongly suggest that co-targeting of EGFR and PI3K has synergistic activity, is effective in vivo, and induces apoptosis of some HNC cell lines. Two of the resistant cell lines express a high level of p-cMet as a downstream target of SFK, which confers resistance of these cells to the combination of erlotinib and BKM120. Citation Format: A.R.M. Ruhul Amin, Abu Anisuzzaman, Abedul Haque, Zhuo Chen, Dong Shin. Src-met signaling confers apoptosis resistance to the combination of BKM120 and erlotinib in head and neck cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4097. doi:10.1158/1538-7445.AM2017-4097