Abstract 1736: Src inhibitor dasatinib enhances anti-tumor activity of irreversible or T790M-selective epidermal growth factor receptor-tyrosine kinase inhibitors in non-small cell lung cancer cells with T790M gate-keeper mutation

Abstract

Abstract Despite the therapeutic benefit of epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) in non-small cell lung cancer (NSCLC) patients with EGFR mutation, most if not all eventually develop resistance to these drugs. A secondary mutation of EGFR (T790M) accounts for 50% of all cases of acquired resistance to EGFR-TKIs. Although irreversible EGFR-TKIs are thought to be one of the strategies to overcome T790M, the efficacy of these drugs appears limited. To investigate how signal transduction is altered in NSCLC cells with T790M, we generated PC9GR cells with T790M by long term gefitinib exposure of PC9 cells with exon 19 deletion. Global phospho-proteomics approach revealed that Src family kinases were phosphorylated by erlotinib treatment in PC9GR cells, suggesting that Src family kinases compensate EGFR inhibition in NSCLC cells with T790M. Western blot assays demonstrated that BIBW2992, an irreversible EGFR-TKI currently in several clinical trials, also activated Src family kinases in PC9GR and H1975 NSCLC cells with T790M. The Src inhibitor dasatinib combined with BIBW2992 abolished this Src phosphorylation along with complete suppression of phospho Akt and Erk. In addition, significant PARP cleavage was observed in these cells suggesting apoptotic cell death. Consistent with the effects on cell signaling and apoptosis, dasatinib enhances anti-tumor activity of BIBW2992 in both GLO cell proliferation assay and caspase-3 apoptosis assay in PC9GR and H1975 cells. Additional experiments also demonstrated that dasatinib enhanced the effects of T790M selective EGFR-TKI WZ4002, which was recently reported to be another possible strategy to overcome T790M, in PC9GR and H1975 cells. Finally, the combination of BIBW2992 and dasatinib showed significant in vivo tumor suppression (including tumor regression) in PC9GR xenograft studies. These results suggest a role for Src in maintaining downstream signaling despite irreversible EGFR inhibitors and support further studies of irreversible EGFR combined with dasatinib in NSCLC patients who acquired resistance to EGFR-TKI by T790M. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1736. doi:10.1158/1538-7445.AM2011-1736