Abstract 1907: Heat shock protein 90 inhibition overcomes hepatocyte growth factor-triggering resistance to EGFR tyrosine kinase inhibitors in EGFR mutant lung cancer by decreasing client protein expression and angiogenesis

Abstract

Abstract The three major, clinically relevant mechanisms of acquired resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) in EGFR mutant lung cancer are a second mutation in the EGFR gene (T790M), Met amplification, and increased expression of hepatocyte growth factor (HGF). Heat shock protein90 (Hsp90) is a 90kDa molecular chaperone for proteins that include EGFR, Met and EML4-ALK. Hsp90 inhibitors have been reported to reverse resistance to EGFR-TKIs caused by EGFR T790M mutation and Met amplification. Here, we determined whether inhibition of Hsp90 could overcome HGF-triggered EGFR-TKI resistance in EGFR mutant lung cancer cells. EGFR-TKI erlotinib inhibited the growth of PC-9, HCC827, and Ma-1 cells, with deletions in exon19 of EGFR, but not HGF-gene transfected Ma-1 (Ma-1/HGF) cells and H1975 cells, which contain the EGFR L858R and T790M mutations, respectively. Erlotinib also did not inhibit the growth of PC-9 and Ma-1 cells in the presence of HGF. However, an Hsp90 inhibitor, 17-DMAG, induced apoptosis and markedly inhibited the growth of these cell lines, even in the presence of HGF. This inhibition by 17-DMAG was associated with decreased expression of EGFR and Met, thereby decreasing Akt phosphorylation in tumor cells. In an in vivo model of HGF-triggered erlotinib-resistance, using Ma-1/HGF cells, 17-DMAG markedly suppressed tumor growth by decreasing angiogenesis and increasing apoptosis. These results indicate that Hsp90 inhibitors may overcome HGF-triggered resistance to EGFR-TKIs and that the use of Hsp90 inhibitors may result in more successful treatment of EGFR mutant lung cancers. 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 1907. doi:1538-7445.AM2012-1907