Abstract 4465: Concurrent roles for IGF1R and EGFR in driving acquired resistance to crizotinib and ability to overcome with a combination of the ALK/IGF1R inhibitor AZD3463 and Iressa.
Authors: Drew Lisa , Engelman Jeffrey , Katayama Ryohei , McDermott Brenda , Saeh Jamal , Scarpitti Meghan , Shaw Alice , Shen Minhui , Wang Suping , Smith Graeme 
Published: August 2014

Abstract
Genomic rearrangement of Anaplastic Lymphoma Kinase (ALK) has been observed in several tumor types including 3-6% of non small cell lung cancer (NSCLC). Although the ALK inhibitor crizotinib has clinical efficacy in selected ALK positive NSCLC patients, the majority of patients who show initial responses eventually relapse. Various mechanisms leading to resistance have been proposed and include ALK amplification and resistance mutations, as well as alternative pathway drivers including EGFR and cKIT. To further evaluate potential mechanisms of acquired resistance to crizotinib and potential therapeutic strategies to overcome them, we have developed multiple independently generated cell line derivatives. H3122 cells, a NSCLC line with an EML4-ALK fusion, was selected in increasing concentrations of crizotinib up to 1uM over a period of 4 to 6 months to generate H3122-CR lines. The cell lines generated were confirmed to be resistance to crizotinib as well as the selective ALK inhibitor, CH5424802, in cell proliferation experiments. Evaluation of the levels of potential secondary receptor tyrosine kinase (RTK) drivers by phosphoRTK arrays and western blotting revealed increased levels of total and phosphorylated ALK (pALK), along with increased phosphorylated insulin-like growth factor 1 receptor (pIGF1R). ALK levels were also elevated at the mRNA level. To evaluate potential strategies to most effectively overcome resistance in these cell lines, selective inhibitors of ALK CH5424802, IGF1R OSI-906 and epidermal growth factor receptor (EGFR) Iressa were used alone and in combination to evaluate ability to inhibit growth of two of the H3122-CR lines. In both CR lines, OSI-906 and Iressa had no effect alone on cell growth, however a combination of CH5424802 and OSI-906 or CH5424802 and Iressa increased sensitivity to CH5424802. Most interestingly however, a combination of CH5424802, OSI-906 and Iressa had maximal sensitization effect with complete reversal of resistance observed. A similar finding was obtained with a combination of the ALK/IGF1R inhibitor AZD3463 with Iressa. Further, we were able to demonstrate pathway dependency shifts in the CR lines with OSI-906 inhibiting AKT and Iressa inhibiting ERK and a combination of CH5424802, OSI-906 and Iressa required to effectively repress these main pathways to the level observed with CH5424802 alone in the H3122 parental line. Together, these data support a potential role for both EGFR and IGF1R as secondary RTK drivers occurring concurrently to drive resistance to crizotinib. A combination of approaches inhibiting ALK, IGF1R and EGFR together may therefore be required to most effectively treat crizotinib relapsed patients and delay onset of resistance. This could be achieved by combining multiple selective agents or agents with polypharmacology such as AZD3463 along with Iressa.
Citation Format: Lisa Drew, Jeffrey Engelman, Ryohei Katayama, Brenda McDermott, Jamal Saeh, Meghan Scarpitti, Alice Shaw, Minhui Shen, Suping Wang, Graeme Smith. Concurrent roles for IGF1R and EGFR in driving acquired resistance to crizotinib and ability to overcome with a combination of the ALK/IGF1R inhibitor AZD3463 and Iressa. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4465. doi:10.1158/1538-7445.AM2013-4465