Abstract 742: Effect of Hsp90 inhibitor NVP-AUY922 with radiation on lung adenocarcinoma cell lines with acquired resistance to EGFR-tyrosine kinase inhibitors

Abstract

Abstract Recent progress in understanding of molecular pathology in lung adenocarcinoma has been changing the therapeutic strategy. Especially, tyrosine kinase inhibitors (TKIs) for epidermal growth factor receptor (EGFR) mutant lung adenocarcinoma have improved the outcomes. However acquired resistances to TKIs are observed in most of cases and how to overcome the resistances must be the key factor to make them curable. 90-kDa heat shock protein (Hsp90) is a chaperone protein that assists maturation of client proteins and EGFR is one of them. Reportedly, Hsp90 inhibitors have anti-tumor effect against not only EGFR-TKI sensitive lung adenocarcinomas but also those with EGFR-TKI resistantce. Furthermore Hsp90 inhibitor can increase radiosensitivity through inhibition of hypoxia-inducible factor-1α (HIF-1α), checkpoint kinase 1 (CHK1) and WEE1 G2 checkpoint kinase (WEE1). These facts prompted us to investigate the combined effect of Hsp90 inhibitors and radiation to EGFR-TKI resistant cells. We exposed Hsp90 inhibitor NVP-AUY922 (AUY) to Gefitinib-resistant lung adenocarcinoma cell lines, PC-9 with T790M (PC-9 GRt790m) which is well known secondary mutation with EGFR-TKI resistant cells and HCC827 with MET amplification (HCC827-GRmet) which is also well known mechanism of EGFR-TKI resistant. Our earlier work showed another EGFR-TKI resistant mechanism, acquiring cancer stem cell properties. We also used HCC827 with stem-cell like properties (HCC827-GRstem). To examine the anti-tumor effect, we conducted colonogenic assay with radiation. Then we conducted immunofluorescence staining for γH2AX and counted the foci to observe DNA double strand breaks. We also conducted cell cycle assay with propidium iodide-staining method using flow cytometry. The colonogenic assay showed anti-tumor effect in PC-9 GRt790m and HCC827-GRmet but HCC827-GRstem showed limited effect to AUY and radiation. In γH2AX staining, HCC827-GRmet showed prolonged DNA double strand breaks suggesting leading to apoptosis. In contrast, HCC827-GRstem showed rapid decrease of DNA double strand breaks. In cell cycle analysis, HCC827-GRstem showed smaller population of G2/M compared to HCC827-GRmet and parental HCC827. Taken together, AUY with radiation can be a effective therapy to EGFR-TKI resistant lung adenocarcinoma but stem-cell like properties cause resistant even these therapies. Citation Format: Yuho Maki, Shinsuke Hashida, Hiromasa Yamamoto, Kazuhiko Shien, Tomoaki Ohtsuka, Ken Suzawa, Masashi Furukawa, Junichi Soh, Hiroaki Asano, Kazunori Tsukuda, Shinichiro Miyoshi, Susumu Kanazawa, Shinichi Toyooka. Effect of Hsp90 inhibitor NVP-AUY922 with radiation on lung adenocarcinoma cell lines with acquired resistance to EGFR-tyrosine kinase inhibitors. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 742. doi:10.1158/1538-7445.AM2015-742