Abstract 4098: Tyrosine kinase inhibitor resistance were decreased in spheroid culture platform
Authors: Suzuki Toshihiro , Ito Risa , Yamaoka Toshimitsu , Ohmori Tohru , Nishio Kazuto , Ogasawara Yuki 
Published: July 2017

Abstract
Lung cancer is the leading cause of cancer related death in the world. Platinum-based combination regimen or molecular target drugs, such as EGFR tyrosine kinase inhibitors (EGFR-TKIs) are used for first line chemotherapy of non small cell lung cancer (NSCLC). Somatic mutation in the tyrosine kinase domain of epidermal growth factor receptor (EGFR) have been identified in NSCLC and those mutations confer sensitivity to the EGFR-TKIs such as gefitinib. Unfortunately, it is already known that the almost cases are developed to drug resistance after chemotherapy. Several EGFR-TKI resistant mechanisms have been reported, including T790M gefitinib/erlotinib resistance mutation, C797S osimertinib resistant mutation, c-MET amplification and ErbB3 activation. In the previous study, we revealed that the miRNA biosynthesis pathway was critical for maintain the cisplatin resistant phenotype. Further, it was reported that EGFR modulated miRNA maturation through the phosphorylation of AGO2. Protein phosphorylation is one of most important post transcriptional modification mechanisms and miRNA is also associated with fine tuning of mRNA expression. Thus, we focused on the relationship between miRNA expression and kinase signaling in gefitinib resistance.Generally, developed resistant cell lines and cell culture techniques were used in resistance research. However, some resistance mechanisms observed in cultured cells are not reflected the in vivo. Recently, some three-dimensional (3D) cell culture techniques are developed and expected to bridge the gap between normal cell culture and in vivo models. In this study, we attempted to analyze the resistant mechanism of gefitinib resistant cell lines in suspended spheroid culture using RPMI1640 medium containing suspension polymer, FP001. We screened differences of relative resistance to anticancer compounds in 3D culture and normal culture condition using chemical library and ATP assay. As results; we revealed that ErbB3 and Akt phosphorylation levels were significantly decreased in spheroid formed from resistant cell lines in 3D culture condition compared to these levels with normal culture condition. On the other hand, miR-205 levels remain high in all resistant cell lines. Furthermore, some anticancer agents, including kinase inhibitors showed higher sensitivity in resistant cell lines under 3D condition than that under normal cell culture. We speculate that the decreased resistance depends on normal culture in plastic dish and remaining resistant mechanism in 3D culture is important and similar to in vivo. In conclusion, this approach with 3D culture is more close to in vivo, such as xenograft model, and promising contribute to drug resistance research.
Citation Format: Toshihiro Suzuki, Risa Ito, Toshimitsu Yamaoka, Tohru Ohmori, Kazuto Nishio, Yuki Ogasawara. Tyrosine kinase inhibitor resistance were decreased in spheroid culture platform [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 4098. doi:10.1158/1538-7445.AM2017-4098