Abstract 1199: Overcomes AXL and Met mediated erlotinib/gefitinib cross resistance in non-small cell lung cancer cells by Marsdenia tenacissima extract
Authors: Han Shu-Yan , Sun Hong , Xue Dong , Zhao Wei , Jiao Yan-Na , Li Ping-Ping 
Published: July 2017

Abstract
Apart from EGFR T790M mutation, the bypass activation of c-Met and Axl kinase also can lead to the resistance to tyrosine kinase inhibitors (TKIs) in NSCLC. Axl and c-Met share same downstream pathways with EGFR, thus combined treatments of EGFR inhibitors with Axl or Met inhibitor are promising to overcome acquired resistance of TKIs.
Our previous work showed that the water extract of Marsdenia tenacissima (MTE), which used to treat cancer in clinics for decades, restored gefitinib sensitivity in resistant NSCLC cells with EGFR T790M mutation or K-ras mutations in vitro and in vivo. However, the potential effeicacy of MTE on Axl and c-Met mediated resistance has not yet been fully understood, and the related molecular mechanisms also need to be elucidated.
The present study was performed on HCC827/ER cells, which was established by exposing parental HCC827 cells to erlotinib. HCC827/ER cells are with Axl activiation and c-Met amplification, and show dual-resistance to erlotinib and gefitinib. We evaluated the effects of MTE to restore erlotinib/gefitinib sensitivity with three different combinations. Cell viability and cell apoptosis were determined by MTT and flow cytometry, respectively. The c-Met amplification was assessed with TaqMan real-time PCR. Signaling pathways were examined by Western blotting to reveal the possible mechanisms. The in vivo effects of MTE combined with erlotinib/gefitinib were tested on HCC827/ER xenograft mice, and tumor tissues were subjected to immunohistochemistry analysis and Western blotting.
Our results indicated the MTE→MTE+Erlotinib/Geftinib (M→M+E/G) treatment was the most potent combinations. Compared with control group and each single, M→M+E/G treatment induced significant apoptosis, obviously inhibited EGF-induced phosphorylation of PI3K/Akt/mTOR and ERK1/2, down-regulated HGF/c-Met activation in HCC827/ER cells. Axl is a receptor tyrosine kinase which strongly associated with EMT phenotype. The M→M+E/G treatments could not restrain Axl expressions but remarkably reduced phospho-Axl levels and inhibited EMT phenotype in HCC827/ER cells. Surprisingly, MTE alone caused prominent p-Axl inhibition, along with up-regulated E-cadherin and decreased
mesenchymal markers. The mouse tumors were remarkably restrained by the M→M+E/G combinations, and it was significant compared with each drug alone (P&lt;0.05). Accordingly, cell apoptosis was extended, PCNA expression and tumor angiogenesis (VEGF and CD105) were reduced and EMT phenotype were regulated in tumor tissues. The p-Met and p-AXL were also considerably suppressed by the combined treatments.
The present data revealed that MTE restored TKIs such as erlotinib and gefitinib efficacy in resistant NSCLC cells with Axl activation and c-Met amplification in vitro and in vivo. It suggests that the addition of MTE may be a promising therapeutic strategy to overcome TKIs resistance in NSCLC.
Citation Format: Shu-Yan Han, Hong Sun, Dong Xue, Wei Zhao, Yan-Na Jiao, Ping-Ping Li. Overcomes AXL and Met mediated erlotinib/gefitinib cross resistance in non-small cell lung cancer cells by Marsdenia tenacissima extract [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 1199. doi:10.1158/1538-7445.AM2017-1199