Abstract 3179: The effect of eribulin resistant mechanism in breast cancer on microenvironment
Authors: Goto Wataru , kashiwagi Shinichiro , Takada Koji , Takahashi Katsuyuki , Takashima Tsutomu , Noda Satoru , Onoda Naoyoshi , Tomita Shuhei , Hirakawa Kosei , Ohira Masaichi 
Published: July 2017

Abstract
Backgorund: Erbulin, a nontaxane, synthetic microtuble dynamics inhibitor, is currently in clinical use for advanced or metastatic breast cancer. Eribulin treatment results in improved tumor perfusion in breast cancer and induces the remodeling of tumor vasculature and a reversing effect on the epithelial to mesenchymal transition (EMT) of cancer cells. Although eribulin significantly increased overall survival by monotherapy, most breast cancer cells acquire resistance to eribulin after a series of treatments. The development of resistance to chemotherapy appears to have become a major clinical problem of breast cancer. In this study, we established two eribulin-resistant cell lines, and investigated the mechanisms underlying the development of eribulin resistance in breast cancer cells.
Material and Methods: Eribulin-resistant breast cancer cell lines were obtained by culturing MDA-MB-231 and MCF-7 cells with stepwise increases in the concentration of eribulin for more than 6-months. The relative eribulin resistance of each eribulin-resistant cell line was determined using a MTT assay. To confirm the expression of proteins related to drug resistance, we examined multidrug resistance protein 1 (MDR1), end-binding 1 (EB1) and E-cadherin by western blot analysis. To investigate the effect of eribulin, a flow cytometry analysis for cell-cycle distribution was performed. In addition, we produced MDA-MB-231, MDA-MB-231/Eribulin, MCF-7 and MCF-7/Eribulin subcutaneous xenografts, and analysed protein expression by immunohistochemical study of surgically resected tissues from xenografts.
Results: Compared to parental cell lines, eribulin-resistant cell lines had a higher resistance to eribulin. Eribulin-resistant cell lines acquired resistance to not only eribulin, but also paclitaxel, vinorelbine, doxorubicin, and fluorouracil. After eribulin treatment, MDA-MB-231/Eribulin cell lines showed no morphological change, and expression of E-cadherin did not increase. Also, cell cycle distribution and expression of EB1 did not exhibit significantly differences from parental cell lines. On the other hand, PD-L1 was overexpressed in eribulin-resistant cell lines compared to parental cell lines. Additionally, eribulin-resistant cell lines exhibited increased level of MDR1 protein.
Conclusion: Our established eribulin-resistant cell lines may suppress eribulin effect of inhibiting microtube, EMT, and immune evasion mechanism. These should be useful tools for identifying new mechanism of eribulin resistance.
Citation Format: Wataru Goto, Shinichiro kashiwagi, Koji Takada, Katsuyuki Takahashi, Tsutomu Takashima, Satoru Noda, Naoyoshi Onoda, Shuhei Tomita, Kosei Hirakawa, Masaichi Ohira. The effect of eribulin resistant mechanism in breast cancer on microenvironment [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 3179. doi:10.1158/1538-7445.AM2017-3179