Abstract P3-10-16: Identification of molecules that enhance the efficacy of eribulin in TNBC and IBC cell lines

Abstract

Abstract BACKGROUND: Eribulin mesylate, a non-taxane microtubule-dynamics inhibitor, is an effective chemotherapy drug for patients with metastatic breast cancer who have previously received at least two chemotherapeutic regimens. We are seeking to enhance the anti-tumor activity of eribulin in metastatic breast cancer cell lines. The purpose of this study was to identify kinase targets that markedly enhance the efficacy of eribulin using high-throughput nonbiased synthetic lethal RNA interference (RNAi) screening and to validate these targets in combination with eribulin using triple-negative breast cancer (TNBC) and inflammatory breast cancer (IBC) cell lines which are heterogeneous diseases and characterized by their high metastatic potential and poor prognosis. METHODS: High-throughput RNAi screening (709-human-kinome library) was performed to identify target kinases. The Bliss scoring method was used to identify potential targets from the screening (using a Bliss score cut-off of 0.15), and protein-protein interactome analysis (STRING V.11) and Ingenuity Pathway Analysis (IPA) were used to identify therapeutic target pathways. To validate the in vitro efficacy of selected targets, we performed CellTiter-Blue or sulforhodamine B cell proliferation and anchorage-independent colony-formation assays in 18 TNBC and 6 IBC cell lines treated with eribulin with or without inhibitors of the discovered targets. RESULTS: In vitro proliferation data demonstrated that single-agent eribulin had a nanomolar range of half-maximal inhibitory concentrations (0.2 - 4.0 nM) in most of the tested cell lines. RNAi screening identified 130 relevant kinase targets. IPA and STRING analysis revealed PI3K/AKT/mTOR, MAPK, JNK, and PAK1 as major canonical pathways that could be targeted to enhance the cytotoxic effect of eribulin. In in vitro cell line validation, PAK1 inhibitor NVS-PAK1-1 and mTOR inhibitor everolimus showed strong combinational anti-tumor effect (combination index values = 0.1 - 0.9), and JNK inhibitor JNK-In-8 showed moderate combinational anti-tumor effect (combination index values = 0.5 - 0.9) in combination with eribulin. Inhibitors of PI3K (copanlisib) and MEK (trametinib) showed combinational anti-tumor effect in some cell lines. CONCLUSION: We identified that PAK1, mTOR, and JNK inhibitors enhanced the anti-proliferation effects of eribulin in TNBC and IBC cell lines. Our data inform new treatment strategies with eribulin for TNBC and IBC that could lead to clinical trials of innovative combination therapy based on eribulin. Citation Format: Jangsoon Lee, Jon A Fuson, Huey Liu, Troy Pearson, Debu Tripathy, Bora Lim, Naoto T Ueno. Identification of molecules that enhance the efficacy of eribulin in TNBC and IBC cell lines [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-10-16.