Abstract P4-04-04: Eribulin impairs TGF-β type I receptor localization and signaling in BT-549 cells

Abstract

Abstract Microtubule targeting agents (MTAs) continue to be some of the most valuable drugs used to treat breast cancer. While decades of research have shown that these drugs cause mitotic arrest in cells by suppressing the dynamic instability of microtubules, recent evidence demonstrates that the ability of MTAs to disrupt microtubule-dependent transport of key signaling components, including proteins and microRNAs, in interphase cells likely contributes to their anticancer actions. TGF-β signaling is a driver of oncogenesis and epithelial-to-mesenchymal transition (EMT) that involves multiple protein trafficking and intracellular signaling events. Ligand mediated activation of the cell surface TGF-β receptors leads to downstream signaling in the canonical and the non-canonical pathways that collectively lead to the expression of proteins implicated in EMT, including Snail and Slug. Additionally, TGF-β type 1 receptor (TGF-βR1) undergoes constant cycling from the plasma membrane to the cytosol, a microtubule-dependent process. We tested the hypothesis that a short-term treatment of breast cancer cells with eribulin or 3 other clinically relevant MTAs would differentially disrupt interphase microtubules and alter the transport and downstream signaling of TGF-βR1. BT-549 cells were treated for 2 h with concentrations of MTAs that cause comparable disruption of the interphase microtubule network; 100 nM was used for the destabilizers, eribulin or vinorelbine and 1 µm was used for the stabilizers, paclitaxel or ixabepilone. The results show that TGF-βR1 was extensively localized along the stabilizer-induced microtubule bundles, a phenomenon not observed with destabilizer-treated cells. The downstream consequences were further assessed. The expression of Snail and Slug were evaluated in cells pretreated with MTAs followed by TGF-β stimulation. Eribulin and vinorelbine significantly inhibited the TGF-β-induced expression of Snail and Slug while stabilizers did not alter their expression levels. We hypothesize that eribulin and vinorelbine are inhibiting the non-canonical TGF-β signaling pathway since they had no effect on the localization and expression of Smad2/3, proteins involved in the canonical pathway. Eribulin induced inhibition of TGF-β signaling is consistent with previous studies that show that a 7 day treatment reversed TGF-β mediated EMT in breast cancer cells1. Data from patients shows that eribulin decreases the plasma concentration of TGF-β within 7 days of treatment initiation2. Our data suggest that eribulin rapidly inhibits non-canonical TGF-β signaling indicating that this is a potential mechanism for the eribulin-mediated EMT reversal. This information, together with previously published reports, suggest that eribulin has multiple effects leading to inhibition of TGF-β signaling. These studies begin to shed light into the diverse mechanisms of action of MTAs. 1. Yoshida T, et al., Brit J Cancer 110(6): 1497-505, 2014 2. Ueda S, et al., Brit J Cancer, 2016 This work is funded by Eisai Inc. Citation Format: Kaul R, Risinger AL, Mooberry SL. Eribulin impairs TGF-β type I receptor localization and signaling in BT-549 cells [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-04-04.