Abstract 2031: Antitumoral synergy of iron chelators and chemotherapies in triple-negative breast cancer cell lines and patient-derived xenograft

Introduction: Tumor cells present an iron metabolic disorder with high proliferation rate, increased iron storage (ferritin and Labile Iron Pool - LIP) and high sensibility to iron deprivation, which could be a therapeutic target. Anticancer effect of iron chelators deferoxamine (DFO) and deferasirox (DFX) has been revealed in several types of cancers. In breast cancer (BC), the development of new therapeutic approaches is urgently needed for triple negative (TN) subtype which presents poor prognosis and lacks targeting therapy. We investigated the therapeutic potential of iron chelators combined with chemotherapeutic agents in TNBC cell lines and patient-derived xenografts (PDX). Methods: Anticancer effects of iron chelators combined with chemotherapeutic agents (doxorubicin, cisplatin or carboplatin) were evaluated in vitro in 4 TNBC cell lines by MTT assay, annexin V/PI staining and assessment of caspase 3/7 activity. Assessment of LIP, transferrin receptor 1 (TfR1) expression level, Reactive Oxygen Species (ROS) production and mitochondrial membrane potential variations were performed by flow cytometry, and ELISA assay for ferritin level. The activity of DFX alone or combined with doxorubicin/cyclophosphamide (AC) was tested in the HBCx-10 TNBC PDX selected because of its relapse to AC. Iron homeostasis, hypoxia and PI3K pathway were analyzed by immunohistochemistry (IHC) and Western-blot in both cell lines and PDX tumors. In DFX+/-AC treated and untreated tumors, induction of apoptosis was performed by TUNEL assay and a transcriptome analysis is ongoing. Results: Iron chelators acted in synergy effect with three chemotherapies in all cell lines which were tested to inhibit cell proliferation and induce apoptosis. Chelators increased cytotoxicity until 60% compared to chemotherapies alone. In all cell lines, chelators treatment increased TfR1 expression level and decreased LIP and ferritin. Furthermore, down-regulation of PI3K pathway, hypoxia, mitochondrial membrane potential, and the production increasing of ROS were observed. In HBCx-10 PDX, a trend for antitumoral activity of DFX alone was observed (p=0.09) at the end of the experiment (day 81). A significant difference of Relative Tumor Volume (RTV) was observed since day 18 between the AC group and the DFX+AC group (tumor growth inhibition: 37 to 61%, tumor growth delay: 10 to 14 days, 0.005 Conclusions: Iron chelators may increase the effectiveness of conventional chemotherapies for TNBC treatments. This antitumoral synergy involves PI3K pathway downregulation, ROS production and decrease mitochondrial membrane potential. Citation Format: Sandrine Tury, Sophie Vacher, Véronique Becette, Franck Assayag, Sophie Chateau-Joubert, Jean-Luc Servely, Elisabetta Marangoni, Ivan Bièche, Céline Callens. Antitumoral synergy of iron chelators and chemotherapies in triple-negative breast cancer cell lines and patient-derived xenograft [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 2031. doi:10.1158/1538-7445.AM2017-2031