Glutamine Sensitivity Analysis Identifies the xCT Antiporter as a Common Triple-Negative Breast Tumor Therapeutic Target

UCSF/Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA 94115, USA. Electronic address: .
Cancer cell (Impact Factor: 23.52). 10/2013; 24(4). DOI: 10.1016/j.ccr.2013.08.020
Source: PubMed


A handful of tumor-derived cell lines form the mainstay of cancer therapeutic development, yielding drugs with an impact typically measured as months to disease progression. To develop more effective breast cancer therapeutics and more readily understand their clinical impact, we constructed a functional metabolic portrait of 46 independently derived breast cell lines. Our analysis of glutamine uptake and dependence identified a subset of triple-negative samples that are glutamine auxotrophs. Ambient glutamine indirectly supports environmental cystine acquisition via the xCT antiporter, which is expressed on one-third of triple-negative tumors in vivo. xCT inhibition with the clinically approved anti-inflammatory sulfasalazine decreases tumor growth, revealing a therapeutic target in breast tumors of poorest prognosis and a lead compound for rapid, effective drug development.

Download full-text


Available from: Anneleen Daemen,
  • Source
    • "Increased reliance on xCT for import of cysteine for glutathione synthesis also suggests that targeting of this receptor will provide greater therapeutic margins than direct inhibition of glutathione synthesis that would be expected to result in wide-ranging toxicities [32]. Thus, xCT is considered an attractive target for cancer [28] [29]. Activation of oncogenes reprogram cancer cells toward aerobic glycolysis to support their proliferation and growth, a phenomenon known as the Warburg effect [2]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Reprogramming of energy metabolism is one of the emerging hallmarks of cancer. Up-regulation of energy metabolism pathways fuels cell growth and division, a key characteristic of neoplastic disease, and can lead to dependency on specific metabolic pathways. Thus, targeting energy metabolism pathways might offer the opportunity for novel therapeutics. Here, we describe the application of a novel in vivo screening approach for the identification of genes involved in cancer metabolism using a patient-derived pancreatic xenograft model. Lentiviruses expressing short hairpin RNAs (shRNAs) targeting 12 different cell surface protein transporters were separately transduced into the primary pancreatic tumor cells. Transduced cells were pooled and implanted into mice. Tumors were harvested at different times, and the frequency of each shRNA was determined as a measure of which ones prevented tumor growth. Several targets including carbonic anhydrase IX (CAIX), monocarboxylate transporter 4, and anionic amino acid transporter light chain, xc- system (xCT) were identified in these studies and shown to be required for tumor initiation and growth. Interestingly, CAIX was overexpressed in the tumor initiating cell population. CAIX expression alone correlated with a highly tumorigenic subpopulation of cells. Furthermore, CAIX expression was essential for tumor initiation because shRNA knockdown eliminated the ability of cells to grow in vivo. To the best of our knowledge, this is the first parallel in vivo assessment of multiple novel oncology target genes using a patient-derived pancreatic tumor model. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.
    Neoplasia (New York, N.Y.) 06/2015; 144(6). DOI:10.1016/j.neo.2015.05.001 · 4.25 Impact Factor
  • Source
    • "RPPA analysis confirmed that high expression of SLC1A5 is associated with basal-like and luminal B types of BCa, as well poorer responsiveness to therapy, whereas low SLC1A5 expression coincided with reactive, luminal type tumors. Along these lines, tumors more dependent on Gln, such as triple-negative BCa cells (Timmerman et al., 2013) and melanoma cells (Filipp et al., 2012), could benefit from therapies that target Gln-pathway components in combination with other therapies. Our data also show that RNF5-medi- ated control of Gln carrier proteins does not function in all BCa (E) MDA-MB-231 cells transfected with indicated constructs were incubated with 2.5 mg/ml BFA for 24 hr, stained with Annexin-V-EGFP and PI, and analyzed by FACS. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Many tumor cells are fueled by altered metabolism and increased glutamine (Gln) dependence. We identify regulation of the L-glutamine carrier proteins SLC1A5 and SLC38A2 (SLC1A5/38A2) by the ubiquitin ligase RNF5. Paclitaxel-induced ER stress to breast cancer (BCa) cells promotes RNF5 association, ubiquitination, and degradation of SLC1A5/38A2. This decreases Gln uptake, levels of TCA cycle components, mTOR signaling, and proliferation while increasing autophagy and cell death. Rnf5-deficient MMTV-PyMT mammary tumors were less differentiated and showed elevated SLC1A5 expression. Whereas RNF5 depletion in MDA-MB-231 cells promoted tumorigenesis and abolished paclitaxel responsiveness, SLC1A5/38A2 knockdown elicited opposing effects. Inverse RNF5(hi)/SLC1A5/38A2(lo) expression was associated with positive prognosis in BCa. Thus, RNF5 control of Gln uptake underlies BCa response to chemotherapies. Copyright © 2015 Elsevier Inc. All rights reserved.
    Cancer cell 03/2015; 27(3):354-69. DOI:10.1016/j.ccell.2015.02.006 · 23.52 Impact Factor
  • Source
    • "Breast cancer (BC) is a heterogeneous disease that can be classified into estrogen receptor a-positive (ERa + ) and HER2 + tumors as well as triple-negative (TN) tumors, which do not express high levels of these or the progesterone receptors (Prat & Perou, 2011). TNBCs include two major subtypes: basal-like, expressing basal-cell markers such as cytokeratin 14, and claudin-low/mesenchymal-like, expressing low levels of tight junction proteins including certain claudins and E-cadherin, and high levels of genes associated with epithelial-to-mesenchymal transition (EMT) (Prat et al, 2010; Lehmann et al, 2011; Timmerman et al, 2013). Interest in the latter tumors is driven by observations that following conventional therapy , residual tumors exhibit features of cancer stem cells and EMT (Mani et al, 2008; Creighton et al, 2009; Guo et al, 2012). "
    [Show abstract] [Hide abstract]
    ABSTRACT: The tumor suppressors Pten and p53 are frequently lost in breast cancer, yet the consequences of their combined inactivation are poorly understood. Here, we show that mammary-specific deletion of Pten via WAP-Cre, which targets alveolar progenitors, induced tumors with shortened latency compared to those induced by MMTV-Cre, which targets basal/luminal progenitors. Combined Pten-p53 mutations accelerated formation of claudin-low, triple-negative-like breast cancer (TNBC) that exhibited hyper-activated AKT signaling and more mesenchymal features relative to Pten or p53 single-mutant tumors. Twenty-four genes that were significantly and differentially expressed between WAP-Cre:Pten/p53 and MMTV-Cre:Pten/p53 tumors predicted poor survival for claudin-low patients. Kinome screens identified eukaryotic elongation factor-2 kinase (eEF2K) inhibitors as more potent than PI3K/AKT/mTOR inhibitors on both mouse and human Pten/p53-deficient TNBC cells. Sensitivity to eEF2K inhibition correlated with AKT pathway activity. eEF2K monotherapy suppressed growth of Pten/p53-deficient TNBC xenografts in vivo and cooperated with doxorubicin to efficiently kill tumor cells in vitro. Our results identify a prognostic signature for claudin-low patients and provide a rationale for using eEF2K inhibitors for treatment of TNBC with elevated AKT signaling.
    EMBO Molecular Medicine 10/2014; 6(12):1542-1560. DOI:10.15252/emmm.201404402 · 8.67 Impact Factor
Show more