Genome-independent hypoxic repression of estrogen receptor alpha in breast cancer cells

Averages and standard deviations of band intensities calculated for all repeats of each western blot in Fig. 2a. Specific band intensities normalized to the loading control bands (β-actin). Calculations derived from at least three independent experiments. (DOCX 17 kb

xCT inhibition sensitizes tumors to γ-radiation via glutathione reduction

About 3 million US cancer patients and 1.7 million EU cancer patients received multiple doses of radiation therapy (RT) in 2012, with treatment duration limited by normal adjacent tissue damage. Tumor-specific sensitization could allow treatment with lower radiation doses, reducing normal tissue damage. This is a longstanding, largely unrealized therapeutic goal. The cystine:glutamate exchanger xCT is expressed on poor prognosis subsets of most solid tumors, but not on most normal cells. xCT provides cells with environmental cystine for enhanced glutathione synthesis. Glutathione is used to control reactive oxygen species (ROS), which are therapeutic effectors of RT. We tested whether xCT inhibition would sensitize xCT+ tumor cells to ionizing radiation. We found that pretreatment with the xCT inhibitor erastin potently sensitized xCT+ but not xCT- cells, in vitro and in xenograft. Similarly, targeted gene inactivation also sensitized cells, and both modes of sensitization were overcome by glutathione supplementation. Sensitization prolongs DNA damage signaling, increases genome instability, and enhances cell death, revealing an unforeseen role for cysteine in genome integrity maintenance. We conclude that an xCT-specific therapeutic would provide tumor-specific sensitization to RT, allowing treatment with lower radiation doses, and producing far fewer side effects than other proposed sensitizers. Our data speaks to the need for the rapid development of such a drug

xCT inhibition sensitizes tumors to γ-radiation via glutathione reduction

About 3 million US cancer patients and 1.7 million EU cancer patients receivedmultiple doses of radiation therapy (RT) in 2012, with treatment duration limited bynormal adjacent tissue damage. Tumor-specific sensitization could allow treatmentwith lower radiation doses, reducing normal tissue damage. This is a longstanding,largely unrealized therapeutic goal. The cystine:glutamate exchanger xCT is expressedon poor prognosis subsets of most solid tumors, but not on most normal cells. xCTprovides cells with environmental cystine for enhanced glutathione synthesis.Glutathione is used to control reactive oxygen species (ROS), which are therapeuticeffectors of RT. We tested whether xCT inhibition would sensitize xCT+ tumor cells toionizing radiation. We found that pretreatment with the xCT inhibitor erastin potentlysensitized xCT+ but not xCT- cells, in vitro and in xenograft. Similarly, targeted geneinactivation also sensitized cells, and both modes of sensitization were overcome byglutathione supplementation. Sensitization prolongs DNA damage signaling, increasesgenome instability, and enhances cell death, revealing an unforeseen role for cysteinein genome integrity maintenance. We conclude that an xCT-specific therapeutic wouldprovide tumor-specific sensitization to RT, allowing treatment with lower radiationdoses, and producing far fewer side effects than other proposed sensitizers. Our dataspeaks to the need for the rapid development of such a drug

Notch promotes epithelial-mesenchymal transition during cardiac development and oncogenic transformation

Epithelial-to-mesenchymal transition (EMT) is fundamental to both embryogenesis and tumor metastasis. The Notch intercellular signaling pathway regulates cell fate determination throughout metazoan evolution, and overexpression of activating alleles is oncogenic in mammals. Here we demonstrate that Notch activity promotes EMT during both cardiac development and oncogenic transformation via transcriptional induction of the Snail repressor, a potent and evolutionarily conserved mediator of EMT in many tissues and tumor types. In the embryonic heart, Notch functions via lateral induction to promote a selective transforming growth factor-β (TGFβ)-mediated EMT that leads to cellularization of developing cardiac valvular primordia. Embryos that lack Notch signaling elements exhibit severely attenuated cardiac snail expression, abnormal maintenance of intercellular endocardial adhesion complexes, and abortive endocardial EMT in vivo and in vitro. Accordingly, transient ectopic expression of activated Notch1 (N1IC) in zebrafish embryos leads to hypercellular cardiac valves, whereas Notch inhibition prevents valve development. Overexpression of N1IC in immortalized endothelial cells in vitro induces EMT accompanied by oncogenic transformation, with corresponding induction of snail and repression of VE-cadherin expression. Notch is expressed in embryonic regions where EMT occurs, suggesting an intimate and fundamental role for Notch, which may be reactivated during tumor metastasis

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

SummaryA 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