caa a22 4500 606234551 CHVBK 20210128101237.0 cr unu---uuuuu 210128e20150701xx s 000 0 eng 10.1007/s11010-015-2412-4 doi (NATIONALLICENCE)springer-10.1007/s11010-015-2412-4 Signal transducer and activator of transcription 3 and 5 regulate system Xc- and redox balance in human breast cancer cells [Elektronische Daten] [Katja Linher-Melville, Sina Haftchenary, Patrick Gunning, Gurmit Singh] System Xc- is a cystine/glutamate antiporter that contributes to the maintenance of cellular redox balance. The human xCT (SLC7A11) gene encodes the functional subunit of system Xc-. Transcription factors regulating antioxidant defense mechanisms including system Xc- are of therapeutic interest, especially given that aggressive breast cancer cells exhibit increased system Xc- function. This investigation provides evidence that xCT expression is regulated by STAT3 and/or STAT5A, functionally affecting the antiporter in human breast cancer cells. Computationally analyzing two kilobase pairs of the xCT promoter/5′ flanking region identified a distal gamma-activated site (GAS) motif, with truncations significantly increasing luciferase reporter activity. Similar transcriptional increases were obtained after treating cells transiently transfected with the full-length xCT promoter construct with STAT3/5 pharmacological inhibitors. Knock-down of STAT3 or STAT5A with siRNAs produced similar results. However, GAS site mutation significantly reduced xCT transcriptional activity, suggesting that STATs may interact with other transcription factors at more proximal promoter sites. STAT3 and STAT5A were bound to the xCT promoter in MDA-MB-231 cells, and binding was disrupted by pre-treatment with STAT inhibitors. Pharmacologically suppressing STAT3/5 activation significantly increased xCT mRNA and protein levels, as well as cystine uptake, glutamate release, and total levels of intracellular glutathione. Our data suggest that STAT proteins negatively regulate basal xCT expression. Blocking STAT3/5-mediated signaling induces an adaptive, compensatory mechanism to protect breast cancer cells from stress, including reactive oxygen species, by up-regulating xCT expression and the function of system Xc-. We propose that targeting system Xc- together with STAT3/5 inhibitors may heighten therapeutic anti-cancer effects. Springer Science+Business Media New York, 2015 System Xc- nationallicence xCT nationallicence SLC7A11 nationallicence STAT3 nationallicence STAT5 nationallicence Oxidative stress nationallicence Linher-Melville Katja Department of Pathology and Molecular Medicine, McMaster University, L8S 4L8, Hamilton, ON, Canada aut Haftchenary Sina Department of Chemical and Physical Sciences, University of Toronto at Mississauga, L5L 1C6, Mississauga, ON, Canada aut Gunning Patrick Department of Chemical and Physical Sciences, University of Toronto at Mississauga, L5L 1C6, Mississauga, ON, Canada aut Singh Gurmit Department of Pathology and Molecular Medicine, McMaster University, L8S 4L8, Hamilton, ON, Canada aut Molecular and Cellular Biochemistry Springer US; http://www.springer-ny.com 405/1-2(2015-07-01), 205-221 0300-8177 405:1-2<205 2015 405 11010 https://doi.org/10.1007/s11010-015-2412-4 text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s11010-015-2412-4 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Linher-Melville Katja Department of Pathology and Molecular Medicine, McMaster University, L8S 4L8, Hamilton, ON, Canada aut NATIONALLICENCE 700 1- Haftchenary Sina Department of Chemical and Physical Sciences, University of Toronto at Mississauga, L5L 1C6, Mississauga, ON, Canada aut NATIONALLICENCE 700 1- Gunning Patrick Department of Chemical and Physical Sciences, University of Toronto at Mississauga, L5L 1C6, Mississauga, ON, Canada aut NATIONALLICENCE 700 1- Singh Gurmit Department of Pathology and Molecular Medicine, McMaster University, L8S 4L8, Hamilton, ON, Canada aut NATIONALLICENCE 773 0- Molecular and Cellular Biochemistry Springer US; http://www.springer-ny.com 405/1-2(2015-07-01), 205-221 0300-8177 405:1-2<205 2015 405 11010