Nrf2 is the key to chemotherapy resistance in MCF7 breast cancer cells under hypoxia
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Jhih-Pu Syu1, Jen-Tsan Chi2,3, Hsiu-Ni Kung1
1Department of Anatomy and Cell Biology, College of Medicine, National Taiwan University, Taipei, Taiwan
2Center for Genomic and Computational Biology, Duke University, Durham, NC, USA
3Department of Molecular Genetics & Microbiology, Duke University, Durham, NC, USA
Hsiu-Ni Kung, e-mail: [email protected]
Keywords: Nrf2, hypoxia, drug resistance, antioxidant activity, breast tumor
Received: September 02, 2015 Accepted: January 29, 2016 Published: February 15, 2016
Hypoxia leads to reactive oxygen species (ROS) imbalance, which is proposed to associate with drug resistance and oncogenesis. Inhibition of enzymes of antioxidant balancing system in tumor cells was shown to reduce chemoresistance under hypoxia. However, the underlying mechanism remains unknown. The key regulator of antioxidant balancing system is nuclear factor erythroid 2-related factor 2 (NFE2L2, Nrf2). In this study, we showed that hypoxia induced ROS production and increased the Nrf2 activity. Nrf2 activation increased levels of its downstream target antioxidant enzymes, including GCLC and GCLM. The Nrf2-overexpressing also confers chemo-resistant MCF7 cells under normoxia. The in vivo mouse model also demonstrated that the chemical inhibition of Nrf2 can increase cisplatin (CDDP) cytotoxicity. Together, these results showed that Nrf2 serves as a key regulator in chemotherapeutic resistance under hypoxia through ROS-Nrf2-GCLC-GSH pathway. Therefore, targeting Nrf2 can be a potential treatment for hypoxia-induced drug resistance in breast cancer cells.
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