The tumor suppressor interferon regulatory factor 8 inhibits β-catenin signaling in breast cancers, but is frequently silenced by promoter methylation
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Xinrong Luo1,2,*, Xin Xiong1,*, Qing Shao1, Tingxiu Xiang1, Lili Li3, Xuedong Yin1,2, Xia Li1, Qian Tao1,3 and Guosheng Ren1,2
1Chongqing Key Laboratory of Molecular Oncology and Epigenetics, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
2Department of Endocrine and Breast Surgery, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
3Cancer Epigenetics Laboratory, Department of Clinical Oncology, State Key Laboratory of Oncology in South China, Sir YK Pao Center for Cancer and Li Ka Shine Institute of Health Sciences, The Chinese University of Hong Kong and CUHK Shenzhen Research Institute, Shatin, Hong Kong
*These authors contributed equally to this work
Qian Tao, email: email@example.com
Guosheng Ren, email: firstname.lastname@example.org
Keywords: interferon regulatory factor 8, methylation, tumor suppressor, breast cancer, β-catenin
Received: August 11, 2016 Accepted: March 13, 2017 Published: March 23, 2017
Interferon (IFN) regulatory factor 8 is encoded by a novel candidate tumor suppressor gene (IRF8), its promotor is frequently methylated in multiple cancers. However, the promoter methylation status, functions and underlying mechanisms of IRF8 in breast cancer remain unclear. We found that IRF8 was downregulated in breast cancer cell lines and primary tumors, compared with normal breast tissues, mainly because of aberrant promoter methylation. However, its expression was not associated with pathological characteristics. Restoration of IRF8 expression suppressed cell proliferation, colony formation, 5-ethynyl-2'-deoxyuridine incorporation, cell migration and invasion, and induced apoptosis and cell cycle arrest in vitro. IRF8 also inhibited xenograft growth in nude mice in vivo. Competition with IRF8 function by IRF8 mutant (K79E) enhanced cell migration and invasion in 4T1 murine cells in vitro. Importantly, IRF8, as both downstream target gene and regulator of IFN-γ/STAT1 signaling, inhibited canonical β-catenin signaling. These findings identify IRF8 as a novel tumor suppressor regulating IFN-γ/STAT1 signaling and β-catenin signaling in breast cancer.
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