title: E2/ERβ Inhibits PPARα to Regulate Cell-Proliferation and Enhance Apoptosis in Hep3B-Hepatocellular Carcinoma.
abstract: Peroxisome proliferator-activated receptor-α (PPARα) is a member of the nuclear receptor superfamily involved in hepatocarcinogenesis in rodents. In previous studies on liver tumor tissues, PPARα mRNA expression was found to be significantly higher and overexpression of ERα inhibited the PPARα expression, cell-proliferation and also induced apoptosis in Hep3B cell. However, the role of ERβ is not known yet. Therefore, the aim of this study is to define the role of ERβ on PPARα in Hep3B cells. The effect of PPARα signaling cascade were monitored by inducing Hep3B cells by fenofibrate. Further the cells were transfected with pCMV-ERβ and the consequences of ERβ-overexpression on the PPARα induced changes such as enhanced cell-proliferation and suppressed apoptosis were determined using western blot analysis and TUNEL assay. The EMSA was used to identify whether ERβ modulates PPARα expression by binding to PPARα promoter region to repress PPARα promoter activity. In addition, the direct interaction between ERβ and PPARα proteins was verified by co-immunoprecipitation assay. Our results show that the overexpressed ERβ not only attenuated the effects of fenofibrate to induce the levels of apoptosis protein such as Cyt.c, Caspase 9 and Caspase 3 but also inhibited the levels of survival protein such Bcl-xL, p-Bad, cyclin A and cyclin E. All these effects of E2/ERβ resulted in the enhancement of mitochondria dependent apoptotic pathway and the attenuation of cell proliferation. Moreover, the overexpressed ERβ reduced the mRNA and protein levels of PPARα and its downstream Acyl-CoA oxidase (ACO). EMSA results show that ERβ directly binds to PPRE and inhibit PPARα gene expression and according to immunoprecipitation assay ERβ also binds strongly with PPARα. The E2/ERβ further inhibited the fenofibrate-induced nuclear translocation of PPARα. Taken together, ERβ might directly downregulate PPARα gene expression and inhibit the nuclear translocation to suppress the proliferation and induce the apoptosis of Hep3B cells.
authors.affiliation: Department of Healthcare Administration, Asia University, Taichung, 413, Taiwan.
authors.forename: Shu Nu
authors.initials: SN
authors.lastname: Chang-Lee
authors.affiliation: Division of Colorectal Surgery, Mackay Memorial Hospital, Taipei, 104, Taiwan.|Mackay Medicine, Nursing and Management College, Taipei, 11260, Taiwan.
authors.forename: Hsi-Hsien
authors.initials: HH
authors.lastname: Hsu
authors.affiliation: Graduate Institute of Basic Medical Science, China Medical University, Taichung, 404, Taiwan.
authors.forename: Marthandam Asokan
authors.initials: MA
authors.lastname: Shibu
authors.affiliation: Graduate Institute of Chinese Medicine, China Medical University, Taichung, 404, Taiwan.|Chinese Medicine Department, China Medical University Beigang Hospital, Yunlin, 651, Taiwan.
authors.forename: Tsung-Jung
authors.initials: TJ
authors.lastname: Ho
authors.affiliation: Graduate Institute of Basic Medical Science, China Medical University, Taichung, 404, Taiwan.
authors.forename: Chih-Hao
authors.initials: CH
authors.lastname: Tsai
authors.affiliation: Division of Colorectal Surgery, Taichung Veterans General Hospital, Taichung, 407, Taiwan.
authors.forename: Ming-Cheng
authors.initials: MC
authors.lastname: Chen
authors.affiliation: Division of Chest Medicine, Department of Internal Medicine, Taichung Armed Force General Hospital, Taichung, 411, Taiwan.
authors.forename: Chuan-Chou
authors.initials: CC
authors.lastname: Tu
authors.affiliation: Department of Biotechnology, Bharathiar University, Coimbatore, 641046, India.
authors.forename: Vijaya Padma
authors.initials: VP
authors.lastname: Viswanadha
authors.affiliation: Department of Biological Science and Technology, China Medical University, Taichung, 402, Taiwan.
authors.forename: Wei- Wen
authors.initials: WW
authors.lastname: Kuo
authors.affiliation: Graduate Institute of Basic Medical Science, China Medical University, Taichung, 404, Taiwan. cyhuang@mail.cmu.edu.tw.|Graduate Institute of Chinese Medicine, China Medical University, Taichung, 404, Taiwan. cyhuang@mail.cmu.edu.tw.|Department of Health and Nutrition Biotechnology, Asia University, Taichung, 413, Taiwan. cyhuang@mail.cmu.edu.tw.
authors.forename: Chih-Yang
authors.initials: CY
authors.lastname: Huang
mesh_terms: D000071443:12E7 Antigen / Q000235:genetics*; D017209:Apoptosis / Q000235:genetics*; D006528:Carcinoma, Hepatocellular / Q000235:genetics* / Q000473:pathology; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000235:genetics; D049109:Cell Proliferation / Q000235:genetics*; D015536:Down-Regulation / Q000235:genetics; D047629:Estrogen Receptor beta / Q000235:genetics*; D015870:Gene Expression / Q000235:genetics; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics* / Q000473:pathology; D047493:PPAR alpha / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics; D015398:Signal Transduction / Q000235:genetics; D014178:Translocation, Genetic / Q000235:genetics
chemical_list: D000071443:12E7 Antigen; D047629:Estrogen Receptor beta; D047493:PPAR alpha
keywords: Estrogen; Estrogen receptor, peroxisome proliferator-activated receptor; Hepatocellular carcinoma