title: Protein phosphatase 2A-B55δ enhances chemotherapy sensitivity of human hepatocellular carcinoma under the regulation of microRNA-133b.
abstract: BACKGROUND
  Hepatocellular carcinoma (HCC) remains a major public health problem worldwide. The identification of effective chemotherapeutic targets for advanced HCC patients is urgently required. In this study, we investigated the role of protein phosphatase 2A-B55δ subunit (PP2A-B55δ, encoded by the PPP2R2D gene) and related mechanisms affecting chemotherapy sensitivity of HCC.
  
  
  METHODS
  Experimental approaches for measuring the levels of PPP2R2D mRNA and B55δ protein in HCC included bioinformatics analyses, quantitative real-time polymerase chain reaction (qRT-PCR), western blotting (WB), immunofluorescence and immunohistochemistry assays. Cell cycle, migration, colony formation, apoptosis, and cell proliferation assays in stable PPP2R2D-knockdown and -overexpression cell lines in vitro, and tumorigenicity assays in vivo, were performed to explore the function of B55δ in cisplatin (cDDP) chemotherapy of HCC. Bioinformatics prediction, luciferase reporter assays, qRT-PCR, WB, and cell cycle analyses were used to reveal the regulatory relationship between microRNA-133b (miR-133b) and PPP2R2D expression. miR-133b mimic and inhibitor were used to elucidate the regulatory mechanism.
  
  
  RESULTS
  Our studies showed that PPP2R2D expression was down-regulated in both HCC tumors and HCC cell lines. Treatment with cDDP increased the amount of B55δ protein. Artificially increasing the expression of B55δ counteracted cyclin-dependent kinase 1 activation, modulated transitions of the cell cycle, and increased the suppressive effect of cDDP on cell migration, colony formation, apoptosis, and proliferation in vitro and tumor growth in vivo, thus enhancing therapeutic efficiency. In contrast, knockdown of B55δ partially inhibited the effect of cDDP chemotherapy. miR-133b was shown to regulate PPP2R2D expression by binding to the 3'-untranslated region of PPP2R2D mRNA. The miR-133b/PPP2R2D signaling pathway affects the effectiveness of cDDP chemotherapy.
  
  
  CONCLUSIONS
  PP2A-B55δ, regulated by miR-133b, enhances the sensitivity of HCC to cDDP chemotherapy. Our data indicate that PP2A-B55δ might be a novel and attractive target for increasing chemotherapy sensitivity of HCC.
authors.affiliation: State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, School of Public Health, Xiamen University, Xiang'an South Rd., Xiamen, Fujian, 361102, PR China.
authors.forename: Qunying
authors.initials: Q
authors.lastname: Zhuang
authors.affiliation: State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, School of Public Health, Xiamen University, Xiang'an South Rd., Xiamen, Fujian, 361102, PR China.
authors.forename: Tengjian
authors.initials: T
authors.lastname: Zhou
authors.affiliation: State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, School of Public Health, Xiamen University, Xiang'an South Rd., Xiamen, Fujian, 361102, PR China.
authors.forename: Chengyong
authors.initials: C
authors.lastname: He
authors.affiliation: State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, School of Public Health, Xiamen University, Xiang'an South Rd., Xiamen, Fujian, 361102, PR China.
authors.forename: Shili
authors.initials: S
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, School of Public Health, Xiamen University, Xiang'an South Rd., Xiamen, Fujian, 361102, PR China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Qiu
authors.affiliation: State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, School of Public Health, Xiamen University, Xiang'an South Rd., Xiamen, Fujian, 361102, PR China.
authors.forename: Bing
authors.initials: B
authors.lastname: Luo
authors.affiliation: State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, School of Public Health, Xiamen University, Xiang'an South Rd., Xiamen, Fujian, 361102, PR China.
authors.forename: Ran
authors.initials: R
authors.lastname: Zhao
authors.affiliation: State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, School of Public Health, Xiamen University, Xiang'an South Rd., Xiamen, Fujian, 361102, PR China.
authors.forename: Hengchuan
authors.initials: H
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, School of Public Health, Xiamen University, Xiang'an South Rd., Xiamen, Fujian, 361102, PR China. linych@xmu.edu.cn.
authors.forename: Yuchun
authors.initials: Y
authors.lastname: Lin
authors.affiliation: State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, School of Public Health, Xiamen University, Xiang'an South Rd., Xiamen, Fujian, 361102, PR China. linzhn@xmu.edu.cn.
authors.forename: Zhongning
authors.initials: Z
authors.lastname: Lin
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage* / Q000494:pharmacology; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D002945:Cisplatin / Q000008:administration & dosage* / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D056945:Hep G2 Cells; D006801:Humans; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000235:genetics; D051379:Mice; D035683:MicroRNAs / Q000235:genetics*; D054648:Protein Phosphatase 2 / Q000235:genetics* / Q000378:metabolism*; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; C548234:MIRN133 microRNA, human; D035683:MicroRNAs; C525687:PPP2R2D protein, human; D054648:Protein Phosphatase 2; D002945:Cisplatin
keywords: B55δ; Chemotherapy sensitivity; Cisplatin; Hepatocellular carcinoma; PP2A; microRNA-133b