title: Silencing of human phosphatidylethanolamine-binding protein 4 sensitizes breast cancer cells to tumor necrosis factor-alpha-induced apoptosis and cell growth arrest.
abstract: OBJECTIVE
  The current therapeutic approach is not so effective in breast cancer patients. Alternative treatment protocols aimed at different targets need to be explored. We recently reported a novel phosphatidylethanolamine-binding protein, human phosphatidylethanolamine-binding protein 4 (hPEBP4), as an antiapoptotic molecule. The finding led us to explore a promising approach for breast cancer therapy via silencing the expression of hPEBP4.
  
  
  METHODS
  hPEBP4 expression in clinical breast specimens was examined by Tissue Microarrays. RNA interference was used to silence hPEBP4 expression in MCF-7 breast carcinoma cells and the effects on cell proliferation, cell cycle progression, apoptosis, as well as underlying mechanisms, were investigated.
  
  
  RESULTS
  hPEBP4 was found to be expressed in up to 50% of breast cancers but in only <4% of normal breast tissues. Silencing of hPEBP4 potentiated tumor necrosis factor-alpha (TNF-alpha)-induced apoptosis and cell cycle arrest in MCF-7 cells, which was due to the increased mitogen-activated protein kinase activation and the enhanced phosphatidylethanolamine externalization. Further investigation showed that silencing of hPEBP4 in MCF-7 cells promoted TNF-alpha-induced stability of p53, up-regulation of phospho-p53ser15, p21waf/cip, and Bax, and down-regulation of Bcl-2 and Bcl-xL, which were shown to depend on extracellular signal-regulated kinase 1/2 and c-jun NH2-terminal kinase activation by hPEBP4 silencing. Moreover, the increased proportion of cells in the G0-G1 phase of cell cycle was observed in hPEBP4-silenced MCF-7 cells on TNF-alpha treatment and the expression of cyclin A and cyclin E was down-regulated more significantly.
  
  
  CONCLUSIONS
  The antiapoptotic effect and the preferential expression pattern in breast cancer tissues make hPEBP4 a new target for breast cancer therapy. Silencing of hPEBP4 expression may be a promising approach for the treatment of breast carcinoma.
authors.affiliation: Institute of Immunology, Zhejiang University, Hangzhou, PR China.
authors.forename: Xiaojian
authors.initials: X
authors.lastname: Wang
authors.forename: Nan
authors.initials: N
authors.lastname: Li
authors.forename: Hongzhe
authors.initials: H
authors.lastname: Li
authors.forename: Bin
authors.initials: B
authors.lastname: Liu
authors.forename: Jianming
authors.initials: J
authors.lastname: Qiu
authors.forename: Taoyong
authors.initials: T
authors.lastname: Chen
authors.forename: Xuetao
authors.initials: X
authors.lastname: Cao
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D019925:Cyclin A / Q000378:metabolism; D019927:Cyclin E / Q000378:metabolism; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D049488:Phosphatidylethanolamine Binding Protein / Q000235:genetics* / Q000378:metabolism; D011485:Protein Binding; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D019925:Cyclin A; D019927:Cyclin E; D049488:Phosphatidylethanolamine Binding Protein; D014409:Tumor Necrosis Factor-alpha; D016159:Tumor Suppressor Protein p53; D019908:Proto-Oncogene Proteins c-raf; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases