title: Silencing of osteopontin promotes the radiosensitivity of breast cancer cells by reducing the expression of hypoxia inducible factor 1 and vascular endothelial growth factor.
abstract: BACKGROUND
  Osteopontin (OPN) is a secreted phosphoglycoprotein (SSP) that is overexpressed in a variety of tumors and was regarded as a molecular marker of tumors. In this study, we intended to demonstrate the role of OPN in human breast cancer cell line MDA-MB-231.
  
  
  METHODS
  Recombinant plasmid expressing small interfering RNA (siRNA) specific to OPN mRNA was transfected into MDA-MB-231 cells to generate the stable transfected cell line MDA-MB-343, and the empty plasmid tansfected cells (MDA-MB-neg) or wildtype MDA-MB-231 cells were used as control cells respectively. Expression of OPN, hypoxia inducible factor-1 (HIF-1) and vascular endothelial growth factor (VEGF) proteins was analyzed by Western blotting analysis. The radiosensitivity of cells was determined by detecting cell apoptosis, cell proliferation and cell senescence.
  
  
  RESULTS
  HIF-1 and VEGF proteins in MDA-MB-343 cells were significantly downregulated upon the efficient knockdown of OPN expression under either hypoxia or normoxia environment. Moreover, expression of OPN protein was upregualted upon hypoxic culture. Stable OPN-silencing also decreased cell invasion, increased cell apoptosis and cell senescence, as well as reduced clonogenic survival, resulting in increase radiation tolerance.
  
  
  CONCLUSIONS
  Suppression of OPN gene expression can enhance radiosensitivity and affect cell apoptosis in breast cancer cells. OPN seems to be an attractive target for the improvement of radiotherapy.
authors.affiliation: Breast Cancer Center, Shandong Cancer Hospital & Institute, Jinan, Shandong 250117, China.
authors.forename: Li
authors.initials: L
authors.lastname: Yang
authors.forename: Wei
authors.initials: W
authors.lastname: Zhao
authors.forename: Wen-Shu
authors.initials: WS
authors.lastname: Zuo
authors.forename: Ling
authors.initials: L
authors.lastname: Wei
authors.forename: Xian-Rang
authors.initials: XR
authors.lastname: Song
authors.forename: Xing-Wu
authors.initials: XW
authors.lastname: Wang
authors.forename: Gang
authors.initials: G
authors.lastname: Zheng
authors.forename: Mei-Zhu
authors.initials: MZ
authors.lastname: Zheng
mesh_terms: D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000235:genetics; D006801:Humans; D051793:Hypoxia-Inducible Factor 1 / Q000235:genetics / Q000378:metabolism*; D053495:Osteopontin / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering; D011836:Radiation Tolerance / Q000235:genetics / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism*
chemical_list: D051793:Hypoxia-Inducible Factor 1; D034741:RNA, Small Interfering; D042461:Vascular Endothelial Growth Factor A; D053495:Osteopontin