title: Silencing of heat shock protein 70 expression enhances radiotherapy efficacy and inhibits cell invasion in endometrial cancer cell line.
abstract: OBJECTIVE
  To investigate the role of heat shock proteins 70 (HSP70) in radiosensitivity and invasiveness of endometrial cancer in vitro.
  
  
  METHODS
  HSP70 expression was silenced in relatively radioresistant, well-differentiated human endometrial cancer cell line ISK, using small interference RNA method, or by HSP70 overexpression after transfecting a HSP70-expressing vector. The effect of HSP70 on ISK cell line response to irradiation was evaluated. The surviving fraction was measured using colony-formation assay. Apoptosis was detected by flow cytometry and HSP70 expression was determined by quantitative real-time polymerase chain reaction, western-blot, and/or immunocytochemistry. Cell invasiveness was measured using transwell invasion assay.
  
  
  RESULTS
  HSP70 silencing caused a significant increase in irradiation-induced cell killing in comparison with control cells, with an enhancement factor of 1.27, and in the percentage of apoptotic cells (14.22% vs 6.74%, P = 0.021). After 4 Gy irradiation, mean +/- standard deviation survival fraction in ISK cells was reduced to 0.32 +/- 0.04 in comparison with control values but in ISK/siRNA-HSP70 cells the survival fraction was higher and amounted to 0.51 +/- 0.08 (P = 0.026). Silencing HSP70 significantly inhibited cell invasion before and after irradiation (106 +/- 19 vs 219 +/- 18 and 119 +/- 16 vs 256 +/- 31, P = 0.007). On the contrary, ectopic overexpression of HSP70 attenuated irradiation-induced apoptosis (7.15% vs 4.08%, P = 0.043) and induced more ISK/HSP70 cells invaded through the filters than mock-infected cells before and after irradiation (274 +/- 21 vs 194 +/- 16 before irradiation, and 298 +/- 24 vs 227 +/- 19 after irradiation, respectively, P = 0.032).
  
  
  CONCLUSIONS
  Disruption of HSP70-induced cytoprotection during irradiation enhances therapeutic effect of irradiation, which makes HSP70 a promising target in the research of endometrial cancer.
authors.affiliation: Department of Gynecologic Oncology, Shandong Tumor Hospital, Shandong University, No. 440, Jiyan Road, Jinan, China 250117. melody23800@yahoo.com.cn
authors.forename: Xue-lian
authors.initials: XL
authors.lastname: Du
authors.forename: Tao
authors.initials: T
authors.lastname: Jiang
authors.forename: Ze-qing
authors.initials: ZQ
authors.lastname: Wen
authors.forename: Rong
authors.initials: R
authors.lastname: Gao
authors.forename: Min
authors.initials: M
authors.lastname: Cui
authors.forename: Fei
authors.initials: F
authors.lastname: Wang
mesh_terms: D000704:Analysis of Variance; D017209:Apoptosis / Q000235:genetics / Q000502:physiology; D015153:Blotting, Western; D045744:Cell Line, Tumor / Q000378:metabolism / Q000528:radiation effects*; D002470:Cell Survival / Q000528:radiation effects; D016889:Endometrial Neoplasms / Q000235:genetics / Q000378:metabolism / Q000532:radiotherapy*; D005260:Female; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D011336:Probability; D012333:RNA, Messenger / Q000032:analysis; D011829:Radiation Dosage; D011836:Radiation Tolerance / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D014162:Transfection
chemical_list: D018840:HSP70 Heat-Shock Proteins; D012333:RNA, Messenger