Silencing of heat shock protein 70 expression enhances radiotherapy efficacy and inhibits cell invasion in endometrial cancer cell line

• Published in: Croatian medical journal 2009-04, Vol.50 (2), p.143-150
• Main Authors: Du, Xue-lian, Jiang, Tao, Wen, Ze-qing, Gao, Rong, Cui, Min, Wang, Fei
• Format: Article
• Language: English
• Subjects: Analysis of Variance; Apoptosis; Apoptosis - genetics; Apoptosis - physiology; Blotting, Western; Care and treatment; Cell Line, Tumor - metabolism; Cell Line, Tumor - radiation effects; Cell Survival - radiation effects; Clinical Science; Endometrial cancer; Endometrial Neoplasms - genetics; Endometrial Neoplasms - metabolism; Endometrial Neoplasms - radiotherapy; Female; Flow Cytometry; Gene expression; Gene Expression Regulation, Neoplastic; Gene Silencing; Health aspects; Heat shock proteins; HSP70 Heat-Shock Proteins - genetics; HSP70 Heat-Shock Proteins - metabolism; Humans; Physiological aspects; Probability; Radiation Dosage; Radiation Tolerance - genetics; Radiotherapy; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - analysis; Sensitivity and Specificity; Transfection
• ISSN: 0353-9504; 1332-8166
• DOI: 10.3325/cmj.2009.50.143

To investigate the role of heat shock proteins 70 (HSP70) in radiosensitivity and invasiveness of endometrial cancer in vitro. 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. 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). Disruption of HSP70-induced cytoprotection during irradiation enhances therapeutic effect of irradiation, which makes HSP70 a promising target in the research of endometrial cancer.