title: [Down-regulation of TopI by RNA interference reduces the drug-sensitivity of small cell lung cancer cell lines to topotecan].
abstract: OBJECTIVE
  To investigate the expressions of TopI gene in small cell lung cancer cell line H446, and explore the influence of TopI on the chemosensitivity of the cell line to topotecan (TPT).
  
  
  METHODS
  Western blot was performed to detect the TopI expression in H446 cells. Lipofectamine 2000 was used for the transient transfection of H446 cells by siRNA, and the transfection efficacy was detected. TopI mRNA was analyzed by quantitative RT-PCR and TopI protein was detected by Western blot to selected effective siRNA. The drug-sensitivity to topotecan (TPT) was evaluated by MTT assay.
  
  
  RESULTS
  TopI gene was expressed in H446 cells. Lipofectamine 2000 mediated the siRNA effectively (88.67%). Compared with its parental cells, RT-PCR results showed that TopI mRNAs in transfected cells were reduced by (95.7 +/- 1.6)%, (90.8 +/- 1.6)%, (96.1 +/- 2.7)% and (96.3 +/- 1.8)%, respectively, and decreased significantly at protein level. By MTT assay, the inhibition rate of TPT to H446 cells transfected by siRNA was lower than that of control group at same concentrations (P < 0.01).
  
  
  CONCLUSIONS
  siRNAs can silence the expression of TopI and decrease the drug-sensitivity of H446 cells to TPT.
authors.affiliation: Department of Chemotherapy, Shandong Tumor Hospital, Jinan 250117, China.
authors.forename: Xiu-ju
authors.initials: XJ
authors.lastname: Liu
authors.forename: Qi-sen
authors.initials: QS
authors.lastname: Guo
authors.forename: Qiong
authors.initials: Q
authors.lastname: Zhang
authors.forename: Xian-rang
authors.initials: XR
authors.lastname: Song
authors.forename: Yong-lei
authors.initials: YL
authors.lastname: Liu
authors.forename: Chen
authors.initials: C
authors.lastname: Guo
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004264:DNA Topoisomerases, Type I / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation; D019008:Drug Resistance, Neoplasm; D006801:Humans; D008175:Lung Neoplasms / Q000378:metabolism / Q000473:pathology*; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics*; D055752:Small Cell Lung Carcinoma / Q000378:metabolism / Q000473:pathology; D019772:Topotecan / Q000494:pharmacology*; D014162:Transfection
chemical_list: D000970:Antineoplastic Agents; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D019772:Topotecan; D004264:DNA Topoisomerases, Type I