title: Overexpression of E2F1 in human gastric carcinoma is involved in anti-cancer drug resistance.
abstract: BACKGROUND
  Routine chemotherapy often cannot achieve good therapeutic effects because of multidrug resistance (MDR). MDR is frequently caused by the elevated expression of the MDR1 gene encoding P-glycoprotein (P-gp). E2F1 is a frequently overexpressed protein in human tumor cells that increases the activity of the MDR1 promoter, resulting in higher P-gp levels. The upregulation of P-gp might contribute to the survival of tumor cells during chemotherapy. E2F1 confers anticancer drug resistance; however, we speculate whether E2F1 affects MDR through other pathways. This study investigated the possible involvement of E2F1 in anticancer drug resistance of gastric carcinoma in vitro and in vivo.
  
  
  METHODS
  A cisplatin-resistant SGC7901/DDP gastric cancer cell line with stable overexpression of E2F1 was established. Protein expression levels of E2F1, MDR1, MRP, TAp73, GAX, ZEB1, and ZEB2 were detected by western blotting. The influence of overexpression of E2F1 on anticancer drug resistance was assessed by measuring IC50 of SGC7901/DDP cells to cisplatin, doxorubicin, and 5-fluorouracil, as well as the rate of doxorubicin efflux, apoptosis, and cell cycle progression detected by flow cytometry. We determined the in vivo effects of E2F1-overexpression on tumor size in nude mice, and apoptotic cells in tumor tissues were detected by deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling and hematoxylin and eosin staining.
  
  
  RESULTS
  The SGC7901/DDP gastric cancer cell line stably overexpressing E2F1 exhibited significantly inhibited sensitivity to cisplatin, doxorubicin, and 5-fluorouracil. Flow cytometry confirmed that the percentage of apoptotic cells decreased after E2F1 upregulation, and that upregulation of E2F1 potentiated S phase arrest of the cell cycle. Furthermore, upregulation of E2F1 significantly decreased intracellular accumulation of doxorubicin. Western blot revealed that E2F1 upregulation suppressed expression of GAX, and increased the expression of MDR1, MRP, ZEB1, TAp73, and ZEB2.
  
  
  CONCLUSIONS
  Overexpression of E2F1 promotes the development of MDR in gastric carcinoma, suggesting that E2F1 may represent an efficacious target for gastric cancer therapy.
authors.forename: Lin-Hai
authors.initials: LH
authors.lastname: Yan
authors.forename: Wei-Yuan
authors.initials: WY
authors.lastname: Wei
authors.forename: Wen-Long
authors.initials: WL
authors.lastname: Cao
authors.forename: Xiao-Shi
authors.initials: XS
authors.lastname: Zhang
authors.forename: Yu-Bo
authors.initials: YB
authors.lastname: Xie
authors.affiliation: Department of Surgery, The First Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi Zhuang Autonomous Region 530021, China. xiaoqiang20050@aliyun.com.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Xiao
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000235:genetics / Q000378:metabolism; D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000493:pharmacokinetics; D000970:Antineoplastic Agents / Q000627:therapeutic use; D017209:Apoptosis; D002277:Carcinoma / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000627:therapeutic use; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004317:Doxorubicin / Q000493:pharmacokinetics; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D050687:E2F1 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D020128:Inhibitory Concentration 50; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D013274:Stomach Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D000072160:Tumor Protein p73; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation; D000074165:Zinc Finger E-box Binding Homeobox 2; D000071799:Zinc Finger E-box-Binding Homeobox 1
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D000903:Antibiotics, Antineoplastic; D000970:Antineoplastic Agents; D002945:Cisplatin; D004268:DNA-Binding Proteins; D004317:Doxorubicin; D050687:E2F1 Transcription Factor; D018398:Homeodomain Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009687:Nuclear Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; D000072160:Tumor Protein p73; D025521:Tumor Suppressor Proteins; D000074165:Zinc Finger E-box Binding Homeobox 2; D000071799:Zinc Finger E-box-Binding Homeobox 1; C513055:ABCB1 protein, human; C493753:E2F1 protein, human; C484193:MEOX2 protein, human; C000606368:Trp73 protein, mouse; C486307:ZEB1 protein, human; C492363:ZEB2 protein, human; C421109:multidrug resistance-associated protein 1