title: Reversal of multidrug resistance in gastric cancer cells by E2F-1 downregulation in vitro and in vivo.
abstract: Transcription Factor E2F-1 plays a critical role in cell cycle regulation and other biological processes in cells. However whether or not it is involved in the multi-drug resistance (MDR) process of gastric cancer has not been fully elucidated yet. To explore the role of E2F-1 in the MDR process of gastric cancer in vitro and in vivo, a cisplatin-resistant gastric cancer cell line with stable downregulation of E2F-1 was established. E2F-1 shRNA led to downregulation of endogenous E2F-1 mRNA and protein. It significantly promoted the sensitivity of SGC7901/DDP cells to cisplatin, doxorubicin, and fluorouracil. Flow cytometry confirmed that the percentage of apoptotic cells increased after E2F-1 downregulation. This notion was further supported by the observation that downregulation of E2F-1 blocked entry into the S-phase of the cell cycle. Furthermore, downregulation of E2F-1 significantly increased intracellular accumulation of doxorubicin. In addition, we determined the in vivo effects of E2F-1 small interfering RNA (shRNA) on tumor size, and apoptotic cells in tumor tissues were detected by deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling and hematoxylin and eosin staining. In molecular studies, semiquantitative RT-PCR and western blotting revealed that E2F-1 downregulation could inhibit expression of MDR1, MRP, Bcl-2/Bax, c-Myc, Skp2, Survivin, and Cyclin D1.
  
  
  CONCLUSIONS
  E2F-1 may be involved in regulating multiple signaling pathways in reversing MDR, suggesting that E2F-1 may represent a novel target for gastric cancer therapy.
authors.affiliation: Department of Surgery, The First Affiliated Hospital of Guangxi Medical University, Nanning, 530021, Guangxi Zhuang Autonomous Region, China.
authors.forename: Lin-Hai
authors.initials: LH
authors.lastname: Yan
authors.forename: Xiao-Tong
authors.initials: XT
authors.lastname: Wang
authors.forename: Jie
authors.initials: J
authors.lastname: Yang
authors.forename: Fan-Biao
authors.initials: FB
authors.lastname: Kong
authors.forename: Chao
authors.initials: C
authors.lastname: Lian
authors.forename: Wei-Yuan
authors.initials: WY
authors.lastname: Wei
authors.forename: Wen
authors.initials: W
authors.lastname: Luo
authors.forename: Yu-Bo
authors.initials: YB
authors.lastname: Xie
authors.forename: Qiang
authors.initials: Q
authors.lastname: Xiao
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000494:pharmacology; D019938:Cyclin D1 / Q000235:genetics; D015536:Down-Regulation / Q000187:drug effects; D004317:Doxorubicin / Q000494:pharmacology; D018432:Drug Resistance, Multiple / Q000187:drug effects / Q000235:genetics; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000235:genetics; D050687:E2F1 Transcription Factor / Q000235:genetics* / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D016259:Genes, myc; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000235:genetics; D008297:Male; D051379:Mice; D008819:Mice, Nude; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D044786:S-Phase Kinase-Associated Proteins / Q000235:genetics; D013274:Stomach Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D000077022:Survivin
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000970:Antineoplastic Agents; C107489:BIRC5 protein, human; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D051034:Inhibitor of Apoptosis Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D044786:S-Phase Kinase-Associated Proteins; D000077022:Survivin; D019938:Cyclin D1; D004317:Doxorubicin; D002945:Cisplatin
keywords: E2F-1 TRANSCRIPTION FACTOR; GASTRIC CANCER; MULTIDRUG RESISTANCE; MURINE MODEL; RNA INTERFERENCE