title: Decreased expression of long noncoding RNA GAS5 indicates a poor prognosis and promotes cell proliferation in gastric cancer.
abstract: BACKGROUND
  Gastric cancer is the second leading cause of cancer death and remains a major clinical challenge due to poor prognosis and limited treatment options. Long noncoding RNAs (lncRNAs) have emerged recently as major players in tumor biology and may be used for cancer diagnosis, prognosis, and potential therapeutic targets. Although downregulation of lncRNA GAS5 (Growth Arrest-Specific Transcript) in several cancers has been studied, its role in gastric cancer remains unknown. Our studies were designed to investigate the expression, biological role and clinical significance of GAS5 in gastric cancer.
  
  
  METHODS
  Expression of GAS5 was analyzed in 89 gastric cancer tissues and five gastric cancer cell lines by quantitative reverse-transcription polymerase chain reaction (qRT-PCR). Over-expression and RNA interference (RNAi) approaches were used to investigate the biological functions of GAS5. The effect of GAS5 on proliferation was evaluated by MTT and colony formation assays, and cell apoptosis was evaluated by hochest stainning. Gastric cancer cells transfected with pCDNA3.1 -GAS5 were injected into nude mice to study the effect of GAS5 on tumorigenesis in vivo. Protein levels of GAS5 targets were determined by western blot analysis. Differences between groups were tested for significance using Student's t-test (two-tailed).
  
  
  RESULTS
  We found that GAS5 expression was markedly downregulated in gastric cancer tissues, and associated with larger tumor size and advanced pathologic stage. Patients with low GAS5 expression level had poorer disease-free survival (DFS; P = 0.001) and overall survival (OS; P < 0.001) than those with high GAS5 expression. Further multivariable Cox regression analysis suggested that decreased GAS5 was an independent prognostic indicator for this disease (P = 0.006, HR = 0.412; 95%CI = 2.218-0.766). Moreover, ectopic expression of GAS5 was demonstrated to decrease gastric cancer cell proliferation and induce apoptosis in vitro and in vivo, while downregulation of endogenous GAS5 could promote cell proliferation. Finally, we found that GAS5 could influence gastric cancer cells proliferation, partly via regulating E2F1 and P21 expression.
  
  
  CONCLUSIONS
  Our study presents that GAS5 is significantly downregulated in gastric cancer tissues and may represent a new marker of poor prognosis and a potential therapeutic target for gastric cancer intervention.
authors.forename: Ming
authors.initials: M
authors.lastname: Sun
authors.forename: Fei-yan
authors.initials: FY
authors.lastname: Jin
authors.forename: Rui
authors.initials: R
authors.lastname: Xia
authors.forename: Rong
authors.initials: R
authors.lastname: Kong
authors.forename: Jin-hai
authors.initials: JH
authors.lastname: Li
authors.forename: Tong-peng
authors.initials: TP
authors.lastname: Xu
authors.forename: Yan-wen
authors.initials: YW
authors.lastname: Liu
authors.forename: Er-bao
authors.initials: EB
authors.lastname: Zhang
authors.affiliation: Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing 210029, People's Republic of China. liuxianghua@njmu.edu.cn.
authors.forename: Xiang-hua
authors.initials: XH
authors.lastname: Liu
authors.forename: Wei
authors.initials: W
authors.lastname: De
mesh_terms: D000818:Animals; D017209:Apoptosis; D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D016009:Chi-Square Distribution; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D018572:Disease-Free Survival; D015536:Down-Regulation; D050687:E2F1 Transcription Factor / Q000378:metabolism; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D008875:Middle Aged; D015999:Multivariate Analysis; D009367:Neoplasm Staging; D016016:Proportional Hazards Models; D034622:RNA Interference; D062085:RNA, Long Noncoding / Q000235:genetics / Q000378:metabolism*; D013274:Stomach Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000401:mortality / Q000473:pathology; D013997:Time Factors; D014162:Transfection; D047368:Tumor Burden
chemical_list: D014408:Biomarkers, Tumor; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; C561567:GAS5 long non-coding RNA, human; D062085:RNA, Long Noncoding