title: The tumor suppressor gene RBM5 inhibits lung adenocarcinoma cell growth and induces apoptosis.
abstract: BACKGROUND
  The loss of tumor suppressor gene (TSG) function is a critical step in the pathogenesis of human lung cancer. RBM5 (RNA-binding motif protein 5, also named H37/LUCA-15) gene from chromosome 3p21.3 demonstrated tumor suppressor activity. However, the role of RBM5 played in the occurrence and development of lung cancer is still not well understood.
  
  
  METHODS
  Paired non-tumor and tumor tissues were obtained from 30 adenocarcinomas. The expression of RBM5 mRNA and protein was examined by RT-PCR and Western blot. A549 cell line was used to determine the apoptotic function of RBM5 in vitro. A549 cells were transiently transfected with pcDNA3.1-RBM5. AnnexinV analysis was performed by flow cytometry. Expression of Bcl-2, cleaved caspase-3, caspase-9 and PAPP proteins in A549 lung cancer cells and the A549 xenograft BALB/c nude mice model was determined by Western blot. Tumor suppressor activity of RBM5 was also examined in the A549 xenograft model treated with pcDNA3.1-RBM5 plasmid carried by attenuated Salmonella typhi Ty21a.
  
  
  RESULTS
  The expression of RBM5 mRNA and protein was decreased significantly in adenocarcinoma tissues compared to that in the non-tumor tissues. In addition, as compared to the vector control, a significant growth inhibition of A549 lung cancer cells was observed when transfected with pcDNA3.1-RBM5 as determined by cell proliferation assay. We also found that overexpression of RBM5 induced both early and late apoptosis in A549 cells using AnnexinV/PI staining as determined by flow cytometry. Furthermore, the expression of Bcl-2 protein was decreased, whereas the expression of cleaved caspase-3, caspase-9 and PARP proteins was significantly increased in the RBM5 transfected cells; similarly, expression of decreased Bcl-2 and increased cleaved caspase-3 proteins was also examined in the A549 xenograft model. More importantly, we showed that accumulative and stable overexpression of RBM5 in the A549 xenograft BALB/c nude mice model significantly inhibited the tumor growth rate in vivo as compared to that in the control.
  
  
  CONCLUSIONS
  Our study demonstrates that RBM5 can inhibit the growth of lung cancer cells and induce apoptosis both in vitro and in vivo, which suggests that RBM5 might be used as a potential biomarker or target for lung cancer diagnosis and chemotherapy. Moreover, we propose a novel animal model set up in BALB/c nude mice treated with attenuated Salmonella as a vector carrying plasmids to determine RBM5 function in vivo.
authors.affiliation: Department of Pathophysiology, Norman Bethune College of Medicine of Jilin University, Changchun, Jilin 130021, China.
authors.forename: Chen
authors.initials: C
authors.lastname: Shao
authors.forename: Lijing
authors.initials: L
authors.lastname: Zhao
authors.forename: Ke
authors.initials: K
authors.lastname: Wang
authors.forename: Wei
authors.initials: W
authors.lastname: Xu
authors.forename: Jie
authors.initials: J
authors.lastname: Zhang
authors.forename: Baoxue
authors.initials: B
authors.lastname: Yang
mesh_terms: D000230:Adenocarcinoma / Q000235:genetics* / Q000473:pathology; D000077192:Adenocarcinoma of Lung; D000818:Animals; D017209:Apoptosis; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000502:physiology; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000502:physiology; D016147:Genes, Tumor Suppressor; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics* / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D009368:Neoplasm Transplantation; D016601:RNA-Binding Proteins / Q000235:genetics* / Q000502:physiology; D012485:Salmonella typhi / Q000235:genetics; D014183:Transplantation, Heterologous; D025521:Tumor Suppressor Proteins / Q000235:genetics* / Q000502:physiology
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C473448:RBM5 protein, human; D016601:RNA-Binding Proteins; D025521:Tumor Suppressor Proteins