title: MiR-467a is upregulated in radiation-induced mouse thymic lymphomas and regulates apoptosis by targeting Fas and Bax.
abstract: It has been reported dysregulation of certain microRNAs (miRNAs / miRs) is involved in tumorigenesis. However, the miRNAs associated with radiocarcinogenesis remain undefined. In this study, we validated the upregulation of miR-467a in radiation-induced mouse thymic lymphoma tissues. Then, we investigated whether miR-467a functions as an oncogenic miRNA in thymic lymphoma cells. For this purpose, we assessed the biological effect of miR-467a on thymic lymphoma cells. Using miRNA microarray, we found four miRNAs (miR-467a, miR-762, miR-455 and miR-714) were among the most upregulated (>4-fold) miRNAs in tumor tissues. Bioinformatics prediction suggests miR-467a may potentially regulate apoptosis pathway via targeting Fas and Bax. Consistently, in miR-467a-transfected cells, both proliferation and colony formation ability were significantly increased with decrease of apoptosis rate, while, in miR-467a-knockdown cells, proliferation was suppressed with increase of apoptosis rate, indicating that miR-467a may be involved in the regulation of apoptosis. Furthermore, miR-467a-knockdown resulted in smaller tumors and better prognosis in an in vivo tumor-transplanted model. To explain the mechanism of apoptosis suppression by miR-467a, we explore the expression of candidate target genes (Fas and Bax) in miR-467a-transfected relative to negative control transfected cells using flow cytometry and immunoblotting. Fas and Bax were commonly downregulated in miR-467a-transfected EL4 and NIH3T3 cells, and all of the genes harbored miR-467a target sequences in the 3'UTR of their mRNA. Fas and Bax were actually downregulated in radiation-induced thymic lymphoma tissues, and therefore both were identified as possible targets of miR-467a in thymic lymphoma. To ascertain whether downregulation of Fas and / or Bax is involved in apoptosis suppression by miR-467a, we transfected vectors expressing Fas and Bax into miR-467a-upregulated EL4 cells. Then we found that both Fas- and Bax-overexpression decreased cell viability with increase of apoptosis rate, indicating that downregulation of Fas and Bax may be at least partly responsible for apoptosis suppression by miR-467a. These data suggest that miR-467a may have oncogenic functions in radiation-induced thymic lymphoma cells and that its increased expression may confer a growth advantage on tumor cells via aberrant expression of Fas and Bax.
authors.affiliation: 1. Department of Radiation Medicine, Faculty of Naval Medicine, Second Military Medical University, Shanghai 200433, PR China;
authors.forename: Fu
authors.initials: F
authors.lastname: Gao
authors.affiliation: 2. Department of Radiological Protection, Naval Medical Research Institute, Shanghai 200433, PR China;
authors.forename: Song
authors.initials: S
authors.lastname: Chen
authors.affiliation: 3. Department of Biochemistry and Molecular Biology, Second Military Medical University, Shanghai 200433, PR China;
authors.forename: Mingjuan
authors.initials: M
authors.lastname: Sun
authors.affiliation: 4. Radiological Protection Research and Instrumentation Branch, Atomic Energy of Canada Limited, Chalk River Laboratories, Chalk River, ON, K0J1J0, Canada.
authors.forename: Ronald E J
authors.initials: RE
authors.lastname: Mitchel
authors.affiliation: 1. Department of Radiation Medicine, Faculty of Naval Medicine, Second Military Medical University, Shanghai 200433, PR China;
authors.forename: Bailong
authors.initials: B
authors.lastname: Li
authors.affiliation: 2. Department of Radiological Protection, Naval Medical Research Institute, Shanghai 200433, PR China;
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Chu
authors.affiliation: 1. Department of Radiation Medicine, Faculty of Naval Medicine, Second Military Medical University, Shanghai 200433, PR China;
authors.forename: Jianming
authors.initials: J
authors.lastname: Cai
authors.affiliation: 1. Department of Radiation Medicine, Faculty of Naval Medicine, Second Military Medical University, Shanghai 200433, PR China;
authors.forename: Cong
authors.initials: C
authors.lastname: Liu
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics*; D015153:Blotting, Western; D002460:Cell Line; D019295:Computational Biology; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics*; D005822:Genetic Vectors / Q000235:genetics; D053208:Kaplan-Meier Estimate; D008156:Luciferases; D008223:Lymphoma / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D046228:Microarray Analysis; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013953:Thymus Neoplasms / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D014410:Tumor Stem Cell Assay; D051028:bcl-2-Associated X Protein / Q000378:metabolism; D019014:fas Receptor / Q000378:metabolism
chemical_list: C494827:Bax protein, mouse; C491899:Fas protein, mouse; C569061:MIRN467 microRNA, mouse; D035683:MicroRNAs; D051028:bcl-2-Associated X Protein; D019014:fas Receptor; D008156:Luciferases
keywords: Bax; Fas; apoptosis.; miR-467a; radiocarcinogenesis; thymic lymphoma