Microrna-27a Functions As An Oncogene In Gastric Adenocarcinoma By Targeting Prohibitin

[Background and Aims] MicroRNAs (miRNAs) are a class of small non-coding RNAs that post-transcriptionally regulate gene expression. MiRNAs are involved in many physiological and pathological progress. Recent evidence indicates that special miRNAs may function as oncogenes or tumor suppressors and play a critical role in cancer initiation and progression by negatively regulating their target genes. Using oligonucleotide microarray, we found that microRNA-27a (miR-27a) was significantly up-regulated in human gastric adenocarcinoma tissue samples. In this study, we focused on the effects of miR-27a on the phenotypes of gastric adenocarcinoma cells as well as the identification of the direct target genes of miR-27a, in order to illuminate the molecular mechanisms of miR-27a in the initiation and progression of gastric adenocarcinoma.[Methods] The endogenous miR-27a was blocked in human gastric adenocarcinoma cell line MGC803 and the changes of cell phenotypes were detected with MTT assay and colony formation assay. Subsequently, we combined bioinformation and cDNA microarray analysis and identified the candidate target genes for miR-27a. The reliability of the direct target genes was confirmed by fluorescent reporter assay. Furthermore, the mRNA levels and protein levels of target genes in miR-27a-inhibited gastric cancer cells or tissues were detected with semi-quantitative RT-PCR and Western blot, in order to confirm the regulating role of miR-27a in target gene expression.[Results] We report that after suppression of miR-27a, the MGC803 cell proliferation activity and the colony formation activity were both inhibited. Subsequently, we identified tumor suppressor prohibitin as one of the candidate target genes for miR-27a. The prohibitin mRNA 3'untranslated region (3'UTR) contains the potential binding site of miR-27a. The fluorescent reporter assay also confirmed that miR-27a can directly bind to the specific site of prohibitin mRNA 3'UTR and negatively regulate the gene expression. When miR-27a function was inhibited in gastric cells or tissues, mRNA level and protein level of prohibitin were both elevated.[Conclusions] Our results indicate that in gastric adenocarcinoma cells, miR-27a functions as an oncogene and promotes cell proliferation. The over-expressed miR-27a in gastric adenocarcinoma cells can directly down-regulate the expression level of tumor suppressor prohibitin and result in the loss-of-function of prohibitin, leading to the activation of cell proliferation. The elucidation of common mechanisms of miR-27a in gastric adenocarcinoma helps us to further understand cancer initiation and progression, and provides new clues to cancer diagnosis and therapy.