MicroRNA-7Downregulates XIAP Expression To Suppress Cell Growth And Promote Apoptosis In Cervical Cancer Cells

[Objective] MicroRNAs (miRNAs) are a class of small non-coding RNAs that include19-25nucleotides, which post-transcriptionally regulate gene expression. MiRNAs are involved in many physiological and pathological progress. Recent evidence indicates that many miRNAs function as oncogenes or tumor suppressors and play an important role in cancer initiation and progression by regulating their target genes negatively. Using Real-time PCR, we found that microRNA-7were significantly down-regulated in human cervical cancer tissues compared with the normal tissues. In this study, we focused on the effects of miR-7on the phenotypes of cervical cancer cells as well as the identification of their direct target genes, in order to illuminate the molecular mechanisms of miR-7in the initiation and progression of human cervical cancer.[Methods] The changes of cell proliferation and apoptosis were detected by MTT assay and colony formation assay with the up-regulation of miR-7in HeLa and C-33A cells, TUNEL assay in in HeLa cells. Subsequently, we combined bioinformatics and BLAST analysis and identified the candidate target genes for miR-7. Then fluorescent reporter assay was performed to confirm the reliability of the direct target genes. Furthermore, the mRNA levels and protein levels of target genes in miR-7overexpressed cervical cancer cells were detected with Real-time PCR and Western blot, in order to confirm the regulative role of miR-7on XIAP expression. Finally, the target gene was knocked down using RNA interference and changes of cell proliferation and apoptosis were detected with MTT assay, colony formation assay and TUNEL assay.[Results] We report that after overexpression of miR-7, the cell viability and the colony formation activity of HeLa and C-33A cells were both suppressed, the HeLa cells apoptosis was increased. Subsequently, we identified oncogene XIAP as congenerous candidate target gene for miR-7. The XIAP mRNA3’UTR contains the potential binding site of miR-7. The fluorescent reporter assay also confirmed that miR-7can directly bind to the specific site of XIAP mRNA3’UTR and negatively regulate the gene expression. When miR-7was over-expressed in HeLa and C-33A cells, mRNA level and protein level of XIAP were both depressed. We also discovered that when the target gene was knocked down, the cell viability and colony formation activity of cervical cancer cells were suppressed apparently, the cell apoptosis was increased. These results were consistent with the results of the overexpression of miR-7.[Conclusions] miR-7downregulates XIAP expression to suppress cell growth and promote apoptosis in cervical cancer cells, miR-7functions as a tumor suppressor in cervical cancer. Oncogene XIAP promotes cell growth and suppresses apoptosis in cervical cancer cells. The elucidation of the mechanisms of miR-7in cervical cancer helps us to further understand the mechanism of cervical cancer initiation and progression, and pave a way for clinical diagnosis and therapy of cervical cancer.