gms | German Medical Science

MicroRNAs are a class of small noncoding RNA molecules of 22 nucleotides in length that modulate gene expression post-transcriptionally. miR-205 is a highly conserved miRNA among different species, and is repressed in many tumors and cancer cell lines, including head and cancers. By using RT-PCR, we have firstly demonstrated that miR-205 was shown to be down-regulated in the primary laryngeal carcinoma. We next used a plasmid vector system that incorporates GFP as a reporter gene to express hsa-miR-205 to up-regulate miR-205 in Hep-2 cell line. Compared to the control, a high percentage of Hep-2 cells expressed GFP with has-miR-205 plasmid at 48 h after the transfection. MTT assays showed that the cell lines revealed significantly lower percent of surviving cells when treated with hsa-miR-205 plasmid compared to controls at each different time point. Flow-cytometric analysis demonstrated that transfected Hep-2 cells resulted in a significant increase in the percentage of apoptotic cells, compared with the control cells. Interestingly, up-regulation of miR-205 could suppress 2 oncogenes, such as DHFR and Bcl-2 expressions of Hep-2 cell lines, and this suppression was further confirmed immunohistochemically in xenograft tumor. In-vivo experiments showed that a significant growth reduction for the xenograft tumors resulted from Hep-2 cells transfected with has-miR-205 plasmid compared to the controls. Our data demonstrated for the first time that up-regulation of miR-205 could inhibit cell growth and promote apoptosis of Hep-2 cells and because an inverse correlation was found between the expression of miR-205 and DHFR and Bcl-2 oncogenes, miR-205 is probably a promising tumor suppressor.