574456

MIR497

epithelial to mesenchymal transition (EMT) is a critical step in the growth and dissemination of malignant diseases, including breast cancer. It is known that microRNAs (miRNAs) play important roles in the regulation of tumor properties in cancers. However, whether miR-497 contributes to EMT in breast cancer cells remains unknown. Our study demonstrated that the expression of miR-497 was significantly decreased in human breast cancer cell lines and breast cancer specimens. In breast cancer cells, EMT was inhibited and promoted by the over-expression as well as depletion of miR-497, respectively. Dual-Luciferase ReporterAassay confirmed that Slug was a direct target of miR-497. The upregulation of miR-497 in breast cancer cells suppressed cell proliferation and induced apoptosis both in vitro and in vivo. Correlation analysis indicated that miR-497 was highly negatively correlated with Slug expression in breast cancer specimens. The knockdown of Slug expression in breast cancer cells significantly suppressed cell proliferation and promoted apoptosis. Our results suggested that the expression of miR-497 is significantly correlated with EMT in breast cancer cells by regulating Slug at the transcriptional as well as translational levels. Therefore, targeting miR-497 may provide a novel strategy for the treatment of breast cancer.

Skin carcinogenesis is known to be a multi-step process with several stages along its malignant evolution. We hypothesized that transformation of normal epidermis to cutaneous squamous cell carcinoma (cSCC) is causally linked to alterations in microRNAs (miRNA) expression. For this end we decided to evaluate their alterations in the pathologic states ending in cSCC. Total RNA was extracted from formalin fixed paraffin embedded biopsies of five stages along the malignant evolution of keratinocytes towards cSCC: Normal epidermis, solar elastosis, actinic keratosis KIN1-2, advanced actinic keratosis KIN3 and well-differentiated cSCC. Next-generation small RNA sequencing was performed. We found that 18 miRNAs are overexpressed and 28 miRNAs are underexpressed in cSCC compared to normal epidermis. miR-424, miR-320, miR-222 and miR-15a showed the highest fold change among the overexpressed miRNAs. And miR-100, miR-101 and miR-497 showed the highest fold change among the underexpressed miRNAs. Heat map of hierarchical clustering analysis of significantly changed miRNAs and principle component analysis disclosed that the most prominent change in miRNAs expression occurred in the switch from 'early' stages; normal epidermis, solar elastosis and early actinic keratosis to the 'late' stages of epidermal carcinogenesis; late actinic keratosis and cSCC. We found several miRNAs with 'stage specific' alterations while others display a clear 'gradual', either progressive increase or decrease in expression along the malignant evolution of keratinocytes. The observed alterations focused in miRNAs involved in the regulation of AKT/mTOR or in those involved in epithelial to mesenchymal transition. We chose to concentrate on the evaluation of the molecular role of miR-497. We found that it induces reversion of epithelial to mesenchymal transition. We proved that SERPINE-1 is its biochemical target. The present study allows us to further study the pathways that are regulated by miRNAs along the malignant evolution of keratinocytes towards cSCC.