MicroRNA expression profile of MCF-7 human breast cancer cells and the effect of green tea polyphenon-60.

This study reports for the first time the microRNA expression profile of human breast cancer MCF-7 cells and the effect of green tea. Although hundreds of miRNAs have been identified in humans, only a small proportion (25.6%) of miRNAs are expressed in MCF-7 cells. Low concentration treatment with Polyphenon-60 significantly alters the miRNA expression profile in MCF-7 cells. Twenty three miRNAs have been identified with differential expression after a 48 h treatment with 10 μg/ml Polyphenon-60 (green tea extract). These miRNAs include miR-21 and miR-27 that were found to be down-regulated following treatment with green tea. These two miRNAs have previously been identified as being overexpressed in MCF-7 breast cancer cells, with miR-21 specifically implicated in down-regulating the tumor suppressor gene, tropomyosin-1. This data supports the hypothesis that Polyphenon-60-induced modification of the breast cancer miRNA expression profile contributes to the efficacy of green tea treatment. The resulting decrease in carcinogenesis is further supported by the altered miRNA regulation of potential oncogenes and tumor-suppressor genes.