Altered expression of selected microRNAs in melanoma: Antiproliferative and proapoptotic activity of miRNA-155

Altered expression of microRNAs (miRNAs) has been detected in cancer, suggesting that these small non-coding RNAs can act as oncogenes or tumor suppressor genes. In the present study, we investigated the expression of miRNA-17-Sp, miRNA-18a, miRNA-20a, miRNA-92a, miRNA-146a, miRNA-146b and miRNA-155 by real-time quantitative RT-PCR in a panel of melanocyte cultures and melanoma cell lines and explored the possible role of miRNA-155 in melanoma cell proliferation and survival. The analyzed miRNAs were selected on the basis of previous studies strongly supporting their involvement in cancer development and/or progression. We found that miRNA-17-Sp, miRNA-18a, miRNA-20a, and miRNA-92a were overexpressed, whereas miRNA-146a, miRNA-146b and miRNA-155 were down-regulated in the majority of melanoma cell lines with respect to melanocytes. Ectopic expression of miRNA-155 significantly inhibited proliferation in 12 of 13 melanoma cell lines with reduced levels of this miRNA and induced apoptosis in 4 out of 4 cell lines analyzed. In conclusion, our data further support the finding of altered miRNA expression in melanoma cells and establish for the first time that miRNA-155 is a negative regulator of melanoma cell proliferation and survival.