Down-regulation of miR-181b promotes apoptosis by targeting CYLD in thyroid papillary cancer.

MicroRNAs (miRNAs) are a small class of non-coding RNAs that are widely deregulated in various cancers. They act as either oncogenes or tumor suppressor genes in human cancer. The purpose of this study was to examine the potential role of miR-181b in human thyroid papillary cancer. The expression levels of different miRNAs were measured by micro array analysis in 10 thyroid papillary cancer specimens and adjacent normal thyroid cancer tissues. MTT assays, colony formation assays, apoptosis assays were used to explore the potential function of miR-181b inhibitor in TPC1 human thyroid papillary cancer cells. Luciferase reporter assays were performed to validate the regulation of a putative target of miR-181b, in corroboration with qPCR and western blot assays. We found that the expression of miR-181b was higher in thyroid papillary cancer specimens compared with adjacent normal tissues (P < 0.05). Downregulation of miR-181b inhibited cellular growth and promoted cellular apoptosis. Luciferase assays indicated that miR-181b can bind with its putative target site in the 3'-untranslated region (3'-UTR) of CYLD, suggesting that CYLD is a direct target of miR-181b. Western blot analysis indicated that downregulation of miR-181b results in the upregulation of CYLD at protein levels. Taken together, downregulation of miR-181b expression causes cellular growth inhibition, promoting cellular apoptosis by targeting CYLD. These findings suggest that downregulation of the expression of miR-181b may be a therapeutic target for the treatment of human thyroid papillary cancer.