microRNA-141 inhibits thyroid cancer cell growth and metastasis by targeting insulin receptor substrate 2.

microRNA-141 (miR-141), a member of the miR-200 family, and has been reported to involve in tumor initiation and development in many types of cancers. However, the function and underlying molecular mechanism of miR-141 in thyroid cancer remains unclear. Therefore, the aim of this study is to identify its expression, function, and molecular mechanism in thyroid cancer. In this study, we found that miR-141 expression levels were downregulated in human thyroid cancer specimens compared to the adjacent normal tissues, and its expression were strongly correlated with clinical stages and lymph node metastases. Function assays showed that overexpression of miR-141 inhibited cell proliferation, induced cell apoptosis, and decreased migration, invasion in thyroid cancer cells, as well as tumor growth in nude mice. Moreover, insulin receptor substrate 2 (IRS2), a known oncogene, was confirmed as a direct target of miR-141, and IRS2 expression levels were upregulated in thyroid cancer, and its expression were inversely correlated with miR-141 expression levels in human thyroid cancer specimens. Forced expression of IRS2 reversed the inhibition effect induced by miR-141 overexpression in thyroid cancer cells. Taken together, our study provides the first evidence that miR-141 suppressed thyroid cancer cell growth and metastasis through inhibition of IRS2. Thus, miR-141 might serve as a promising therapeutic strategy for thyroid cancer treatment.