Purpose: This study aims to determine the expression of miR-34b-5p in thyroid carcinomas and to investigate the role of miR34b-5p in the modulation of proteins involved in angiogenesis of thyroid carcinoma cells.
Methods: The expressions of miR-34b-5p levels in five cell lines and 65 tissue samples from thyroid carcinomas were examined by real-time polymerase chain reaction. An exogenous miR-34b-5p (mimic) transiently overexpress miR-34b-5p in theses thyroid carcinoma cells. The effects of miR-34b-5p overexpression on the proteins involved in angiogenesis and cell cycle regulations (VEGF-A, Bcl-2 and Notch1) were investigated by Western blot, immunofluorescence, enzyme-linked immunosorbent assay followed by cell cycle analysis and apoptosis assays.
Results: miR-34b-5p is markedly downregulated in all thyroid carcinoma cell lines and tissues samples when compared with non-neoplastic immortalised thyroid cell line and non-neoplastic thyroid tissues, respectively. The expression levels of miR-34b were significantly associated with T-stages of thyroid carcinomas (p = 0.042). Downregulation of VEGF-A, Bcl-2 and Notch1 proteins in thyroid carcinoma cells were noted in cells that transiently transfected with miR-34b-5p mimic. In addition, enzyme-linked immunosorbent assay confirmed the decreased expression of VEGF in thyroid carcinoma cells after transfection with miR-34b-5p mimic. Furthermore, miR-34b-5p mimic transfection induces significant accumulation of cells in G0-G1 of the cell cycle by blocking of their entry into the S transitional phase as well as increasing the total apoptosis.
Conclusions: miR-34b-5p functions as a potent regulator of angiogenesis, apoptosis and cell proliferation via modulation of VEGF-A, Bcl-2 and Notch1 proteins. It could be a target for developing treatment strategies of thyroid carcinoma with aggressive clinical behaviour.
Keywords: Angiogenesis; Bcl-2; Notch1; Thyroid carcinoma; VEGF; miR-34b.