MicroRNA-126 suppresses proliferation of undifferentiated (BRAFV600E and BRAFWT) thyroid carcinoma through targeting PIK3R2 gene and repressing PI3K-AKT proliferation-survival signalling pathway

• miR-126 expression was low in BRAF mutated undifferentiated thyroid carcinoma.
• miR-126 suppresses p85β expression in undifferentiated thyroid carcinoma.
• miR-126 suppresses AKT kinase activity in undifferentiated thyroid carcinoma.
• miR-126 suppresses proliferation of undifferentiated thyroid carcinoma.

BackgroundThe objectives of this study are to investigate the expression of miR-126 and evaluate its effect on proliferation in undifferentiated thyroid carcinoma.MethodsmiR-126 expression of undifferentiated thyroid carcinoma cell lines 8505C (BRAFV600E/V600E), BHT-101 (BRAFV600E/WT) and MB-1 (BRAFWT/WT) were quantified with q-PCR. These cell lines were transiently transfected with exogenous miR-126 (mimic). Following transfection, proliferation effects were observed through MTS proliferation assay and colony formation abilities. Immunofluorescence imaging and Western blot assay were also done to check target proteins expression.ResultsUnder-expression (p<0.05) of miR-126 was noted in BRAFV600E mutated undifferentiated thyroid carcinoma cells (8505C and BHT-101), but no change in expression was noted in non BRAFV600E mutated undifferentiated thyroid carcinoma cells (MB-1). In addition, a 30–50% drop in proliferation ability and a 35–45% reduction in colony formation capability were noticed in miR-126 mimic transfected group when compared to control group. Furthermore, immunofluorescence images showed reduced expression of p85β and p-AKT protein in miR-126 mimic transfected cells when compared to un-transfected cells. Also, Western blot analysis revealed a 34–40% suppression of p85β protein and a 21–53% drop in active AKT kinase (p-AKT) protein in miR-126 mimic transfected group when compared to control group.ConclusionsExpression of miR-126 was down-regulated in BRAFV600E mutated undifferentiated thyroid carcinoma. In addition, miR-126 was found to act as proliferation suppressor targeting PIK3R2 gene and reducing p85β (a regulatory subunit of PI3K kinase) protein translation and lower AKT kinase activity. Therefore, miR-126 could be a potential therapeutic tool in the treatment of undifferentiated thyroid carcinoma.