Study on the mechanism of miR-497-induced laryngeal squamous cell carcinoma growth inhibition by targeting CDK6

Abstract

Objective: To study the effects of miR-497 and CDK6 on the growth of laryngeal squamous cell carcinoma (LSCC). Methods: The expressions of CDK6 mRNA in fresh LSCC specimens, the adjacent normal mucosa of LSCC, and cell lines of LSCC were detected with quantitative real time polymerase chain reaction, pcDNA3.1(+) CDK6 plasmids were respectively transfected into the LSCC cells, and MTT assay and clone formation assay were performed to evaluate the growth of LSCC cells. Flow cytometry was employed for cell cycle analysis. SPSS17.0 software was used to analyze the data. Results: CDK6 was highly expressed in LSCC(t=14.01, P=0.009) and the overall survival rate of the patients with high CDK6 expression was less than that with low CDK6 expression, with a significant difference (HR=3.236, P<0.001). Double luciferase reporter gene analysis showed that fluorescence activity in wild type CDK6 group was significantly different from that in control group (P<0.01), while there was no significant difference in the fluorescence activity between mutant CDK6 group and control group (P>0.05). A(490) values were respectively 0.42±0.14 (Mean±SD) in siRNA Hep-2 group, 0.51±0.13 in siRNA TU-212 group; 0.98±0.16 in control Hep-2 group and 1.17±0.20 in control TU-212 group. Colonies were 55±4 in siRNA Hep-2 group, 51±3 in siRNA TU-212 group, 108±6 in control Hep-2 group and 105±7 in control TU-212 group, namely, cell growth and clone formation ability in CDK6 siRNA group were significantly lower than those in the control group. Cells cycle was blocked in G0/G1 phase (G0/G1: 65.20%±10.12% in siRNA Hep-2 group; 63.42%±8.97% in siRNA TU-212 group; 45.31%±7.55% in control Hep-2 group; and 42.37%±7.28% in control TU-212 group), and cells decreased obviously in S phase (S: 25.39%±5.51% in siRNA Hep-2 group; 27.21%±5.43% in siRNA TU-212 group; 42.87%±6.85% in control Hep-2 group; and 44.76%±7.02% in control TU-212 group). Compared with miR-497 group, cell growth and clone formation ability in miR-497/CDK6 group were partly restored (all P<0.05). Conclusions: CDK6 expression in LSCC is upregulated, functioning as an oncogene. High expression of CDK6 is a predictor for poor prognosis. miR-497, functioning as a tumor suppressor gene, inhibits the growth of LSCC by targeting CDK6.