Study on molecular mechanism of MiRNA-29a in promoting proliferation and invasion of non-small-cell lung cancer by inhibiting MTSS1.

OBJECTIVE

To investigate the biological role of micro-ribonucleic acid (miR)-29a in non-small-cell lung cancer (NSCLC).

PATIENTS AND METHODS

55 cases of NSCLC tissue specimens and paired normal lung tissue specimens collected in the Department II of Oncology, Ruikang Hospital Affiliated to Guangxi University of Chinese Medicine from July 2012 to April 2015 were randomly included. The fluorescent quantitative polymerase chain reaction, Western blotting, and immunohistochemistry were performed to detect the expression levels of miR-29a and metastasis suppressor 1 (MTSS1). Pearson correlation analysis was utilized to investigate the relationship between miR-29a expression and MTSS1 expression in NSCLC tissues, and the Kaplan-Meier survival curves were constructed to analyze the association of miR-29a expression with the survival time of NSCLC patients. A54 proliferation and invasion abilities were measured by means of plate clone formation assay, and transwell assay after the miR-29a was suppressed by miRNA inhibitor. Luciferase assay was used to detect the target gene of miR-29a.

RESULTS

In NSCLC tissues, the miR-29a expression level was higher than that in normal lung tissues (p<0.05), while the expression level of MTSS1 protein was remarkably lower than that in normal lung tissues (p<0.05). The median survival time of the patients was 15.1 months in high miR-29a expression group and 18.3 months in low miR-29a expression group (p<0.05). The miR-29a expression was negatively correlated with the expression level of MTSS1 protein in NSCLC tissues (r=-0.762, p<0.05). Luciferase results suggest that miR-29a binds to the promoter region of MTSS1 and inhibits its transcription level. The expression of MTSS1 protein was up-regulated notably after miR-29a knockdown by an inhibitor. It was revealed in the results of transwell assay and plate clone formation assay that the proliferative and invasive capacity of A549 cells was significantly decreased after knockdown of miR-29a.

CONCLUSIONS

The transcribed miR-29a down-regulates the protein level of MTSS1, suppressor of tumor proliferation and invasion, thereby promoting the proliferative and invasive capacity of NSCLC cells. Both miR-29a and MTSS1 are expected to become potential therapeutic targets for NSCLC.