MiR‐339 depresses cell proliferation via directly targeting S‐phase kinase‐associated protein 2 mRNA in lung cancer

BACKGROUND S-phase kinase-associated protein 2 (Skp2) takes great part in the development of multiple tumors. However, the post-transcriptional modulation mechanism of Skp2 remains unclear. Here, we present a new regulatory microRNA of Skp2, miR-339, which directly targets Skp2 to inhibit cell proliferation in lung cancer. METHODS The expression of miR-339 or Skp2 in lung cancer samples was tested by real time-PCR. The correlation between miR-339 and Skp2 in lung cancer samples was analyzed by Pearson's correlation coefficient. The effect of miR-339 or anti-miR-339 on Skp2 was evaluated by immunoblotting. The luciferase reporter gene assay was used to test the targeting of miR-339 on Skp2. 3-(4,5-Dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide and colony formation analysis were applied to examine the function of miR-339 targeting Skp2 in lung cancer cells. RESULTS The negative correlation of miR-339 with Skp2 was found in clinical human lung cancer tissues. Furthermore, Skp2 expression was obviously abated by miR-339 in lung cancer A549 cells. Mechanistically, we used bioinformatics to predict that miR-339 could target the 3'-untranslated region of Skp2 mRNA. Luciferase reporter gene assay demonstrated that miR-339 could decrease the luciferase activities of the 3'-untranslated region vector of Skp2. In terms of function, ectopic miR-339 expression significantly suppressed cell proliferation in lung cancer. Overexpressed Skp2 accelerated miR-339-bated proliferation of lung cancer cells. MiR-339 inhibitor promoted cell proliferation in lung cancer, but Skp2 RNA interference reversed miR-339 inhibitor-driven cell proliferation. CONCLUSION MiR-339 targets the 3'-untranslated region of Skp2 mRNA to depress the proliferation of lung cancer cells.