Effects of miR‑340 overexpression and knockdown on the proliferation and metastasis of NSCLC cell lines.

The present study aimed to investigate the potential biological functions of microRNA‑340 (miR‑340) in non‑small cell lung cancer (NSCLC) beyond its role as a critical regulator of tumorigenesis and tumor progression. The expression levels of miR‑340 and RAB27B were analyzed by reverse transcription‑quantitative polymerase chain reaction. Subsequently, the protein expression levels of RAB27A, RAB27B, RAB9A, RAB11A and BRAB21 were determined by western blot analysis. The expression levels of the aforementioned proteins in NSCLC tissues were analyzed by immunohistochemistry. RAB27B, as a potential target of miR‑340 was investigated via a dual‑luciferase reporter assay. The proliferative ability of PC9, A549 and BEAS‑2B cells was detected with a Cell Counting kit‑8 assay, while the migration and invasion of the NSCLC cells were analyzed using a Transwell assay. The results revealed that the expression levels of miR‑340 in the NSCLC cells were significantly decreased compared with those in normal cells (BEAS‑2B cells). RAB27B was proposed as a potential target gene of miR‑340, and its expression was notably increased in the NSCLC cells. miR‑340 overexpression inhibited the migration and invasion of the NSCLC cells by targeting RAB27B, while the knockdown of miR‑340 exerted opposite effects. On the whole, these findings indicate that the miR‑340/RAB27B axis may be actively involved in the occurrence of NSCLC. Thus, miR‑340 and RAB27B may be novel therapeutic targets for the treatment of NSCLC.