OBJECTIVETo elucidate the regulatory mechanism underlying proliferation and anti-apoptosis in NSCLC by overexpression of miR-21.

METHODSReal-time PCR was used to measure miR-21 abundance in non-small cell lung cancer (NSCLC) tumor samples and adjacent normal tissues, as well as NSCLC cell lines. Tumor suppressor genes as potential targets of miR-21 were predicted by sequence analysis. Luciferase assay and Western blot were used to assess the regulatory effect. The effect on A549 cell viability and apoptosis by miR-21-induced gene repression was tested by trypan-blue exclusion and flow cytometry.

RESULTSmiR-21 expression was 2.24-fold higher in the NSCLC tumor samples and 3.06-fold higher in the A549 cells than that in the adjacent normal tissues. Sequence prediction and gene expression regulation assays showed that miR-21 could reversely regulate the expression of PDCD4 (P < 0.01). Suppression of miR-21 expression is associated with an elevation of Pdcd4, resulting in a significant reduction of proliferation and the apoptosis rate (2.6%) was increased to 10.9%. Moreover, the anti-proliferation and pro-apoptotic effect by miR-21 suppression could be reversed by PDCD4 knock down.

CONCLUSIONSuppression of the tumor suppressor PDCD4 expression may be one of the important regulatory pathways of the miR-21-mediated cell proliferation and decrease of apoptosis in non-small cell lung cancer.