Decreased miR-940 expression can predict a negative prognosis in early-stage nonsmoking female lung adenocarcinoma

Background: Early-stage female lung adenocarcinoma is the most common type of lung cancer encountered in thoracic surgery departments. Tumor-node-metastasis (TNM) staging does not adequately explain a significant stratification phenomenon in the prognosis of patients with stage I lung adenocarcinoma. We aimed to investigate the contributory role of miR-940 in the prognosis prediction. Methods: We analyzed the microRNA (miRNA) expression level in tumor tissues (high-risk group vs. low-risk group) from 12 non-smoking female patients with stage I lung adenocarcinoma using miRNA array. Bioinformatic analyses of miR-940 were also carried out based on the public database. Then, quantitative reverse-transcription polymerase chain reaction (qRT-PCR) tests of the tissue samples were further validated. And miR-940's function was analyzed and potential target genes were predicted. Results: In all, 24 miRNAs were found to be significantly different between the high-risk group and low-risk group. The expression level of miR-940 was lower in tumor tissue (P=0.011), and the survival rate in the high miR-940 group was higher [hazard ratio (HR) =0.688; P=0.011]. Gene Ontology (GO) analysis showed that the assembly functions of targets regulated by miR-940 were mainly enriched in regulation of myeloid cell differentiation, G1/S transition of mitotic cell cycle, and cellular response to environmental stimulus. miR-940 is involved in transforming growth factor-beta (TGF-beta) signaling pathway; TNF signaling pathway; and estrogen signaling pathway. The number of lung adenocarcinoma cells (A549) was significantly decreased after miR-940 was transfected. Ten epithelial-to-mesenchymal-transition (EMT)-associated genes (MMP9, ZEB1, CDH1, KRT8, KRT18 KET19, TWIST1, VIM, SNAI1, and SNAI2) were found to be significantly related to miR-940. Conclusions: The present study showed that miR-940 might be a protective factor for positive prognosis in early stage nonsmoking female lung adenocarcinoma, with transforming growth factor-beta (TGF-beta) pathway, TNF pathway, and matrix metalloprotein (MMP9) being potential targets.