Abstract. The aim of the present study was to investigate the expression and role of microRNA-26a (miR-26a) in lung cancer, and to verify whether differentially expressed in adenocarcinoma of the lung (DAL-1) is the target protein of miR-26a. mRNA expression levels of miR-26a and DAL-1 were detected using reverse transcription-quantitative polymerase chain reaction. Protein expression levels of DAL-1 and annexin A1 (ANXA1) were evaluated by western blot analysis. Cell Counting Kit-8, Transwell and wound scratch healing assays were used to characterize the function of miR-26a in lung cancer cells. The association of DAL-1 with miR-26a or ANXA1 was determined by dual-luciferase reporter or two-dimensional gel electrophoresis assays. miR-26a revealed decreased expression levels in lung cancer tissues compared with normal lung tissues, and decreased expression levels in lung cancer cells compared with 16HBE cells. Inhibition of miR-26a promoted lung cancer cell growth, migration and invasion. The DAL-1 protein exhibited downregulated expression levels in lung cancer tissues. DAL-1 was not the direct target gene of miR-26a. The two-dimensional gel electrophoresis assay confirmed that DAL-1 and ANXA1 were associated proteins. Expression levels of the ANXA1 protein were increased following DAL-1 gene silencing. The altered expression level of miR-26a affected the expression of ANXA1, and not of DAL-1. miR-26a demonstrated decreased expression levels in lung cancer cells, and it has an important effect on the biological function of lung cancer cells. However, DAL-1 was not a target gene of miR-26a. As a DAL-1 associated protein, ANXA1 was regulated by miR-26a. IntroductionLung cancer has a high incidence of tumor recurrence and metastasis, and is the most common cause of cancer-associated morality worldwide (1). The overall 5-year survival rate among patients with lung cancer is <15%, and a high rate of metastasis is the primary cause of lung cancer-associated mortality (2). A previous study confirmed that differentially expressed in adenocarcinoma of the lung (DAL-1), a protein that belongs to the membrane-associated cytoskeleton protein 4.1 family, is an efficient suppressor of epithelial-mesenchymal transition (EMT) in lung cancer (3). EMT is a pivotal event in lung cancer metastasis progression (4-6). However, the regulators of DAL-1 in EMT remain unknown.Recently, a novel batch of endogenous small non-coding regulatory RNAs (microRNA's; miRNA's) have received attention in the development of cancer, miRNA's bind complementary sequences in target mRNAs, resulting in selective degradation or selective inhibition of their translation (7). The present study investigated the possible miRNAs of DAL-1 using bioinformatic assays, which included miR-26b, miR-26a, miR-96 and miR-223. Among them, the regulation of DAL-1 by miR-223 has been demonstrated to serve a role in gastric cancer (8). The present study revealed that the gene silencing of DAL-1 induced annexin A1 (ANXA1) protein expression levels to increase in H460 cells...