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The development of chemotherapeutic dug resistance hinders the clinical treatment of cancer. MicroRNAs (miRNAs/miRs) have been revealed to serve essential roles in the drug resistance of numerous types of cancer. miR-139-5p was previously reported to be associated with cisplatin (DDP) sensitivity in human nasopharyngeal carcinoma cells and colorectal cancer cells. However, the effect and underlying mechanism of miR-139-5p in DDP sensitivity in non-small cell lung cancer (NSCLC) cells has not yet been fully elucidated. In the present study, the expression of miR-139-5p and Homeobox protein Hox-B2 (HOXB2) in NSCLC tissues was examined by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blotting. Subsequently, the effect of miR-139-5p on the DDP sensitivity of NSCLC cells in vitro was investigated. Cell proliferation was examined using a Cell Counting Kit-8 assay. Western blotting was used to evaluate the protein expression of HOXB2, phosphorylated (p)-PI3K, p-AKT, caspase-3 and cleaved-caspase-3, and RT-qPCR was used to evaluate the expression of miR-139-5p, and the mRNA expression levels of HOXB2, PI3K, AKT and caspase-3. The apoptotic rate of the cells was detected using flow cytometry. miR-139-5p expression in NSCLC tissues was shown to be significantly lower compared with that in adjacent tissues. Additionally, miR-139-5p increased cell apoptosis and inhibited NSCLC cell proliferation induced by DDP in vitro via modulating the PI3K/AKT/caspase-3 signaling pathway. Furthermore, HOXB2 was identified to be a target of miR-139-5p, and miR-139-5p was revealed to sensitize NSCLC cells to DDP via the targeting of HOXB2. Taken together, the results of the present study demonstrated that regulating the expression of miR-139-5p could provide a novel approach to reverse DDP resistance and increase chemosensitivity in the treatment of NSCLC. [ABSTRACT FROM AUTHOR]