Lung cancer is one of the main causes of cancer mortality globally. Most patients received radiotherapy during the course of disease. However, radioresistance generally occurs in the majority of these patients, leading to poor curative effect, and the underlying mechanism remains unclear. In the present study, miR‐18a‐5p expression was downregulated in irradiated lung cancer cells. Overexpression of miR‐18a‐5p increased the radiosensitivity of lung cancer cells and inhibited the growth of A549 xenografts after radiation exposure. Dual luciferase report system and miR‐18a‐5p overexpression identified ataxia telangiectasia mutated (ATM) and hypoxia inducible factor 1 alpha (HIF‐1α) as the targets of miR‐18a‐5p. The mRNA and protein expressions of ATM and HIF‐1α were dramatically downregulated by miR‐18a‐5p in vitro and in vivo. Clinically, plasma miR‐18a‐5p expression was significantly higher in radiosensitive than in radioresistant group (P < .001). The cutoff value of miR‐18a‐5p >2.28 was obtained from receiver operating characteristic (ROC) curve. The objective response rate (ORR) was significantly higher in miR‐18a‐5p‐high group than in miR‐18a‐5p‐low group (P < .001). A tendency demonstrated that the median local progression‐free survival (PFS) from radiotherapy was longer in miR‐18a‐5p‐high than in miR‐18a‐5p‐low group (P = .082). The median overall survival (OS) from radiotherapy was numerically longer in miR‐18a‐5p‐high than in miR‐18a‐5p‐low group (P = .281). The sensitivity and specificity of plasma miR‐18a‐5p to predict radiosensitivity was 87% and 95%, respectively. Collectively, these results indicate that miR‐18a‐5p increases the radiosensitivity in lung cancer cells and CD133⁺ stem‐like cells via downregulating ATM and HIF‐1α expressions. Plasma miR‐18a‐5p would be an available indicator of radiosensitivity in lung cancer patients.

Acquired resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs), such as gefitinib and erlotinib, is a critical issue for the treatment of EGFR mutant-positive non-small cell lung cancer (NSCLC). Recent evidence supports the role of microRNA-223 (miR‑223) in modulating chemotherapeutic drug sensitivity, but its role in the resistance to EGFR-TKIs in NSCLC remains unclear. To this end, we investigated the involvement of miR‑223 in erlotinib resistance, using two pairs of TKI-sensitive or resistant cell lines, PC9 vs PC9/ER, and HCC827 vs HCC827/ER, as well as PC9/CD133+, which are lung cancer stem-like cells derived from PC9 cells. Downregulation of miR‑223 expression in PC9/ER and PC9/CD133+ cells was detected, and the reverse correlation of miR-233 and insulin-like growth factor 1 receptor (IGF1R) in these cells was also revealed. Next, levels of IGF1R mRNA and p-Akt were significantly reduced in miR‑223 stably transfected PC9/ER and PC9/CD133+ cells. However, the sensitivity of PC9/ER and PC9/CD133+ cells to erlotinib was partially restored, after overexpression of miR‑223 in those cells. Similar results were also observed in vivo. Furthermore, miR‑223-mediated inhibition of the IGF1R/PI3K/Akt signaling pathway may have been reversed by the agonist of IGF1R in miR‑223 transfected cells. Our findings indicated that downregulation of miR‑223, which can induce activation of the IGF1R/phosphatidylinositol 3-kinase (PI3K)/Akt pathway in PC9/ER and PC9/CD133+ cells, may be responsible for the resistance of PC9/ER and PC9/CD133+ cells to erlotinib, suggesting that miR‑223 is a potential therapeutic target for overcoming EGFR-TKIs resistance.

Lung cancer is the leading cause of cancer-related fatalities worldwide, and non-small cell lung cancer (NSCLC) is the main pathological type. MicroRNAs (miRNAs or miRs) are a class of small non-coding RNAs, which are involved in tumor initiation and progression. miR‑223 is a tumor suppressor miRNA that has been reported in various types of cancer, including lung cancer. In the present study, to characterize the biological behavior of miR‑223 in NSCLC, we established an miR‑223 overexpression model in erlotinib-resistant PC‑9 (PC‑9/ER) cells by infection with lentivirus to induce the overexpression of miR‑223. As a result, miR‑223 enhanced the sensitivity of the PC‑9/ER cells to erlotinib by inducing apoptosis in vitro. Additionally, in vivo experiments were performed using nude mice which were injected with the cancer cells [either the PC‑9 (not resistant), PC‑9/ER, or the PC‑9/ER cells infected with miR‑223)]. We found that the tumor volumes were reduced in the rats injected with the cells infected with miR‑223. To further explore the underlying mechanisms, reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot analysis were used to identify the target molecules of miR‑223. miR‑223 was demonstrated to act as a local regulator of insulin-like growth factor-1 receptor (IGF-1R) in the acquired resistance to tyrosine kinase inhibitors (TKIs). Notably, the οverexpression of IGF-1R in NSCLC was downregulated by miR‑223, and the activation of Akt/S6, the downstream pathway, was also inhibited. The inhibition of IGF-1R by miR‑223 was attenuated by exogenous IGF-1 expression. Therefore, miR‑223 may regulate the acquired resistance of PC‑9/ER cells to erlotinib by targeting the IGF-1R/Akt/S6 signaling pathway. The overexpression of miR‑223 may partially reverse the acquired resistance to epidermal growth factor receptor-TKIs, thus, providing a potential therapeutic strategy for TKI-resistant NSCLC.

The ability of non-small cell lung cancer (NSCLC) cells to invade and metastasize is associated with epithelial-to-mesenchymal transition (EMT). The process of EMT is, at least in part, regulated by microRNAs. However, it is unknown whether microRNAs regulate EMT in cancer stem-like cells (CSLCs), or which microRNAs are involved. In the present study, we compared microRNA expression in A549 cells, TGF‑β1-treated A549 cells, CSLCs characterized by the CD133+/CD326+ phenotype, and TGF‑β1-treated CSLCs. We found that miR‑181b‑5p expression was upregulated by TGF‑β1. Moreover, the overexpression of the miR‑181b‑5p in A549 cells and CD133+/CD326+ cells resulted in the downregulation of the E-cadherin and increased invasion and metastasis in vitro and in vivo. Accordingly, the knockdown of miR‑181b‑5p partially restored E-cadherin expression. These results suggest that miR‑181b‑5p regulates TGF‑β1-induced EMT by targeting E-cadherin not only in normal A549 cells but also in CD133+/CD326+ cells which have characteristics of CSLCs. Thus, miR‑181b‑5p represents a new therapeutic target in NSCLC.

The combination of dendritic cells (DCs) and cytokine-induced killer cells (CIKs) can induce the anti-tumor immune response and radiotherapy may promote the activity. We aimed to explore the feasibility of DCs/CIKs combined with thoracic radiotherapy (TRT) for patients with locally advanced or metastatic non-small-cell lung cancer (NSCLC). In this study, patients with unresectable stage III/IV NSCLC and an Eastern Cooperative Oncology Group performance status (ECOG PS) of 0–2 and previously receiving two or more cycles of platinum-based doublet chemotherapy without disease progression received TRT plus DCs/CIKs or TRT alone until disease progression or unacceptable toxicity. The primary endpoint was median progression-free survival (mPFS). In treatment group, patients received four-cycle autologous DCs/CIKs infusion starting from the 6th fraction of irradiation. From Jan 13, 2012 to June 30, 2014, 82 patients were enrolled, with 21 patients in treatment group and 61 in control group. The mPFS in treatment group was longer than that in control group (330 days vs 233 days, hazard ratio 0.51, 95 % CI 0.27–1.0, P < 0.05), and the objective response rate (ORR) of treatment group (47.6 %) was significantly higher that of control group (24.6 %, P < 0.05). There was no significant difference in disease control rate (DCR) and median overall survival (mOS) between two groups (P > 0.05). The side effects in treatment group were mild and there was no treatment-related deaths. The combination of DCs/CIKs with TRT could be a feasible regimen in treating locally advanced or metastatic NSCLC patients. Further investigation of the regimen is warranted.