BackgroundEpidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) are approved for patients with recurrent non-small cell lung cancer (NSCLC). However, the efficacy of EGFR-TKIs in NSCLC therapy is limited by primary and acquired resistance. Recent studies have revealed that long non-coding RNAs (LncRNA) may be involved in EGFR-TKI resistance. Therefore, a better understanding of the interactive mechanisms underlying LncRNA-mediated EGFR-TKIs resistance may help us to improve clinical response rates.MethodTo investigate the expression of growth arrest-specific 5 (GAS5) in lung adenocarcinoma, we performed real-time reverse-transcriptase polymerase chain reaction. The correlation between GAS5 expression levels and the samples’ clinicopathological features was also analyzed. Primary resistance to EGFR-TKIs was identified in the human lung adenocarcinoma cell line A549. Plasmid vectors were used to overexpress GAS5 in A549 cells. MTT (3-(4,5-dimethylthiazol-2-Yl)-2,5-diphenyltetrazolium bromide) colony formation assays and EdU (5-ethynyl-2’-deoxyuridine) assays were used to assess cell proliferation, and flow-cytometric analysis was used to evaluate the apoptosis rate. The expression levels of our target proteins, namely, EGFR, p-EGFR, ERK, p-ERK, Akt, p-Akt, IGF-1R (insulin-like growth factor 1 receptor), and p-IGF-1R, were analyzed by western blotting. A549 cells transfected with pcDNA-GAS5 were injected into nude mice. The transplanted mice were treated with gefitinib to study the effect of GAS5 on the resistance to EGFR-TKIs in vivo.ResultsOur results showed that GAS5 was significantly downregulated in lung adenocarcinoma tissues compared with the paired adjacent non-tumorous tissue samples. Furthermore, lower GAS5 expression levels were associated with larger tumor sizes, poor tumor differentiation, and advanced pathological stages. However, GAS5 was almost equally expressed between benign tumors compared with the adjacent normal tissues. GAS5 was also overexpressed in EGFR-TKI sensitive cell lines compared with the resistant cell line. Using MTT, EdU incorporation, and colony formation assays, we showed that GAS5-expressing A549 cells displayed an elevated level of cell death. In addition to its pro-apoptotic effect in the A549 cell line, GAS5 overexpression also suppressed the growth of A549-derived tumors in nude mice treated with gefitinib. GAS5 overexpression was inversely correlated with the expression of the EGFR pathway and IGF-1R proteins.ConclusionsCollectively, our results indicated that GAS5 LncRNA may represent a potential biomarker for the diagnosis of lung adenocarcinoma and that GAS5 might play a novel role in the development of the resistance to gefitinib, which could be reversed by overexpressing GAS5.

The purpose of this study is to identify a better potential biomarker for the prognosis of patients with non-small cell lung cancer (NSCLC). The expressions of Nek2, MCM7, and Ki-67 were evaluated in 270 NSCLC tissues using immunohistochemical and immunofluorescence techniques. Associations between protein expression and clinical pathologic characters were assessed, and the impact on overall survival was analyzed. We detected high levels of Nek2, MCM7, and Ki-67 expression in 25.9, 35.2, and 24.4 % of NSCLC tissues, respectively. Overexpressions of Nek2 were detected more frequently in high T-stage and N-stage cases (P = 0.000, 0.011). The expressions of Nek2, MCM7, and Ki-67 were correlated with each other. Kaplan-Meier curves indicated that patients with overexpression of Nek2, MCM7, and Ki-67 had a poorer overall survival rate compared to those with low expression for all stages (P = 0.000). In particular, the patients with Nek2 overexpression had the most negative prognosis. Multivariate Cox regression analysis showed that Nek2, MCM7, and Ki-67 are independent prognostic indicators for NSCLC. Our data suggest that among Nek2 kinase, MCM7, and Ki-67, it is Nek2 kinase that is the more effective tumor proliferation marker of poor prognosis for NSCLC patients. Thus, Nek2 may represent a new potential target for NSCLC therapeutic intervention.