Functional inactivation of human runt-related transcription factor 3 (RUNX3) through mutation or epigenetic silencing has been well-documented in many cancerous entities. In addition to gene mutation and promoter hypermethylation, cytoplasmic mislocalization has emerged as another major manifestation of RUNX3 dysfunction in malignancies including breast, colorectal and gastric cancers. The aim of the present study was to investigate whether patients with non-small cell lung cancer (NSCLC) and different RUNX3 expression patterns would have different overall survival (OS), and the associations between different patterns of clinicopathological parameters and clinical outcome. Expressions of RUNX3 and Ki-67 were immunohistochemically detected in normal lung tissue (n=5) and surgically resected tissues from NSCLC patients (n=188). The optimal cutoff of RUNX3 was determined by X-tile software associated with their survival. Apoptotic index in cancerous tissue was evaluated using the terminal deoxynucleotidyl transferase mediated dUTP-biotin nick end labelling method. The prognostic significance of different expression patterns of RUNX3 was determined by means of Kaplan-Meier survival estimates and log-rank tests. It was revealed that loss of RUNX3 expression in NSCLC was correlated with a low cancerous apoptotic index (P<0.001), shorter OS and worse prognosis (P=0.0142), while no statistical difference of apoptotic index (P=0.73) or survival (P=0.3781) was determined between patient subgroups with different localization of RUNX3 expression, which was quite different from the situation demonstrated in other malignancies. In conclusion, loss of expression rather than cytoplasmic mislocalization of RUNX3 predicted worse outcome in NSCLC, which was quite different from what manifested in other cancer types, and thus, the underlying mechanism may deserve further investigation.

Smoking frequently leads to epigenetic alterations, including DNA methylation and histone modifications. The effect that smoking has on the DNA methylation levels at CCGG sites, the expression of trimethylation of histone H3 at lysine 27 (H3K27me3) and enhancer of zeste homolog 2 (EZH2), and their interactions in patients with non-small cell lung cancer (NSCLC) were analyzed. There were a total of 42 patients with NSCLC, 22 with adenocarcinomas and 20 with squamous cell carcinomas enrolled in the present study. Expression of H3K27me3, EZH2 and proliferating cellular nuclear antigen (PCNA) were immunohistochemically detected. DNA methylation at CCGG sites was evaluated via histoendonuclease-linked detection of DNA methylation sites. The apoptotic index of cancerous tissues obtained from patients of different smoking statuses was evaluated via the terminal deoxynucleotidyl-transferase-mediated dUTP-biotin nick end labeling method. The association with clinicopathological data was calculated relative to different smoking statuses. Compared with the non-smokers, smokers with NSCLC exhibited a significantly lower apoptotic index (P<0.05), and frequently had a lower level of DNA methylation at CCGG sites, lower H3K27me3 expression and a higher EZH2 expression (P<0.05). DNA methylation levels at CCGG sites were negatively correlated to the Brinkman index (P=0.017). Furthermore, there was a parallel association between the H3K27me3 and EZH2 expression levels in the majority of smokers, whereas in the majority of non-smokers, there was a diverging association (P=0.015). There was a diverging association between the PCNA and EZH2 expression levels in the majority of smokers; however, in the majority of non-smokers, there was a parallel association (P=0.048). In addition, the association between the CCGG methylation ratio and immunohistochemical expression of H3K27me3 was a parallel association in the majority of smokers, while in the majority of non-smokers there was a diverging association (P=0.049). Conclusively, patients with NSCLC and different smoking statuses exhibit different epigenetic characteristics. Additionally, DNA methylation levels at the CCGG sites may have the ability to determine associations between the expression levels of H3K27me3, EZH2 and PCNA.

Emerging studies have indicated that the dysregulation of microRNAs (miRNAs or miRs) plays a vital role in the development and metastasis of tumors. However, the role of miR-93-5p in esophageal carcinoma (Ec) has not been extensively reported. The present study thus focused on the role of miR-93-5p and its downstream target in the occurrence and development of EC. Firstly, miRNA expression profiles associated with Ec were accessed from the TcGA_EScA dataset and analyzed. Subsequently, the expression patterns of miR-93-5p and TGFβR2 were characterized in the human esophageal cell line, Het-1A, and the human Ec cell lines, TE-1, Eca-109 and Ec9706, by RT-qPcR and western blot analysis. WST-1 assay, flow cytometry, Transwell assay, wound healing assay and bioinformatics analysis were used to explore their functions in Ec cells. Finally, a dual-luciferase reporter assay was employed to determine the targeted association between miR-93-5p and TGFβR2. The results revealed that the expression of miR-93-5p was markedly higher in Ec cell lines compared with that in the normal cell line. The overexpression of miR-93-5p facilitated cell proliferation, migration and invasion, and inhibited cell apoptosis. Additionally, TGFβR2 was identified as a functional target of miR-93-5p in EC cells, as judged by a series of in vitro experiments. Furthermore, it was found that the simultaneous overexpression of miR-93-5p and TGFβR2 almost had no effect on the biological behaviors of Ec cells. On the whole, the present study demonstrates that miR-93-5p promotes the proliferation, migration and invasion, and inhibits the apoptosis of Ec cells by targeting TGFβR2.