Detection of methylation of the RAR-β gene in patients with non-small cell lung cancer

Epigenetic modulation of FBW7/Mcl-1 pathway for lung cancer therapy

Methylation induces epigenetic silencing of tumor suppressor genes in human lung cancer. Inhibition of DNA methyltransferases by decitabine (DAC) can demethylate and activate epigenetically silenced tumor suppressor genes. Epigenetic therapy using DAC should be an attractive strategy for lung cancer therapy. FBW7 is a tumor suppressor that functions as an Mcl-1 E3 ligase to degrade Mcl-1 by ubiquitination. Here we discovered that treatment of various human lung cancer cells with DAC resulted in activation of FBW7 expression, decreased levels of Mcl-1 protein, and growth inhibition. DAC-activated FBW7 expression promoted Mcl-1 ubiquitination and degradation leading to a significant reduction in the half-life of Mcl-1 protein. Mechanistically, treatment of lung cancer cells or lung cancer xenografts with DAC induced the conversion of the FBW7 gene from a methylated form to an unmethylated form, which was associated with the increased expression of FBW7 and decreased expression of Mcl-1 in vitro and in vivo. DAC suppressed lung cancer growth in a dose-dependent manner in vivo. Combined treatment with DAC and a Bcl2 inhibitor, venetoclax, exhibited strong synergistic potency against lung cancer without normal tissue toxicity. These findings uncover a novel mechanism by which DAC suppresses tumor growth by targeting the FBW7/Mcl-1 signaling pathway. Combination of DAC with Bcl2 inhibitor venetoclax provides more effective epigenetic therapy for lung cancer.

Association between Retinoic acid receptor-β hypermethylation and NSCLC risk: a meta-analysis and literature review

Emerging evidence indicates that Retinoic acid receptor-β (RARβ) is a tumor suppressor in many types of tumor. However, whether or not RARβ is a risk factor and is correlated to clinicopathological characteristics of non-small cell lung cancer (NSCLC) remains unclear. In this report, we performed a meta-analysis to determine the effects of RARβ hypermethylation on the incidence of NSCLC and clinicopathological characteristics in human NSCLC patients. Final valuation and analysis of 1780 cancer patients from 16 eligible studies was performed. RARβ hypermethylation was found to be significantly higher in NSCLC than in normal lung tissue, the pooled OR from 7 studies including 646 NSCLC and 580 normal lung tissues, OR = 6.05, 95% CI = 3.56-10.25, p<0.00001. RARβ hypermethylation was significantly higher in adenocarcinoma (AC) compared to squamous cell carcinoma (SCC), pooled OR is 0.68 (95% CI = 0.52-0.89, p = 0.005). RARβ hypermethylation was also found to occur significantly higher in smoker (n = 232) than non-smoker (n = 213) (OR = 2.46, 95% CI = 1.54-3.93, p = 0.0002). Our results indicate that RARβ hypermethylation correlates well with an increased risk in NSCLC patients. RARβ geneinactivation caused by RARβ methylation contributes the NSCLC tumorigenesis and may serve as a potential risk factor, diagnostic marker and drug target of NSCLC.

MicroRNA-26a regulates ANXA1, rather than DAL-1, in the development of lung cancer

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.

Clinicopathological significance and a potential drugtarget of RARβ in non-small-cell lung carcinoma: a meta-analysis and a systematic review

Lung cancer is the leading cause of cancer-related mortality in men worldwide. Aberrant RARβ promoter methylation has been frequently investigated in non-small-cell lung carcinoma (NSCLC), the most common form of lung cancer. The aim of present study was to carry out a meta-analysis and a systematic review to evaluate clinicopathological significance of RARβ promoter hypermethylation in NSCLC. A systematic literature search was carried out. The data were extracted and assessed by two reviewers independently. The Cochrane software Review Manager 5.2 was used to conduct the review. Odds ratios (ORs) with 95% corresponding confidence intervals (CIs) were calculated. A total of 18 relevant articles were available for meta-analysis which included 1,871 participants. The frequency of RARβ hypermethylation was significantly increased in NSCLC than in nonmalignant lung tissue, and the pooled OR was 5.69 (P<0.00001). RARβ hypermethylation was significantly more frequently observed in adenocarcinoma (AC) than in squamous cell carcinoma (SCC), and the pooled OR was 1.47 (P=0.005). Hypermethylation of RARβ gene in NSCLC was 2.46 times higher in smoking than in nonsmoking individuals, and the pooled OR was 2.46 (P=0.0002). RARβ hypermethylation rate was not significantly correlated with stage of the disease and sex. RARβ gene methylation status was not associated with prognosis of patients with NSCLC. In conclusion, RARβ promoter hypermethylation significantly increased in NSCLC than in non-neoplastic lung tissue and is predominant in AC, suggesting that RARβ methylation contributes to the development of NSCLC, especially AC. RARβ gene is a potential novel target for development of personalized therapy in patients with NSCLC, and is promising in restoration of retinoic acid-target gene induction via demethylation of RARβ1' promoter.

Association of methylation of the RAR-β gene with cigarette smoking in non-small cell lung cancer with Southern-Central Chinese population

Pathogenesis of lung cancer is a complicated biological process including multiple genetic and epigenetic changes. Since cigarette smoking is confirmed as the most main risk factor of non-small cell lung cancer (NSCLC), the aim of this study was to determine whether tobacco exposure plays a role in gene methylation. Methylation of the RAR-β gene were detected using methylation-specific polymerase chain reaction in DNA from 167 newly diagnosed cases with NSCLC and corresponding 105 controls. A significant statistical association was found in the detection rate of the promoter methylation of RAR-β gene between NSCLC and controls (x2=166.01; p<0.01), and hypermethylation of the RAR-β gene was significantly associated with smoking status (p=0.038, p<0.05). No relationship was found between RAR-β gene methylation and pathologic staging including clinical stage, cell type, gender and drinking (p>0.05), and the methylation of RAR-β gene rate of NSCLC was slightly higher in stages III+IV (80.0%) than in I+II (70.8%). Similar results were obtained for methylation of the RAR-β gene between squamous cell carcinoma (77.9%) and other cell type lung cancer (73.9%). These results showed that the frequency of methylation increased gradually with the development of clinical stage in smoking-associated lung cancer patients, and tobacco smoke may be play a potential role in RAR-β gene methylation in the early pathogenesis and process in lung cancer, particularly squamous cell carcinoma. Aberrant promoter methylation is considered to be a promising marker of previous carcinogen exposure and cancer risk.