[DNA methylation of tumor suppressor genes located on chromosome 3p in non-small cell lung cancer]

PM2.5 exposure and DLEC1 promoter methylation in Taiwan Biobank participants

BACKGROUND

Particulate matter (PM) < 2.5 μm (PM2.5) or fine PM is a serious public health concern. It affects DNA methylation and heightens carcinogenesis. Deleted in lung and esophageal cancer 1 (DLEC1) is a tumor suppressor gene. However, aberrant methylation of the gene is associated with several cancers. We evaluated the association between PM2.5 and DLEC1 promoter methylation in Taiwanese adults based on regular outdoor exercise.

METHODS

We obtained DNA methylation and exercise data of 496 participants (aged between 30 and 70 years) from the Taiwan Biobank (TWB) database. We also extracted PM2.5 data from the Air Quality Monitoring Database (AQMD) and estimated participants' exposure using residential addresses.

RESULTS

DLEC1 methylation and PM2.5 were positively associated: beta coefficient (β) = 0.114 × 10-3; p value = 0.046. The test for interaction between exercise and PM2.5 on DLEC1 methylation was significant (p value = 0.036). After stratification by exercise habits, PM2.5 and DLEC1 methylation remained significantly associated only among those who exercised regularly (β = 0.237 × 10-3; p value = 0.007). PM2.5 quartile-stratified analyses revealed an inverse association between regular exercise and DLEC1 methylation at PM2.5 < 27.37 μg/m3 (β = - 5.280 × 10-3; p value = 0.009). After combining exercise habits and PM2.5 quartiles, one stratum (i.e., regular exercise and PM2.5 < 27.37 μg/m3) was inversely associated with DLEC1 methylation (β = -5.160 × 10-3, p value = 0.007).

CONCLUSIONS

We found significant positive associations between PM2.5 and DLEC1 promoter methylation. Regular exercise at PM2.5 < 27.37 μg/m3 seemingly regulated DLEC1 promoter methylation.

Application of artificial neural network model combined with four biomarkers in auxiliary diagnosis of lung cancer

The purpose of the study was to explore the application of artificial neural network model in the auxiliary diagnosis of lung cancer and compare the effects of back-propagation (BP) neural network with Fisher discrimination model for lung cancer screening by the combined detections of four biomarkers of p16, RASSF1A and FHIT gene promoter methylation levels and the relative telomere length. Real-time quantitative methylation-specific PCR was used to detect the levels of three-gene promoter methylation, and real-time PCR method was applied to determine the relative telomere length. BP neural network and Fisher discrimination analysis were used to establish the discrimination diagnosis model. The levels of three-gene promoter methylation in patients with lung cancer were significantly higher than those of the normal controls. The values of Z(P) in two groups were 2.641 (0.008), 2.075 (0.038) and 3.044 (0.002), respectively. The relative telomere lengths of patients with lung cancer (0.93 ± 0.32) were significantly lower than those of the normal controls (1.16 ± 0.57), t = 4.072, P < 0.001. The areas under the ROC curve (AUC) and 95 % CI of prediction set from Fisher discrimination analysis and BP neural network were 0.670 (0.569-0.761) and 0.760 (0.664-0.840). The AUC of BP neural network was higher than that of Fisher discrimination analysis, and Z(P) was 0.76. Four biomarkers are associated with lung cancer. BP neural network model for the prediction of lung cancer is better than Fisher discrimination analysis, and it can provide an excellent and intelligent diagnosis tool for lung cancer.

[Research Progress of PR Domain Zinc Finger Protein 14]

正性调节区锌指蛋白14（PR domain zinc finger protein 14, PRDM14）是PRDM家族中的重要成员，PRDM14基因对维持细胞的完整性和控制细胞的分化、生长及凋亡起着关键作用，在原始生殖细胞的形成、干细胞全能性的维持和其他组织器官的形成中都发挥了重要作用。PRDM14具有1个PR结构域和6个锌指结构，PRDM14参与了组蛋白的去乙酰化及甲基化过程，通过启动子区甲基化水平的改变参与肿瘤的形成。PRDM14异常甲基化能够引起染色质结构、DNA构象及DNA与蛋白质作用方式的改变，使基因的转录和表达受抑制，这些改变引起了肿瘤的发生、发展及转移。本文根据国内外发表的相关文献对PRDM14的研究现状进行综述。

The clinicopathological significance and ethnic difference of FHIT hypermethylation in non-small-cell lung carcinoma: a meta-analysis and literature review

Emerging evidence indicates that FHIT is a candidate tumor suppressor in many types of tumors including non-small-cell lung carcinoma (NSCLC). However, the prognostic value and correlation between FHIT hypermethylation and clinicopathological characteristics of NSCLC remains unclear. In this report, we performed a meta-analysis to evaluate the effects of FHIT hypermethylation on the incidence of NSCLC and clinicopathological characteristics of human NSCLC patients. Final analysis of 1,801 NSCLC patients from 18 eligible studies was performed. FHIT hypermethylation was found to be significantly higher in NSCLC than in normal lung tissue. The pooled odds ratio (OR) from ten studies included 819 NSCLC and 792 normal lung tissues (OR =7.51, 95% confidence interval [CI] =2.98-18.91, P<0.0001). Subgroup analysis based on ethnicity implied that FHIT hypermethylation level was higher in NSCLC tissues than in normal tissues in both Caucasians (P=0.02) and Asians (P<0.0001), indicating that the difference in Asians was much more significant. FHIT hypermethylation was also correlated with sex status, smoking status, as well as pathological types. In addition, patients with FHIT hypermethylation had a lower survival rate than those without (hazard ratio =1.73, 95% CI =1.10-2.71, P=0.02). The results of this meta-analysis suggest that FHIT hypermethylation is associated with an increased risk and poor survival in NSCLC patients. FHIT hypermethylation, which induces the inactivation of FHIT gene, plays an important role in the carcinogenesis and clinical outcome and may serve as a potential diagnostic marker and drug target of NSCLC.

[Meta-analysis of the Association between RASSF1A Gene Promoter Methylation and Non-small Cell Lung Cancer]

BACKGROUND AND OBJECTIVE

The CpG island aberrant promoter methylation in the tumor suppressor gene region plays an important role in the process of tumorigenesis. Relevant evidence shows that the promoter methylation of RAS association domain family 1A (RASSF1A) gene, a tumor suppressor gene, has a close relationship with non-small cell lung cancer (NSCLC) development; therefore, RASSF1A may be a potential NSCLC biomarker. This paper discussed and summarized the relationship between RASSF1A gene promoter methylation frequency and NSCLC through meta-analysis.

METHODS

By searching Medline, EMBASE, CNKI, and Wanfang database, we selected and collected the published articles regarding RASSF1A gene promoter methylation and NSCLC risk according to the marked inclusion and exclusion criteria. Through meta-analysis, combined odds ratio (OR) and 95% confidence interval (CI) data were used to analyze the RASSF1A gene promoter methylation and NSCLC relationship.

RESULTS

A total of 23 articles were utilized in this study. Results indicated that the RASSF1A gene promoter methylation rate was 41.50% (95%CI: 34%-49%) in NSCLC tissue and was 5.58% (95%CI: 2%-9%) for the control group. Compared with normal lung tissue, RASSF1A methylation frequency in tumor tissue was significantly higher than that of the control group (OR=8.72, 95%CI: 4.88-15.58, P<0.05). Subgroup analysis showed that the RASSF1A gene promoter methylation rate of tumor tissue was higher than that of plasma group (OR=10.99, 95%CI: 2.48-48.68) and normal control tissue group (OR=8.74, 95%CI: 4.39-17.41).

CONCLUSIONS

The rate of RASSF1A promoter gene methylation in NSCLC patient tissue samples was higher than that of normal lung samples, whereas the rate of RASSF1A promoter gene methylation in the tissue has more significant effect on lung cancer occurrence. This finding indicates that RASSF1A gene promoter methylation could be used as an NSCLC biomarker and was involved in NSCLC carcinogenic effects.

The clinicopathological significance of FHIT hypermethylation in non-small cell lung cancer, a meta-analysis and literature review

Emerging evidence indicates that FHIT is a candidate tumor suppressor in non-small cell lung cancer (NSCLC). However, the correlation between FHIT hypermethylation and clinicopathological characteristics of NSCLC remains unclear. Thus, we conducted a meta-analysis to quantitatively evaluate the effects of FHIT hypermethylation on the incidence of NSCLC and clinicopathological characteristics. Final analysis of 1717 NSCLC patients from 16 eligible studies was performed. FHIT hypermethylation was found to be significantly higher in NSCLC than in normal lung tissue, the pooled OR from 8 studies including 735 NSCLC and 708 normal lung tissue, OR = 5.45, 95% CI = 2.15-13.79, p = 0.0003. FHIT hypermethylation was also correlated with sex status, smoking status, as well as pathological types. We did not find that FHIT hypermethylation was correlated with the differentiated types or clinical stages in NSCLC patients. However, patients with FHIT hypermethylation had a lower survival rate than those without, HR = 1.73, 95% CI = 1.10-2.71, p = 0.02. The results of this meta-analysis suggest that FHIT hypermethylation is associated with an increased risk and worsen survival in NSCLC patients. FHIT hypermethylation, which induces the inactivation of FHIT gene, plays an important role in the carcinogenesis and clinical outcome and may serve as a potential drug target of NSCLC.

DNA methylation of hMLH1 correlates with the clinical response to cisplatin after a surgical resection in Non-small cell lung cancer

Our previous study demonstrated that promoter methylation of human mutL homolog 1 (hMLH1) is involved in determining sensitivity to cisplatin in NSCLC A549/DDP cell line, The present study was designed to determine whether DNA methylation of hMLH1 affects the prognosis of non-small cell lung cancer patients who received cisplatin-based adjuvant chemotherapy. Methylation status of hMLH1 was examined by nested methylation-specific PCR (nested MSP) in 84 archived NSCLC surgically resected tissue specimens from patients receiving cisplatin-based adjuvant chemotherapy. Univariate and multivariate analysis were used to investigate the relationship between hMLH1 methylation status and the clinical prognosis of the patients mentioned above. In the cohort of 84 NSCLC cases, 80 tissue samples were successfully amplified by nested MSP. Among them, 36 samples (45%) were identified to be methylated. Moreover, hMLH1 methylation was not associated with age, gender, smoking status, T stage, histology and differentiation, but correlated with lymphatic metastasis (P=0.021). Multivariate logistic regression analysis showed that hMLH1 methylation may function as a significant independent prognostic factor for tumor recurrence in NSCLC patients treated with adjuvant cisplatin (HR 3.114, 95% CI 1.032-9.399; P=0.044). However, Kaplan-Meier method (P=0.093) and multivariate Cox regression analysis (P=0.598) revealed that hMLH1 methylation was not associated with the survival of these patients. To conclude, the cisplatin-based adjuvant chemotherapy is more beneficial for NSCLC patients without hMLH1 methylation. hMLH1 methylation may have a potential to become a biomarker of individualized therapy for NSCLC patients.

Development of a multiplex methylation specific PCR suitable for (early) detection of non-small cell lung cancer

Lung cancer is a worldwide health problem and a leading cause of cancer-related deaths. Silencing of potential tumor suppressor genes (TSGs) by aberrant promoter methylation is an early event in the initiation and development of cancer. Thus, methylated cancer type-specific TSGs in DNA can serve as useful biomarkers for early cancer detection. We have now developed a "Multiplex Methylation Specific PCR" (MMSP) assay for analysis of the methylation status of multiple potential TSGs by a single PCR reaction. This method will be useful for early diagnosis and treatment outcome studies of non-small cell lung cancer (NSCLC). Genome-wide CpG methylation and expression microarrays were performed on lung cancer tissues and matched distant non-cancerous tissues from three NSCLC patients from China. Thirty-eight potential TSGs were selected and analyzed by methylation PCR on bisulfite treated DNA. On the basis of sensitivity and specificity, six marker genes, HOXA9, TBX5, PITX2, CALCA, RASSF1A, and DLEC1, were selected to establish the MMSP assay. This assay was then used to analyze lung cancer tissues and matched distant non-cancerous tissues from 70 patients with NSCLC, as well as 24 patients with benign pulmonary lesion as controls. The sensitivity of the assay was 99% (69/70). HOXA9 and TBX5 were the 2 most sensitive marker genes: 87% (61/70) and 84% (59/70), respectively. RASSF1A and DLEC1 showed the highest specificity at 99% (69/70). Using the criterion of identifying at least any two methylated marker genes, 61/70 cancer samples were positive, corresponding to a sensitivity of 87% and a specificity of 94%. Early stage I or II NSCLC could even be detected with a 100% specificity and 86% sensitivity. In conclusion, MMSP has the potential to be developed into a population-based screening tool and can be useful for early diagnosis of NSCLC. It might also be suitable for monitoring treatment outcome and recurrence.

A meta-analysis of the relationship between RARβ gene promoter methylation and non-small cell lung cancer

Background

Hypermethylation of CpG islands in tumor suppressor gene plays an important role in carcinogenesis. Many studies have demonstrated that hypermethylation in promoter region of RARβ gene could be found with high prevalence in tumor tissue and autologous controls such as corresponding non-tumor lung tissue, sputum and plasma of the NSCLC patients. But with the small number subjects included in the individual studie, the statistical power is limited. Accordingly, we performed this meta-analysis to further asses the relationship of methylation prevalence between the cancer tissue and atuologous controls (corresponding non-tumor lung tissue, sputum and plasma).

Methods

The published articles about RARβ gene promoter hypermethyltion were identified using a systematic search strategy in PubMed, EMBASE and CNKI databases. The pooled odds ratio (OR) of RARβ promoter methylation in lung cancer tissue versus autologous controls were calculated.

Results

Finally, eleven articles, including 1347 tumor tissue samples and 1137 autologous controls were included in this meta-analysis. The pooled odds ratio of RARβ promoter methylation in cancer tissue was 3.60 (95%CI: 2.46–5.27) compared to autologous controls with random-effect model. Strong and significant correlation between tumor tissue and autologous controls of RARβ gene promoter hypermethylation prevalence across studies (Correlation coefficient 0.53) was found.

Conclusion

RARβ promoter methylation may play an important role in carcinogenesis of the NSCLC. With significant methylation prevalence correlation between tumor tissue and autologous of this gene, methylation detection may be a potential method for searching biomarker for NSCLC.

[The relationship between FHIT gene promoter methylation and lung cancer risk: a meta-analysis]

背景与目的

抑癌基因启动子序列DNA甲基化与该基因在肿瘤细胞中表达下调有关。FHIT（fragile histindine triad）基因被认为是重要的肿瘤抑制基因，文献报道其启动子序列DNA在肿瘤组织中常发生甲基化改变。本研究采用meta分析的方法探讨FHIT基因启动子序列DNA甲基化与肺癌的相关性。

方法

检索Pubmed、CNKI及万方数据库，收集公开发表的关于FHIT基因启动子序列DNA甲基化与肺癌相关性的论文。对比分析肺癌组织与其配对的癌旁/正常肺组织、支气管盥洗液或血浆中FHIT基因启动子序列DNA甲基化发生率有无差别。以优势比（odd ratio, OR）为效应量，采用STATA 11.0统计软件进行合并分析。

结果

最终纳入符合要求的文献11篇，肺癌组织、癌旁/正常肺组织、支气管盥洗液和血浆中FHIT基因启动子序列甲基化率分别为P_median=40.0%（0-68.3%）、P_median=8.7%（0-35.0%）、P_median=33.3%（17.1%-38.3%）和P_median=35.9%（31.1%-50.8%）。肺癌中FHIT基因启动子序列甲基化率明显高于正常肺组织（OR=5.82, 95%CI: 3.74-9.06, P < 0.05），而与支气管盥洗液和血浆比较差别无统计学意义，（OR=1.55, 95%CI: 0.89-2.70, P > 0.05; OR=1.41, 95%CI: 0.90-2.20, P > 0.05）。

结论

与癌旁/正常肺组织相比患者肺癌组织中FHIT基因启动子序列DNA甲基化率明显增高，该基因的启动子甲基化与肺癌的发生可能存在相关性。

The significance of epigenetic alterations in lung carcinogenesis

Lung cancer is recognized as a leading cause of cancer-related death worldwide and its frequency is still increasing. The prognosis in lung cancer is poor and limited by the difficulties of diagnosis at early stage of disease, when it is amenable to surgery treatment. Therefore, the advance in identification of lung cancer genetic and epigenetic markers with diagnostic and/or prognostic values becomes an important tool for future molecular oncology and personalized therapy. As in case of other tumors, aberrant epigenetic landscape has been documented also in lung cancer, both at early and late stage of carcinogenesis. Hypermethylation of specific genes, mainly tumor suppressor genes, as well as hypomethylation of oncogenes and retrotransposons, associated with histopathological subtypes of lung cancer, has been found. Epigenetic aberrations of histone proteins and, especially, the lower global levels of histone modifications have been associated with poorer clinical outcome in lung cancer. The recently discovered role of epigenetic modifications of microRNA expression in tumors has been also proven in lung carcinogenesis. The identified epigenetic events in lung cancer contribute to its specific epigenotype and correlated phenotypic features. So far, some of them have been suggested to be cancer biomarkers for early detection, disease monitoring, prognosis, and risk assessment. As epigenetic aberrations are reversible, their correction has emerged as a promising therapeutic target.