Detection of DNA Methylation Changes in Body Fluids. Epigenetics and Cancer, Part B. Elsevier; 2010. pp. 177-207. [DOI: 10.1016/b978-0-12-380864-6.00006-7]

Clinicopathological Significance and Diagnostic Value of DLEC1 Hypermethylation in Lung Cancer: A Meta-analysis

BACKGROUND

DLEC1 is a tumor-suppressor gene which plays a role in carcinogenesis. The purpose of the current study was to help establish the diagnostic performance of DLEC1 methylation in lung cancer.

METHODS

PubMed, Embase, CNKI, and Wanfang databases were searched to obtain eligible studies. The pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to estimate the strength of the associations. The diagnostic value was assessed by the summary receiver operating characteristics test.

RESULTS

A total of 7 articles, with 8 studies that included 673 lung cancer and 581 control samples, were collected in this meta-analysis. Our results showed a significant association of DLEC1 hypermethylation with lung cancer (P < 0.00001, OR = 13.93, 95% CI = 9.44-20.55). The frequency of DLEC1 methylation was significantly higher in squamous cell carcinoma (SCC) than adenocarcinoma (AC). Moreover, DLEC1 was more frequently methylated in patients with lung cancer aged 60 years or over, patients with lymphatic metastasis, or patients with stage III/IV lung cancer. In addition, there was a sensitivity value of 0.90 (95% CI = 0.86-0.93) and a specificity value of 0.60 (95% CI = 0.56-0.63), a pooled positive-likelihood ratio (PLR) of 2.27 (95% CI = 2.08-2.48), a pooled negative-likelihood ratio (NLR) of 0.17 (95% CI = 0.12-0.23), a diagnostic odds ratio (DOR) of 14.72 (10.09-21) and an area under the curve (AUC) of 0.8146 using DLEC1 methylation in the prediction of lung cancer risk.

CONCLUSION

This meta-analysis confirms that DLEC1 methylation is a promising biomarker for lung cancer.

DNA methylation and cancer diagnosis

DNA methylation is a major epigenetic modification that is strongly involved in the physiological control of genome expression. DNA methylation patterns are largely modified in cancer cells and can therefore be used to distinguish cancer cells from normal tissues. This review describes the main technologies available for the detection and the discovery of aberrantly methylated DNA patterns. It also presents the different sources of biological samples suitable for DNA methylation studies. We discuss the interest and perspectives on the use of DNA methylation measurements for cancer diagnosis through examples of methylated genes commonly documented in the literature. The discussion leads to our consideration for why DNA methylation is not commonly used in clinical practice through an examination of the main requirements that constitute a reliable biomarker. Finally, we describe the main DNA methylation inhibitors currently used in clinical trials and those that exhibit promising results.

DNA methylation biomarkers offer improved diagnostic efficiency in lung cancer

The exceptional high mortality of lung cancer can be instigated to a high degree by late diagnosis. Despite the plethora of studies on potential molecular biomarkers for lung cancer diagnosis, very few have reached clinical implementation. In this study, we developed a panel of DNA methylation biomarkers and validated their diagnostic efficiency in bronchial washings from a large retrospective cohort. Candidate targets from previous high-throughput approaches were examined by pyrosequencing in an independent set of 48 lung tumor/normal paired. Ten promoters were selected and quantitative methylation-specific PCR (qMSP) assays were developed and used to screen 655 bronchial washings from the Liverpool Lung Project (LLP) subjects divided into training (194 cases and 214 controls) and validation (139 cases and 109 controls) sets. Three statistical models were used to select the optimal panel of markers and to evaluate the performance of the discriminatory algorithms. The final logit regression model incorporated hypermethylation at p16, TERT, WT1, and RASSF1. The performance of this 4-gene methylation signature in the validation set showed 82% sensitivity and 91% specificity. In comparison, cytology alone in this set provided 43% sensitivity at 100% specificity. The diagnostic efficiency of the panel did not show any biases with age, gender, smoking, and the presence of a nonlung neoplasm. However, sensitivity was predictably higher in central (squamous and small cell) than peripheral (adenocarcinomas) tumors, as well as in stage 2 or greater tumors. These findings clearly show the impact of DNA methylation-based assays in the diagnosis of cytologically occult lung neoplasms. A prospective trial is currently imminent in the LLP study to provide data on the enhancement of diagnostic accuracy in a clinical setting, including by additional markers.

DNA methylation testing and marker validation using PCR: diagnostic applications

DNA methylation provides a fundamental epigenetic mechanism to establish and promote cell-specific gene-expression patterns, which are inherited by subsequent cell generations. Thus, the epigenome determines the differentiation into a cell lineage but can also program cells to become abnormal or malignant. In humans, different germline and somatic diseases have been linked to faulty DNA methylation. In this article, we will discuss the available PCR-based technologies to assess differences in DNA methylation levels mainly affecting 5-methylcytosine in the CpG dinucleotide context in hereditary syndromal and somatic pathological conditions. We will discuss some of the current diagnostic applications and provide an outlook on how DNA methylation-based biomarkers might provide novel tools for diagnosis, prognosis or patient stratification for diseases such as cancer.