Aberrant promoter methylation of CDH13 and MGMT genes is associated with clinicopathologic characteristics of primary non-small-cell lung carcinoma

Introduction: Systemic methylation changes may be a diagnostic marker for tumor development or prognosis. Here, we investigate the relationship between gene methylation in lung tumors relative to normal lung tissue and whether DNA methylation changes can be detected in paired blood samples. Material and Methods: Sixty-five patients were enrolled in a surgical case series of non-small-cell lung carcinoma at a single institution. By using bisulfite pyrosequencing, CpG methylation was quantified at 5 genes (RASSF1A, CDH13, MGMT, ESR1, and DAPK) in lung tumor, pathologically normal lung tissue, and circulating blood from enrolled cases. Results: The analyses of methylation in tumors compared with normal lung tissue identified higher methylation of CDH13, RASSF1A, and DAPK genes, whereas ESR1 and MGMT methylation did not differ significantly between these tissue types. We then examined whether the 3 aberrantly methylated genes could be detected in blood. The difference in methylation observed in tumors was not reflected in methylation status of matching blood samples, which indicated a low feasibility of detecting lung cancer by analyzing these genes in a blood-based test. Lastly, we probed whether tumor methylation was associated with clinical and demographic characteristics. Histology and sex were associated with methylation at the CDH13 gene, whereas, stage was associated with methylation at MGMT. Conclusion: Our results showed higher methylation of RASSF1A, CDH13, and DAPK genes in lung tumors compared with normal lung. The lack of reflection of these methylation changes in blood samples from patients with non-small-cell lung carcinoma indicates their poor suitability for a screening test.