Identification of epigenetic aberrant promoter methylation in pleural fluid DNA is useful for diagnosis of malignant pleural effusion

Abstract

9567 Lung cancer and malignant mesothelioma are major cause of pleural effusion, and management of lung cancer patients with pleural effusion requires effective treatment based on timely and accurate diagnosis. Thus, differentiating between malignant and nonmalignant pleural effusions is a critical clinical problem, and conventional methods have proven to be inadequate. Aberrant methylation of CpG islands, one of the major mechanisms to inactivate tumor suppressor genes in human cancers, has been found in lung cancer and other malignancies. Recent studies revealed that detection of aberrant methylation of DNA in serum or BAL might be available to diagnose malignancies. Based on these studies, we investigated to identify aberrant promoter methylation of DNA in pleural effusion and evaluate the usefulness of this approach for differential diagnosis of pleural effusion. We examined methylation status of RARβ, p16INK4a, DAPK, RASSF1A, and MGMT in 81 pleural effusion samples using methylation-specific PCR. Forty-seven patients were given a diagnosis of malignancies (median age 69 years; range 29–87; male/female 35/12). 34 patients were non-malignant pleural effusion. In patients with malignancies, DNA methylation of pleural effusion was detected in 6.4% for MGMT, 21.3% for p16INK4a, 27.7% for RASSF1A, 29.8% for DAPK, and 40.4% for RARβ. Of 47 patients with malignancies, 34 (72.3%) had methylation of at least one gene. The total number of methylation in five genes per patient was significantly higher in malignancies (1.26 genes/patient) than in non-malignant pulmonary diseases (0.56 genes/patient, p<0.001). A crude unconditional logistic regression model correlating methylation status and risk of malignancies showed that the patients with at least one methylated gene showed 3.31 times higher probability of having mlignancies compared to patients without any methylated genes (p = 0.01). These results suggested that patients with methylation have significant high risk for malignancies,and identification of aberrant promoter methylation in pleural effusion DNA could be a useful tool for differential diagnosis of pleural effusion. No significant financial relationships to disclose.