Aberrant promoter methylation in pleural fluid DNA for diagnosis of malignant pleural effusion

Accumulating evidence implicates epigenetic changes such as hypermethylation in carcinogenesis. We investigated whether DNA methylation of 5 tumor suppressor genes in pleural fluid samples could aid in diagnosis of malignant effusion. In samples from 47 patients with malignant pleural effusions and 34 with nonmalignant effusions, we used a methylation-specific polymerase chain reaction to detect aberrant hypermethylation of the promoters of the DNA repair gene O⁶-methylguanine-DNA methyltransferase (MGMT), p16 ^INK4a, ras association domain family 1A (RASSF1A), apoptosis-related genes, death-associated protein kinase (DAPK), and retinoic acid receptor β (RARβ). Promoter hypermethylation was associated with malignant effusion for MGMT (Odds ratio (OR) = ∞), p16^INK4a (OR = ∞), RASSF1A (OR = 13.8; CI, 1.71-112), and RARβ (OR = 3.17; CI, 1.10-9.11), but not for DAPK. Instead, DAPK methylation was associated with the length of smoking (p < 0.05). Patients with hypermethylation of MGMT, p16 ^INK4a, RASSF1A or RARβ were 5.68 times more likely to have malignant effusions than patients without methylation (p = 0.008). Methylations per patient were more numerous for lung cancer than nonmalignant pulmonary disease (0.915 vs. 0.206, p < 0.001). Sensitivity, specificity, and positive predictive value of methylation in one or more genes for diagnosis of malignant effusion were 59.6%, 79.4%, and 80.0% respectively. In conclusion, aberrant promoter methylation of tumor suppressor genes in pleural fluid DNA could be a valuable diagnostic marker for malignant pleural effusion.