Incidence and prognostic value of multiple gene promoter methylations in gliomas

Aberrant CpG island methylation is a common phenomenon in malignancy. The methylation status of multiple tumor suppressor genes may serve as a biomarker for early diagnostics and the prediction of prognosis. In this study, we quantitatively determined the promoter methylation status of five tumor-related genes in tumor tissue and paired serum from 240 patients with gliomas. The relationship between hyper-methylation and clinic-pathological parameters was evaluated, and the prognostic value of the methylation status was determined. Hypermethylation in serum was shown to be accompanied by hypermethylation in paired tumor tissues. In both tumors and serum, methylation of polymerase-1 (PARP-1), SHP-1, DAPK-1 and TIMP-3 genes was at significantly higher levels in high-grade compared with low-grade gliomas, indicating that the promoter methylation status positively correlates with tumor grade. In malignant gliomas, the serum methylation levels of PARP-1, and SHP-1 together with IDH-1 mutations were found to be independent prognostic factors for overall survival. Moreover, hypermethylation of PARP-1 in serum correlated with a shorter progression-free survival time. These results suggest that hypermethylation in gliomas correlates with increased malignancy and poor prognosis. Analysis of the serum promoter methylation status of multiple genes could therefore be used as a biomarker for the detection and evaluation of the prognosis of glioma patients.