MGMT, GATA6, CD81, DR4, CASP8 and NPTX2 gene promoter methylation study in glioblastomas

Abstract

Glioblastoma is the most common malignant astrocytic tumor of the central nervous system. It is characterized by various genetic alterations, affecting genes that control cell growth, apoptosis, angiogenesis, and invasion. Epigenetic alterations also affect the expression of cancer genes alone, or in combination with genetic mechanisms. Given the resistance of glioblastoma to standard treatment, the deeper understanding of the underlying genetic and epigenetic lesions is vital. Cytosine methylation in CpG dinucleotides in gene promoters is a common reason for DNA silencing and transcriptional repression that can modulate features of glioblastoma. The best known is O6-methylguanine-DNA methyltransferase (MGMT) promoter methylation determining tumors response to DNA alkylating agents [1]. GATA binding protein 6 (GATA6) was identified as a tumor suppressor gene in human cells of the central nervous system [2]. CD81 antigen gene encodes protein of tetraspanin family that is involved in signal transduction. DR4 (death receptor 4) gene is pro-apoptotic death receptor activated by TRAIL, which induces apoptosis. The epigenetic silencing of CASP8 might lead to inactivation of Fas-apoptotic pathway. NPTX2 (neuronal pentraxin 2) gene is normally expressed in the central nervous system and increased NPTX2 was associated with poorer survival of glioblastoma patients [3]. In this investigation the genomic DNA from glioblastoma tissue was bisulfite modified. Promoter methylation was detected by methylation-specific PCR (MSP). Each MSP reaction incorporated 20 ng of bisulfite treated DNA as template. The promoter methylation in MGMT, GATA6, CD81, DR4, CASP8 and NPTX2 genes is investigated and biomarkers’ significance in disease prognosis is estimated. Aknowledgements: This research was funded by a grant (No. LIG-17/2010) from the Research Council of Lithuania.