title: Optimization of quantitative MGMT promoter methylation analysis using pyrosequencing and combined bisulfite restriction analysis.
abstract: Resistance to chemotherapy is a major complication during treatment of cancer patients. Hypermethylation of the MGMT gene alters DNA repair and is associated with longer survival of glioblastoma patients treated with alkylating agents. Therefore, MGMT promoter methylation plays an important role as a predictive biomarker for chemotherapy resistance. To adopt this established correlation into a molecular diagnosis procedure, we compared and optimized three experimental techniques [combined bisulfite restriction analysis, a primer extension- and denaturing high-performance liquid chromatography-based method named SIRPH (SNuPE ion pair-reverse phase high-performance liquid chromatography), and pyrosequencing] with regard to their accuracy of detecting MGMT promoter methylation. Initially, bisulfite sequencing was used to obtain a comprehensive methylation profile of the MGMT promoter region in 22 glioblastoma samples and in three normal brain controls. Next, we statistically identified CpG sites that best discriminate between methylated and unmethylated MGMT promoters. These results were then used to design optimal combined bisulfite restriction analysis, SIRPH, and pyrosequencing assays for accurate and cost-efficient assessment of MGMT promoter methylation. We compared all three techniques with regard to their reliability and reproducibility on well-characterized tumor samples. The optimized pyrosequencing assay performed best and provides a sensitive, robust, and easy-to-use method for quantitative assessment of MGMT methylation, for both snap-frozen and paraffin-embedded specimens.
authors.affiliation: Department of Neuropathology, University of Bonn Medical Center, Sigmund-Freud-Str. 25, D-53105 Bonn, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Mikeska
authors.forename: Christoph
authors.initials: C
authors.lastname: Bock
authors.forename: Osman
authors.initials: O
authors.lastname: El-Maarri
authors.forename: Anika
authors.initials: A
authors.lastname: Hübner
authors.forename: Denise
authors.initials: D
authors.lastname: Ehrentraut
authors.forename: Johannes
authors.initials: J
authors.lastname: Schramm
authors.forename: Jörg
authors.initials: J
authors.lastname: Felsberg
authors.forename: Philip
authors.initials: P
authors.lastname: Kahl
authors.forename: Reinhard
authors.initials: R
authors.lastname: Büttner
authors.forename: Torsten
authors.initials: T
authors.lastname: Pietsch
authors.forename: Andreas
authors.initials: A
authors.lastname: Waha
mesh_terms: D000465:Algorithms; D014408:Biomarkers, Tumor / Q000032:analysis; D016000:Cluster Analysis; D019175:DNA Methylation; D015254:DNA Modification Methylases / Q000032:analysis* / Q000235:genetics*; D045643:DNA Repair Enzymes / Q000032:analysis* / Q000235:genetics*; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D005557:Formaldehyde / Q000494:pharmacology; D005629:Frozen Sections; D005909:Glioblastoma / Q000175:diagnosis / Q000235:genetics; D006801:Humans; D016612:Paraffin Embedding; D016133:Polymerase Chain Reaction / Q000379:methods*; D011401:Promoter Regions, Genetic; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D017422:Sequence Analysis, DNA / Q000379:methods*; D013447:Sulfites / Q000494:pharmacology*; D014021:Tissue Preservation; D025521:Tumor Suppressor Proteins / Q000032:analysis* / Q000235:genetics*
chemical_list: D014408:Biomarkers, Tumor; D013447:Sulfites; D025521:Tumor Suppressor Proteins; D005557:Formaldehyde; D015254:DNA Modification Methylases; C515491:MGMT protein, human; D045643:DNA Repair Enzymes; C042345:hydrogen sulfite