MGMT, GATA6, CD81, DR4, and CASP8 gene promoter methylation in glioblastoma.
BACKGROUND
Methylation of promoter region is the major mechanism affecting gene expression in tumors. Recent methylome studies of brain tumors revealed a list of new epigenetically modified genes. Our aim was to study promoter methylation of newly identified epigenetically silenced genes together with already known epigenetic markers and evaluate its separate and concomitant role in glioblastoma genesis and patient outcome.


METHODS
The methylation status of MGMT, CD81, GATA6, DR4, and CASP8 in 76 patients with primary glioblastomas was investigated. Methylation-specific PCR reaction was performed using bisulfite treated DNA. Evaluating glioblastoma patient survival time after operation, patient data and gene methylation effect on survival was estimated using survival analysis.


RESULTS
The overwhelming majority (97.3%) of tumors were methylated in at least one of five genes tested. In glioblastoma specimens gene methylation was observed as follows: MGMT in 51.3%, GATA6 in 68.4%, CD81 in 46.1%, DR4 in 41.3% and CASP8 in 56.8% of tumors. Methylation of MGMT was associated with younger patient age (p < 0.05), while CASP8 with older (p < 0.01). MGMT methylation was significantly more frequent event in patient group who survived longer than 36 months after operation (p < 0.05), while methylation of CASP8 was more frequent in patients who survived shorter than 36 months (p < 0.05). Cox regression analysis showed patient age, treatment, MGMT, GATA6 and CASP8 as independent predictors for glioblastoma patient outcome (p < 0.05). MGMT and GATA6 were independent predictors for patient survival in younger patients' group, while there were no significant associations observed in older patients' group when adjusted for therapy.


CONCLUSIONS
High methylation frequency of tested genes shows heterogeneity of glioblastoma epigenome and the importance of MGMT, GATA6 and CASP8 genes methylation in glioblastoma patient outcome.
Laboratory of Neurooncology and Genetics, Neuroscience Institute, Medical Academy, Lithuanian University of Health Sciences, Eiveniu str, 4, Kaunas, LT, 50009, Lithuania. dainski@gmail.com
Daina
D
Skiriute
Paulina
P
Vaitkiene
Viktoras
V
Saferis
Virginija
V
Asmoniene
Kestutis
K
Skauminas
Vytenis Pranas
VP
Deltuva
Arimantas
A
Tamasauskas
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D053181:Caspase 8 / Q000235:genetics*; D019175:DNA Methylation; D015254:DNA Modification Methylases / Q000235:genetics*; D045643:DNA Repair Enzymes / Q000235:genetics*; D005260:Female; D050993:GATA6 Transcription Factor / Q000235:genetics*; D005909:Glioblastoma / Q000235:genetics* / Q000401:mortality; D006801:Humans; D008297:Male; D008875:Middle Aged; D011401:Promoter Regions, Genetic; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000235:genetics*; D060225:Tetraspanin 28 / Q000235:genetics*; D025521:Tumor Suppressor Proteins / Q000235:genetics*
D050993:GATA6 Transcription Factor; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D060225:Tetraspanin 28; D025521:Tumor Suppressor Proteins; D015254:DNA Modification Methylases; C515491:MGMT protein, human; D053181:Caspase 8; D045643:DNA Repair Enzymes