Methylated tumor-specific DNA as a plasma biomarker in patients with glioma.
OBJECTIVE
Patients with systemic malignancies have substantial quantities of tumor-specific DNA in their plasma which may serve as a potential biomarker for tumor burden. This approach has not been studied in gliomas.


METHODS
Methylation specific polymerase chain reaction (MSP) was used to determine the methylation status the promoters for p16/(INK4a), MGMT, p73, and RARbeta within glioma tissue and plasma. Blood was collected prior to craniotomy in 10 patients with glioma. DNA was extracted from tumor and plasma samples and assayed with MSP. Total plasma DNA also was quantified. Tumor-specific plasma DNA was defined as identification of the same methylated promoter (MP) in both tumor and plasma.


RESULTS
Total plasma DNA concentration was markedly elevated (mean 6,503 ng/ml, SEM 1,400 ng/ml). Glioma tissue contained methylation of at least one promoter in 9 out of 10 (90 percent) of patients studied. Of these patients, 6 out of 9 (67 percent) demonstrated methylation of at least one of the same promoters in plasma. Five of these had one MP identified in the plasma and one had 2 MP. Overall, glioma-specific plasma DNA was present in plasma of 6 out of 10 (60 percent) of patients. Each MP DNA marker found in the plasma also was present in the intracranial tumor.


CONCLUSIONS
Patients with high grade gliomas have large amounts of DNA in the plasma. Of these primary brain tumors, 90 percent contained methylated gene promoters, and in over 60 percent of these patients the same methylated promoters present in the tumor also were found in the plasma. This represents the first step to developing a quantitative plasma biomarker that could be used to monitor glioma status.
Weaver
Kyle D
KD
Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, TN 37232, USA. kyle.weaver@vanderbilt.edu
Grossman
Stuart A
SA
Herman
James G
JG
D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000097:blood* / Q000235:genetics; D001932:Brain Neoplasms / Q000097:blood* / Q000235:genetics; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics; D019175:DNA Methylation; D017931:DNA Primers; D004273:DNA, Neoplasm / Q000097:blood* / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics; D005260:Female; D016147:Genes, Tumor Suppressor; D005910:Glioma / Q000097:blood* / Q000235:genetics; D006801:Humans; D008297:Male; D008875:Middle Aged; D009687:Nuclear Proteins / Q000235:genetics; D019853:O(6)-Methylguanine-DNA Methyltransferase / Q000235:genetics; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D018168:Receptors, Retinoic Acid / Q000235:genetics; D000072160:Tumor Protein p73; D025521:Tumor Suppressor Proteins
D014408:Biomarkers, Tumor; D019941:Cyclin-Dependent Kinase Inhibitor p16; D017931:DNA Primers; D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D018168:Receptors, Retinoic Acid; C000606460:TP73 protein, human; D000072160:Tumor Protein p73; D025521:Tumor Suppressor Proteins; C082925:retinoic acid receptor beta; D019853:O(6)-Methylguanine-DNA Methyltransferase