Quantitative plasma hypermethylated DNA markers of undifferentiated nasopharyngeal carcinoma.
OBJECTIVE
Gene-specific methylation is common in primary undifferentiated nasopharyngeal carcinoma (NPC). DNA released from apoptotic or necrotic cell death including those aberrantly methylated promoter DNA of cancer cells is absorbed into the circulation as cell-free plasma DNA of the patient. This study aims at evaluation of the potential use of methylated gene promoter DNA as a serological tumor marker of primary and potentially salvageable local or nodal recurrent NPC.


METHODS
The quantity of plasma hypermethylated gene promoters of CDH1, DAPK1, p15, p16, RASSF1A, and MLH1 of 41 NPC patients before treatment and 43 normal individuals were studied using real-time quantitative PCR. The post-treatment plasma hypermethylated CDH1, DAPK1,and p16 were also measured in 13 NPC patients with locoregional recurrence and 17 patients in remission.


RESULTS
Concentrations of cell-free circulating DNA were significantly higher in NPC patients than normal controls (28.79 ng/ml versus 16.57 ng/ml, respectively). There was no significant difference in plasma DNA concentration of EBV-positive and -negative normal individuals. Methylated DNA was detectable in plasma of NPC patients before treatment including 46% for CDH1,42% for p16,20% for DAPK1,20% for p15,and 5% for RASSF1A. Hypermethylated MLH1 was not detected in plasma of all of the NPC patients and normal individuals. Aberrantly hypermethylated promoter DNA of at least one of the five genes was detectable in 29 of 41 (71%) plasma of NPC patients before treatment. Hypermethylated promoter DNA of at least one of the three genes (CDH1, DAPK1, and p16) was detectable in post-treatment plasma of 5 of 13 (38%) recurrent NPC patients and none of the patients in remission.


CONCLUSIONS
Our results suggested that cell-free circulating methylated gene promoter DNA is a possibly useful serological marker in assisting in screening of primary and potentially salvageable local or regional recurrent NPC.
Wong
Thian-Sze
TS
Department of Surgery, The University of Hong Kong, Hong Kong, China.
Kwong
Dora Lai-Wan
DL
Sham
Jonathan Shun-Tong
JS
Wei
William Ignace
WI
Kwong
Yok-Lam
YL
Yuen
Anthony Po-Wing
AP
D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor; D002277:Carcinoma / Q000097:blood* / Q000175:diagnosis / Q000235:genetics*; D002454:Cell Differentiation; D002474:Cell-Free System; D004247:DNA / Q000097:blood / Q000235:genetics; D019175:DNA Methylation; D018572:Disease-Free Survival; D005260:Female; D005819:Genetic Markers; D004854:Herpesvirus 4, Human / Q000235:genetics; D006801:Humans; D007070:Immunoglobulin A / Q000737:chemistry; D008297:Male; D008875:Middle Aged; D009303:Nasopharyngeal Neoplasms / Q000097:blood* / Q000175:diagnosis / Q000235:genetics*; D011401:Promoter Regions, Genetic; D012008:Recurrence; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013447:Sulfites / Q000494:pharmacology; D013997:Time Factors
D014408:Biomarkers, Tumor; D005819:Genetic Markers; D007070:Immunoglobulin A; D013447:Sulfites; D004247:DNA; C009279:sodium bisulfite