A highly sensitive method for the detection of p16 methylation in the serum of colorectal cancer patients.
BACKGROUND
For the purpose of early detection of carcinomas, detection of p16 hypermethylation by methylation-specific polymerase chain reaction (MSP) in the serum of many kinds of malignancies has been introduced. An attempt to increase the sensitivity of this assay is reported for colorectal cancer.


METHODS
DNA samples were subjected to limiting dilution before being divided into ten smaller samples. Subsequently, hemi-nested MSP was performed on those ten samples. The limiting dilution-MSP (LD-MSP) provided a 10-fold increase in sensitivity of the detection of methylated DNA compared with conventional MSP.


RESULTS
Of 44 colorectal cancer patients, 30 (68%) exhibited abnormal promoter methylation of p16 in their serum DNA by LD-MSP, while 13 (30%) exhibited it by conventional MSP. As a control, the serum DNA of 50 patients with colorectal carcinomas whose corresponding tumor DNA had no methylation in the p16 promoter was screened for aberrant methylation. No methylation was found in the serum DNA of this control group by LD-MSP or conventional MSP.


CONCLUSIONS
The high sensitivity of LD-MSP makes it possible to detect smaller amounts of tumor DNA in the serum than conventional MSP. This technique also has great specificity and no abnormal methylation in serum has yet been observed if the corresponding tumor does not exhibit methylation. This observation supports the idea that LD-MSP could be applied in clinical use for the detection of tumor DNA in serum.
Nakayama
Goro
G
Gastroenterological Surgery, Nagoya University Graduate School of Medicine, Showa-ku, Nagoya 466-8560, Japan.
Hibi
Kenji
K
Nakayama
Hiroshi
H
Kodera
Yasuhiro
Y
Ito
Katsuki
K
Akiyama
Seiji
S
Nakao
Akimasa
A
D002277:Carcinoma / Q000175:diagnosis*; D015179:Colorectal Neoplasms / Q000175:diagnosis*; D019175:DNA Methylation; D004273:DNA, Neoplasm / Q000097:blood*; D019942:Genes, p16; D006801:Humans; D008297:Male; D008875:Middle Aged; D016133:Polymerase Chain Reaction / Q000379:methods*; D011401:Promoter Regions, Genetic; D012680:Sensitivity and Specificity
D004273:DNA, Neoplasm