Abstract:

Objective To investigate the value of methylation determination of fecal adhesin syndecan 2（SDC2） gene in the auxiliary diagnosis of colorectal cancer. Methods Totally,51 patients with colorectal cancer（colorectal cancer group）,22 patients with adenoma（adenoma group） and 39 healthy subjects（healthy control group） were enrolled. The stool and serum samples of all the subjects were collected to determine fecal SDC2 gene methylation and serum carcinoembryonic antigen（CEA） and carbohydrate antigen 19-9（CA19-9）levels. Among them,26 fecal samples were pretreated by P12 automatic sample pretreatment instrument and manual method,and the correlation of the determination results after pretreatment by the 2 methods was compared. Pearson correlation analysis and kappa test were used to evaluate the correlation and consistency between the 2 methods. Results The methylation positive rate of fecal SDC2 gene in colorectal cancer group was higher than those in adenoma group and healthy control group（P<0.01）. In colorectal cancer group,the methylation positive rate of fecal SDC2 gene was higher than those of serum CEA and CA19-9（P<0.01）. There was no statistical significance in methylation positive rate of fecal SDC2 gene between patients with colorectal cancer stage Ⅰ-Ⅳ（P>0.05）. The methylation positive rate of fecal SDC2 gene in patients with colorectal cancer stage Ⅰ-Ⅲ was higher than those of CEA and CA19-9 in serum（P<0.01）. Receiver operating characteristic（ROC） curve analysis showed that the areas under curves（AUC） of the methylation of fecal SDC2 gene,serum CEA,serum CA19-9 and the combined determination for colorectal cancer diagnosis were 0.965,0.694,0.567 and 0.976,respectively. Serum CEA combined with the methylation of fecal SDC2 gene can increase the positive rate of colorectal cancer to 90.2%（46/51）. There was a positive correlation between the determination results of P12 automatic sample pretreatment instrument and manual method（r=0.994,P<0.001）,and the consistency was good（kappa=0.845,P<0.001）. Conclusions The methylation of fecal SDC2 gene has high sensitivity and specificity,which can be used as an auxiliary diagnosis of colorectal cancer,and it also has high clinical value in early colorectal cancer screening.

Key words: Syndecan 2, Methylation, Carcinoembryonic antigen, Carbohydrate antigen 19-9, Colorectal cancer