Methylation of TFPI2 No Longer Detected in the Serum DNA of Colorectal Cancer Patients after Curative Surgery

In our previous study, we used quantitative methylation-specific polymerase chain reaction (qMSP) to examine the methylation status of tissue factor pathway inhibitor 2 (TFPI2) in the preoperative serum DNA of 215 colorectal cancer patients and found that TFPI2 was methylated in serum DNA from 39 of these patients. In this study, we examined postoperative serum DNA, obtained within one month after surgery from 38 out of the 39 patients and found that TFPI2 was methylated in the serum DNA of only 18 (47%) of these patients, suggesting that TFPI2 methylation in the serum of the remaining colorectal cancer patients was abolished by surgical tumor reduction. Next, we examined the correlation between the presence of TFPI2 methylation in postoperative serum DNA and residual cancer status after surgery. If R0 (no residual cancer) operations were successfully performed, TFPI2 methylation was not detected in postoperative serum. However, if R2 (obvious residual cancer) operations were performed, 17 (77%) out of 22 postoperative sera, still exhibited TFPI2 methylation. Taken together, our results confirm that detection of methylated TFPI2 in serum DNA was derived from colorectal cancer and could serve as a marker of surgical outcome. Previous studies have proposed that enriched circulating DNA can be found in the serum of cancer patients (1, 2). On the basis of these studies, many attempts have been made for the early detection of tumor-related aberrant DNA in the serum of patients with various malignancies (3, 4). Our previous studies have shown that it is possible to detect tumor-specific DNA in the serum of various cancer patients by using a mismatch ligation assay for KRAS and mitochondrial DNA mutations (5-8). Recently, methylation of tissue factor pathway inhibitor 2 (TFPI2) has been detected in the stools of colorectal cancer patients (9), suggesting that TFPI2 methylation is a potential novel marker for the detection of colorectal cancer. Furthermore, TFPI2 has been shown to be a potential tumor suppressor gene, which is expressed and is unmethylated in the colonic epithelium from cancer-free individuals. TFPI2 methylation in stool and serum is cancer specific and can be used to detect colorectal cancer (9). Therefore, we examined whether TFPI2 methylation can be used as a molecular marker for colorectal cancer by detecting TFPI2 methylation with quantitative methylation- specific polymerase chain reaction (qMSP) in the sera of colorectal cancer patients (10). The qMSP analysis showed that 39 out of 215 (18%) patients exhibited TFPI2 methylation in their serum DNA, suggesting that TFPI2 methylation occurred in the sera of colorectal cancer patients. The aim of this study was to determine whether TFPI2 methylation in serum is derived from colorectal cancer and could be used as a marker for determining surgical outcome. To address this, we examined the TFPI2 methylation status in serum DNA of colorectal cancer patients after curative surgery.