Detection of caudal type homeobox 1 (CDX1) gene methylated DNA,as a stool-based diagnostic biomarker in colorectal cancer.

Colorectal cancer (CRC) is known to develop due to the accumulation of both genetic and epigenetic alterations, resulting in the conversion of intestinal epithelial cells to malignant adenocarcinoma cells. Caudal type homeobox 1 (CDX1) gene is a homeobox transcription factor and a selective tumour suppressor gene that is an important factor for the development of intestinal cells. This gene plays a role in the differentiation of intestinal epithelial cells, and its expression decreases in a number of cell lines derived from CRC, which suggests that a lack of CDX1 expression is a risk factor for the development of colorectal carcinoma. Therefore, the methylated DNA amounts of CDX1 gene in stool samples were investigated as a noninvasive method for the detection of CRC. In the present study, the methylation of CDX1 gene promoter region was assessed in stool samples of 50 CRC patients and 50 healthy individuals by MethyLight PCR using two primers and a Taq Man probe, which was completely specifically designed for fully methylated DNA of the gene promoter region. The percentage of methylated reference (PMR) of the studied gene in all samples was calculated similarly to previous studies. Statistical analysis was performed using SPSS 16. The PMR medians were 3.25 (95% CI: 0.1-100) and 0.1 (95% CI: 0.07-1) in the stool samples of CRC patients and healthy individuals, respectively. The results showed a significant difference in CDX1 gene PMR between stool samples of CRC patients and controls (P-value\0.001). According to the results of this study, it can be argued that measurement of CDX1 gene DNA in stool samples using the MethyLight PCR has acceptable sensitivity and specificity, and is adequately potential to be used as a noninvasive complementary method for the diagnosis of CRC, along with colonoscopy as the gold standard to this end. This study is the first report on CDX1 methylation in stool samples of CRC patients. Therefore, further research should be carried out with a larger sample size to evaluate its efficacy as a diagnostic biomarker in clinical laboratories.