Serum DNA analysis can be used for early detection of diseases

Patients with metastatic colorectal cancer (CRC) in Philadelphia, Pennsylvania, have an average 5-year survival rate of less than 10%. If they can be detected and treated early, their 5-year survival rate can reach 90%. Now, a new non-invasive test method for measuring the methylation of SDC2 gene in tissues and serum has been developed. In this test, the detection rate of colorectal cancer cases at various stages is 87% (sensitivity), there is no significant difference between early and late stages, and the negative rate for non-colorectal cancer patients is 95% (specificity). A paper with this result will be published in the July Journal of Molecular Diagnostics.

According to information released by the US Centers for Disease Control and Prevention, CRC is the second largest cancer killer in the United States for men and women. In 2009, nearly 137,000 people were diagnosed with CRC in the United States, with a mortality rate close to 40%.

Other options for screening CRC include fecal occult blood test (FOBT), fecal immunochemical test, and colonoscopy. Colonoscopy is the gold standard for CRC screening, but patients have a frustrating resistance — most people have uncomfortable psychological preparations — limiting the widespread acceptance of this method. FOBT is non-invasive, but its sensitivity is limited, especially in the early stages of the disease. A sensitive and specific non-invasive test using blood or feces may be a better choice to save many lives.

The biomarker they studied may be used for the early detection of CRC. Researchers from Genomic Tree Co., Ltd. and Yonsei University School of Medicine in Seoul, South Korea The methylated DNA in the DNA was analyzed by paired DNA microarray. After step filtering, they found a group of highly methylated genes in all CRC tumors. In the end, they identified an SDC2 gene encoding a membrane-covalent glycan-2 protein, which is known to be a protein involved in cell division, migration, and expression in colonic mesenchymal cells. It was found that the methylation level of SDC2 target area in tumor tissue was significantly higher than that of paired adjacent non-tumor tissue.

Next, a clinical verification was conducted by analyzing the SDC2 methylation level in the primary tumors of 133 CRC patients and their paired adjacent non-tumor tissue samples. The researchers found that in the transcriptional regulatory region of the SDC2 gene, tumor tissue samples showed significantly higher methylation levels than adjacent non-tumor tissue samples from controls. Depending on the stage of cancer, the positive samples of SDC2 methylation taken from the samples ranged from 92.9% to 100%.

In addition, the researchers found that SDC2 biomarkers in serum samples of CRC patients and healthy people can be quantitatively determined. The first author of the research paper, TaeJeong Oh, Ph.D., said: "The SDC2 methylation test can detect a stage I cancer patient with a positive rate of 92%, indicating that SDC2 is suitable for early detection of CRC. At this time, with therapeutic intervention, cancer patients have the greatest possibility of cure. "

The authors believe that the SDC2 methylation test they describe may be used as an alternative to colonoscopy or in conjunction with colonoscopy. It can also be used to monitor cancer progression and treatment. Corresponding author of the paper, Dr. Sungwhan An, CEO of The Genome Tree Co., Ltd. commented: "We are very excited about this result using a small amount of serum DNA less than 1mL of blood. I think, The use of more blood will further improve the clinical effect of this trial. At present, we are preparing another group of clinical validation studies to evaluate SDC2 methylation in the serum of patients with early adenocarcinoma. "The authors' future research In this article, we will explore whether this biomarker is unique to CRC or common in other cancers.