Researchers develop new, more-sensitive assay for detecting DNA methylation in co...( CLEVELAND A study published in this...)

CLEVELAND A study published in this week's online issue of Nature Biotechnology, demonstrates a unique and highly sensitive method for detecting methylation-associated cancers.

Chemical modification of DNA via the addition or deletion of methyl groups has been established as a common biological means of activating or silencing genes. Abnormal levels of DNA methylation, which effectively disrupt the genes responsible for normal cell cycle regulation, has been implicated in a number of different cancers, and has led to the development of novel cancer biomarkers.

However, methylation events are rare and difficult to detect in clinically relevant samples of blood, serum, sputum, urine or feces using currently available methods of analysis. In a joint effort between Case Western Reserve University and John's Hopkins University, researchers have developed a highly sensitive method for detecting methylated DNA.

The authors say the new method, known as Methyl-BEAMing (beads, emulsion, amplification and magnetics) technology, enables absolute quantification of the number of methylated molecules in a sample, and can detect as few as one methylated molecule in approximately 5000 unmethylated molecules in DNA from plasma and fecal samples, an over 60-fold improvement over an alternative commonly used detection method.

The enhanced sensitivity of the test was achieved through the use of PCR amplification of individual DNA fragments covalently attached to specially coated magnetic beads. The process of amplification involved suspending the magnetic beads in tiny water-based nano-compartments immersed in droplets of oil. The beads contained a DNA sequence specific for exon1 of the vimentin gene a gene known to be hypermethylated in colorectal cancer. If the vimentin gene sequence was present in the sample, subsequent PCR resulted in thousands of copies of the gene attached to each individual magnetic bead. Following amplifica
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