September 25, 2008: Researchers at The Johns Hopkins U. School of Medicine in Baltimore have developed a novel nanotechnology-based test to screen for chemical modifications to DNA known as methylation. The technology, which uses quantum dots coated with the protein streptavidin to attract DNA segments, could be used both for early cancer diagnoses and for assessing patients’ response to cancer therapies.

During methylation, healthy genes can be switched on or off potentially causing cancer without any changes in the underlying DNA sequence. The current methods for methylation screening have significant drawbacks, explains lead study author Vasudev Bailey, a biomedical engineering Ph.D. candidate at Hopkins.

Methylation specific PCR, which copies specific DNA sequences millions of times within a few hours, may not be sensitive enough to detect small amounts of methylation. And real time PCR, which allows scientists to view increases in the amount of DNA as it is copied, needs to be run several times and can be expensive, he says.

The Hopkins-developed test makes PCR technology more sensitive and efficient, Bailey said. In addition, they demonstrated detection capability in as few as eight PCR cycles. The work was presented at the American Association for Cancer Research’s third International Conference on Molecular Diagnostics in Cancer Therapeutic Development (September 22-25 in Philadelphia).

“The impact of detecting DNA methylation is profound, as it has been demonstrated that a larger number of tumor suppressor genes become inactivated through DNA methylation than by mutations,” Bailey said. “Our method of methylation screening provides an easy, cost-effective and valuable tool for the early diagnosis of cancer, monitoring tumor behavior and measuring the response of tumors to targeted cancer therapies.”