Hypermethylation Test May Aid Certain Cancer Patients

In a new study, hypermethylation of the BRCA1 gene was found to turn off gene expression and resulted in a breast cancer tumor. The study, conducted by scientists from the U.S. National Institutes of Health at the Johns Hopkins Oncology Center (Baltimore, MD, USA), was published in the February 22 issue of The New England Journal of Medicine.

The study was intended to investigate the mutations in the BRACA1 gene that can turn off its tumor suppression effects, commonly leading to the development of cancer. These mutations can be inherited. Unexpectedly, the researchers discovered one breast cancer tumor typically associated with BRCA1 mutation that was found not to be mutated but, rather, hypermethylated. This turns off tumor-suppressing activities, enabling the development of cancer. Unlike mutation, hypermethylation cannot be inherited.

About 10-15% of breast cancers and 15-20% of ovarian cancers may be associated with hypermethylation. This alteration appears to occur in the most common, non-hereditary forms of breast and ovarian cancers rather than the more rare familial cancers associated with the BRCA1 gene. A diagnostic test would allow physicians to differentiate between the two kinds of tumors.

Virco (Mechelen, Belgium), an international pharmacogenomcis group, holds a patent for any diagnostic test based on methylation. The company is already in the process of developing a test for hypermethylation of the MGMT gene in brain tumor patients. A study has shown that brain tumor patients who tested positive for hypermethylation were 16 times more likely to respond to treatment with the most common form of chemotherapy. They were also ten times less likely to die during the three years of follow-up than those who tested negative.

"These are unexpected and interesting results,” commented Brendan Larder, Ph.D., chief scientific officer at Virco. "It appears that the use of methylation as a diagnostic tool may have application in a number of cancers.”



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