Lead investigator Joseph Califano, M.D., says his group at the Johns Hopkins Kimmel Cancer Center asked 211 head and neck cancer patients and 527 individuals without cancers of the mouth, larynx or pharynx to brush the inside of their mouths, then rinse and gargle with a salt solution.
The researchers collected the rinsed saliva and filtered out cells thought to contain one or more of 21 bits of chemically altered genes common only to head and neck cancers. Tumor and blood samples also were collected.
The cellular mishaps occur when small molecules called methyl groups clamp on to the DNA ladder structure of a gene. In the grip of too many methyl groups, these genes can incorrectly switch on or off in a process called hypermethylation. “Mass-methylation” of particular genes can lead to cancer, the researchers say. Methylation mistakes in other genes could be triggered simply by aging and amount to no more than fine lines and wrinkles.
“The challenge is to predict which hypermethylated genes are most specific to cancer,” says Califano, an associate professor of otolaryngology – head and neck cancer and oncology at Johns Hopkins. And because every cancer process involves a unique genetic fingerprint, combining several gene signatures for the disease rather than using single ones may identify a larger percentage of cancer patients.
Califano and his colleagues’ report noted that of 21 hypermethylated genes, seven of them were the best predictors of cancer within cell-laden saliva. Of the seven best, he tested panels of three to five genes on saliva rinses.
One panel correctly identified 66 out of 154 patients (42.9 percent) with the disease, and accurately ruled out the disease in 203 of 248 healthy subjects (81.9 percent). A saliva test, Califano says, is easy to do, painless and cheap, capturing cells from a wide area of the mouth. Some head and neck tumors do not shed genetic material into the blood, making the saliva test a better bet.
MEDICA.de; Source: Johns Hopkins Medical Institutions