The screen, developed by Sara Sukumar, Ph.D. and Mary Jo Fackler, Ph.D., first separates cells from fluid, then sifts through the cells' DNA for chemical tags on certain genes associated with cancer.
Reporting in the June 1 issue of Clinical Cancer Research, the scientists say they have tested their screening tool on breast fluid, in search of cells shed from growing tumors.
"This screening method can see what the eye cannot see," says Sukumar, who is the Barbara B. Rubenstein Professor of Oncology at the Johns Hopkins Kimmel Cancer Center. "It can be a valuable tool, in combination with pathological review, for breast cancer as well as other diseases where fluid can be obtained relatively easily, such as lung, head and neck cancers, pancreatic and cervical cancers."
Pathologists look for telltale shapes of cells to determine if cancer is present, but molecular changes in cells, especially for early cancers, are beyond the reach of even the most powerful microscopes.
Sukumar's test searches for unusually high amounts of chemical tags embedded by a process called methylation within critical regions of DNA. The tags attach to the "on" switch of genes which starts the message-manufacturing process. Cancer cells have abnormal levels of methylation, which turns the gene switch off halting the assembly line of critical proteins found in normal cells.
The Hopkins test, called quantitative multiplex methylation-specific PCR or QM-MSP, determines the percentage of methylation present in each of five to ten cancer genes. The percentages are added together for a cumulative score, which is compared to a threshold value. Levels above the threshold indicate the potential presen
Source:Johns Hopkins Medical Institutions