Blood test could help track cancer
CHICAGO - Tiny sacs released from tumor cells circulate in the bloodstream and carry genetic information about the tumors, offering a new way to track and treat the cancer, researchers said yesterday.
"If you just look at these packets, you basically know what kind of mutations are in the tumor cell," said Xandra Breakefield of Massachusetts General Hospital in Boston, whose study appears in Nature Cell Biology.
The membrane-covered packets, called exosomes, represent a new way of getting information about a cancer, offering a means of choosing the best therapy and seeing how a patient responds to treatment, Breakefield said.
"It's a whole new concept of cell communication we didn't know tumors used," Breakefield said in a telephone interview.
She said for most forms of cancer, there is no good way to know what genetic mutations are in a tumor, short of doing a biopsy. Many current blood tests, such as the prostate specific antigen, or PSA, test for prostate cancer, simply check for elevated levels of a specific protein.
By using exosomes, doctors might be able to get specific information about a cancer from a simple blood test.
Johan Skog, who works in Breakefield's lab and led the study, said many types of cells release exosomes as part of normal cell-to-cell communication, and several types of tumors are known to shed exosomes containing proteins that can alter the environment to make it more favorable to tumor growth.
For the study, the researchers analyzed the contents of the exosomes shed from glioblastoma cells. Glioblastoma is a type of aggressive brain cancer.
Inside, they found fragments of ribonucleic acid, or RNA, including messengers related to cell growth and immune response. When they exposed these exosomes to normal cells in the lab, the tumor RNA delivered its genetic message into the cells.
REUTERS 