Changes in tumor cells circulating in the blood may help to explain how breast cancer spreads.
Breast cancer cells that break away from primary tumors undergo changes as part of “a wound-healing response gone wrong” that appear to improve their ability to reattach in distant locations in the body, according to a new study by researchers at the University of Maryland Marlene and Stewart Greenebaum Cancer Center.
The process promotes the creation of “microtentacles,” or extensions of the plasma membrane, on free-floating tumor cells in the blood that researchers believe play a critical role in helping cancer to spread, or metastasize.
“Tumor cells in the bloodstream react as if they are wounded, seeking to stabilize their inner structure and repair the damage. It’s essentially a wound-healing response gone wrong, which makes the detached cells stronger, more mobile and better able to survive in distant parts of the body,” explains senior author Stuart S. Martin, Ph.D.
The study findings appear in the Oct. 15, 2010, issue of the journal Cancer Research. The issue also features images of microtentacles on the cover and a review article about the significance of these filament-like cell extensions in understanding metastasis.
Researchers have identified a specific molecular mechanism involving an enzyme that decreases as tumors progress, which facilitates the growth of microtentacles. The changes in the cancer cells occur during a developmental process in which the cells gain the ability to migrate and invade other tissue. “The microtentacles on the circulating tumor cells help them to attach to the endothelial lining of small blood vessels, creating new sites where the cancer can grow,” Dr. Martin says.
The researchers believe that developing new drugs to target these microtentacles might be a way to prevent or slow the growth of secondary cancers. “Metastasis is the leading cause of death in people who have cancer, but methods used to treat the primary tumors have limited success in treating metastases,” Dr. Martin says. “In breast cancer, metastases can develop years after primary tumors are discovered, but we are aiming to target metastatic tumor cells much earlier, when they first begin to spread.”
The study, which was funded by grants from the National Cancer Institute, the USA Medical Research and Materiel Command and the Susan G. Komen Breast Cancer Foundation, is the latest research by Dr. Martin and his colleagues into microtentacles and the “cytoskeleton” of cancer cells.