MONDAY, Oct. 1, 2012 (HealthDay News) -- New animal research suggests it may be possible to use a form of smallpox virus to infect and kill the tumor cells of a particularly virulent form of breast cancer.
To date, this novel approach to attacking what's known as triple-negative breast cancer has centered exclusively around work with mice.
By loading up the live "vaccinia" virus in the smallpox vaccine with a specific type of protein, researchers from Memorial Sloan-Kettering Cancer Center in New York City and Stanford University Medical Center in Palo Alto, Calif., found they could target and disable these particular cancer cells.
"One of the reasons I wanted to focus on [triple-negative breast cancer] is that there aren't many long-term treatment options for these patients," lead author Dr. Sepideh Gholami explained in an American College of Surgeons news release.
The findings were scheduled for presentation Monday at a meeting of the American College of Surgeons in Chicago.
Triple-negative breast cancer is an aggressive form of breast cancer that accounts for between 10 percent and 20 percent of all cases. Younger women (under 35) are the most vulnerable, as are black and Hispanic women.
Although chemotherapy has been shown to have some impact, standard breast cancer hormone and immune therapies are ineffective against triple-negative breast cancer, given that this type of cancer lacks normal hormone receptor cells. The result: Patients often experience cancer recurrence.
According to the researchers, expression of vascular endothelial growth factor -- which is thought to predict cancer spreading to distant sites and shorter survival -- is higher in triple-negative breast cancers than in other types of breast cancer.
That led the team to outfit a vaccinia virus called GLV-1h164 with a protein to see if it could target and kill vascular endothelial growth factor.
In infected mice, the team observed that roughly 60 percent of the triple-negative breast cancer tumors shrank following the smallpox therapy, while the other 40 percent showed evidence of tumor cell death with very little tumor activity remaining.
"The reason we used the vaccinia virus is that it is a member of the smallpox family and, as we know, smallpox vaccine has been given to millions of people to eradicate smallpox," Gholami said. As such, it should be safer than other agents, she said.
Commenting on the study, Dr. Julie Gralow, director of breast medical oncology at the University of Washington's Seattle Cancer Care Alliance, suggested that the smallpox virus strategy "is promising and makes sense."
However, while some of the laboratory animals had some substantial benefit, not all the mice benefitted, she cautioned. "So while they've shown that the idea works, and that this could do something for a subset of triple-negative breast cancer patients, it's probably not going to work in all patients," Gralow said.
Nevertheless, Dr. Laura Kruper, director of the Cooper Finkel Women's Health Center and co-director of the Breast Oncology Program at the City of Hope National Medical Center in Duarte, Calif., chose to accent the positive.
"If the results of this study can be translated into a form which can be given to women with triple-negative breast cancer, this would be a huge advance in breast cancer therapies," Kruper said.
Gholami said the researchers hope to evaluate the safety of this new virus in real patients. However, results achieved in laboratory settings aren't always repeated in humans.
Data and conclusions of research presented at meetings should be considered preliminary until published in a peer-reviewed medical journal.
The U.S. National Cancer Institute explains triple-negative breast cancer.