In mouse models of colon cancer, the combination therapy eliminated all tumors and prevented their recurrence, resulting in a 100% survival rate.

The therapy's two key ingredients are cowpea mosaic virus, which is a plant virus that infects legumes but is harmless to animals and humans, and an antibody called anti-4-1BB. Cowpea mosaic virus attracts natural killer cells to the tumor microenvironment, while anti-4-1BB binds to receptors on these cells to snap them out of their immunosuppressed state.

Researchers also tested the combination therapy on mouse models of melanoma in which it reduced tumor growth and protected the surviving mice from recurrence of the disease when rechallenged with melanoma.

"While the combination therapy was most impressive in the colon cancer model, improvement was also seen in the melanoma model," said senior author of the study Nicole Steinmetz, professor of nanoengineering and director of the Center for Nano Immuno Engineering at the UCSD Jacobs School of Engineering.

"Based on the data, more research is needed to understand whether this therapy is effective against a broad range of cancers, or whether the real potential is for intraperitoneal disseminated disease," Steinmetz said.