This new treatment involves a bodily injection of a plant virus called the cowpea mosaic virus. The virus is harmless to animals and humans, but it still registers as a foreign invader that triggers an immune response to fight against cancer effectively.
To draw this immune response to lung tumors, researchers engineered nanoparticles made from the cowpea mosaic virus to target a protein called S100A9, which is expressed and secreted by immune cells that help fight infection in the lungs.
“Because these nanoparticles tend to localize in the lungs, they can change the tumor microenvironment there to become more adept at fighting off cancernot just established tumors, but future tumors as well,” said Eric Chung, a bioengineering Ph.D. student in Steinmetz’s lab who is one of the co-first authors on the paper.
Researchers grew black-eyed pea plants in the lab, infected them with cowpea mosaic virus, and harvested the virus in the form of ball-shaped nanoparticles. Later, they attached S100A9-targeting molecules to the surfaces of the particles.
Researchers also performed both prevention and treatment studies. In the prevention studies, they first injected the plant virus nanoparticles into the bloodstreams of healthy mice, and then later injected either triple negative breast cancer or melanoma cells in these mice. Treated mice showed a dramatic reduction in the cancers spreading to their lungs compared to untreated mice.
In the treatment studies, the researchers administered the nanoparticles to mice with metastatic tumor in their lungs. These mice exhibited smaller lung tumors and survived longer than untreated mice.
Before the new treatment reaches clinical stage, researchers need to do more detailed immunotoxicity and pharmacology studies. Future studies will also explore combining this with other treatments such as chemotherapy, checkpoint drugs or radiation.