Researchers at the University of Texas Southwestern Medical Center said the combination therapy is significantly more effective in treating lung cancer than either approach alone.

University of Texas Professor Philip Thorpe and colleagues found radiation generates a chemical reaction in the membranes of endothelial cells that line the blood vessels feeding tumors. The reaction causes membrane components called anionic phospholipids to "flip" inside out, exposing them. In normal blood vessels, they face the interior of the cell.

"The flipping is likely due to stress conditions present in the tumor micro-environment, and radiation increases the number of exposed phospholipids," he said.

Once they induced more flipping with radiation, the researchers administered bavituximab -- a monoclonal antibody binds to the phospholipids. The binding signals white blood cells from the immune system to attack and destroy the vessels feeding the tumor.

Treating the mice with bavituximab and radiation therapy together reduced tumor growth by 80 percent and was more effective than administering either treatment by itself.

The study appears in the journal Clinical Cancer Research.