A study by researchers at the Keck School of Medicine, University of Southern California, says when the protein fragment called PEP (permeability-enhancing peptide) is attached to a tumor-targeting antibody, it can prompt tumors to soak up more than 300 percent of the normal amount of chemotherapy drugs.
The research appears in the May 21 issue of the Journal of the National Cancer Institute.
PEP increases tumor uptake of chemotherapy drugs by making the tumor's blood vessel walls more permeable to the drugs. PEP acts on epithelial cells that form the blood vessel walls. These cells are usually tightly joined together. PEP loosens up the junctions between the epithelial cells, making it easier for molecules to enter or leave.
The Keck researchers isolated PEP and determined it enhanced blood vessel permeability while they were doing research on IL-2, which can help fight cancer by revving up the body's immune system.
However, IL-2 can only be used in small doses. At the higher doses necessary to provide therapeutic benefit to cancer patients, IL-2 causes widespread edema (excessive accumulation of tissue fluid) and other problems caused by blood vessel leakiness.
When the Keck scientists investigated why this happened, they identified PEP. Once they found PEP, they did further research with mice that revealed PEP's ability to increase tumor uptake of drugs.
Here's where you can learn more about interleukin 2.