The tumor vasculature has become an attractive target in the treatment of cancer. The U.S. Food and Drug Administration approved the first antiangiogenic cancer drug, bevacizumab (Avastin), last year, and other drugs in this category are under development. One approach in the design of these treatments is to develop molecules that effectively induce coagulation in the tumor vasculature when delivered systemically (i.e., intravenously) but that do not induce coagulation in nontumor vessels.
Claudia Gottstein, M.D., of the University Hospital Cologne in Germany, and colleagues created fusion proteins consisting of soluble tissue factor (sTF) genetically fused to antibody fragments directed against mouse or human vascular cell adhesion molecule 1 (VCAM-1), an antigen found on the inner surface of tumor blood vessels, which is the first site within the body that is exposed to intravenous drugs. They examined the activity of the proteins in laboratory studies and tested their antitumor effects when administered systemically to mouse models of human Hodgkin lymphoma and small-cell lung carcinoma and a mouse model of small-cell lung carcinoma that contained human tumor vasculature.
A single systemic administration of the fusion protein led to tumor tissue death. Long-term treatment produced delays in tumor growth and some tumor regressions. The researchers could find no evidence for the development of blood clots or cellular death in normal tissues related to the treatment.
The authors note that this research is one step beyond vascular occluding drugs, which have been effective in clinical studies when applied locally but that could not be administered intravenously be
Contact: Sarah L. Zielinski
Journal of the National Cancer Institute