Development of a Novel, Proteinase-Activated Toxin Targeting Tumor Neovascularization

摘要

The purpose of this research is to target Clostridium septicum alpha toxin to the cells in blood vessels that are undergoing angiogenesis during these invasion of tumors. This will be accomplished by altering the normal proteolytic activation site of alpha toxin to one which is activated by gelatinase enzymes which are primarily active in this endothelial cells. The presentation of the gelatinase cleavage in alpha toxin appeared to be problematic since we were unable to generate mutants of alpha toxin with the normal furin activation site replaced with a gelatinase A and B that could be efficiently activated with gelatinase B. It was clear that when alpha toxin was largely misfolded and inactive that the engineered gelatinase site could be efficiently cleaved by gelatinase B. Therefore, in the light of this information and new information that we and others have generated with respect to gelatinase activity and the structure-function relationships of alpha toxin we are pursuing several different approaches to solve the gelatinase activation problem of alpha toxin. We have also begun the application of our approach to other cytolytic toxins which may be more amenable to the engineering of gelatinase switches into their structures so that they can be targeted them to blood vessels which are feeding tumors.