The objective of this Phase I application is to test the feasibility of using spores of obligate anaerobes of the genus clostridium as vectors for anticancer gene therapy. We will express the (3-lactamase gene derived from Enterobacter cloacae, since the protein encoded by this gene does not occur in humans, and can convert cephalosporin derivatives of anticancer agents (nontoxic prodrugs) into their respective toxic anticancer drugs. The basis for the targeting strategy is that spores of these obligate anaerobes are converted into the active vegetative form only in the necrotic/hypoxic regions of tumors and, therefore, the enzymes produced by these organisms are expressed solely in the tumors. The specific aims of the project are first, to express the Beta-lactamase gene in C. beijerinckii, and second to determine whether the expressed protein is active in metabolizing the two cephalosporin prodrugs, C-Dox and CCM, and whether it is produced exclusively in transplanted tumors in mice. The significance of the research for cancer treatment lies in the fact that, if successful, this approach will enable high concentrations of active anticancer drugs to be produced specifically in tumors allowing major advances in the therapeutic ratio.Proposed commercial application:There is, at present, no effective means of targeting specific genes to tumors, so the ability to do this would have enormous commercial potential. The attached letter from Dr. Peter Senter indicates not only his willingness to supply the necessary reagents for this project, but his eagerness to test our system in parallel with the one Bristol-Myers is developing based on antibody-directed enzyme prodrug therapy. Should our targeting approach prove more effective than the antibody approach, we will seek commercial partners, such as Bristol- Myers Squibb. to develop the product.National Cancer Institute (NCI)
