| We are interested in the identification and characterization of novel suicide genes and their combined use with replication-selective viruses. Currently, the possibility to employ mutant Fanconi anemia (FA) genes as a means to sensitize tumor cells is being explored. FA is a genetically inheritable disorder characterized at the cellular level by hypersensitivity to the cell death-inducing effect of a class of potent anticancer drugs, the cross-linking agents, that include mitomycin c and cisplatin. Cells from FA patients typically die at more than 10-fold lower concentrations of cross-linkers then that are required for an equivalent level of cell killing in normal cells. Seven distinct FA complementation groups have been identified, designated group A to G, and currently four FA genes have been cloned. Their sequences reveal no functional clues and their primary function is still unclear, however, defective FA genes that abolish FA protein expression or lead to the expression of non-functional variants are at the basis of the disorder and the observed drug hypersensitivity. We discovered that overexpression of dominant negative-acting mutant FA alleles can mimic the cellular phenotype of FA by causing hypersensitivity towards cross-linking agents. The possible clinical applicability of using these dominant-negative FA mutants as suicide genes in targeted gene therapy approaches in combination with low dose cross-linking agent treatment is explored. This project is in collaboration with the division of Pharmacology (Prof. G. Giaccone). Enzyme-prodrug therapy aims at the delivery of an enzyme, capable of converting a non-toxic prodrug into an active drug, selectively at the tumor site. This should result in a high local drug concentration in the tumor, which leads to an improved anti-tumor effect. In addition, systemic drug concentrations should be lower, thus reducing the side-effects accompanying conventional cancer chemotherapy. The enzyme can either be delivered by an antibody-enzyme fusion protein (Antibody-Directed Enzyme Prodrug Therapy, ADEPT) or by a vector carrying a gene encoding the enzyme (Gene-Directed Enzyme Prodrug Therapy, GDEPT). Currently, we are evaluating three different enzyme-prodrug systems based on doxorubicin, 5-FU and irinotecan (in collaboration with Dr. H. Haisma). |
