The long-term objective of this application is to develop novel recombinant immunotoxins for therapeutic use in human bone marrow transplantation and for the in vivo treatment of human leukemias and lymphomas. Recombinant immunotoxins comprise a new class of pharmacologic agents designed to be selectively cytotoxic. They are fusion proteins in which the antigen-binding (variable) regions of antibodies are linked to potent, catalytic toxins. Genetically engineered immunotoxins have several hypotheses concerning the efficacies of recombinant versus chemically-linked immunotoxins. Recombinant immunotoxins specific for the pan -T cell antigen CD7 will be used as a model immunotoxins may prove to be effective in the treatment of T -ALL. In the first specific aim, the variable region genes expressed by a CD7 will be used as a model system. CD7 is expressed on virtually all T cell acute lymphoblastic leukemias (T-ALL) and so these immunotoxins may prove to be effective in the treatment of T-ALL. In the first specific aim the variable region genes expressed by a CD7-specific hybridoma will be linked to the ricin toxin A chain (RTA) gene in different ways to determine which encodes the most efficacious immunotoxin. The potency of the these chemically conjugated to RTA. The in vivo comparisons will employ SCID mouse models for T-ALL. Internalization, pharmacokinetic, and biodistribution studies will examine what factors influence the in vivo efficacy of the recombinant and chemical immunoconjugates. In the second specific aim recombinant CD7-specific immunotoxins containing a variant of Pseudomonas exotoxin A (PE38KDEL) will be constructed and assayed. The purpose of these experiments is to determine if RTA and PE38KDEL differ in cytotoxicity when targeted to CD7. The third specific aim addresses a problem encountered in all clinical trials of RTA-immunotoxins: dose-limiting toxicity caused by endothelial cell damage. The hypothesis is that RTA alone can kill endothelial cells via receptor-mediated endocytosis. Mutants of RTA will be generated and screened for enzymatically active variants that no longer bind and kill endothelial cells. The identification of these mutants should allow for the construction of more therapeutically effective immunotoxins.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
First Independent Research Support & Transition (FIRST) Awards (R29)
Project #
5R29CA059510-05
Application #
2633847
Study Section
Experimental Therapeutics Subcommittee 1 (ET)
Program Officer
Yovandich, Jason L
Project Start
1994-01-01
Project End
1999-12-31
Budget Start
1998-01-01
Budget End
1999-12-31
Support Year
5
Fiscal Year
1998
Total Cost
Indirect Cost
Name
University of Minnesota Twin Cities
Department
Pathology
Type
Schools of Medicine
DUNS #
168559177
City
Minneapolis
State
MN
Country
United States
Zip Code
55455
Pennell, Christopher A; Erickson, Heidi A (2002) Designing immunotoxins for cancer therapy. Immunol Res 25:177-91
Pennell, C A; Pauza, M E (2001) CD7-specific single chain Fv immunotoxins. Design and expression. Methods Mol Biol 166:17-29
Pennell, C A; Eldin, P (1998) In vitro production of recombinant antibody fragments in Pichia pastoris. Res Immunol 149:599-603
Lindstrom, A L; Erlandsen, S L; Kersey, J H et al. (1997) An in vitro model for toxin-mediated vascular leak syndrome: ricin toxin A chain increases the permeability of human endothelial cell monolayers. Blood 90:2323-34
Eldin, P; Pauza, M E; Hieda, Y et al. (1997) High-level secretion of two antibody single chain Fv fragments by Pichia pastoris. J Immunol Methods 201:67-75
Dudek, A Z; Pennell, C A; Decker, T D et al. (1997) Platelet factor 4 binds to glycanated forms of thrombomodulin and to protein C. A potential mechanism for enhancing generation of activated protein C. J Biol Chem 272:31785-92