Prodrug Therapy for Breast Cancer Targeted by Single-Chain Antibodies F19 and 3S193
Abstract
In Antibody-Directed Enzyme-Prodrug Therapy (ADEPT), antibody - enzyme constructs localize to tumor tissue the toxification of non-toxic prodrugs. Recombinant fusion proteins are expected to overcome the limitations of chemical conjugates. We have constructed fusion proteins of antibodies against the tumor antigens A33, Lewis-Y and fibroblast associated protein (FAP) with cytosine deaminase (CD), which converts 5-fluorocytosine (5-FC) into cytotoxic 5-fluorouracil (5-FU). After initial inefficient expression in an E. coli system, the intended use of a Pichia pastoris system made necessary the replacement of E.coli CD with the yeast isoenzyme. In addition, a second line of fusion constructs with green fluorescent protein instead of cytosine deaminase was designed for histological and intracellular distribution studies. With the A33 antibody construct as a pilot project, the desired fusion proteins were cloned, expressed in E. coli and purified. In vitro function assays confirmed bispecific activity of the fusion proteins. Based on these results, experimental mice tumor models were established based on antigen-positive cell lines, and tumor targeting and biodistribution experiments were completed again with A33 as the pilot system. These experiments showed good tumor localization and favorable biodistribution, but little anti-tumor effect, which may be due to particular conditions of this pilot system. Encouraged by these results, additional animal experiments are currently underway.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 2003
- Accession Number
- ADA423458
Entities
People
- Peter M. Deckert