Metal-Chelating Polymers for Auger Electron Radioimmunotherapy.

摘要

Radioimmunotherapy is a promising strategy for cancer treatment. The incorporation of metal-chelating polymers (MCPs) into radioimmunoconjugates (RICs) can increase the specific activities of RICs due to the multiple radioactive isotope binding sites provided by MCPs. This thesis describes the synthesis and characterization of a library of biotin end-capped MCPs (Bi-MCP). These Bi-MCP are designed to conjugate with the Fab fragment of trastuzumab modified with streptavidin (tmFab-SAv) and labeled with 111In, to form RICs. Trastuzumab has specific targeting ability towards human epidermal growth factor receptor-2 (HER2), which is overexpressed on certain types of breast cancer cells. 111In can generate Auger electrons which are able to induce the lethal cleavage of nuclear DNA. The strategy of labeling tmFab-SAv with Bi-MCP should enhance the number of 111In delivered per HER2 targeting event, and thereby increase the radiotoxicity delivered to the HER2+ cancer cells.;Auger electrons have ultrashort tissue penetration ranges (< 1 microm). Therefore, to exert their effects, the RICs have to internalize into the cells and reach close proximity to the nucleus. In an attempt to enhance the nuclear uptake of the tmFab-SAv-Bi-MCP, I chemically incorporated Doxorubicin (Dox) into the Bi-MCP as a nuclear targeting moiety and compared this RIC with a similar Bi-MCP-RIC without Dox. A series of in vitro experiments were carried out to evaluate the immunoreactivity and subcellular localization of these MCP-containing RICs. The results showed that upon complexation of the MCPs, HER2-targeting ability of tmFab was retained, ensuring the cell-selectivity of these RICs. The Dox did not increase nuclear uptake, whereas the Bi-MCP itself appeared to encourage internalization, nuclear uptake and chromatin (DNA) binding of tmFab-SAv-Bi-MCP.;Biodistribution profiles of the RICs containing MCPs were screened in a Balb/c mouse model. The MCPs bearing negative charges along the polymer backbone caused the ultrafast clearance of the tmFab-SAv from blood circulation via the hepatic route. On the contrary, Bi-MCPs bearing zwitterionic pendant groups upon complexation with indium ions, showed substantially reduced liver uptake of the tmFab-SAv complex and a longer plasma half-life.