A Proof-of-Concept Investigation of CPP-Modified ATTEMPTS for Enhanced Toxin-Based Colorectal Cancer Therapy.
Year: 2013
Type: dissertation
Abstract: One of the major hurdles to cure cancer lies in the low potency of currently available drugs, which could eventually be solved by using more potent therapeutic macromolecules. However, although these macromolecules possess greater potency inside the cancer cells, the barely permeable cell membrane remains a formidable barrier in reducing their efficacy. For instance, gelonin, a typical ribosome inactivating protein (RIP) possesses exceptionally high N-glycosidase activity, but the anti-cancer effects of gelonin are rather negligible, due to its inability to enter tumor cells. To overcome the cell membrane barrier, we modified gelonin with two model cell penetrating peptides (CPPs), TAT peptide and low molecular weight protamine (LMWP), via both chemical conjugation and genetic recombination methods. Through in vitro and in vivo studies, these CPP-modified gelonins (i.e. gelonin-LMWP chemical conjugate (cG-L), recombinant gelonin-LMWP chimera (rG-L) and TAT-gelonin chimera (TAT-Gel)) displayed markedly improved cell uptake efficiency and, thereby, significantly enhanced tumoricidal activity, compared with unmodified recombinant gelonin (rGel). On the other hand, this CPP-modification aggravated the potential toxicity concerns of gelonin as the non-specific fashion of CPP-mediated cell uptake led to internalization of the CPP-modified gelonins into any type of cells. Thus, to curb the cell penetration activity of CPP and expose it only to the tumor cells, a modified version of ATTEMPTS (Antibody Targeted Triggered Electrically Modified Prodrug Type Strategy), a heparin/protamine-based drug delivery system (DDS), featured by ‘antibody-mediated tumor targeting’ and ‘prodrug strategy’ was explored. For targeting, a heparin functionalized monoclonal antibody (mAb) was developed with T84.66 (i.e. T84.66-Hep), an anti-CEA mAb, via chemical conjugation. When T84.66-Hep and TAT-Gel was mixed together, they automatically formed a tight complex via electrostatic interaction between anionic heparin and cationic TAT. Systemic administration of this T84.66-Hep/TAT-Gel complex enabled much higher accumulation of TAT-Gel (58-fold higher tumor exposure) in LS174T xenograft tumor, compared with injection of TAT-Gel alone. Furthermore, heparin/protamine-based prodrug feature of the DDS provided significantly enhanced tumoricidal efficacy with yet reduced toxicity, compared with administration of TAT-Gel alone. Overall, this study provides a general rationale to enhance the therapeutic efficacy of potent but cell-impermeable macromolecules and, further, safely deliver to their target site.
Author: Meong Cheol Shin
Language: English
Subfield: Immunology
Field: Immunology and Microbiology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W204935275