PTD-Modified ATTEMPTS for Enhanced Toxin-based Cancer Therapy: An In Vivo Proof-of-Concept Study

Abstract

Purpose To investigate the feasibility of applying PTD-modified ATTEMPTS (Antibody Targeted Triggered Electrically Modified Prodrug-Type Strategy) for enhanced toxin therapy for the treatment of cancer. Methods A heparin-functionalized murine anti-CEA monoclonal antibody (mAb), T84.66-heparin (T84.66-Hep), was chemically synthesized and characterized for specific binding to CEA overexpressed cells. The T84.66-Hep was then applied to the PTD-modified ATTEMPTS approach and the crucial features of the drug delivery system (DDS), ‘antibody targeting’ and ‘heparin/protamine-based prodrug’, were evaluated in vitro to examine whether it could selective delivery a PTD-modified toxin, recombinant TAT-gelonin chimera (TAT-Gel), to CEA high expression cancer cells (LS174T). Furthermore, the feasibility of the drug delivery system (DDS) was assessed in vivo by biodistribution and efficacy studies using LS174T s.c. xenograft tumor bearing mice. Results T84.66-Hep displayed specific binding, but limited internalization (35% after 48 h incubation) to CEA high expression LS174T cells over low expression HCT116 cells. When mixed together with TAT-Gel, the T84.66-Hep formed a strong yet reversible complex. This complex formation provided an effective means of active tumor targeting of TAT-Gel, by 1) directing the TAT-Gel to CEA overexpressed tumor cells and 2) preventing nonspecific cell transduction to non-targeted normal cells. The cell transduction of TAT-Gel could, however, be efficiently reversed by addition of protamine. Feasibility of in vivo tumor targeting and “protamine-induced release” of TAT-Gel from the T84.66-Hep counterpart was confirmed by biodistribution and preliminary efficacy studies. Conclusions This study successfully demonstrated in vitro and in vivo the applicability of PTD-modified ATTEMPTS for toxin-based cancer therapy.

Intein-mediated site-specific synthesis of tumor-targeting protein delivery system: Turning PEG dilemma into prodrug-like feature

“…It could account for the MMP-2-mediated activation, and thus trigger CPP-mediated cell penetration after the EPR effect-related tumor preferential distribution of rTLM-PEG. The treatment efficacy of this system was comparable to our previous studies using antibody-directed protein toxin (gelonin) delivery [28]. It could be further improved for achieving complete tumor regression by combination with small chemo drugs.…”

“Catch-and-Release” Anti-Carcinoembryonic Antigen Monoclonal Antibody Leads to Greater Plasma and Tumor Exposure in a Mouse Model of Colorectal Cancer

“…Many types of cancers show a substantial overexpression of CEA (Hammarstrom, 1999), and CEA overexpression has been found in ∼90% of colorectal tumors (Goldstein and Mitchell, 2005). The selective overexpression of CEA has led to significant interest in developing anti-CEA mAb for imaging and treatment (Mach et al, 1981;Rowland et al, 1986;Baum et al, 1989;Kraeber-Bodéré et al, 2006;Shin et al, 2015).…”

Molecular tumor targeting of gelonin by fusion with F3 peptide

“…However, despite the high potency of gelonin, its clinical translation as an anticancer drug remains a challenge because of its poor cellular uptake. To overcome this challenge of intracellular delivery, we previously synthesized various gelonin fusion proteins with different membrane-active peptides (eg, low molecular weight protamine, TAT peptide and melittin) and tested the constructs in different tumor cell lines [24][25][26] . Despite achieving significantly improved cellular uptake, these fusion proteins lacked cell selectivity for their activity, and the toxicity concern remained a great obstacle for clinical application of these fusion proteins.…”