Combination of antibody targeting and PTD-mediated intracellular toxin delivery for colorectal cancer therapy.

Abstract

The bottlenecks of current chemotherapy in the treatment of colorectal cancer lie in the ineffectiveness of the existing anti-cancer small molecule drugs as well as the dose-limiting toxicity caused by the nonselective action on normal tissues by such drugs. To address these problems, we introduce a novel therapeutic strategy based on tumor targeting using a non-internalizing anti-carcinoembryonic antigen (CEA) monoclonal antibody (mAb) and intracellular delivery of the extremely potent yet cell-impermeable protein toxin gelonin via the aid of a cell-penetrating peptide (also termed as protein transduction domain; PTD). A chimeric TAT-gelonin fusion protein was genetically engineered, and it displayed remarkably enhanced anti-cancer activity against human colorectal cancer cells, with IC50 values being several orders of magnitude lower than the unmodified gelonin. On the other hand, a chemically synthesized conjugate of heparin and a murine anti-CEA mAb, T84.66 (termed T84.66-Hep) was found able to bind highly specifically to CEA over-expressing LS174T colorectal cancer cells. When mixing together, TAT-gelonin and T84.66-Hep could associate tightly and automatically through an electrostatic interaction between the cationic TAT and anionic heparin. In preliminary in vivo studies using LS174T s.c. xenograft tumor bearing mouse, selective and significantly augmented (58-fold) delivery of TAT-gelonin to the tumor target was observed, when compared with administration of TAT-gelonin alone. More importantly, efficacy studies also revealed that only the TAT-gelonin/T84.66-Hep complex yielded a significant inhibition of tumor growth (46%) without causing gelonin-induced systemic toxicity. Overall, this study suggested a generic strategy to effectively yet safely deliver potent PTD-modified protein toxins to the tumor.

• Authors: Meong Cheol Shin, Jian Zhang, Kyoung Ah Min, Kyuri Lee, Cheol Moon, Joseph P Balthasar, Victor C Yang
• Journal: Journal of controlled release : official journal of the Controlled Release Society (J Control Release) Vol. 194 Pg. 197-210 (Nov 28 2014) ISSN: 1873-4995 [Electronic] Netherlands
• PMID: 25204286 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2014 Elsevier B.V. All rights reserved.

Chemical References

• Antibodies, Monoclonal
• Antineoplastic Agents, Phytogenic
• Carcinoembryonic Antigen
• Cell-Penetrating Peptides
• DNA Primers
• Gene Products, tat
• Ribosome Inactivating Proteins, Type 1
• GEL protein, Gelonium multiflorum
• Heparin

Topics

• Animals
• Antibodies, Monoclonal (administration & dosage, metabolism, therapeutic use)
• Antineoplastic Agents, Phytogenic (administration & dosage, metabolism, therapeutic use)
• Carcinoembryonic Antigen (metabolism)
• Cell-Penetrating Peptides (therapeutic use)
• Colorectal Neoplasms (drug therapy)
• DNA Primers (administration & dosage)
• Drug Delivery Systems
• Gene Products, tat (chemistry)
• Genetic Vectors
• Heparin (chemistry)
• Humans
• Male
• Maximum Tolerated Dose
• Mice
• Mice, Nude
• Protein Binding
• Ribosome Inactivating Proteins, Type 1 (administration & dosage, metabolism, therapeutic use)
• Tissue Distribution
• Xenograft Model Antitumor Assays