Utilizing chimeric proteins for exploring the cellular fate of endogenous proteins

Human toxin-based recombinant immunotoxins/chimeric proteins as a drug delivery system for targeted treatment of human diseases

INTRODUCTION

The development of specific immunosuppressive reagents remains the major goal in the treatment of human diseases. One such approach is the use of recombinant immunotoxins/chimeric proteins, composed of targeting and killing moieties, fused at the cDNA level. Most of these 'magic bullets' use bacterial or plant toxins to induce cell death. These toxins are extremely potent, but they also cause severe toxicity and systemic side effects that limit the maximal doses given to patients. Moreover, being of non-human origin, they are highly immunogenic, and the resulting neutralizing antibody production impairs their efficacy.

AREAS COVERED

This review describes recombinant immunotoxins/chimeric proteins composed of the classical delivering, cell-targeting molecules, fused to highly cytotoxic human proteins capable of generating an intense apoptotic response within the target cell. This review focuses on the new 'Human Killing Moieties' of these targeted proteins and describes recent progress in the development of these promising molecules.

EXPERT OPINION

Human toxin-based immunotoxins/chimeric proteins for the targeted delivery of drugs are still in their early stages of development. However, they are certain to advance in the very near future to become an extra weapon in the everlasting war against human diseases, mainly cancer.

Recombinant adenovirus IL-24-Bax promotes apoptosis of hepatocellular carcinoma cells in vitro and in vivo

Gene therapy promises to become an alternative choice for the treatment of hepatic cancer. In many cancers, the delivery of chimeric proteins by adenovirus vector has been reported to induce apoptosis. This study was performed to evaluate whether the recombinant adenovirus interleukin (IL)-24-Bax can induce apoptosis in hepatocellular carcinoma cells in vitro and in vivo. Several recombinant adenoviruses were constructed, and the expression of their encoded proteins was measured. The effects of the recombinant adenovirus on hepatocellular carcinoma cells and the normal hepatocyte cell line were investigated through cell viability and apoptosis assays after the cells were treated with Ad.Luc, Ad.IL-24, Ad.Bax or Ad.IL-24-Bax. The mechanism involved was also explored. A tumor-bearing mouse model was used to evaluate the effects of the adenovirus on tumor volume and cell apoptosis in vivo. Ad.IL-24-Bax selectively suppressed growth of hepatocellular carcinoma cells and induced apoptosis, but it had little influence on the normal hepatocytes. The mechanism of this response may include the effect of the 10HRE/VEGF385 promoter and the synergistic effect of IL-24 and Bax. Ad.IL-24-Bax also suppressed tumor growth in nude mice and induced apoptosis. Ad.IL-24-Bax may be a useful tool for gene therapy of hepatic cancer.