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Updated: Aug 19, 2026
Profiling Ubiquitin and Ubiquitin-like Dependent Post-translational Modifications and Identification of Significant Alterations
Published on: November 7, 2019
Construction of tumor-specific toxins using ubiquitin fusion technique
Sergey O Tcherniuk1, Jadwiga Chroboczek, Maxim Y Balakirev
1Laboratoire de Biophysique Moléculaire, Institut de Biologie Structurale J. P. Ebel (CEA/CNRS/UJF), 41 rue Jules Horowitz, 38027 Grenoble, France.
Abstract:
The use of cytotoxic agents to eliminate cancer cells is limited because of their nonselective toxicity and unwanted side effects. One of the strategies to overcome these limitations is to use latent prodrugs that become toxic in situ after being enzymatically activated in target cells. In this work we describe a method for producing tumor-specific toxins by using a ubiquitin fusion technique. The method is illustrated by the production of recombinant toxins by in-frame fusion of ubiquitin to saporin, a toxin from the plant Saponaria officinalis. Ubiquitin-fused toxins were rapidly degraded via the ubiquitin-proteasome system, significantly reducing their nonspecific toxicity. The insertion of the protease-cleavage sequence between ubiquitin and saporin led to the removal of ubiquitin by the protease and resulted in protease-dependent stabilization of the toxin. We engineered toxins that can be stabilized by specific proteases such as deubiquitinating enzymes and prostate-specific antigen (PSA). Both constructs were activated in vitro and in cultured cells by the appropriate enzyme. Processing by the protease resulted in a greater than 10-fold increase in the toxicity of these constructs. Importantly, the PSA-cleavable toxin was able to kill specifically the PSA-producing prostate cancer cells. The ubiquitin fusion technique is thus a versatile and reliable method for obtaining selective cytotoxic agents and can easily be adapted for different kinds of toxins and activating proteases.
Insights
This study introduces a ubiquitin fusion technique to create tumor-specific toxins. This method enhances cancer cell targeting by activating toxins only within cancer cells, reducing side effects.
Area of Science:
- Biotechnology
- Molecular Biology
- Cancer Therapeutics
Background:
- Cytotoxic agents for cancer treatment face limitations due to nonselective toxicity and side effects.
- Prodrug strategies aim to activate toxins specifically within target cancer cells to improve efficacy and safety.
Purpose of the Study:
- To develop a novel method for producing tumor-specific cytotoxic agents using a ubiquitin fusion technique.
- To engineer recombinant toxins activated by specific proteases for targeted cancer therapy.
Main Methods:
- Constructed ubiquitin-saporin fusion proteins with protease-cleavable sequences.
- Investigated the degradation and activation of these fusion toxins via the ubiquitin-proteasome system and specific proteases.
- Evaluated the enzymatic activation and cytotoxic activity in vitro and in cultured cells, including prostate cancer cells.
Main Results:
- Ubiquitin fusion significantly reduced nonspecific toxicity of toxins through rapid degradation.
- Engineered toxins were selectively stabilized and activated by specific proteases like prostate-specific antigen (PSA).
- Protease-mediated processing increased toxin toxicity by over 10-fold, with PSA-cleavable toxins specifically killing PSA-producing prostate cancer cells.
Conclusions:
- The ubiquitin fusion technique provides a versatile and reliable platform for developing selective cytotoxic agents.
- This approach can be adapted for various toxins and activating proteases, offering a promising strategy for targeted cancer therapy.
- The engineered toxins demonstrate potential for reducing side effects and improving treatment outcomes in specific cancers.
