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Targeted toxin therapy for the treatment of cancer
1Laboratory of Molecular Biology, National Cancer Institute, Bethesda, MD 20892.
Abstract:
Protein toxins such as Pseudomonas exotoxin, diphtheria toxin, and ricin may be useful in cancer therapy because they are among the most potent cell-killing agents. One molecule of a toxin delivered to the cytoplasm of a cancer cell will be lethal for that cell. However, to be therapeutically useful, these toxins need to be targeted to specific sites on the surface of cancer cells, then be internalized and ultimately reach the cell cytoplasm. This process is accomplished by eliminating binding to toxin receptors and redirecting the cell-killing activity of the toxin to receptors or antigens present on cancer cells. Typically, toxins are conjugated to cell-binding proteins such as monoclonal antibodies or growth factors. These conjugates bind and kill cancer cells selectively while normal cells, which don't bind the conjugates, are spared. Because the genes for many protein toxins have been cloned, it is possible to make genetic modifications to their structure. By deleting the DNA that codes for the toxin binding region and replacing it with various complementary DNA encoding other cell-binding proteins, it has been possible to make chimeric toxins that kill cells on the basis of the newly acquired binding activity. The ability to make these chimeras may be useful in designing future toxin-based anticancer therapies.
Insights
Protein toxins can kill cancer cells. Researchers are engineering these toxins, creating chimeric toxins, to specifically target and eliminate cancer cells while sparing healthy ones for improved cancer therapy.
Area of Science:
- Biochemistry
- Molecular Biology
- Oncology
Background:
- Protein toxins like Pseudomonas exotoxin, diphtheria toxin, and ricin are potent cell-killing agents.
- Targeting toxins to cancer cells requires specific cell-surface binding and internalization into the cytoplasm.
- Current methods involve conjugating toxins to cell-binding proteins to achieve selective cancer cell targeting.
Purpose of the Study:
- To explore the potential of protein toxins in cancer therapy.
- To investigate methods for redirecting toxin activity to cancer-specific antigens.
- To develop strategies for creating targeted, genetically modified toxins for cancer treatment.
Main Methods:
- Genetic modification of protein toxin genes to alter their binding specificities.
- Creation of chimeric toxins by replacing native toxin binding regions with DNA encoding cancer-targeting proteins.
- Conjugation of toxins to cell-binding proteins like monoclonal antibodies or growth factors.
Main Results:
- Chimeric toxins can be engineered to bind to specific cancer cell receptors or antigens.
- Genetically modified toxins demonstrate targeted cell-killing activity based on their new binding properties.
- Selective killing of cancer cells is achieved while sparing normal cells lacking the target antigens.
Conclusions:
- Protein toxins can be genetically engineered into chimeric toxins for targeted cancer therapy.
- This approach offers a promising strategy for developing novel anticancer treatments with improved selectivity.
- The ability to create chimeric toxins may significantly advance future toxin-based therapeutic designs.