Production growth
Scientists from the USA have found a way to increase the production of proteins for cancer treatment
Tatiana Matveeva, "Scientific Russia"
A new method of controlling synthetic genes, developed by scientists from the Massachusetts Institute of Technology (MIT, USA), can help fine-tune the production of monoclonal antibodies, which are used to treat cancer, and other useful proteins, MIT reports. The development is described in detail in the journal Nature Communications (Chen et al., A synthetic transcription platform for programmable gene expression in mammalian cells).
Many therapeutic proteins, including monoclonal antibodies, are produced in large bioreactors containing mammalian cells. A few years ago, researchers from the Center for Synthetic Biology at the Massachusetts Institute of Technology began working with Pfizer Inc. on a project to develop synthetic biology tools with which it would be possible to increase the production of these useful proteins that can be used to treat diseases.
To do this, the scientists targeted the promoters of the genes they wanted to activate. In all mammalian cells, genes have a promoter region that binds to transcription factors — proteins that trigger gene transcription into informational RNA.
In previous work, scientists have developed synthetic transcription factors, including proteins that help activate target genes. However, these proteins and most other types of synthetic transcription factors must be processed for each gene they target, making their development difficult and time-consuming.
In 2013, researchers developed a CRISPR-based transcription factor that allowed them to more easily control the transcription of naturally occurring genes in mammalian and yeast cells. In the new study, the authors intended to build on this work to create a library of synthetic biological parts that would allow them to deliver a transgen— a gene that is not normally expressed by a cell — and precisely control its expression.
The system that the researchers have developed includes several components. One of them is a transcribed gene together with an "operator" sequence consisting of a number of binding sites of artificial transcription factors. Another component is the guide RNA that binds to these operator sequences. Finally, the system also includes a transcription activation domain attached to the "switched off" Cas9 protein. When Cas9 binds to a guide RNA in an artificially created promoter site, a CRISPR-based transcription factor may include gene expression.
The promoter sites used for this synthetic system have been designed in such a way that they differ from naturally occurring promoter sites and that the system thus does not affect the genes in the cells' own genomes.
The developers tested their system on several types of mammalian cells, including Chinese hamster ovary cells, which are commonly used for the production of therapeutic proteins in industrial bioreactors. They found very similar results in hamster cells and other cells they tested, including myoblasts (precursors of muscle cells) mice and rats, human embryonic kidney cells and human induced pluripotent stem cells.
The results showed that the system can work in various mammalian cells with very stable results. It can be used for different cell types and different target genes and get the expected result.
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