Light-Controlled Gene Editor Shows Promise in Silencing Oncogenes

Why Do People Develop Cancer? The human body carries proto-oncogenes; when these genes undergo malignant transformation due to stimulation by external physical or chemical carcinogens, cancer develops. Gene therapy refers to the introduction of exogenous normal genes into target cells to correct or compensate for diseases caused by genetic defects and abnormalities, thereby achieving therapeutic goals.

In theory, this is indeed a feasible approach. Current gene-editing technologies primarily rely on the CRISPR gene-editing system, which can delete or replace any targeted segment of genes in living cells. Recently, researchers at MIT have added an extra layer of control, enabling precise regulation of gene editing by triggering the system’s response to light.

With this new system, researchers can achieve gene editing simply by exposing target cells to ultraviolet light. This level of control enables scientists to investigate in greater detail how cells and genetic material influence embryonic development and genetic diseases. It even allows for the precise silencing of oncogenes in tumor cells.

“The advantage of this transducer is that it enables precise control over temporal and spatial nodes,” said Sangeeta Bhatia, a scientist in MIT’s Department of Electrical Engineering and Computer Science and an integrated cancer researcher at the Koch Institute for Integrative Cancer Research at MIT.

Piyush Jain, a postdoctoral fellow at the Massachusetts Institute of Technology’s Institute for Medical Engineering and Science, developed a method to control RNA interference using light, which involves delivering small strands of RNA into cells to temporarily block specific genes. Inspired by this work, Jain applied the same technique to CRISPR editors.

CRISPR gene editing is a complex process that requires a short strand of RNA to guide the DNA endonuclease Cas9 to a specific genomic region, where Cas9 cleaves the DNA. The cell’s DNA repair machinery then rejoins the two broken ends, resulting in the permanent deletion of a small segment of the gene and rendering it nonfunctional.

To engineer a CRISPR photosensitive system, researchers modified Cas9 so that it exhibits cleavage activity only when exposed to light of a specific wavelength. The MIT team opted for a different approach by engineering the guide RNA segments to confer light sensitivity. According to Bhatia, in the future, it will be easier to achieve photosensitive Cas9 by delivering modified guide RNA segments to program target cells.

“You don’t need anything else except adding a photoactivatable protector,” she explained. “This attempt makes the system more modular.”To facilitate guidanceRNA possesses photosensitive properties. The MIT team developed a “protector”—a DNA sequence with a backbone composed of photocleavable bonds. These DNA segments can be bound to different guide RNAs as needed, thereby preventing the RNA from interacting with other target genes.

When researchers irradiated target cells with light at a wavelength of 365 nanometers, the protective DNA broke into several smaller fragments, and the RNA was released and bound to the marker gene, guiding the Cas9 endonuclease to cleave it.

Researchers stated that through this study, they could use light to control the gene editing of green fluorescent protein (GFP), targeting two gene segments encoding this protein that are typically located on the cell surface and overexpressed in certain cancer cells.

“If this approach is feasible, you can design protector sequences to target different sequences,” Bhatia revealed. “We designed different protectors against different genes, and the results showed that they could all be photoactivated.”

“CRISPR-Cas9 is a powerful technology that can help scientists study how genes influence cellular activities.” James Dahlman, Assistant Professor of Bioengineering at the Georgia Institute of Technology, believes that this significant step will enable precise control over genetic modifications. Therefore, this research provides the scientific community with a highly useful tool to achieve substantial improvements and optimizations in gene editing.

Precise control over the timing of gene editing can help researchers study cellular activities at different stages of disease, enabling the silencing of specific genes at appropriate times to achieve a cure.The Bhatia laboratory is striving to realize the clinical application of this technology. Among the potential applications, the most feasible one at present is using it to silence oncogenes in skin cancer, as the skin is readily exposed to ultraviolet radiation.

Currently, this research has received funding from multiple sources, including the Ludwig Center for Molecular Oncology, the Marie-D. and Pierre Casimir-Lambert Fund, and the Koch Institute. The team remains dedicated to developing a “universal protector” compatible with any guide RNA segment, thereby eliminating the need to design a specific protector for each RNA molecule and enabling the inhibition of CRISPR-Cas9 binding to multiple targets simultaneously. It is believed that through the efforts of researchers, this technology will eventually translate into clinical practice, improving people’s lives.