Scientists have developed a new CAR T-cell immunotherapy strategy that uses light to activate the immune cells specifically in cancerous regions. The approach, which worked well in mice, may help reduce treatment-related side effects in cancer patients.
The study, “Engineering light-controllable CAR T cells for cancer immunotherapy,” was published in the journal Science Advances.
Chimeric antigen receptor T-cell therapy, or simply CAR T-cell therapy, is a type of immunotherapy that uses a person’s own T-cells — immune cells with the ability to fight threats — and modifies them to more effectively eliminate cancer.
First, blood samples are taken from the patient to collect the T-cells. The cells are then modified in the lab to produce a protein on their surface called chimeric antigen receptor, or CAR, which enables them to recognize a specific protein in cancer cells. These modified cells are then expanded to millions and infused back into the patient, where they will find and kill cancer cells.
While the treatment has been proven effective, there are limitations to CAR T-cell therapies. One issue is the targeting of normal cells producing the target protein, which can be dangerous. The therapy also can cause the release of pro-inflammatory molecules or cause the tumor to break down rapidly, which can lead to problems such as kidney damage, abnormal heartbeats, muscle cramps, or seizures.
To address these problems, scientists at the University of California San Diego developed a new CAR T-cell approach that uses blue light as a controllable “on” switch that can be specifically focused on cancer cells, even in solid tumors, avoiding normal tissue.
This new method is called the light-inducible nuclear translocation and dimerization system, or LINTAD. A special protein complex designed to activate the production of CAR was split into two parts. One was designed to be in the cell nucleus, which is a cell’s control center, while the other remained outside the nucleus. Upon light stimulation, the outside protein moved inside the nucleus (nuclear translocation) and formed a whole complex (dimerization), triggering CAR expression.
The team first tested the system in a common human kidney cell line and showed blue light-stimulated CAR production. A second test, conducted in a common T-cell line known as Jurkat cells, demonstrated that LINTAD non-invasively induced gene expression with light stimulation.
Using primary human T-cells, like those found in the body, light stimulation triggered the production of CAR, and killed lymphoma cancer cells. After only 12 hours of light stimulation, the LINTAD CAR T-cells were over seven times more effective than cells in the control groups, which were either LINTAD cells kept in the dark or normal T-cells.
To test whether the blue light could penetrate the skin, the mice were injected with lymphoma cells on both sides of their bodies. The blue light was shined on one side only. After 24 hours of light or dark treatment, the light-exposed side showed significant CAR production compared with the side kept dark. That demonstrated that blue light can penetrate the skin.
Light-activated, LINTAD-carrying primary human T-cells were injected into the mice four days after they received cancer cells. Compared with the control group, tumor growth in the treated mice was significantly reduced by day 12, demonstrating the cytotoxicity or cell-killing effect of light-induced T-cells against tumor cells.
In a final test of the precision of this method, the mice were injected with lymphoma cells on both the right and left flanks. The light-activated T-cells were then injected four days later and the light was focused on one side only. After a three weeks, tumor growth on the side exposed to light was significantly inhibited compared with that on the dark side.
The team then tested whether these cells were able to eliminate cancer cells in mice. They activated the CAR T-cells with light in the lab and injected them into animals with lymphoma. The tumors remained relatively small in the animals infused with the light-induced CAR T-cells. Meanwhile, the animals infused with CAR T-cells that were kept in the dark, and those with non-modified T-cells experienced significant increases in tumor burden.
“The results showed that pulsed light stimulations can activate LINTAD CAR T cells with strong cytotoxicity against target cancer cells, both in vitro [in the lab] and in vivo [in the body],” the scientists wrote.
“Therefore, our LINTAD system can serve as an efficient tool to noninvasively control gene activation and activate inducible CAR T-cells for precision cancer immunotherapy,” they concluded.
