Using Light to Guide T Lymphocytes to Attack Tumors


Solid tumors have a whole bag of tricks to avoid the immune system. Fortunately, new therapies aim at these strategies to sensitize the patient’s immune system to the tumor. A new study from the University of Rochester Medical Center laboratory has discovered a simple, practical way that uses light and optics to turn killer immune cells to the tumors.

The lead author of this study, Minsoo Kim, Ph.D., works as a professor of Microbiology and Immunology, and is also an investigator at the Wilmot Cancer Institute. This work from Kim’s laboratory were published in the online journal Nature Communications. Kim described the method devised in his laboratory as similar to “sending light on a spy mission to track down cancer cells.”

A new therapy for treating hard-to-crack cancers is called immunotherapy. Immunotherapy does not utilize radiation or chemotherapy, but instructs the patient’s T lymphocytes to attack the cancerous cells. For example, CAR T-cell therapy removes the patient’s T cells, grows them in the laboratory, genetically engineers them to recognize, attack and kill the cancer, and then reintroduces these cells back into the patient. This is one type of immunotherapy. While this ingenuous technique shows remarkable promise, the immune system can overreact or under-react sometimes. Also, slippery cancers can find ways to hide from marauding T cells. Likewise, aggressive tumors often have mechanisms by which they suppress the immune system and surround themselves with a kind of “no-go” zone that prevents any immune cells from coming near the tumor. These immunosuppressive microenvironments that surround the malignant tumor keeps T cells out.

While it is true that T cells can be engineered to be more efficient killers, unleashing such supercharged T cells into the body can produce a tempest of toxicities. Is there a safer way?

Kim and his colleagues tried to find a kinder, gentler way to crack the tumor. They used a two-prong approach. First, Kim and others discovered that light-sensitive molecules could effectively guide T cells toward tumors. Kim and his coworkers even discovered that a molecule from algae called “channelrhodopsin” (CatCh) that is light-sensitive, could be introduced into immune cells by genetically engineering them with viruses. This technology is so novel that the university’s technology transfer office has filed for patent protection on the invention. Secondly, Kim collaborated with University of Rochester optics and photonics experts to design a Light Emitting Diode (LED) chip that could be implanted and shine light on the tumor.

Next, the Kim group fitted their mice with a small battery pack that sent a wireless signal to the implanted LED chip. When the ears of the mice were implanted with aggressive melanoma cells taken from a patient, the chip remotely shines light on the implanted tumor and surrounding areas. The light-guided T cells ran headlong to the tumor, ignoring the no-go zone where they killed the implanted tumor.

Even more interestingly, the LED chip with the battery pack were used in many control mice and no toxic side effects were observed. In the tumor-implanted mice, the light-guided T cells completely destroyed the implanted melanoma was destroyed without dangerous side effects.

In the future, Kim wants to determine if the wireless LED signal can deliver light to tumors deep within the body instead only on the surface. Also, can light shined into deep areas of the body still guide the T cells to the tumor to attack the tumor.

Kim cautiously emphasized that while his discovery is exciting, it is only meant to be combined with immunotherapy to make it safer, more effective, and traceable. Perhaps with additional improvements, Kim’s optical method might allow doctors to see, in real-time, if cancer therapies are reaching their target. Currently when patients receive immunotherapy, they must wait for several weeks and then have imaging scans to determine if the treatment worked.

“The beauty of our approach is that it’s highly flexible, non-toxic, and focused on activating T cells to do their jobs,” Kim said.

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