Light can trick immune system to attack cancer

Washington: Scientists have discovered a simple and practical way to kill cancer cells by using light to steer immune cells to attack the tumours.

Researchers at University of Rochester Medical Center in the US describe their method as similar to "sending light on a spy mission to track down cancer cells."

Immunotherapy is different from radiation or chemotherapy. Instead of directly killing cancer cells, immunotherapy tells the immune system to act in certain ways by stimulating T cells to attack the disease.

However, the problem is that immunotherapy can cause the immune system to overreact or under-react, said Minsoo Kim, professor University of Rochester.

Kim's laboratory conducted a study to understand and develop light-sensitive molecules that could efficiently guide T cells towards tumours.

They discovered that a molecule called channelrhodopsin (CatCh), which is active in algae and is light sensitive, could be introduced to the immune system via a virus and activated to control the T-cell response to cancer.

They also tested an LED chip in mice which could eventually be implanted in humans.

The team evaluated their methods in mice with melanoma on the ears.

The animals wore a tiny battery pack that sent a wireless signal to the LED chip - allowing researchers to remotely shine light on the tumour and surrounding areas, giving T cells a boost for their cancer-killing function.

The optical control was sufficient to allow the immune system to nearly wipe out the melanoma with no toxic side effects, the study found.

Future studies, Kim said, would determine whether the wireless LED signal can deliver light to a tumour deep within the body instead of on the surface area, and still have the ability to stimulate T cells to attack.

Kim said that the discovery is meant to be combined with immunotherapy to make it safer, more effective, and traceable.

With improvements, the optical method might allow doctors to see, in real time, if the cancer therapy is reaching its target.

Currently when patients receive immunotherapy they must wait for several weeks and then undergo imaging scans to find out if the treatment worked.

The study was published in the journal Nature Communications.