Simple, cheap nanoparticles activate immune system against cancer

The best way to fight off cancer might be to strengthen the body’s immune system and help it identify and kill tumors. This field of study is known as immunotherapy, and while it’s showing promise it can be quite expensive. Now, researchers at the University of Wisconsin-Madison have developed artificial nanoparticles that should be cheaper and easier to produce.

Immunotherapy takes several forms, but the one in question here uses targeted antibodies. This technique involves engineering antibodies that latch onto the cancer cells and alert the immune system to its presence. But according to the researchers on the new study, there may be a better way.

“Immunotherapy basically boosts the patient’s own immune system to fight against cancer cells better,” says Seungpyo Hong, co-lead author of the study. “The antibodies that are used right now are large, they’re expensive, they’re hard to engineer, and they don’t always show the highest level of efficacy either. So we wanted to explore other ways to activate the immune system.”

To that end, the team investigated whether artificial nanoparticles could be made to work instead of engineered antibodies. Their nanoparticles are branched, allowing peptides to be attached to them. In this case, the peptides were fragments of PD-1, a protein that’s been at the heart of immunotherapy research almost from the beginning.

PD-1 acts like a brake on the immune system’s T cells, stopping them attacking healthy cells. The problem is, tumors have figured this out and used it to their advantage, producing their own proteins called PD-L1 which essentially makes the immune system think they’re healthy cells so it ignores them.

By using PD-1 antibodies, immunotherapy counters this trick and makes the immune system aware of the cancer cells again. This earned the team who discovered it the 2018 Nobel Prize in Medicine.

The researchers on the new study found that their nanoparticles containing PD-1 peptides were just as effective as using natural antibodies. In lab tests, the nanoparticles were able to cling to PD-L1 just as strongly as others, inhibiting the cancer’s ability to hide from T cells by about 50 percent. In other tests, this technique made the chemotherapy drug doxorubicin more effective against tumors.

It’s a promising first step, but so far it’s only been tested in cultured cancer cells. The team is now testing the technique in animal models, and if all goes well human trials may follow a few years down the track. The team says that the peptides and nanoparticles are simple and inexpensive to produce, and can be tweaked easily to see if there’s a way to improve them further.