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Dr. Seth Pollack, a Fred Hutch researcher who led the study on G100. (Fred Hutch Photo / Bo Jungmayer)

When we think of the immune system, we generally think of one, unified system that works to fight infections and other diseases.

But there are actually two distinct parts to the immune system: the active immune system, which is made up of agents like T cells, and the innate immune system, which developed over millennia to protect our bodies from ancient bacteria and viruses.

Now a new study from the Fred Hutchinson Cancer Research Center found that using a bacteria-like drug to activate this innate immune system helped shrink the tumors of sarcoma patients, a catch-all term for tumors that occur in soft tissues. Even more importantly, researchers saw signs that the drug could be used to make emerging immunotherapy treatments more effective.

The results will be presented Monday at the annual meeting of the American Association for Cancer Research.

The study was led by Fred Hutch researcher Dr. Seth Pollack. He and his team had been using the drug, known as G100, as an assisting agent in a cancer vaccine they were developing. But they started to wonder if the drug could work against cancer on its own.

“While most of cancer immunology research correctly focuses on directly ‘boosting’ the adaptive immune response — as this is really the part of the immune system that is best at fighting cancer — we recognized that adaptive and innate immune responses work closely with one another,” Pollack told GeekWire in an email. “We thought that by activating the innate response, we could activate the adaptive response as well – which is indeed what we saw as evidenced by the increased T cells infiltrating into the tumors.”

This first study was designed to test the drug’s safety, so it was very small. But of the fifteen patients that received the drug, fourteen saw their tumors shrink or disappear, making Pollack optimistic that the drug will prove to be effective in future, larger studies.

Here’s how it works: G100 contains a small component called lipopolysaccharide, which is found in the cell walls of some bacteria. Our innate immune systems respond very strongly to this molecule, triggering inflammation that acts like a bat signal for the active immune system.

“We thought that if we could activate these infiltrating immune cells we could generate a more robust inflammatory response in the tumor,” Pollack said. In other words, the inflammation would attract active immune cells, which would then see the tumor and attack it.

That seems to be exactly what happened, as researchers saw signs of the active immune system attacking patients’ tumors.

“This is very important because it may make these tumors susceptible to some other emerging immunotherapies,” Pollack explained.

Immunotherapies, or treatments that use the body’s immune system to attack cancer, are showing great promise in research across the country, and some have even been approved by the FDA for widespread use.

But there are still many unanswered questions in the field, including why some patients respond to these therapies while others do not. Although Pollack’s study is still in its early stages, the drug could help make some of these treatments more effective.

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