Priming the Immune System to Fight Cancer

PHILADELPHIA, Dec. 17, 2020 /PRNewswire/ -- Immunotherapies, such as checkpoint inhibitor drugs, have made worlds of difference for the treatment of cancer. Most clinicians and scientists understand these drugs act on what's known as the adaptive immune system, the T cells and B cells that respond to specific threats to the body.

New research from a team co-led by Penn Dental Medicine's George Hajishengallis suggests that the innate immune system, which responds more generally to bodily invaders, may be an important yet overlooked component of immunotherapy's success.

Their work, published in the journal Cell, found that "training" the innate immune system with β-glucan, a compound derived from fungus, inspired the production of innate immune cells, specifically neutrophils, that were programmed to prevent or attack tumors in an animal model.

"The focus in immunotherapy is placed on adaptive immunity, like checkpoint inhibitors inhibit the interaction between cancer cells and T cells," says Hajishengallis. "The innate immune cells, or myeloid cells, have not been considered so important. Yet our work suggests the myeloid cells can play a critical role in regulating tumor behavior."

The current study builds on earlier work by Hajishengallis and a multi-institutional team of collaborators, which showed that trained immunity, elicited through exposure to the fungus-derived compound β-glucan, could improve immune recovery after chemotherapy in a mouse model.

In that previous study, the researchers also showed that the "memory" of the innate immune system was held within the bone marrow, in hematopoietic stem cells that serve as precursors of myeloid cells, such as neutrophils, monocytes, and macrophages.

The team next wanted to get at the details of the mechanism by which this memory was encoded. "The fact that β-glucan helps you fight tumors doesn't necessarily mean it was through trained immunity," says Hajishengallis.

To confirm that link, the researchers isolated neutrophils from mice that had received the innate immune training via exposure to β-glucan and transferred them, along with cells that grow into melanoma tumors, to mice that had not received β-glucan. Tumor growth was significantly dampened in animals that received cells from mice that had been trained. 

β-glucan is already in clinical trials for cancer immunotherapy, but the researchers say this finding suggests a novel mechanism of action with new treatment approaches.  

"This is a breakthrough concept that can be therapeutically exploited for cancer immunotherapy in humans," Hajishengallis says, "specifically by transferring neutrophils from β-glucan-trained donors to cancer patients who would be recipients."

Contact: Beth Adams, [email protected]

SOURCE Penn Dental Medicine

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