Researchers at Oregon Health & Science University announced on Apr. 11 that they have identified a key reason why immunotherapy has not been effective for pancreatic cancer and outlined a potential new strategy to address this resistance.
Pancreatic cancer is known as one of the most difficult cancers to treat, with most patients eventually no longer responding to available therapies. Immunotherapies, which have shown success in treating cancers such as melanoma and lung cancer, have largely failed in pancreatic cases.
The study, published in the journal Immunity, found that pancreatic tumors reshape their immune environment by recruiting regulatory T cells (Tregs) that suppress tumor-killing immune responses. "Tregs are very suppressive immune cells," said Byrne. "If there are a lot of them in a tumor, it's extremely hard to get an anti-tumor immune response going." In many cases, these regulatory cells overpower the body's ability to fight the tumor and neutralize standard immunotherapies before they can take effect.
Byrne's team tested an experimental therapy called agonistic CD40 in mouse models. Unlike typical checkpoint inhibitors that target single signals within the immune system, this approach broadly activates the upstream immune response. The researchers observed that this method did not only stimulate tumor-fighting cells but also reprogrammed Tregs from being suppressors into supporters of anti-tumor activity. "We didn't expect this," Byrne said. "The therapy doesn't directly target Tregs, but as a secondary effect of turning on the immune response, those Tregs changed their behavior. Cells that were shutting down the immune reaction suddenly started supporting tumor killing." Byrne added: "Until now, if a tumor had a lot of Tregs and didn't respond to checkpoint inhibitors, we didn't have many other immunotherapy options... This approach could make resistant tumors more permissive, meaning they could respond to immunotherapy when they previously couldn't."
The findings suggest future treatments may need both to activate the immune system and overcome mechanisms tumors use to block it. The research also opens up possibilities for combining immunotherapies with newer targeted drugs like KRAS inhibitors for potentially better outcomes against pancreatic cancer.
"You can imagine hitting the cancer cell with a targeted drug while also reprogramming the immune environment around it," Byrne said. "That combination could be much more effective than either approach alone." The study highlights patient-specific differences—some tumors contain many suppressed immune cells while others do not—indicating personalized treatment strategies may be necessary moving forward.
Clinical trials using this combination therapy could begin within several years according to Byrne's lab plans. Further research will focus on mapping communication between different types of immune cells inside pancreatic tumors and determining whether these reprogrammed cells provide long-term protection against recurrence.
"The more we understand every step of this process, the more precisely we can intervene," Byrne said. "That's what will allow us to move closer to durable, long-lasting immune responses for pancreatic cancer patients."
