To better understand what was happening in the human patients, the researchers turned to laboratory mice that had been genetically engineered to develop pancreatic cancer.

"And we were able to test this antibody in these mice to understand exactly how it was that their immune system is being turned on," he says. "And it was the insights that we were able to gather in this regard in the laboratory that allowed us to understand what was happening in our patients."

Vonderheide says the information could help scientists working on new drugs for cancer patients.

"What's important about that is we now have this tool, this ability to test our ideas in the mice with pancreatic cancer, and only pick those therapies that are successful in the mice before bringing any other therapy forward to patients."

The study by Robert Vonderheide and his colleagues is published in the journal Science.