Cui and Willingham said the killing of the cancer cells in the cancer-resistant mouse requires three distinct steps:
The ordinary mice lack the first two steps.
The researchers found that the anti-tumor response involved white blood cells of the so-called innate immune system, which the body ordinarily employs to fight off bacteria, but which had not been thought to be effective in fighting off cancer. Instead, in these cancer-resistant mice, three white-blood-cell types of the innate immune system ?neutrophils, macrophages and natural killer cells ?all infiltrate the tumor site in a multi-pronged killing response.
"Each cell type had independent killing activity against the cancer cells," the authors said, using different molecules. Macrophages, for instance, have to be in physical contact with the cancer cell before unleashing its combination of killer molecules.
White blood cells from the cancer-resistant mice apparently have the same ability to attack a range of tumors when transplanted to ordinary mice.
Cui and Willingham also want to explore how this one process can detect a wide range of cancer cells of so many different types. The dogma of cancer fighters has always postulated that there are many different cancers. "This new research in mice suggests that there may be some things that most cancers have in common," said Willingham, a pathologist and head of the Section on Tumor Biology.