White blood cells from mice that are naturally immune to cancer cured tumors in other mice and provided them with lifelong immunity to the disease, researchers reported Monday.
The finding indicates the existence of a biological pathway previously unsuspected in any species. A small team of researchers is working to understand the genetic and immunological basis of the surprising phenomenon.
Preliminary studies hint at the existence of a similar resistance in humans. Researchers hope that harnessing the biological process could lead to a new approach to treating cancer.
"The idea of cells being able to kill tumor cells ... is very exciting," said biologist Howard Young of the National Cancer Institute's Center for Cancer Research in Frederick, Md. "But this is a mouse, and there is no guarantee that the same gene will exist in people."
The findings have not been replicated in any other laboratory, primarily because the researchers who discovered the cancer-immune mice have only recently bred enough to supply them to other scientists.
"Our initial ability to collaborate was very limited by the number of mice that were actually available," said Dr. Mark C. Willingham of the Wake Forest University School of Medicine, a coauthor of the paper.
But Dr. Zhen Cui of Wake Forest, whose team published the findings in the Proceedings of the National Academy of Science, said he expected rapid replication of the results because the findings were so clear-cut and easily observed.
"This is a truly remarkable phenomenon ... and it really needs confirmation from other institutions," he said.
Cui and his colleagues stumbled on the immune mice by accident in 1999. They were injecting mice with a highly virulent form of cancer cells as part of an ongoing study of the biological mechanisms that cause cancer to spread.
On April 13 of that year, a graduate student told Cui that one of the mice she had injected did not develop a tumor. Assuming the student had simply overlooked the mouse, he told her to do it again. And again.
After a total of five injections -- the last equal to 10% of the animal's body weight -- the mouse remained free of tumors.
Intrigued, they bred the mouse and found that about half its offspring had the same resistance. The trait bred true through subsequent generations and the team eventually had a colony of about 700 resistant mice. Cross-breeding the mice with other strains transferred the resistance to them as well.
