A virus that in nature infects only rabbits could become a cancer-fighting tool for humans. Myxoma virus kills cancerous blood-precursor cells in human bone marrow while sparing normal blood stem cells, a multidisciplinary team at the University of Florida College of Medicine has found. The findings are now online and will appear in an upcoming issue of the journal Leukemia.

The discovery could help make more cancer patients eligible for bone marrow self-transplant therapy and reduce disease relapse rates after transplantation.

"This is a new strategy to remove cancer cells before the transplant," said virologist Grant McFadden, Ph.D., senior author of the paper and a member of the UF Genetics Institute. "This is the first time anyone has shown in a living animal that a virus can distinguish normal bone marrow stem cells from cancerous stem cells."

The major therapeutic applications will likely be for blood cancers such as leukemia, lymphoma and bone marrow cancers, the researchers say.

In mouse studies, myxoma virus was used to purge cancerous cells from leukemia patient bone marrow samples before they were infused into the test animals. The technique was effective against an aggressive form of leukemia that is resistant to conventional chemotherapy.

Microorganisms have been used to fight cancer before. More than 100 years ago, physicians treating patients who had bone and head and neck cancers used mixtures of bacteria to jumpstart the immune system, which also happened to attack the cancer. While the approach helped some people it sometimes also caused harm.

Today, patients who have certain types of cancer such as acute myelogenous leukemia are usually treated with using high doses of chemotherapy. But that can destroy the patient's own immune system unless he or she receives a transplant of blood stem cells, which can be from the patient's own marrow samples or from a donor.

Although reinfusion of a patient's own bone marrow stem cells is generally safer in the short run, those patients are at high risk of dying from return of disease because of leukemia contaminating the infused bone marrow.

"That's one of the major frustrations, so we're looking for ways to clean these stem cells before putting them back into patients," said Christopher R. Cogle, M.D., an assistant professor in the division of hematology and oncology and a leader of the research team.

University of Florida

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