Preliminary data from one of the first clinical trials to test a stem cell-targeting drug in cancer patients shows that while the drug did not prolong survival, its suppressing effect on patients' stem cells was impressive enough to send investigators looking for a better drug to try.
As an emerging field of study in cancer research, stem cells are believed to sprout cancer much like the hidden roots of weeds that elude efforts to get rid of them.
Rituximab, a drug currently approved to treat B-cell lymphomas, plus a common chemotherapy agent, cyclophosphamide, were given to 21 patients whose multiple myeloma, a cancer of the bone marrow, had relapsed or was defined as high-risk first remission. A previous study using the drug alone in multiple myeloma patients suggested that the disease in some participants progressed more slowly.
During the study, the Johns Hopkins team examined the stem cells under the microscope. “We found cancer stem cells coated with rituxumab, but the drug wasn't killing them,” said Carol Ann Huff, M.D., assistant professor of oncology. “We think the idea is correct, but the drug itself wasn't the right one.” Rituximab is sold under the trade name Rituxan.
Huff and her team believe that several therapies are required to kill cancer - one to get rid of the bulk of the tumor, like mowing the lawn, and another to hit the root of the cancer, its stem cells. “We think one reason that cancer comes back is because stem cells, which are resistant to chemotherapy, repopulate the body with new cancer cells,” says William Matsui, M.D., assistant professor of medicine at the Johns Hopkins Kimmel Cancer Center.