June 6, 2011

Wiping Out Leukemia Stem Cells

(Ivanhoe Newswire) -- Researchers have discovered a way of eliminating leukemic stem cells, which could lead to new treatments that may help leukemia patients achieve complete remission. The study showed leukemic stem cells can be abolished by suppressing two proteins found in the bodies of mice.

Researchers say leukemic stem cells are responsible for sustaining the disease and are most likely responsible for relapse. Eliminating these cells is believed to be the key for complete remission.

Scientists from King's College London looked at leukemic stem cells found in a type of leukemia that involves mutations of the MLL gene. This accounts for about 70 percent of infant leukemias and 10 percent of adult acute leukemias. Only about 50 percent of children with MLL survive past two years after receiving standard treatment.

A protein known as Bmi1 is known to play a key role in the survival and proliferation of various cancer stem cells. For the first time, this new study showed that although the protein is needed for survival of acute myeloid leukemias (AML), the cancer stem cells actually survive independently of Bmi1 in MLL patients.

The team of researchers also found high levels of another protein -- known as Hoxa9 -- in the MLL mice and human patients. Hoxa9 is similar to Bmi1. It ensures leukemia cells divide and grow by allowing their escape from the inherent surveillance system, which will otherwise cause cell death. In mice with MLL leukemic stem cells (that can proliferate without Bmi1), suppression of both Bmi1 and Hoxa9 abolishes the ability of MLL mutation to induce leukemia.

"These findings take us a step forward in our understanding of how this devastating disease can return in patients after they have received the standard treatment," Professor Eric So, Head of the Leukaemia and Stem Cell Biology group at King's, was quoted as saying. "Now, we know that leukemic stem cells in certain types of leukemia, such as MLL, can survive and proliferate independently of the Bmi1 protein, we need to consider more carefully the future of stem cell therapy to treat the disease. It's not as easy as people originally thought it might be. But these findings provide us with vital information that will help us look at alternative ways of combating different forms of the disease, which will ultimately allow patients to achieve long-term complete remission."

SOURCE: Cell Stem Cell, June 2, 2011