UHN Researchers Discover New Types of Leukemia Stem Cells

Scientists with University Health Network have discovered different types of leukemia stem cells that may explain why this blood-borne cancer can recur so often in patients after treatment.

The study is an important advancement in understanding how leukemia develops and points to the need for new cancer therapies that target these stem cells as well as the regular leukemia cells.

“For the first time, we know where we should be focusing our research in order to end this deadly cancer,” said Dr. John Dick, lead author of the study, senior scientist with UHN, and a professor in the University of Toronto’s Department of Molecular and Medical Genetics. “We’ve painted a target on these specific cancer stem cells, and now we need to know how best to eradicate them.”

Like ordinary blood stem cells, the leukemia stem cells are very rare and act as the originator of all the other leukemia cells that develop and end up killing more than 2,000 Canadians every year. The researchers discovered that there are several types of leukemia stem cells, some fast acting, and others that may lay dormant for long periods of time before bursting into activity. This study may explain why there is such a high rate of recurrence, typically between 60-90 per cent, in cases of acute myeloid leukemia (the specific type involved in this study). The high recurrence may be due to the fact that chemotherapy treatments are designed to target leukemia cells that are dividing – potentially missing dormant leukemia stem cells that created the disease in the first place, said Dr. Dick.

The discovery of different classes of leukemia stem cells mirrors similar categories of regular blood stem cells. “This shows that the development of leukemia has strong similarities with the development of a regular blood system and gives us clues as to how the first leukemia stem cell arises in the first place,” said Dr. Dick.

This discovery builds on Dr. Dick’s pioneering method of studying human stem cells by transplanting them into immunodeficient mice which will not reject the human cells. The findings may also predict that similar cancer stem cells will be found for solid tumors such as breast cancer, he said.

This work was carried out by graduate student Kristin Hope and research associate Liqing Jin and funded by the Canadian Cancer Society, the Canadian Institutes of Health Research, and the Canada Research Chairs program.

University Health Network is a major landmark in Canada’s healthcare system, and a teaching hospital of the University of Toronto. Building on the strengths and reputation of each of our three hospitals, Toronto General Hospital, Toronto Western Hospital and Princess Margaret Hospital, UHN brings together the talent and resources needed to achieve global impact and provide exemplary patient care, research and education.