Stem cells are the body's "master cells,” which are capable of developing into the various organs and tissues of the body. Mutations in cancer can cause the cancer cells to acquire the same features as normal tissue stem cells – allowing them to make "cancer stem cells.” Cancer stem cells have been theorized to be responsible for the long-term growth of cancers, and an underlying driver of cancer spread and recurrence after therapy. 
An alarming fact is that cancer stem cells (image at right) have properties that allow them to evade therapy, while having the unique ability to self-renew and thereby keep propagating the tumour – which is why there is an urgent need for scientists to unlock clues for more targeted treatments for patients.    
At The Princess Margaret, the “Fathers of Stem Cell Research,” Dr. James Till and the late Dr. Ernest McCulloch, first proved the existence of stem cells in 1961. Now, over 50 years later, The Princess Margaret remains a world leader in cancer stem cell research, making discoveries that are still saving, enhancing and prolonging the lives of people around the world.  
For example, Dr. John Dick, who first identified cancer stem cells in leukemia (1994) and colon cancer (2007), recently found a way to genetically stop a colon cancer stem cell from generating malignant cells. His team, including Dr. Catherine O’Brien, a surgeon scientist, treated these cells with a new drug to see if it would shut down the cancer stem cells before they could spawn a tumour. Not only did it work remarkably well, but the drug also massively reduced existing tumours in mouse models.
This promising development could stop colon cancer stem cells from reactivating after treatment, which could prevent certain types of colon cancer from recurring. Dr. Dick’s discovery could readily translate into its first human clinical trials in the near future.

Dr. Rodger Tiedemann is part of the latest generation of researchers contributing to the renowned legacy of Drs. Till and McCulloch. In the fall of 2013, Dr. Tiedemann found that the root cause of treatment resistance and relapse in multiple myeloma patients is primarily due to immature stem cells, which are untouched by mainstay therapy. This groundbreaking discovery is being widely circulated amongst the scientific community and is expected to revolutionize the treatment experience of multiple myeloma patients across the globe. 

Continuing with our rich history in stem cell discoveries, researchers at The Princess Margaret also focus on understanding solid cancers such as breast cancer. For example, Dr. Rama Khokha recently received the Canadian Cancer Society Research Institute’s Robert L. Noble prize for her work identifying factors that control mammary stem cell status and may influence breast cancer risk.  
In February 2014, Dr. Dick’s team discovered a pre-leukemic stem cell that may be the first step in initiating the disease, and also a culprit that evades therapy and triggers relapse in patients with Acute Myeloid Leukemia (AML).
“This unprecedented research is a significant leap in understanding the steps that a normal cell has to go through as it turns into AML,” says Dr. Dick, “and it sets the stage to advance Personalized Cancer Medicine by screening patients and potentially identifying individuals who might benefit from targeting the pre-leukemic stem cell.”  
Normal stem cells can also be harnessed for life-saving cancer treatments. Multidisciplinary teams around the world are now using Dr. Norman Iscove’s discovery of a specific gene that controls the balance of stem cell self-renewal and differentiation to grow increased numbers of blood stem cells for bone marrow transplantation.
In addition, Dr. Gordon Keller, Director of the McEwan Centre for Regenerative Medicine at UHN, identified a critical regulator for directing cells to make blood-forming stem cells in the fall of 2013. This discovery is bringing him one step closer to his goal of developing a new and unlimited source of these stem cells for transplantation for the treatment of different blood cell diseases.
The Princess Margaret, through our Regenerative Radiation Medicine Program, is striving to create a research program that concentrates on stem cell regeneration, amongst other innovative research in radiation repair. The regenerative radiation team is confident that one day, doctors will be able to use patients’ stem cells to actually repair damaged tissues and reverse scarring.
The program is now working in collaboration with Dr. Keller to capitalize on his team’s ability to regenerate organs and develop innovative technologies. In the long run, these discoveries will benefit our cancer patients after completion of their treatment.
With little government funding for cancer stem cell research, philanthropic support is key to ensuring The Princess Margaret remains at the forefront of discoveries in this field. With your support, further investigation into cancer stem cells will unlock clues to facilitate more targeted treatments that can eliminate cancer without damaging healthy tissue.