Origins of Disease Revealed

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Genetic screening tool discovered that can predict risk for leukemia in healthy people.
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Findings from the study could be used to create a simple blood test capable of identifying those at risk of developing acute myeloid leukemia up to 10 years before the disease strikes.

An international team of leukemia scientists has discovered a way to identify which healthy individuals are at risk of developing acute myeloid leukemia (AML), an aggressive and often deadly blood cancer. 

The findings, published today in Nature, illuminate the ‘black box of leukemia’ and answer the question of where, when and how the disease begins, says co-principal investigator Dr. John Dick, Senior Scientist at Princess Margaret Cancer Centre, University Health Network.

“We have been able to identify people in the general population who have traces of mutations in their blood that represent the first steps in how normal blood cells begin on a pathway of becoming increasingly abnormal and puts them at risk of progressing to AML. We can find these traces up to 10 years before AML actually develops,” says Dr. Dick. “This extended window of time gives us the first opportunity to think about how to prevent AML.”

Dr. Dick is also a Professor in the Department of Molecular Genetics at the University of Toronto, he holds the Canada Research Chair in Stem Cell Biology, and is Co-Leader of the Acute Leukemia Translational Research Initiative at the Ontario Institute for Cancer Research.

Study author Dr. Sagi Abelson, a post-doctoral fellow in the Dick laboratory, says: “AML is a devastating disease diagnosed too late, with a 90% mortality rate after the age of 65. Our findings show it is possible to identify individuals in the general population who are at high risk of developing AML through a genetic test on a blood sample.” Drs. Dick and Abelson talk about the research in this video

“The ultimate goal is to identify these individuals and study how we can target the mutated blood cells long before the disease actually begins.”

The study builds on Dr. Dick’s 2014 discovery that a pre-leukemic stem cell could be found lurking amongst all the leukemia cells that are present in the blood sample taken when a person is first diagnosed with AML. The pre-leukemic stem cell still functions normally but it has taken the first step in generating a pathway through which blood cells become more and more abnormal resulting in AML (Nature, February 12, 2014).

“Our 2014 study predicted that people with early mutations in their blood stem cells, long before the disease appears and makes them sick, should be able to be detected within the general population by testing a blood sample for the presence of the mutation.” says Dr. Dick.

Co-principal investigator Dr. Liran Shlush, a former fellow in the Dick lab, and now Senior Scientist at the Weizmann Institute in Israel, led the approach to use data from a large European population health and lifestyle study that tracked 550,000 people over 20 years to determine correlations to cancer.

The leukemia team extracted the data from more than 100 participants who developed AML six to 10 years after joining the study, plus the data from an age-matched cohort of more than 400 who did not develop the disease.

Dr. Dick says: “We wanted to know if there was any difference between these two groups in the genetics of their ‘normal’ blood samples taken at enrollment. To find out, we developed a gene sequencing tool that captured the most common genes that get altered in AML and sequenced all 500 blood samples.”

The answer was “Yes”. The seeds of the blood system started picking up mutations years before an individual was diagnosed with AML, a finding that enabled the team to accurately predict those at risk of disease progression.

Furthermore, the team used advanced computational technology to assay the information obtained from routinely collected blood tests taken over 15 years in Israel and housed in a massive database of 3.4 million electronic health records.

The study has deepened our understanding of the distinction between AML and a common feature of aging called ARCH–age-related clonal hematopoiesis–whereby blood stem cells acquire mutations and become a little more proliferative. For the vast majority of people this is just a completely benign feature of aging. 

“Every AML patient has ARCH but not everyone with ARCH gets AML,” explains Dr. Dick.

Sagi Abelson, et al. Prediction of acute myeloid leukaemia risk in healthy individuals. Nature, 2018. doi: 10.1038/s41586-018-0317-6.

The UHN research team was funded by the Leukemia and Lymphoma Society, the Ontario Institute for Cancer Research, the Canadian Cancer Society, the Canadian Institutes of Health Research, the International Development Research Centre, the Terry Fox Research Institute, Medicine by Design – Canada First Research Excellence Fund, the Benjamin Pearl Fellowship from the McEwen Centre for Regenerative Medicine, the Ontario Ministry of Health and Long-term Care, and The Princess Margaret Cancer Foundation. Major international collaborators included the Wellcome Sanger Institute and the University of Cambridge in the UK; and the Weizmann Institute of Science and Clalit Research Institute in Israel.

Source: UHN.ca

Follow the above video link to watch Drs. John Dick and Sagi Abelson (pictured above, R-L) discuss the findings of their research.