If cancer is like a dandelion, cancer stem cells are considered the root of the dandelion. You can cut off the top of the dandelion, but unless you destroy the roots, the weed will grow back and spread.
One of the biggest challenges in the cancer field that has fueled decades of research is “how do cancers grow and spread?” The cancer stem cell hypothesis is one model that scientists are studying to answer this question.
Stem cells are the only cells in our body that have the ability to form some or all different types of cells (i.e. breast, brain, blood). They are the cells responsible for humans to grow as well as heal after injury.
Similarly, cancer stem cells are thought to be the only cells within a tumor that are capable of forming another tumor. A helpful way to look at cancer and cancer stem cells is to think of them as dandelions. Cancer stem cells are the root of the dandelion- sure you can cut off the top, but unless you also destroy the roots, the weed will grow back and spread.
Because of this, scientists often refer to cancer stem cells as “tumor initiating cells”. They are thought to be the reason why cancer often returns after treatments, such as chemotherapy. The reason being is that cancer stem cells are highly resistant to chemotherapy. These drugs are designed to target rapidly dividing cells, however, just like normal stem cells, cancer stem cells do not divide very often, allowing them to evade these therapies. As a result, cancer stem cells may be primarily responsible for disease relapse.
Toronto has a strong heritage in stem and cancer stem cell research since 1961 when Drs. James Till and Ernest McCulloch first discovered stem cells at the Ontario Cancer Institute. Since then, Dr. John Dick discovered the first cancer stem cell in leukemia, kicking off this exciting field of research. With many intelligent and clever scientists (and students!), Toronto will continue to be a global leader in cancer stem cell research in years to come.
My lab, along with many others, are helping to get to the root of the problem! We are studying brain cancer stem cells so we can identify what makes them so unique. Our goal is to learn how to specifically target these cells to treat and prevent cancer from coming back.
References and further reading:
The Sleeping Cancer Cell
Nguyen, L.V., Vanner, R., Dirks, P., and Eaves, C.J. (2012). Cancer stem cells: an evolving concept. Nat. Rev. Cancer 12, 133–143.
Reya, T., Morrison, S.J., Clarke, M.F., and Weissman, I.L. (2001). Stem cells, cancer, and cancer stem cells. Nature 414, 105–111
This article was written by Mike Pryszlak. Mike is currently completing the second year of his PhD at the University of Toronto. He studies how normal stem cell genes are changed in cancer stem cells. To learn more about Mike and his research check out the RIOT members page.