Cancer is a class of diseases that are intimately linked to stem cells. In fact, I would go so far as to call some types of cancer cells and stem cells, cousins. This concept, of a tight relationship between stem and cancer cells, is under intense investigation but at the same time it is something that many stem cell scientists would rather not think about. It is simply reality.
A wide variety of cancers exhibit gene expression profiles that share modules with highly pluripotent cells. Many if not most tumors appear to have resident cancer stem cell populations that are thought to be the drivers of treatment resistance and recurrence as well. Most of the genes involved in making IPS cells (Myc, Nanog, KLF4, Sox2, Lin28, Oct3, loss of p53 function) are linked to cancer.
What this all means is that gaining a better understanding of stem cell biology is certain to enhance our understanding of what makes neoplastic cells tick and how to throw a monkey wrench into the works. New treatments specifically targeting cancer stem cells are especially needed.
In addition, even ‘normal’ stem cells have the ability to form tumors including teratoma. Why? At this point we don’t exactly know, but this line of research is crucial for making regenerative medicine safer.
At the same time stem cells may actually be able to be used to treat tumors. What about stem cell-based regenerative medicine approaches to treat cancer? Of course, the most successful regenerative medicine therapy to date, bone marrow/hematopoietic stem cell transplantation has been an enormous success in treating hematopoietic malignancies. What about other types of cancer?
Dendreon’s Provenge treatment for advanced, hormone resistant prostate cancer is a stem cell based immunological treatment. It definitely works, but concern has been raised about it being expensive (almost $100K) and only being moderately effective in terms of life extension (4 months extension).
The cost is an obstacle, but nonetheless, I think it is an enormously important therapy and lays the groundwork for future such approaches that hopefully could be produced in a more cost efficient manner. Other similar approaches are likely to succeed for other cancers. At this point there is little in the way of treatment options for patients with hormone refractory prostate cancer. Provenge is also a proof of principle of sorts that cancer vaccine like drugs can succeed and make it to the market.
Another approach is to take advantage of the characteristic of stem cells to home in on and migrate to sites of injury or damage. Even before a patient becomes clearly symptomatic, the body often perceives cancer as an injury and may (or may not) mount an immune response. Based on this foundation, researchers are exploring the possibility that stem cells may be used in essence as weapons against cancer. The idea is that stem cells equipped with a toxic payload could be transplanted into a patient, the stem cells home in on the cancer, and deliver a toxin. Preclinical studies using this approach are ongoing and seem at least somewhat promising.