The Role of Stem Cells in Cancer
Sabina - To begin my quest in exploring the role of stem cells in cancer, I thought I'd find out what a stem cell is; so I went to the Wellcome Centre for Stem Cell Research, and I asked a stem cell researcher.Jason Wray: Stem cells are a really amazing cell type, they are defined by two very special properties; the first is self renewal, the capacity to make identical copies of themselves, and the second property which defines a stem cell is the ability to differentiate into more specialised cell types. We break stem cells into two different categories: Embryonic, which have the capacity to make any type of tissue, and more specialised stem cells which we call adult stem cells, which are restricted to a particular type of tissue, be it brain tissue, skin tissue and so on.Sabina - I'm off to see John Stingl, breast cancer specialist in Cambridge University's Pathology department, to ask him what cancer is and how stem cells are involved.John Stingl: We actually believe that cancer is a disease of stem cells. Stem cells are normally involved in the formation of an organ, and all cancer is, is organ formation gone wrong. Cancer is a disease where you require multiple genetic mutations to get a tumour. For example, you don't just have one mutation and get a tumour, because if that were the case, we would all be dead. We actually find we need 5-7 mutations. The probability of a cell getting a mutation is actually very low, like one in a million, like trying to win a lottery prize. However, if you have a cell that has the capacity to produce lots of daughter cells, such as a stem cell, if you can mutate a stem cell, then that stem cell produces a million daughter cells, now you have a million cells which already have one genetic mutation. The probability of one of those cells getting another mutation is actually quite high, and then the cell that has mutated will produce a million daughter cells and one of those will become mutated and so on. That's how you can acquire five mutations.Sabina - A lot of research is being conducted to look at how stem cells work and what their role in cancer is. Brian Huntley is an expert in stem cell self renewal and he's working with leukaemia at the Cambridge Institute for Medical Research. I asked him how current research is directed by a need for cancer treatment.Brian Huntley: Treatment of malignant disease is still very ineffective and most patients have relapse and progressional disease, many still die from malignant disorders. However when you initially have a tumour, regardless of the tumour type and regardless of the therapy; whether that be chemotherapy, radiotherapy or some of the newer immunotherapies, there is usually a reduction in the size of the tumour mass. Sometimes it's very dramatic and sometimes it actually disappears. However we know that the vast majority of patients have re-growth of that tumour, either in the same place of what's known as a metastasis, growth in another place. That would suggest, following on from the cancer stem cell hypothesis, that we are killing the cells that form the bulk of the tumour, but are not able to re-grow it, whilst we are sparing the cancer stem cells. We would ideally want to target the critical cells which cause the propagation and the re-growth of the tumour. We need to know more about these cancer stem cells and how they differ from normal stem cells, and we need to be specifically targeting them to show improvements in cancer therapy.