Question: How is the safety of stem cells in patients guaranteed that it will not grow uncontrollably and perhaps form cancer one day. Are pregenitor cells perhaps safer to use? What else is considered to prevent this?

Sharon Sneddon answered on 23 Mar 2011:

HI Karthika,
You are right, the main danger of using embryonic stem cells is that if we do not control their growth properly, they sometimes form cancer cells, or other type of cells that we do not want which would be a disaster if we were to transplant stem cells into a patient, and maybe cure their liver disease, but as a side effect give them cancer. That is why it seems that stem cell research is taking a really long time, we need to be 100% sure that the stem cells will do EXACTLY what we want them to.

The way we stop them from forming the wrong types of cells all depends on the way in which they are grown in the laboratory, we give them certain kinds of chemicals, called growth factors, and sometimes hormones and other things to make sure they behave themselves and act like they should, but we need to do the experiments over and over again, so we are sure that we are not going to harm anyone if they were to get put into a patient. Using other cells is good, and works in many cases, like in bone marrow transplants which are a kind of adult stem cell transplant are very effective and safe so we at least know that stem cells can behave themselves in the human body! However, not all cell types can be made from adult stem cells which is why we are using and testing embryonic stem cells.