In fairness what else is Stemson going to say? Are they going to say "it might cause cancer, invest in us so that we can find out"?Nah it's not, the cell cultures happen outside of the body and the risk isn't there according to Stemson.
That said, I don't think there is much risk either. This could happen in culture and they can remove any bad cells. As long as none sneak through and get implanted then there should be no risk.