Anyone know of a human gene that could be knocked out in genetically engineered cells so that those cells and their clones may be killed with a local injection of some chemical? Or, perhaps a gene that can be added that would cause those cells to be sensitive to some chemical? I am supposed to design a theoretical tissue engineering construct, and my goal is to implant engineered cells that will produce a cytokine which will promote tendon and ligament healing. But a potential problem is that of oncogenesis, and I was thinking of letting the cells recruite the fibroblasts and secrete the necessary proteins, then kill off those cells by injecting a chemical to the wound site. So the chemical should be normally safe to human cells. It would be sort of the opposite of adding antibiotic resistance along with some other gene to select for those cells. One idea I had was a membrane protein which would cause the cell to take up the chemical but other cells would ignore it. Any ideas?