TKT and cancer: These ADSCs have also been employed as delivery vehicles in prodrug cancer gene therapy, including herpes simplex virus type 1 thymidine kinase (HSV1-TK)/ganciclovir (GCV) [32], cytosine deaminase (CD)/5-fluorocytosine (5-FC) [33], cytosine deaminase-uracil phosphoribosyl transferase (CD/UPRT)/5-FC [34], and rabbit carboxylesterase(rCE)/irinotecan-7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (CPT-11) [35].