Because persistent transgene expression is not necessary for the maintenance of mouse iChon cells as long as they are cultured in a chondrogenic medium containing TGF-β and BMPs [12], it will be ideal to generate human iChon cells by transient expression of c-MYC and KLF4 using integration-free vectors, to minimize the risk of tumor formation. Here, TGFB1 is linked to neoplasm.