Another major concern of integrative delivery systems is related to a possible transgene reactivation that could lead to the overexpression of potentially tumorigenic genes such as c-MYC or KLF4. For instance, the presence of c-MYC is a major limitation, as chimeras derived from iPSCs frequently develop tumours due to the reactivation of c-MYC [40,41]. The gene discussed is MYC; the disease is neoplasm.