Since undesired differentiation and malignant transformation are major safety issues regarding transplantation of induced pluripotent stem cells and induced pluripotent stem cell-derived cells, protocols for differentiation of induced pluripotent stem cells should be optimized in order to ensure the purity of induced pluripotent stem cell-derived populations of differentiated cells before their clinical use. Considering the fact that mesenchymal stem cells are frequently and worldwide offered as human remedy but may promote tumor growth and metastasis, studies which use mesenchymal stem cells should be focused in continuous monitoring and long-term follow up of mesenchymal stem cell-treated animal models in order to determine possible pro-tumorigenic and other detrimental effects of mesenchymal stem cells-based therapy.