Fig. 2.

Strategy to prevent tumorigenicity after transplantation. (A) A γ-secretase inhibitor (GSI) promotes maturation and neuronal differentiation of neural precursor cells (NPCs). As a result, tumor-initiating cells are removed before transplantation. (B) Thorough investigation is important for the iPSCs and the derivative NPCs prior to transplantation. Only safe and effective cells after a proper quality check should be transplanted. (C) The NPCs are pushed to become more mature oligodendrocyte progenitor cells (OPCs) before transplantation. (D) Suicide genes are integrated into NPCs beforehand. If transplanted cells show tumorigenicity, an apoptosis inducer should be injected systematically.