STMC-09. ASSESSMENT OF TUMORIGENIC POTENTIAL OF HUMAN INDUCED PLURIPOTENT STEM CELL-DERIVED NEURAL STEM/PROGENITOR CELLS

Previously, we demonstrated the therapeutic potential of transplanting human induced pluripotent stem cell-derived neural stem/progenitor cells (iPSC-NS/PCs) for spinal cord injury (SCI). On the other hand, we have found that some iPSC-NS/PC cell lines produce tumors resembling low grade glioma after transplantation. The purpose of this study is to investigate the genetic and epigenetic alterations in iPSC-NS/PCs that may be related to tumor pathogenesis, and to establish the evaluation criteria of iPSC-NS/PCs associated with tumorigenicity. Samples are prepared as two groups of human iPSC-NS/PCs (tumorigenic cell lines; 253G1-NS/PCs, non-tumorigenic cell lines; 201B7-NS/PCs). Infinium OmniExpress-24 and Methylation450 BeadChip were used to evaluate genome wide CNV and DNA methylation analyses of these iPSC-NS/PCs. Single nucleotide variants (SNV) were evaluated using Ion AmpliSeq Cancer Panel. Several SNVs related to cancer pathogenesis such as AKT1 were detected in 253G1-NS/PCs, whereas 201B7-NS/PC had no cancer related SNV. Several CNVs related to cancer pathogenesis were also detected in 253G1-NS/PCs, especially in the chromosome 2. Distinct differences in DNA methylation pattern were observed between 253G1-NS/PCs and 201B7-NS/PCs. In particular, the large differences of DNA methylation status were involved in several tumor suppressor genes such as PSMD5 and RBP1. Interestingly, the CNVs and DNA methylation patterns were affected not only by the difference in cell lines but also by the difference in the passage numbers. Our research group is working vigorously to pursue a clinical trial for patients with SCI within the next several years. Therefore, it is crucial to establish criteria to choose the “safe” iPSC-NS/PCs. Here, we revealed differences in their SNVs, CNVs and DNA methylation patterns, which enables us to control the quality of iPSC-NS/PCs with respect to their tumorigenicity.