Gene therapy using CRISPR/Cas9-edited iPS cells with HSVtk for malignant glioma

2020 Fiscal Year Final Research Report

• Project/Area Number: 18K15289
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 50020:Tumor diagnostics and therapeutics-related
• Research Institution: Keio University
• Principal Investigator: MORIMOTO Yukina 慶應義塾大学, 医学部(信濃町), 助教 (10793119)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: iPS細胞 / 神経幹細胞 / 自殺遺伝子 / HSVtk / 遊走 / CRISPR/Cas9 / 悪性神経膠腫 / グリオーマ

Outline of Final Research Achievements

Neural stem cells (NSCs) are known to possess the tumor-tropic migratory capacity and thus can be used as cellular vehicles for targeted delivery of therapeutic agents. The HSV-TK gene, in combination with ganciclovir, is the most widely used enzyme/prodrug suicide system from basic research to clinical applications. In the present study, we attempted to establish human induced pluripotent stem cells (hiPSCs) that stably expressed HSV-TK with either lentiviral vectors or CRISPR/Cas9-mediated genome editing. A nucleotide metabolism analysis suggested that high-level and/or constitutive expression of HSV-TK resulted in the induction of cell death or silencing of HSV-TK expression during differentiation to NSCs. We also demonstrated that the Tet-inducible system was a feasible solution for overcoming the cytotoxicity of HSV-TK expression. Our results provided a warning against using the HSV-TK gene in human iPSCs, particularly in clinical applications.

Free Research Field

脳神経外科学

Academic Significance and Societal Importance of the Research Achievements

神経幹細胞(NSC)は、脳腫瘍へ遊走する性質を持つため、治療遺伝子を搭載する運搬体として注目される。本研究では、グリオーマ細胞の根絶を目指しiPS細胞から分化誘導したNSCを用いた自殺遺伝子細胞治療の開発を行った。HSVtkはiPS細胞に細胞毒性を有することを同定し、NSCへの分化過程で遺伝子発現の不活性化を生じる事も明らかにした。安定した遺伝子発現を可能とする導入部位をゲノム編集技術であるCRISPR/Cas9を用いて評価した。本研究概念はヒトiPS細胞に治療遺伝子を導入するあらゆる研究に応用できるものであり、将来のヒトiPS細胞を用いた様々な遺伝子治療のプラットフォームになり得る。