Viral Vector-Based Innovative Approaches to Directly Abolishing Tumorigenic Pluripotent Stem Cells for Safer Regenerative Medicine

Abstract

Human pluripotent stem cells (hPSCs) are a promising source of regenerative material for clinical applications. However, hPSC transplant therapies pose the risk of teratoma formation and malignant transformation of undifferentiated remnants. These problems underscore the importance of developing technologies that completely prevent tumorigenesis to ensure safe clinical application. Research to date has contributed to establishing safe hPSC lines, improving the efficiency of differentiation induction, and indirectly ensuring the safety of products. Despite such efforts, guaranteeing the clinical safety of regenerative medicine products remains a key challenge. Given the intrinsic genome instability of hPSCs, selective growth advantage of cancer cells, and lessons learned through failures in previous attempts at hematopoietic stem cell gene therapy, conventional strategies are unlikely to completely overcome issues related to hPSC tumorigenesis. Researchers have recently embarked on studies aimed at locating and directly treating hPSC-derived tumorigenic cells. In particular, novel approaches to directly killing tumorigenic cells by transduction of suicide genes and oncolytic viruses are expected to improve the safety of hPSC-based therapy. This article discusses the current status and future perspectives of methods aimed at directly eradicating undifferentiated tumorigenic hPSCs, with a focus on viral vector transduction.

Current Challenges in Providing Good Leukapheresis Products for Manufacturing of CAR-T Cells for Patients with Relapsed/Refractory NHL or ALL

“…Stem cells in the leukapheresis product pose the risk of malignant transformation during the process of genetic modification by viral transduction. Therefore G-CSF should be stopped prior to leukapheresis [20][21][22]. Vaccinations with live vaccines should be stopped 6 weeks prior to leukapheresis to prevent virus particles in the CAR-T cell product from being transmitted to the immunosuppressed patient potentially causing a serious viral infection [23].…”

A Novel Construction of Lentiviral Vectors for Eliminating Tumorigenic Cells from Pluripotent Stem Cells

“…Whereas such combinations may be useful, these other methods are basically applicable to undifferentiated pre‐transplant cells, and cannot address aberrant cells that arise after transplant. In this respect, the strategy of introducing a SG into hPSCs serves as a clinical safeguard against tumorigenesis after cell transplantation therapy . Clinical issues should be carefully and extensively examined in future preclinical studies devoted to examining the optimal timing of GCV administration (e.g., after visible tumor formation and/or before transplantation) and transplantation of the differentiated and target cells into clinically relevant disease animals.…”

“…This concern is especially serious given historical precedent, for example, the high incidence of leukemia following transplantation of engineered hematopoietic stem cells in a clinical trial for human patients, despite the lack of tumorigenicity in multiple preclinical animal studies . Therefore, to facilitate safe clinical applications, it is necessary to develop new approaches to directly, completely, and specifically eliminate undifferentiated hPSCs . Current strategies focus on assessment of pre‐transplanted cells; however, as a safeguard against tumor development over the course of clinical applications, novel approaches should also address tumorigenic cells post‐transplant.…”

Cell therapy products: focus on issues with manufacturing and quality control of chimeric antigen receptor T‐cell therapies

“…Despite the appeal of this concept, concerns about genomic unpredictability and associated risks of tumorigenicity remain incompletely resolved at this stage . Efforts to understand transcriptomic profiles associated with ‘safe’ induced pluripotency, combined with improved methodologies for controlled transgene insertion, may advance the exciting possibility of ‘synthetic’ T‐cells . However, technical and safety challenges entailing autologous cell sourcing is likely to remain the mainstay of CAR‐T based treatments, at least in the short to medium term.…”