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Zhang Q, Wan XX, Hu XM, Zhao WJ, Ban XX, Huang YX, Yan WT, Xiong K. Targeting Programmed Cell Death to Improve Stem Cell Therapy: Implications for Treating Diabetes and Diabetes-Related Diseases. Front Cell Dev Biol 2021; 9:809656. [PMID: 34977045 PMCID: PMC8717932 DOI: 10.3389/fcell.2021.809656] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Accepted: 12/06/2021] [Indexed: 12/14/2022] Open
Abstract
Stem cell therapies have shown promising therapeutic effects in restoring damaged tissue and promoting functional repair in a wide range of human diseases. Generations of insulin-producing cells and pancreatic progenitors from stem cells are potential therapeutic methods for treating diabetes and diabetes-related diseases. However, accumulated evidence has demonstrated that multiple types of programmed cell death (PCD) existed in stem cells post-transplantation and compromise their therapeutic efficiency, including apoptosis, autophagy, necroptosis, pyroptosis, and ferroptosis. Understanding the molecular mechanisms in PCD during stem cell transplantation and targeting cell death signaling pathways are vital to successful stem cell therapies. In this review, we highlight the research advances in PCD mechanisms that guide the development of multiple strategies to prevent the loss of stem cells and discuss promising implications for improving stem cell therapy in diabetes and diabetes-related diseases.
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Affiliation(s)
- Qi Zhang
- Department of Anatomy and Neurobiology, School of Basic Medical Sciences, Central South University, Changsha, China
| | - Xin-xing Wan
- Department of Endocrinology, Third Xiangya Hospital, Central South University, Changsha, China
| | - Xi-min Hu
- Department of Anatomy and Neurobiology, School of Basic Medical Sciences, Central South University, Changsha, China
| | - Wen-juan Zhao
- Department of Anatomy and Neurobiology, School of Basic Medical Sciences, Central South University, Changsha, China
| | - Xiao-xia Ban
- Department of Anatomy and Neurobiology, School of Basic Medical Sciences, Central South University, Changsha, China
| | - Yan-xia Huang
- Department of Anatomy and Neurobiology, School of Basic Medical Sciences, Central South University, Changsha, China
| | - Wei-tao Yan
- Department of Anatomy and Neurobiology, School of Basic Medical Sciences, Central South University, Changsha, China
| | - Kun Xiong
- Department of Anatomy and Neurobiology, School of Basic Medical Sciences, Central South University, Changsha, China
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PUMA facilitates EMI1-promoted cytoplasmic Rad51 ubiquitination and inhibits DNA repair in stem and progenitor cells. Signal Transduct Target Ther 2021; 6:129. [PMID: 33785736 PMCID: PMC8009889 DOI: 10.1038/s41392-021-00510-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 11/20/2020] [Accepted: 01/18/2021] [Indexed: 02/07/2023] Open
Abstract
Maintenance of genetic stability via proper DNA repair in stem and progenitor cells is essential for the tissue repair and regeneration, while preventing cell transformation after damage. Loss of PUMA dramatically increases the survival of mice after exposure to a lethal dose of ionizing radiation (IR), while without promoting tumorigenesis in the long-term survivors. This finding suggests that PUMA (p53 upregulated modulator of apoptosis) may have a function other than regulates apoptosis. Here, we identify a novel role of PUMA in regulation of DNA repair in embryonic or induced pluripotent stem cells (PSCs) and immortalized hematopoietic progenitor cells (HPCs) after IR. We found that PUMA-deficient PSCs and HPCs exhibited a significant higher double-strand break (DSB) DNA repair activity via Rad51-mediated homologous recombination (HR). This is because PUMA can be associated with early mitotic inhibitor 1 (EMI1) and Rad51 in the cytoplasm to facilitate EMI1-mediated cytoplasmic Rad51 ubiquitination and degradation, thereby inhibiting Rad51 nuclear translocation and HR DNA repair. Our data demonstrate that PUMA acts as a repressor for DSB DNA repair and thus offers a new rationale for therapeutic targeting of PUMA in regenerative cells in the context of DNA damage.
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Qiao Y, Agboola OS, Hu X, Wu Y, Lei L. Tumorigenic and Immunogenic Properties of Induced Pluripotent Stem Cells: a Promising Cancer Vaccine. Stem Cell Rev Rep 2020; 16:1049-1061. [PMID: 32939647 PMCID: PMC7494249 DOI: 10.1007/s12015-020-10042-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/09/2020] [Indexed: 02/06/2023]
Abstract
Induced pluripotent stem cells (iPSCs) are mainly characterized by their unlimited proliferation abilities and potential to develop into almost any cell type. The creation of this technology has been of great interest to many scientific fields, especially regenerative biology. However, concerns about the safety of iPSC application in transplantation have arisen due to the tumorigenic and immunogenic properties of iPSCs. This review will briefly introduce the developing history of somatic reprogramming and applications of iPSC technology in regenerative medicine. In addition, the review will highlight two challenges to the efficient usage of iPSCs and the underlying mechanisms of these challenges. Finally, the review will discuss the expanding application of iPSC technology in cancer immunotherapy as a potential cancer vaccine and its advantages in auxiliary treatment compared with oncofetal antigen-based and embryonic stem cell (ESC)-based vaccines.
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Affiliation(s)
- Yu Qiao
- Department of Histology and Embryology, Basic Medical Science College, Harbin Medical University, 194 Xuefu Rd, Nangang District, Harbin, Heilongjiang Province, 150081, People's Republic of China
| | - Oluwafemi Solomon Agboola
- Department of Histology and Embryology, Basic Medical Science College, Harbin Medical University, 194 Xuefu Rd, Nangang District, Harbin, Heilongjiang Province, 150081, People's Republic of China
| | - Xinglin Hu
- Department of Histology and Embryology, Basic Medical Science College, Harbin Medical University, 194 Xuefu Rd, Nangang District, Harbin, Heilongjiang Province, 150081, People's Republic of China
| | - Yanshuang Wu
- Department of Histology and Embryology, Basic Medical Science College, Harbin Medical University, 194 Xuefu Rd, Nangang District, Harbin, Heilongjiang Province, 150081, People's Republic of China
| | - Lei Lei
- Department of Histology and Embryology, Basic Medical Science College, Harbin Medical University, 194 Xuefu Rd, Nangang District, Harbin, Heilongjiang Province, 150081, People's Republic of China.
- Key laboratory of Preservation of Human Genetic Resources and Disease Control in China, Harbin Medical University, Ministry of Education, Harbin, China.
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Abstract
Pluripotent stem cells (PSCs) are capable of unlimited self-renewal in culture and differentiation into all functional cell types in the body, and thus hold great promise for regenerative medicine. To achieve their clinical potential, it is critical for PSCs to maintain genomic stability during the extended proliferation. The critical tumor suppressor p53 is required to maintain genomic stability of mammalian cells. In response to DNA damage or oncogenic stress, p53 plays multiple roles in maintaining genomic stability of somatic cells by inducing cell cycle arrest, apoptosis, and senescence to prevent the passage of genetic mutations to the daughter cells. p53 is also required to maintain the genomic stability of PSCs. However, in response to the genotoxic stresses, a primary role of p53 in PSCs is to induce the differentiation of PSCs and inhibit pluripotency, providing mechanisms to maintain the genomic stability of the self-renewing PSCs. In addition, the roles of p53 in cellular metabolism might also contribute to genomic stability of PSCs by limiting oxidative stress. In summary, the elucidation of the roles of p53 in PSCs will be a prerequisite for developing safe PSC-based cell therapy.
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Absence of cyclin-dependent kinase inhibitor p27 or p18 increases efficiency of iPSC generation without induction of iPSC genomic instability. Cell Death Dis 2019; 10:271. [PMID: 30894510 PMCID: PMC6426969 DOI: 10.1038/s41419-019-1502-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Revised: 02/02/2019] [Accepted: 02/26/2019] [Indexed: 12/24/2022]
Abstract
Mechanisms underlying the generation of induced pluripotent stem cells (iPSC) and keeping iPSC stability remain to be further defined. Accumulated evidences showed that iPSC reprogramming may be controlled by the cell-division-rate-dependent model. Here we reported effects of absence of mouse p27 or p18 on iPSC generation efficiency and genomic stability. Expression levels of cyclin-dependent kinases inhibitors (CDKIs), p21, p27, and p18 decreased during iPSC reprogramming. Like p21 loss, p27 or p18 deficiency significantly promoted efficiency of iPSC generation, whereas ectopic expression of p27, p18, or treatment with CDK2 or CDK4 inhibitors repressed the reprogramming rate, suggesting that CDKIs-regulated iPSC reprogramming is directly related with their functions as CDK inhibitors. However, unlike p21 deletion, absence of p27 or p18 did not increase DNA damage or chromosomal aberrations during iPSC reprogramming and at iPSC stage. Our data not only support that cell cycle regulation is critical for iPSC reprogramming, but also reveal the distinction of CDKIs in somatic cell reprogramming.
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Kim J, Yu L, Chen W, Xu Y, Wu M, Todorova D, Tang Q, Feng B, Jiang L, He J, Chen G, Fu X, Xu Y. Wild-Type p53 Promotes Cancer Metabolic Switch by Inducing PUMA-Dependent Suppression of Oxidative Phosphorylation. Cancer Cell 2019; 35:191-203.e8. [PMID: 30712844 DOI: 10.1016/j.ccell.2018.12.012] [Citation(s) in RCA: 131] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 12/04/2018] [Accepted: 12/27/2018] [Indexed: 01/18/2023]
Abstract
The tumor suppressor p53 is somatically mutated in half of all human cancers. Paradoxically, the wild-type p53 (WTp53) is often retained in certain human cancers, such as hepatocarcinoma (HCC). We discovered a physiological and oncogenic role of WTp53 in suppressing pyruvate-driven oxidative phosphorylation by inducing PUMA. PUMA inhibits mitochondrial pyruvate uptake by disrupting the oligomerization and function of mitochondrial pyruvate carrier (MPC) through PUMA-MPC interaction, which depends on IκB kinase-mediated phosphorylation of PUMA at Ser96/106. High expression levels of PUMA are correlated with decreased mitochondrial pyruvate uptake and increased glycolysis in HCCs and poor prognosis of HCC patients. These findings are instrumental for cancer drug discovery aiming at activating WTp53 or restoring WTp53 activity to p53 mutants.
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Affiliation(s)
- Jinchul Kim
- The Eighth Affiliated Hospital, Sun Yat-sen University, Shenzhen, Guangdong 518033, China; Cancer Research Institute, Guangdong Provincial Key Laboratory of Cancer Immunotherapy, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guangdong 510515, China; Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0322, USA
| | - Lili Yu
- Cancer Research Institute, Guangdong Provincial Key Laboratory of Cancer Immunotherapy, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guangdong 510515, China
| | - Wancheng Chen
- Cancer Research Institute, Guangdong Provincial Key Laboratory of Cancer Immunotherapy, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guangdong 510515, China
| | - Yanxia Xu
- Cancer Research Institute, Guangdong Provincial Key Laboratory of Cancer Immunotherapy, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guangdong 510515, China
| | - Meng Wu
- Cancer Research Institute, Guangdong Provincial Key Laboratory of Cancer Immunotherapy, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guangdong 510515, China
| | - Dilyana Todorova
- The Eighth Affiliated Hospital, Sun Yat-sen University, Shenzhen, Guangdong 518033, China; Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0322, USA
| | - Qingshuang Tang
- Cancer Research Institute, Guangdong Provincial Key Laboratory of Cancer Immunotherapy, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guangdong 510515, China
| | - Bingbing Feng
- Cancer Research Institute, Guangdong Provincial Key Laboratory of Cancer Immunotherapy, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guangdong 510515, China
| | - Lei Jiang
- Cancer Research Institute, Guangdong Provincial Key Laboratory of Cancer Immunotherapy, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guangdong 510515, China
| | - Jingjin He
- The Eighth Affiliated Hospital, Sun Yat-sen University, Shenzhen, Guangdong 518033, China
| | - Guihua Chen
- The Eighth Affiliated Hospital, Sun Yat-sen University, Shenzhen, Guangdong 518033, China
| | - Xuemei Fu
- The Eighth Affiliated Hospital, Sun Yat-sen University, Shenzhen, Guangdong 518033, China.
| | - Yang Xu
- The Eighth Affiliated Hospital, Sun Yat-sen University, Shenzhen, Guangdong 518033, China; Cancer Research Institute, Guangdong Provincial Key Laboratory of Cancer Immunotherapy, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guangdong 510515, China; Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0322, USA.
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7
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Artemisitene suppresses tumorigenesis by inducing DNA damage through deregulating c-Myc-topoisomerase pathway. Oncogene 2018; 37:5079-5087. [DOI: 10.1038/s41388-018-0331-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2018] [Revised: 04/03/2018] [Accepted: 04/18/2018] [Indexed: 02/06/2023]
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Kim EJY, Anko ML, Flensberg C, Majewski IJ, Geng FS, Firas J, Huang DCS, van Delft MF, Heath JK. BAK/BAX-Mediated Apoptosis Is a Myc-Induced Roadblock to Reprogramming. Stem Cell Reports 2018; 10:331-338. [PMID: 29358089 PMCID: PMC5830948 DOI: 10.1016/j.stemcr.2017.12.019] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Revised: 12/21/2017] [Accepted: 12/21/2017] [Indexed: 12/15/2022] Open
Abstract
Despite intensive efforts to optimize the process, reprogramming differentiated cells to induced pluripotent stem cells (iPSCs) remains inefficient. The most common combination of transcription factors employed comprises OCT4, KLF4, SOX2, and MYC (OKSM). If MYC is omitted (OKS), reprogramming efficiency is reduced further. Cells must overcome several obstacles to reach the pluripotent state, one of which is apoptosis. To directly determine how extensively apoptosis limits reprogramming, we exploited mouse embryonic fibroblasts (MEFs) lacking the two essential mediators of apoptosis, BAK and BAX. Our results show that reprogramming is enhanced in MEFs deficient in BAK and BAX, but only when MYC is part of the reprogramming cocktail. Thus, the propensity for Myc overexpression to elicit apoptosis creates a significant roadblock to reprogramming under OKSM conditions. Our results suggest that blocking apoptosis during reprogramming may enhance the derivation of iPSCs for research and therapeutic purposes.
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Affiliation(s)
- Esther J Y Kim
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, VIC 3052, Australia; Department of Medical Biology, University of Melbourne, Parkville, VIC 3052, Australia
| | - Minna-Liisa Anko
- Department of Anatomy and Developmental Biology, Biomedicine Discovery Institute, Development and Stem Cells Program, Monash University, Clayton, VIC 3800, Australia
| | - Christoffer Flensberg
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, VIC 3052, Australia; Department of Medical Biology, University of Melbourne, Parkville, VIC 3052, Australia
| | - Ian J Majewski
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, VIC 3052, Australia; Department of Medical Biology, University of Melbourne, Parkville, VIC 3052, Australia
| | - Fan-Suo Geng
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, VIC 3052, Australia; Department of Medical Biology, University of Melbourne, Parkville, VIC 3052, Australia
| | - Jaber Firas
- Department of Anatomy and Developmental Biology, Biomedicine Discovery Institute, Development and Stem Cells Program, Monash University, Clayton, VIC 3800, Australia
| | - David C S Huang
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, VIC 3052, Australia; Department of Medical Biology, University of Melbourne, Parkville, VIC 3052, Australia
| | - Mark F van Delft
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, VIC 3052, Australia; Department of Medical Biology, University of Melbourne, Parkville, VIC 3052, Australia.
| | - Joan K Heath
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, VIC 3052, Australia; Department of Medical Biology, University of Melbourne, Parkville, VIC 3052, Australia.
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9
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Integrating Gene Correction in the Reprogramming and Transdifferentiation Processes: A One-Step Strategy to Overcome Stem Cell-Based Gene Therapy Limitations. Stem Cells Int 2016; 2016:2725670. [PMID: 28074097 PMCID: PMC5198186 DOI: 10.1155/2016/2725670] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Revised: 11/09/2016] [Accepted: 11/16/2016] [Indexed: 12/19/2022] Open
Abstract
The recent advent of induced pluripotent stem cells (iPSCs) and gene therapy tools has raised the possibility of autologous cell therapy for rare genetic diseases. However, cellular reprogramming is inefficient in certain diseases such as ataxia telangiectasia, Fanconi anemia, LIG4 syndrome, and fibrodysplasia ossificans progressiva syndrome, owing to interference of the disease-related genes. To overcome these therapeutic limitations, it is necessary to fundamentally correct the abnormal gene during or prior to the reprogramming process. In addition, as genetic etiology of Parkinson's disease, it has been well known that induced neural stem cells (iNSCs) were progressively depleted by LRRK2 gene mutation, LRRK2 (G2019S). Thus, to maintain the induced NSCs directly derived from PD patient cells harboring LRRK2 (G2019S), it would be ideal to simultaneously treat the LRRK2 (G2019S) fibroblast during the process of TD. Therefore, simultaneous reprogramming (or TD) and gene therapy would provide the solution for therapeutic limitation caused by vulnerability of reprogramming or TD, in addition to being suitable for general application to the generation of autologous cell-therapy products for patients with genetic defects, thereby obviating the need for the arduous processes currently required.
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10
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Ebrahimi B. Reprogramming barriers and enhancers: strategies to enhance the efficiency and kinetics of induced pluripotency. CELL REGENERATION (LONDON, ENGLAND) 2015; 4:10. [PMID: 26566431 PMCID: PMC4642739 DOI: 10.1186/s13619-015-0024-9] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/25/2015] [Accepted: 09/19/2015] [Indexed: 12/13/2022]
Abstract
Induced pluripotent stem cells are powerful tools for disease modeling, drug screening, and cell transplantation therapies. These cells can be generated directly from somatic cells by ectopic expression of defined factors through a reprogramming process. However, pluripotent reprogramming is an inefficient process because of various defined and unidentified barriers. Recent studies dissecting the molecular mechanisms of reprogramming have methodically improved the quality, ease, and efficiency of reprogramming. Different strategies have been applied for enhancing reprogramming efficiency, including depletion/inhibition of barriers (p53, p21, p57, p16(Ink4a)/p19(Arf), Mbd3, etc.), overexpression of enhancing genes (e.g., FOXH1, C/EBP alpha, UTF1, and GLIS1), and administration of certain cytokines and small molecules. The current review provides an in-depth overview of the cutting-edge findings regarding distinct barriers of reprogramming to pluripotency and strategies to enhance reprogramming efficiency. By incorporating the mechanistic insights from these recent findings, a combined method of inhibition of roadblocks and application of enhancing factors may yield the most reliable and effective approach in pluripotent reprogramming.
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Affiliation(s)
- Behnam Ebrahimi
- Yazd Cardiovascular Research Center, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
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11
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Qin H, Diaz A, Blouin L, Lebbink RJ, Patena W, Tanbun P, LeProust EM, McManus MT, Song JS, Ramalho-Santos M. Systematic identification of barriers to human iPSC generation. Cell 2014; 158:449-461. [PMID: 25036638 DOI: 10.1016/j.cell.2014.05.040] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Revised: 03/05/2014] [Accepted: 05/27/2014] [Indexed: 12/13/2022]
Abstract
Reprogramming of somatic cells to induced pluripotent stem cells (iPSCs) holds enormous promise for regenerative medicine. To elucidate endogenous barriers limiting this process, we systematically dissected human cellular reprogramming by combining a genome-wide RNAi screen, innovative computational methods, extensive single-hit validation, and mechanistic investigation of relevant pathways and networks. We identify reprogramming barriers, including genes involved in transcription, chromatin regulation, ubiquitination, dephosphorylation, vesicular transport, and cell adhesion. Specific a disintegrin and metalloproteinase (ADAM) proteins inhibit reprogramming, and the disintegrin domain of ADAM29 is necessary and sufficient for this function. Clathrin-mediated endocytosis can be targeted with small molecules and opposes reprogramming by positively regulating TGF-β signaling. Genetic interaction studies of endocytosis or ubiquitination reveal that barrier pathways can act in linear, parallel, or feedforward loop architectures to antagonize reprogramming. These results provide a global view of barriers to human cellular reprogramming.
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Affiliation(s)
- Han Qin
- Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, CA 94143, USA; Departments of Ob/Gyn and Pathology, Center for Reproductive Sciences, and Diabetes Center, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Aaron Diaz
- Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, CA 94143, USA; Institute for Human Genetics, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Laure Blouin
- Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, CA 94143, USA; Departments of Ob/Gyn and Pathology, Center for Reproductive Sciences, and Diabetes Center, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Robert Jan Lebbink
- Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, CA 94143, USA; Department of Microbiology and Immunology, Diabetes Center, and the WM Keck Center for Noncoding RNAs, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Weronika Patena
- Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, CA 94143, USA; Department of Microbiology and Immunology, Diabetes Center, and the WM Keck Center for Noncoding RNAs, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Priscilia Tanbun
- Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, CA 94143, USA; Departments of Ob/Gyn and Pathology, Center for Reproductive Sciences, and Diabetes Center, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Emily M LeProust
- Genomics Solution Unit, Agilent Technologies Inc., Santa Clara, CA 95051, USA
| | - Michael T McManus
- Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, CA 94143, USA; Department of Microbiology and Immunology, Diabetes Center, and the WM Keck Center for Noncoding RNAs, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Jun S Song
- Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, CA 94143, USA; Institute for Human Genetics, University of California, San Francisco, San Francisco, CA 94143, USA; Department of Epidemiology and Biostatistics and Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, CA 94143, USA.
| | - Miguel Ramalho-Santos
- Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, CA 94143, USA; Departments of Ob/Gyn and Pathology, Center for Reproductive Sciences, and Diabetes Center, University of California, San Francisco, San Francisco, CA 94143, USA.
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12
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Rasmussen MA, Holst B, Tümer Z, Johnsen MG, Zhou S, Stummann TC, Hyttel P, Clausen C. Transient p53 suppression increases reprogramming of human fibroblasts without affecting apoptosis and DNA damage. Stem Cell Reports 2014; 3:404-13. [PMID: 25241739 PMCID: PMC4266010 DOI: 10.1016/j.stemcr.2014.07.006] [Citation(s) in RCA: 101] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2013] [Revised: 07/17/2014] [Accepted: 07/18/2014] [Indexed: 01/10/2023] Open
Abstract
The discovery of human-induced pluripotent stem cells (iPSCs) has sparked great interest in the potential treatment of patients with their own in vitro differentiated cells. Recently, knockout of the Tumor Protein 53 (p53) gene was reported to facilitate reprogramming but unfortunately also led to genomic instability. Here, we report that transient suppression of p53 during nonintegrative reprogramming of human fibroblasts leads to a significant increase in expression of pluripotency markers and overall number of iPSC colonies, due to downstream suppression of p21, without affecting apoptosis and DNA damage. Stable iPSC lines generated with or without p53 suppression showed comparable expression of pluripotency markers and methylation patterns, displayed normal karyotypes, contained between 0 and 5 genomic copy number variations and produced functional neurons in vitro. In conclusion, transient p53 suppression increases reprogramming efficiency without affecting genomic stability, rendering the method suitable for in vitro mechanistic studies with the possibility for future clinical translation. Transient p53 suppression increases reprogramming efficiency through p21 inhibition No adverse effect on DNA damage and apoptosis is observed during reprogramming Stable iPSC lines display normal karyotypes and expression of pluripotency markers The iPSC lines retain their differentiation potential and form functional neurons
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Affiliation(s)
- Mikkel A Rasmussen
- Department of Veterinary Clinical and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Groennegaardsvej 7, Frederiksberg C 1870, Denmark.
| | - Bjørn Holst
- Bioneer A/S, Kogle Alle 2, Hoersholm 2970, Denmark
| | - Zeynep Tümer
- Applied Human Molecular Genetics, Kennedy Center, Copenhagen University Hospital, Rigshospitalet, Gl. Landevej 7, Glostrup 2600, Denmark
| | | | - Shuling Zhou
- Department of Veterinary Clinical and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Groennegaardsvej 7, Frederiksberg C 1870, Denmark
| | | | - Poul Hyttel
- Department of Veterinary Clinical and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Groennegaardsvej 7, Frederiksberg C 1870, Denmark
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13
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Notch inhibition allows oncogene-independent generation of iPS cells. Nat Chem Biol 2014; 10:632-639. [PMID: 24952596 PMCID: PMC4310751 DOI: 10.1038/nchembio.1552] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Accepted: 05/13/2014] [Indexed: 12/17/2022]
Abstract
The reprogramming of somatic cells to pluripotency using defined transcription factors holds great promise for biomedicine. However, human reprogramming remains inefficient and relies either on the use of the potentially dangerous oncogenes KLF4 and CMYC or the genetic inhibition of the tumor suppressor gene p53. We hypothesized that inhibition of signal transduction pathways that promote differentiation of the target somatic cells during development might relieve the requirement for non-core pluripotency factors during iPSC reprogramming. Here, we show that inhibition of Notch significantly improves the efficiency of iPSC generation from mouse and human keratinocytes by suppressing p21 in a p53-independent manner and thereby enriching for undifferentiated cells capable of long-term self-renewal. Pharmacological inhibition of Notch enabled routine production of human iPSCs without KLF4 and CMYC while leaving p53 activity intact. Thus, restricting the development of somatic cells by altering intercellular communication enables the production of safer human iPSCs.
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14
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Understanding the roadmaps to induced pluripotency. Cell Death Dis 2014; 5:e1232. [PMID: 24832604 PMCID: PMC4047905 DOI: 10.1038/cddis.2014.205] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Revised: 03/24/2014] [Accepted: 04/04/2014] [Indexed: 11/23/2022]
Abstract
Somatic cells can be reprogrammed into induced pluripotent stem cells (iPSCs) by ectopic expression of transcription factors Oct4, Sox2, Klf4 and cMyc. Recent advancements have shown that small-molecule compounds can induce pluripotency, indicating that cell fate can be regulated by direct manipulation of intrinsic cell signaling pathways, thereby innovating our current understanding of reprogramming. The fact that lineage specifiers can induce pluripotency suggests that the pluripotent state is a fine balance between competing differentiation forces. Dissection of pluripotent roadmaps indicates that reprogramming is a process of reverse development, involving a series of complicated and distinct reprogramming stages. Evidence from mouse iPSC transplantation studies demonstrated that some certain but not all cells derived from iPSCs are immunogenic. These studies provide new ways to minimize reprogramming-induced abnormalities and maximize reprogramming efficiency to facilitate clinical development and use of iPSCs.
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Fu X, Rong Z, Zhu S, Wang X, Xu Y, Lake BB. Genetic approach to track neural cell fate decisions using human embryonic stem cells. Protein Cell 2014; 5:69-79. [PMID: 24474203 PMCID: PMC3938840 DOI: 10.1007/s13238-013-0007-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Accepted: 11/15/2013] [Indexed: 11/25/2022] Open
Abstract
With their capability to undergo unlimited self-renewal and to differentiate into all cell types in the body, human embryonic stem cells (hESCs) hold great promise in human cell therapy. However, there are limited tools for easily identifying and isolating live hESC-derived cells. To track hESC-derived neural progenitor cells (NPCs), we applied homologous recombination to knock-in the mCherry gene into the Nestin locus of hESCs. This facilitated the genetic labeling of Nestin positive neural progenitor cells with mCherry. Our reporter system enables the visualization of neural induction from hESCs both in vitro (embryoid bodies) and in vivo (teratomas). This system also permits the identification of different neural subpopulations based on the intensity of our fluorescent reporter. In this context, a high level of mCherry expression showed enrichment for neural progenitors, while lower mCherry corresponded with more committed neural states. Combination of mCherry high expression with cell surface antigen staining enabled further enrichment of hESC-derived NPCs. These mCherry(+) NPCs could be expanded in culture and their differentiation resulted in a down-regulation of mCherry consistent with the loss of Nestin expression. Therefore, we have developed a fluorescent reporter system that can be used to trace neural differentiation events of hESCs.
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Affiliation(s)
- Xuemei Fu
- Shenzhen Children’s Hospital, Shenzhen, 518026 China
- Section of Molecular Biology, Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0322 USA
| | - Zhili Rong
- Section of Molecular Biology, Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0322 USA
| | - Shengyun Zhu
- Shenzhen Children’s Hospital, Shenzhen, 518026 China
- Section of Molecular Biology, Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0322 USA
| | - Xiaocheng Wang
- Section of Molecular Biology, Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0322 USA
| | - Yang Xu
- Section of Molecular Biology, Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0322 USA
| | - Blue B. Lake
- Section of Molecular Biology, Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0322 USA
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Guo Z, Higgins CA, Gillette BM, Itoh M, Umegaki N, Gledhill K, Sia SK, Christiano AM. Building a microphysiological skin model from induced pluripotent stem cells. Stem Cell Res Ther 2013; 4 Suppl 1:S2. [PMID: 24564920 PMCID: PMC4029476 DOI: 10.1186/scrt363] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The discovery of induced pluripotent stem cells (iPSCs) in 2006 was a major breakthrough for regenerative medicine. The establishment of patient-specific iPSCs has created the opportunity to model diseases in culture systems, with the potential to rapidly advance the drug discovery field. Current methods of drug discovery are inefficient, with a high proportion of drug candidates failing during clinical trials due to low efficacy and/or high toxicity. Many drugs fail toxicity testing during clinical trials, since the cells on which they have been tested do not adequately model three-dimensional tissues or their interaction with other organs in the body. There is a need to develop microphysiological systems that reliably represent both an intact tissue and also the interaction of a particular tissue with other systems throughout the body. As the port of entry for many drugs is via topical delivery, the skin is the first line of exposure, and also one of the first organs to demonstrate a reaction after systemic drug delivery. In this review, we discuss our strategy to develop a microphysiological system using iPSCs that recapitulates human skin for analyzing the interactions of drugs with the skin.
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17
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ΔNp63 regulates select routes of reprogramming via multiple mechanisms. Cell Death Differ 2013; 20:1698-708. [PMID: 24013722 DOI: 10.1038/cdd.2013.122] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Revised: 07/30/2013] [Accepted: 07/31/2013] [Indexed: 12/12/2022] Open
Abstract
Somatic cells can be converted into induced pluripotent stem cells (iPSCs) by forced expression of various combinations of transcription factors, but the molecular mechanisms of reprogramming are poorly understood. Specifically, evidence that the reprogramming process can take many distinct routes only begins to emerge. It is definitively established that p53 deficiency greatly enhances reprogramming, revealing p53's barrier function for induced pluripotency, but the role of its homologs p63 and p73 are unknown. Here we report that in stark contrast to p53, p73 has no role in reprogramming. However, p63 is an enabling (rather than a barrier) factor for Oct4, Sox2 and Klf4 (OSK) and Oct4 and Sox2 (OS), but not for Oct4 and Klf4 (OK) reprogramming of mouse embryonic fibroblasts. Specifically, p63 is essential during reprogramming for maximum efficiency, albeit not for the ability to reprogram per se, and is dispensable for maintaining stability and pluripotency of established iPSC colonies. ΔNp63, but not TAp63, is the principal isoform involved. Loss of p63 can affect reprogramming via several mechanisms such as reduced expression of mesenchymal-epithelial transition and pluripotency genes, hypoproliferation and loss of the most reprogrammable cell populations. During OSK and OS reprogramming, different mechanisms seem to be critical, such as regulation of epithelial and pluripotency genes in OSK reprogramming versus regulation of proliferation in OS reprogramming. Finally, our data reveal three different routes of reprogramming by OSK, OS or OK, based on their differential p63 requirements for iPSC efficiency and pluripotency marker expression. This supports the concept that many distinct routes of reprogramming exist.
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18
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Kramer AS, Harvey AR, Plant GW, Hodgetts SI. Systematic Review of Induced Pluripotent Stem Cell Technology as a Potential Clinical Therapy for Spinal Cord Injury. Cell Transplant 2013; 22:571-617. [DOI: 10.3727/096368912x655208] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Transplantation therapies aimed at repairing neurodegenerative and neuropathological conditions of the central nervous system (CNS) have utilized and tested a variety of cell candidates, each with its own unique set of advantages and disadvantages. The use and popularity of each cell type is guided by a number of factors including the nature of the experimental model, neuroprotection capacity, the ability to promote plasticity and guided axonal growth, and the cells' myelination capability. The promise of stem cells, with their reported ability to give rise to neuronal lineages to replace lost endogenous cells and myelin, integrate into host tissue, restore functional connectivity, and provide trophic support to enhance and direct intrinsic regenerative ability, has been seen as a most encouraging step forward. The advent of the induced pluripotent stem cell (iPSC), which represents the ability to “reprogram” somatic cells into a pluripotent state, hails the arrival of a new cell transplantation candidate for potential clinical application in therapies designed to promote repair and/or regeneration of the CNS. Since the initial development of iPSC technology, these cells have been extensively characterized in vitro and in a number of pathological conditions and were originally reported to be equivalent to embryonic stem cells (ESCs). This review highlights emerging evidence that suggests iPSCs are not necessarily indistinguishable from ESCs and may occupy a different “state” of pluripotency with differences in gene expression, methylation patterns, and genomic aberrations, which may reflect incomplete reprogramming and may therefore impact on the regenerative potential of these donor cells in therapies. It also highlights the limitations of current technologies used to generate these cells. Moreover, we provide a systematic review of the state of play with regard to the use of iPSCs in the treatment of neurodegenerative and neuropathological conditions. The importance of balancing the promise of this transplantation candidate in the light of these emerging properties is crucial as the potential application in the clinical setting approaches. The first of three sections in this review discusses (A) the pathophysiology of spinal cord injury (SCI) and how stem cell therapies can positively alter the pathology in experimental SCI. Part B summarizes (i) the available technologies to deliver transgenes to generate iPSCs and (ii) recent data comparing iPSCs to ESCs in terms of characteristics and molecular composition. Lastly, in (C) we evaluate iPSC-based therapies as a candidate to treat SCI on the basis of their neurite induction capability compared to embryonic stem cells and provide a summary of available in vivo data of iPSCs used in SCI and other disease models.
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Affiliation(s)
- Anne S. Kramer
- Spinal Cord Repair Laboratory, School of Anatomy, Physiology and Human Biology, The University of Western Australia, Perth, Western Australia
| | - Alan R. Harvey
- Spinal Cord Repair Laboratory, School of Anatomy, Physiology and Human Biology, The University of Western Australia, Perth, Western Australia
| | - Giles W. Plant
- Stanford Partnership for Spinal Cord Injury and Repair, Stanford Institute for Neuro-Innovation and Translational Neurosciences, Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA, USA
| | - Stuart I. Hodgetts
- Spinal Cord Repair Laboratory, School of Anatomy, Physiology and Human Biology, The University of Western Australia, Perth, Western Australia
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Smith AJ, Nelson NG, Oommen S, Hartjes KA, Folmes CD, Terzic A, Nelson TJ. Apoptotic susceptibility to DNA damage of pluripotent stem cells facilitates pharmacologic purging of teratoma risk. Stem Cells Transl Med 2012. [PMID: 23197662 DOI: 10.5966/sctm.2012-0066] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Pluripotent stem cells have been the focus of bioengineering efforts designed to generate regenerative products, yet harnessing therapeutic capacity while minimizing risk of dysregulated growth remains a challenge. The risk of residual undifferentiated stem cells within a differentiated progenitor population requires a targeted approach to eliminate contaminating cells prior to delivery. In this study we aimed to validate a toxicity strategy that could selectively purge pluripotent stem cells in response to DNA damage and avoid risk of uncontrolled cell growth upon transplantation. Compared with somatic cell types, embryonic stem cells and induced pluripotent stem cells displayed hypersensitivity to apoptotic induction by genotoxic agents. Notably, hypersensitivity in pluripotent stem cells was stage-specific and consistently lost upon in vitro differentiation, with the mean half-maximal inhibitory concentration increasing nearly 2 orders of magnitude with tissue specification. Quantitative polymerase chain reaction and Western blotting demonstrated that the innate response was mediated through upregulation of the BH3-only protein Puma in both natural and induced pluripotent stem cells. Pretreatment with genotoxic etoposide purged hypersensitive pluripotent stem cells to yield a progenitor population refractory to teratoma formation upon transplantation. Collectively, this study exploits a hypersensitive apoptotic response to DNA damage within pluripotent stem cells to decrease risk of dysregulated growth and augment the safety profile of transplant-ready, bioengineered progenitor cells.
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Affiliation(s)
- Alyson J Smith
- Department of Medicine and Transplant Center, Mayo Clinic, Rochester, MN 55905, USA
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Progress and bottleneck in induced pluripotency. CELL REGENERATION 2012; 1:5. [PMID: 25408868 PMCID: PMC4230504 DOI: 10.1186/2045-9769-1-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/17/2012] [Accepted: 05/03/2012] [Indexed: 01/05/2023]
Abstract
With their capability to undergo unlimited self-renewal and to differentiate into all cell types in the body, induced pluripotent stem cells (iPSCs), reprogrammed from somatic cells of individual patients with defined factors, have unlimited potential in cell therapy and in modeling complex human diseases. Significant progress has been achieved to improve the safety of iPSCs and the reprogramming efficiency. To avoid the cancer risk and spontaneous reactivation of the reprogramming factors associated with the random integration of viral vectors into the genome, several approaches have been established to deliver the reprogramming factors into the somatic cells without inducing genetic modification. In addition, a panel of small molecule compounds, many of which targeting the epigenetic machinery, have been identified to increase the reprogramming efficiency. Despite these progresses, recent studies have identified genetic and epigenetic abnormalities of iPSCs as well as the immunogenicity of some cells derived from iPSCs. In addition, due to the oncogenic potential of the reprogramming factors and the reprogramming-induced DNA damage, the critical tumor suppressor pathways such as p53 and ARF are activated to act as the checkpoints that suppress induced pluripotency. The inactivation of these tumor suppression pathways even transiently during reprogramming processes could have significant adverse impact on the genome integrity. These safety concerns must be resolved to improve the feasibility of the clinic development of iPSCs into human cell therapy.
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21
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Fu X, Xu Y. Challenges to the clinical application of pluripotent stem cells: towards genomic and functional stability. Genome Med 2012; 4:55. [PMID: 22741526 PMCID: PMC3698533 DOI: 10.1186/gm354] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Human embryonic stem cells (hESCs) can undergo unlimited self-renewal and are pluripotent, retaining the ability to differentiate into all cell types in the body. As a renewable source of various types of human cells, hESCs hold great therapeutic potential. Although significant advances have been achieved in defining the conditions needed to differentiate hESCs into various types of biologically active cells, many challenges remain in the clinical development of hESC-based cell therapy, such as the immune rejection of allogeneic hESC-derived cells by recipients. Breakthroughs in the generation of induced pluripotent stem cells (iPSCs), which are reprogrammed from somatic cells with defined factors, raise the hope that autologous cells derived from patient-specific iPSCs can be transplanted without immune rejection. However, recent genomic studies have revealed epigenetic and genetic abnormalities associated with induced pluripotency, a risk of teratomas, and immunogenicity of some iPSC derivatives. These findings have raised safety concerns for iPSC-based therapy. Here, we review recent advances in understanding the genomic and functional stability of human pluripotent stem cells, current challenges to their clinical application and the progress that has been made to overcome these challenges.
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Affiliation(s)
- Xuemei Fu
- Chengdu Women's and Children's Central Hospital, Chengdu, Sichuan, China ; Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Yang Xu
- Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
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22
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Chen Z, Zhao T, Xu Y. The genomic stability of induced pluripotent stem cells. Protein Cell 2012; 3:271-7. [PMID: 22528751 DOI: 10.1007/s13238-012-2922-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2012] [Accepted: 03/21/2012] [Indexed: 01/11/2023] Open
Abstract
With their capability to undergo unlimited self-renewal and to differentiate into all cell types in the body, induced pluripotent stem cells (iPSCs), reprogrammed from somatic cells of human patients with defined factors, hold promise for regenerative medicine because they can provide a renewable source of autologous cells for cell therapy without the concern for immune rejection. In addition, iPSCs provide a unique opportunity to model human diseases with complex genetic traits, and a panel of human diseases have been successfully modeled in vitro by patient-specific iPSCs. Despite these progresses, recent studies have raised the concern for genetic and epigenetic abnormalities of iPSCs that could contribute to the immunogenicity of some cells differentiated from iPSCs. The oncogenic potential of iPSCs is further underscored by the findings that the critical tumor suppressor p53, known as the guardian of the genome, suppresses induced pluripotency. Therefore, the clinic application of iPSCs will require the optimization of the reprogramming technology to minimize the genetic and epigenetic abnormalities associated with induced pluripotency.
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Affiliation(s)
- Zhao Chen
- Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093-0322, USA
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