RESUMO
Despite improvements in patient outcomes, pediatric cancer remains a leading cause of non-accidental death in children. Recent genetic analysis of patients with pediatric cancers indicates an important role for both germline genetic predisposition and cancer-specific somatic driver mutations. Increasingly, evidence demonstrates that the developmental timepoint at which the cancer cell-of-origin transforms is critical to tumor identity and therapeutic response. Therefore, future therapeutic development would be bolstered by the use of disease models that faithfully recapitulate the genetic context, cell-of-origin, and developmental window of vulnerability in pediatric cancers. Human stem cells have the potential to incorporate all of these characteristics into a pediatric cancer model, while serving as a platform for rapid genetic and pharmacological testing. In this review, we describe how human stem cells have been used to model pediatric cancers and how these models compare to other pediatric cancer model modalities.
Today, pediatric cancer is a leading cause of non-accidental death in children. In order to further improve outcomes, it is important for researchers and clinicians alike to recognize how pediatric cancers are distinct from adult cancers. Inherited risk of cancer may play a greater role in pediatric cancer risk, and subsequent tumor-specific acquired driver mutations initiate tumor formation. However, there is substantial interaction between inherited and acquired mutations, which supports consideration of both simultaneously. Recent advancements in biotechnology, have improved matching between early cells of development and pediatric cancer cells, although cell-of-origin for certain pediatric central nervous system tumors remain elusive. Increasingly, evidence, particularly in pediatric medulloblastoma, demonstrates that the developmental timepoint at which the cancer cell-of-origin transforms is critical to tumor identity and therapeutic response. Therefore, future therapeutic development would be bolstered by the use of disease models that faithfully recapitulate the genetic context, cell-of-origin, and developmental window of pediatric cancers. Human stem cells have the potential to incorporate all of these characteristics into a pediatric cancer model, while serving as a platform for rapid genetic and pharmacological testing. In this review, we describe how human stem cells have been used to model pediatric cancers, how human these models compare to other pediatric cancer model modalities, and how these models can be improved in the future.
Assuntos
Neoplasias , Humanos , Neoplasias/patologia , Criança , Células-Tronco , Modelos BiológicosRESUMO
Extracranial germ cell tumors (GCT) are a biologically diverse group of tumors occurring in children, adolescents, and young adults. The majority of patients have excellent outcomes, but treatment-related toxicities impact their quality of survivorship. A subset of patients succumbs to the disease. Current unmet needs include clarifying which patients can be safely observed after initial surgical resection, refinement of risk stratification to reduce chemotherapy burden in patients with standard-risk disease, and intensify therapy for patients with poor-risk disease. Furthermore, enhancing strategies for detection of minimal residual disease and early detection of relapse, particularly in serum tumor marker-negative histologies, is critical. Improving the understanding of the developmental and molecular origins of GCTs may facilitate discovery of novel targets. Future efforts should be directed toward assessing novel therapies in a biology-driven, biomarker-defined, histology-specific, risk-stratified patient population. Fragmentation of care between subspecialists restricts the unified study of these rare tumors. It is imperative that trials be conducted in collaboration with national and international cooperative groups, with harmonized data and biospecimen collection. Key priorities for the Children's Oncology Group (COG) GCT Committee include (a) better understanding the biology of GCTs, with a focus on molecular targets and mechanisms of treatment resistance; (b) strategic development of pediatric and young adult clinical trials; (c) understanding late effects of therapy and identifying individuals most at risk; and (d) prioritizing diversity, equity, and inclusion to reduce cancer health disparities and studying the impacts of social determinants of health on outcomes.
Assuntos
Recidiva Local de Neoplasia , Neoplasias Embrionárias de Células Germinativas , Adolescente , Adulto Jovem , Criança , Humanos , Neoplasias Embrionárias de Células Germinativas/terapia , Oncologia , Biomarcadores Tumorais , Fatores de RiscoRESUMO
OBJECTIVE: Pediatric low-grade gliomas (pLGGs) frequently exhibit dysregulation of the mitogen-activated protein kinase (MAPK) pathway. Targeted therapies, including mutant BRAF inhibitors (dabrafenib) and MEK inhibitors (trametinib), have shown promise in patients in whom conventional chemotherapy has failed. However, few studies have investigated the use of targeted therapy as a first-line treatment for pLGG. Here, the authors reviewed their institutional experience with using a personalized medicine approach to patients with newly diagnosed pLGGs. METHODS: All pediatric patients at the authors' institution who had been treated with dabrafenib or trametinib for pLGG without first receiving conventional chemotherapy or radiation were retrospectively reviewed. Demographic, clinical, and radiological data were collected. RESULTS: Eight patients underwent targeted therapy as a first-line treatment for pLGG. Five patients had a BRAF alteration (1 with a BRAFV600E mutation, 4 with a KIAA1549:BRAF fusion), and 3 patients had an NF1 mutation. One of the 8 patients was initially treated with dabrafenib, and trametinib was added later. Seven patients were initially treated with trametinib; of these, 2 later transitioned to dual therapy, whereas 5 continued with trametinib monotherapy. Six patients (75%) demonstrated a partial response to therapy during their treatment course, whereas stable disease was identified in the remaining 2 patients (25%). One patient experienced mild disease progression after completing a course of trametinib monotherapy, but ultimately stabilized after a period of close observation. Another patient experienced tumor progression while on dabrafenib, but subsequently responded to dual therapy with dabrafenib and trametinib. The most common adverse reactions to targeted therapy were cutaneous toxicity (100%) and diarrhea (50%). CONCLUSIONS: Targeted therapies have the potential to become a standard treatment option for pLGG due to their favorable toxicity profile and oral route of administration. This case series provides preliminary evidence that targeted therapies can induce an early disease response as a first-line adjuvant treatment; however, large-scale studies are required to assess long-term durability and safety.
Assuntos
Glioma , Proteínas Proto-Oncogênicas B-raf , Criança , Humanos , Proteínas Proto-Oncogênicas B-raf/genética , Estudos Retrospectivos , Oximas/uso terapêutico , Adjuvantes Imunológicos , Glioma/tratamento farmacológico , Glioma/genética , Inibidores de Proteínas Quinases/uso terapêuticoRESUMO
Primordial germ cells (PGCs) are the earliest form of mammalian germ lineage. In humans, PGCs are present during a very early and limited window in development, limiting the ability to study fundamental developmental steps in human reproductive biology. However, recent advancements in generating in-vitro models of gametogenesis have allowed the field to generate human primordial germ cell-like cells (hPGCLCs). In this chapter, we will review the generation of hPGCLCs using the incipient mesoderm-like cell (iMeLC) protocol and the subsequent expansion of hPGCLCs in a long-term culture system.
Assuntos
Células-Tronco Pluripotentes Induzidas , Animais , Humanos , Diferenciação Celular , Células Germinativas , Gametogênese , MamíferosRESUMO
In vitro expansion of human primordial germ cell-like cells (hPGCLCs), a pluripotent stem cell-derived PGC model, has proved challenging due to rapid loss of primordial germ cell (PGC)-like identity and limited cell survival/proliferation. Here, we describe long-term culture hPGCLCs (LTC-hPGCLCs), which actively proliferate in a serum-free, feeder-free condition without apparent limit as highly homogeneous diploid cell populations maintaining transcriptomic and epigenomic characteristics of hPGCLCs. Histone proteomics confirmed reduced H3K9me2 and increased H3K27me3 marks in LTC-hPGCLCs compared with induced pluripotent stem cells (iPSCs). LTC-hPGCLCs established from multiple human iPSC clones of both sexes were telomerase positive, senescence-free cells readily passaged with minimal cell death or deviation from the PGC-like identity. LTC-hPGCLCs are capable of differentiating to DAZL-positive M-spermatogonia-like cells in the xenogeneic reconstituted testis (xrTestis) organ culture milieu as well as efficiently producing fully pluripotent embryonic germ cell-like cells in the presence of stem cell factor and fibroblast growth factor 2. Thus, LTC-hPGCLCs provide convenient access to unlimited amounts of high-quality and homogeneous hPGCLCs.
Assuntos
Células Germinativas , Células-Tronco Pluripotentes Induzidas , Diferenciação Celular , Células Cultivadas , Células Alimentadoras , Feminino , Humanos , MasculinoRESUMO
The development of an in vitro system in which human primordial germ cell-like cells (hPGCLCs) are generated from human pluripotent stem cells (hPSCs) has been invaluable to further our understanding of human primordial germ cell (hPGC) specification. However, the means to evaluate the next fundamental steps in germ cell development have not been well established. In this study we describe a two dimensional extended culture system that promotes proliferation of specified hPGCLCs, without reversion to a pluripotent state. We demonstrate that hPGCLCs in extended culture undergo partial epigenetic reprogramming, mirroring events described in hPGCs in vivo, including a genome-wide reduction in DNA methylation and maintenance of depleted H3K9me2. This extended culture system provides a new approach for expanding the number of hPGCLCs for downstream technologies, including transplantation, molecular screening, or possibly the differentiation of hPGCLCs into gametes by in vitro gametogenesis.
Assuntos
Técnicas de Cultura de Células/métodos , Metilação de DNA , Células Germinativas/citologia , Proliferação de Células , Autorrenovação Celular , Sobrevivência Celular , Células Cultivadas , Montagem e Desmontagem da Cromatina , Desmetilação do DNA , Metilação de DNA/genética , Histonas/metabolismo , Humanos , Transcrição Gênica , Transcriptoma/genéticaRESUMO
We generated three human induced pluripotent stem cell (hiPSC) sublines from human dermal fibroblasts (HDFs) (MZT04) generated from a skin biopsy donated from a previously fertile woman. The skin biopsy was broadly consented for generating hiPSC lines for biomedical research, including unique consent specifically for studying human fertility, infertility and germ cells. hiPSCs were reprogrammed using Sendai virus vectors and were subsequently positive for markers of self-renewal including OCT4, NANOG, TRA-1-81 and SSEA-4. Pluripotency was further verified using teratomas and PluriTest. These sublines serve as controls for hiPSC research projects aimed at understanding the cell and molecular regulation of female fertility and infertility.
Assuntos
Linhagem Celular/citologia , Células-Tronco Pluripotentes Induzidas/citologia , Diferenciação Celular , Linhagem Celular/metabolismo , Células Cultivadas , Reprogramação Celular , Feminino , Fibroblastos/citologia , Fibroblastos/metabolismo , Homozigoto , Humanos , Células-Tronco Pluripotentes Induzidas/metabolismo , Masculino , Pessoa de Meia-Idade , Fator 3 de Transcrição de Octâmero/genética , Fator 3 de Transcrição de Octâmero/metabolismo , Fatores de Transcrição SOXB1/genética , Fatores de Transcrição SOXB1/metabolismoRESUMO
Overcoming infertility with assisted reproduction requires high-quality eggs and sperm. For those young women who no longer make functional eggs, the hope of conceiving a biological child just got one step closer with a recent publication in Science from Yamashiro et al. (2018).
Assuntos
Células-Tronco Pluripotentes Induzidas , Infertilidade , Criança , Feminino , Fertilidade , Humanos , Oogônios , ReproduçãoRESUMO
Germ cell tumors (GCTs) are a heterogeneous group of tumors occurring in gonadal and extragonadal locations. GCTs are hypothesized to arise from primordial germ cells (PGCs), which fail to differentiate. One recently identified susceptibility loci for human GCT is PR (PRDI-BF1 and RIZ) domain proteins 14 (PRDM14). PRDM14 is expressed in early primate PGCs and is repressed as PGCs differentiate. To examine PRDM14 in human GCTs we profiled human GCT cell lines and patient samples and discovered that PRDM14 is expressed in embryonal carcinoma cell lines, embryonal carcinomas, seminomas, intracranial germinomas and yolk sac tumors, but is not expressed in teratomas. To model constitutive overexpression in human PGCs, we generated PGC-like cells (PGCLCs) from human pluripotent stem cells (PSCs) and discovered that elevated expression of PRDM14 does not block early PGC formation. Instead, we show that elevated PRDM14 in PGCLCs causes proliferation and differentiation defects in the germline.
Assuntos
Neoplasias Embrionárias de Células Germinativas/metabolismo , Proteínas Repressoras/metabolismo , Adolescente , Adulto , Diferenciação Celular/genética , Diferenciação Celular/fisiologia , Proliferação de Células/genética , Proliferação de Células/fisiologia , Criança , Pré-Escolar , Proteínas de Ligação a DNA , Feminino , Células Germinativas , Humanos , Lactente , Masculino , Neoplasias Embrionárias de Células Germinativas/genética , Células-Tronco Pluripotentes/metabolismo , Proteínas de Ligação a RNA , Teratoma/metabolismo , Fatores de Transcrição , Adulto JovemRESUMO
Human primordial germ cells (hPGCs) are the first embryonic progenitors in the germ cell lineage, yet the molecular mechanisms required for hPGC formation are not well characterized. To identify regulatory regions in hPGC development, we used the assay for transposase-accessible chromatin using sequencing (ATAC-seq) to systematically characterize regions of open chromatin in hPGCs and hPGC-like cells (hPGCLCs) differentiated from human embryonic stem cells (hESCs). We discovered regions of open chromatin unique to hPGCs and hPGCLCs that significantly overlap with TFAP2C-bound enhancers identified in the naive ground state of pluripotency. Using CRISPR/Cas9, we show that deleting the TFAP2C-bound naive enhancer at the OCT4 locus (also called POU5F1) results in impaired OCT4 expression and a negative effect on hPGCLC identity.
Assuntos
Elementos Facilitadores Genéticos/genética , Regulação da Expressão Gênica no Desenvolvimento , Células Germinativas/metabolismo , Fator 3 de Transcrição de Octâmero/genética , Fator de Transcrição AP-2/metabolismo , Cromatina/metabolismo , Feminino , Células Germinativas/citologia , Humanos , Fator 4 Semelhante a Kruppel , Fatores de Transcrição Kruppel-Like/metabolismo , Masculino , Motivos de Nucleotídeos/genética , Células-Tronco Pluripotentes/metabolismo , Transcriptoma/genéticaRESUMO
Human fertility is dependent upon the correct establishment and differentiation of the germline. This is because no other cell type in the body is capable of passing a genome and epigenome from parent to child. Terminally differentiated germline cells in the adult testis and ovary are called gametes. However, the initial specification of germline cells occurs in the embryo around the time of gastrulation. Most of our knowledge regarding the cell and molecular events that govern human germline specification involves extrapolating scientific principles from model organisms, most notably the mouse. However, recent work using next generation sequencing, gene editing and differentiation of germline cells from pluripotent stem cells has revealed that the core molecular mechanisms that regulate human germline development are different from rodents. Here, we will discuss the major molecular pathways required for human germline differentiation and how pluripotent stem cells have revolutionized our ability to study the earliest steps in human embryonic lineage specification in order to understand human fertility.