RESUMEN
Leukaemia is caused by the clonal evolution of a cell that accumulates mutations/genomic rearrangements, allowing unrestrained cell growth. However, recent identification of leukaemic mutations in the blood cells of healthy individuals revealed that additional events are required to expand the mutated clones for overt leukaemia. Here, we assessed the functional consequences of deleting the Fanconi anaemia A (Fanca) gene, which encodes a DNA damage response protein, in Spi1 transgenic mice that develop preleukaemic syndrome. FANCA loss increases SPI1-associated disease penetrance and leukaemic progression without increasing the global mutation load of leukaemic clones. However, a high frequency of leukaemic FANCA-depleted cells display heterozygous activating mutations in known oncogenes, such as Kit or Nras, also identified but at low frequency in FANCA-WT mice with preleukaemic syndrome, indicating that FANCA counteracts the emergence of oncogene mutated leukaemic cells. A unique transcriptional signature is associated with the leukaemic status of FANCA-depleted cells, leading to activation of MDM4, NOTCH and Wnt/ß-catenin pathways. We show that NOTCH signalling improves the proliferation capacity of FANCA-deficient leukaemic cells. Collectively, our observations indicate that loss of the FANC pathway, known to control genetic instability, fosters the expansion of leukaemic cells carrying oncogenic mutations rather than mutation formation. FANCA loss may contribute to this leukaemogenic progression by reprogramming transcriptomic landscape of the cells.
Asunto(s)
Proteína del Grupo de Complementación A de la Anemia de Fanconi , Leucemia , Animales , Ratones , Heterocigoto , Leucemia/genética , Mutación , Oncogenes/genética , Proteína del Grupo de Complementación A de la Anemia de Fanconi/genéticaRESUMEN
DNA damage and genomic instability contribute to non-small cell lung cancer (NSCLC) etiology and progression. However, their therapeutic exploitation is disappointing. CTC-derived explants (CDX) offer systems for mechanistic investigation of CTC metastatic potency and may provide rationale for biology-driven therapeutics. Four CDX models and 3 CDX-derived cell lines were established from NSCLC CTCs and recapitulated patient tumor histology and response to platinum-based chemotherapy. CDX (GR-CDXL1, GR-CDXL2, GR-CDXL3, GR-CDXL4) demonstrated considerable mutational landscape similarity with patient tumor biopsy and/or single CTCs. Truncal alterations in key DNA damage response (DDR) and genome integrity-related genes were prevalent across models and assessed as therapeutic targets in vitro, in ovo, and in vivo. GR-CDXL1 presented homologous recombination deficiency linked to biallelic BRCA2 mutation and FANCA deletion, unrepaired DNA lesions after mitosis, and olaparib sensitivity, despite resistance to chemotherapy. SLFN11 overexpression in GR-CDXL4 led to olaparib sensitivity and was in coherence with neuroendocrine marker expression in patient tumor biopsy, suggesting a predictive value of SLFN11 in NSCLC histological transformation into small cell lung cancer (SCLC). Centrosome clustering promoted targetable chromosomal instability in GR-CDXL3 cells. These CDX unravel DDR and genome integrity-related defects as a central mechanism underpinning metastatic potency of CTCs and provide rationale for their therapeutic targeting in metastatic NSCLC.
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Carcinoma de Pulmón de Células no Pequeñas , Neoplasias Pulmonares , Células Neoplásicas Circulantes , Carcinoma Pulmonar de Células Pequeñas , Biomarcadores de Tumor/genética , Carcinoma de Pulmón de Células no Pequeñas/tratamiento farmacológico , Carcinoma de Pulmón de Células no Pequeñas/genética , Carcinoma de Pulmón de Células no Pequeñas/patología , Humanos , Neoplasias Pulmonares/tratamiento farmacológico , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/patología , Células Neoplásicas Circulantes/metabolismo , Proteínas Nucleares , Carcinoma Pulmonar de Células Pequeñas/tratamiento farmacológico , Carcinoma Pulmonar de Células Pequeñas/genética , Carcinoma Pulmonar de Células Pequeñas/patologíaRESUMEN
Gatekeeper mutations are identified in only 50% of the cases at resistance to Anaplastic Lymphoma Kinase (ALK)-tyrosine kinase inhibitors (TKIs). Circulating tumor cells (CTCs) are relevant tools to identify additional resistance mechanisms and can be sequenced at the single-cell level. Here, we provide in-depth investigation of copy number alteration (CNA) heterogeneity in phenotypically characterized CTCs at resistance to ALK-TKIs in ALK-positive non-small cell lung cancer. Single CTC isolation and phenotyping were performed by DEPArray or fluorescence-activated cell sorting following enrichment and immunofluorescence staining (ALK/cytokeratins/CD45/Hoechst). CNA heterogeneity was evaluated in six ALK-rearranged patients harboring ≥ 10 CTCs/20 mL blood at resistance to 1st and 3rd ALK-TKIs and one presented gatekeeper mutations. Out of 82 CTCs isolated by FACS, 30 (37%) were ALK+/cytokeratins-, 46 (56%) ALK-/cytokeratins+ and 4 (5%) ALK+/cytokeratins+. Sequencing of 43 CTCs showed highly altered CNA profiles and high levels of chromosomal instability (CIN). Half of CTCs displayed a ploidy >2n and 32% experienced whole-genome doubling. Hierarchical clustering showed significant intra-patient and wide inter-patient CTC diversity. Classification of 121 oncogenic drivers revealed the predominant activation of cell cycle and DNA repair pathways and of RTK/RAS and PI3K to a lower frequency. CTCs showed wide CNA heterogeneity and elevated CIN at resistance to ALK-TKIs. The emergence of epithelial ALK-negative CTCs may drive resistance through activation of bypass signaling pathways, while ALK-rearranged CTCs showed epithelial-to-mesenchymal transition characteristics potentially contributing to ALK-TKI resistance. Comprehensive analysis of CTCs could be of great help to clinicians for precision medicine and resistance to ALK-targeted therapies.
RESUMEN
Circulating tumor cells (CTCs) provide an accessible tool for investigating tumor heterogeneity and cell populations with metastatic potential. Although an in-depth molecular investigation is limited by the extremely low CTC count in circulation, significant progress has been made recently in single-cell analytical processes. Indeed, CTC monitoring through molecular and functional characterization may provide an understanding of genomic instability (GI) molecular mechanisms, which contribute to tumor evolution and emergence of resistant clones. In this review, we discuss the sources and consequences of GI seen through single-cell analysis of CTCs in different types of tumors. We present a detailed overview of chromosomal instability (CIN) in CTCs assessed by fluorescence in situ hybridization (FISH), and we reveal utility of CTC single-cell sequencing in identifying copy number alterations (CNA) oncogenic drivers. We highlight the role of CIN in CTC-driven metastatic progression and acquired resistance, and we comment on the technical obstacles and challenges encountered during single CTC analysis. We focus on the DNA damage response and depict DNA-repair-related dynamic biomarkers reported to date in CTCs and their role in predicting response to genotoxic treatment. In summary, the suggested relationship between genomic aberrations in CTCs and prognosis strongly supports the potential utility of GI monitoring in CTCs in clinical risk assessment and therapeutic choice.
Asunto(s)
Inestabilidad Cromosómica/genética , Variaciones en el Número de Copia de ADN/genética , Daño del ADN/genética , Reparación del ADN/genética , Inestabilidad Genómica/genética , Genómica/métodos , Humanos , PronósticoRESUMEN
Hematopoietic stem cell (HSC) attrition is considered the key event underlying progressive BM failure (BMF) in Fanconi anemia (FA), the most frequent inherited BMF disorder in humans. However, despite major advances, how the cellular, biochemical, and molecular alterations reported in FA lead to HSC exhaustion remains poorly understood. Here, we demonstrated in human and mouse cells that loss-of-function of FANCA or FANCC, products of 2 genes affecting more than 80% of FA patients worldwide, is associated with constitutive expression of the transcription factor microphthalmia (MiTF) through the cooperative, unscheduled activation of several stress-signaling pathways, including the SMAD2/3, p38 MAPK, NF-κB, and AKT cascades. We validated the unrestrained Mitf expression downstream of p38 in Fanca-/- mice, which display hallmarks of hematopoietic stress, including loss of HSC quiescence, DNA damage accumulation in HSCs, and reduced HSC repopulation capacity. Importantly, we demonstrated that shRNA-mediated downregulation of Mitf expression or inhibition of p38 signaling rescued HSC quiescence and prevented DNA damage accumulation. Our data support the hypothesis that HSC attrition in FA is the consequence of defects in the DNA-damage response combined with chronic activation of otherwise transiently activated signaling pathways, which jointly prevent the recovery of HSC quiescence.
Asunto(s)
Trastornos de Fallo de la Médula Ósea/metabolismo , Daño del ADN , Anemia de Fanconi/metabolismo , Células Madre Hematopoyéticas/metabolismo , Sistema de Señalización de MAP Quinasas , Factor de Transcripción Asociado a Microftalmía/metabolismo , Animales , Ácido Ascórbico , Trastornos de Fallo de la Médula Ósea/genética , Trastornos de Fallo de la Médula Ósea/patología , Línea Celular , Colecalciferol , Deshidroepiandrosterona/análogos & derivados , Quinasas MAP Reguladas por Señal Extracelular/genética , Quinasas MAP Reguladas por Señal Extracelular/metabolismo , Anemia de Fanconi/genética , Anemia de Fanconi/patología , Proteínas del Grupo de Complementación de la Anemia de Fanconi/genética , Proteínas del Grupo de Complementación de la Anemia de Fanconi/metabolismo , Células Madre Hematopoyéticas/patología , Ratones , Ratones Noqueados , Factor de Transcripción Asociado a Microftalmía/genética , Ácidos Nicotínicos , Extractos Vegetales , Proteínas Smad/genética , Proteínas Smad/metabolismoRESUMEN
Metastasis is the main cause of cancer-related death owing to the blood-borne dissemination of circulating tumor cells (CTCs) early in the process. A rare fraction of CTCs harboring a stem cell profile and tumor initiation capacities is thought to possess the clonogenic potential to seed new lesions. The highest plasticity has been generally attributed to CTCs with a partial epithelial-to-mesenchymal transition (EMT) phenotype, demonstrating a large heterogeneity among these cells. Therefore, detection and functional characterization of these subclones may offer insight into mechanisms underlying CTC tumorigenicity and inform on the complex biology behind metastatic spread. Although an in-depth mechanistic investigation is limited by the extremely low CTC count in circulation, significant progress has been made over the past few years to establish relevant systems from patient CTCs. CTC-derived xenograft (CDX) models and CTC-derived ex vivo cultures have emerged as tractable systems to explore tumor-initiating cells (TICs) and uncover new therapeutic targets. Here, we introduce basic knowledge of CTC biology, including CTC clusters and evidence for EMT/cancer stem cell (CSC) hybrid phenotypes. We report and evaluate the CTC-derived models generated to date in different types of cancer and shed a light on challenges and key findings associated with these novel assays.
Asunto(s)
Carcinogénesis/patología , Técnicas de Cultivo de Célula/métodos , Modelos Biológicos , Células Neoplásicas Circulantes/patología , Animales , Transición Epitelial-Mesenquimal/fisiología , Humanos , Células Madre Neoplásicas/patología , Ensayo de Tumor de Célula Madre/métodosRESUMEN
Growing evidences for tumor heterogeneity confirm that single-tumor biopsies frequently fail to reveal the widespread mutagenic profile of tumor. Repeated biopsies are in most cases unfeasible, especially in advanced cancers. We describe here how circulating tumor cells (CTCs) isolated from minimally invasive blood sample might inform us about intratumor heterogeneity, tumor evolution and treatment resistance. We also discuss the advances of CTCs research, most notably in molecularly selected non-small cell lung cancer (NSCLC) patients, highlighting challenges and opportunities related to personalized therapy.
RESUMEN
TET2 somatic mutations occur in â¼10% of diffuse large B-cell lymphomas (DLBCL) but are of unknown significance. Herein, we show that TET2 is required for the humoral immune response and is a DLBCL tumor suppressor. TET2 loss of function disrupts transit of B cells through germinal centers (GC), causing GC hyperplasia, impaired class switch recombination, blockade of plasma cell differentiation, and a preneoplastic phenotype. TET2 loss was linked to focal loss of enhancer hydroxymethylation and transcriptional repression of genes that mediate GC exit, such as PRDM1. Notably, these enhancers and genes are also repressed in CREBBP-mutant DLBCLs. Accordingly, TET2 mutation in patients yields a CREBBP-mutant gene-expression signature, CREBBP and TET2 mutations are generally mutually exclusive, and hydroxymethylation loss caused by TET2 deficiency impairs enhancer H3K27 acetylation. Hence, TET2 plays a critical role in the GC reaction, and its loss of function results in lymphomagenesis through failure to activate genes linked to GC exit signals. SIGNIFICANCE: We show that TET2 is required for exit of the GC, B-cell differentiation, and is a tumor suppressor for mature B cells. Loss of TET2 phenocopies CREBBP somatic mutation. These results advocate for sequencing TET2 in patients with lymphoma and for the testing of epigenetic therapies to treat these tumors.See related commentary by Shingleton and Dave, p. 1515.This article is highlighted in the In This Issue feature, p. 1494.
Asunto(s)
Diferenciación Celular/genética , Proteínas de Unión al ADN/genética , Centro Germinal/metabolismo , Linfoma de Células B Grandes Difuso/genética , Células Plasmáticas/metabolismo , Proteínas Proto-Oncogénicas/genética , Animales , Proteína de Unión a CREB/genética , Proteína de Unión a CREB/metabolismo , Proteínas de Unión al ADN/metabolismo , Dioxigenasas , Epigénesis Genética/genética , Perfilación de la Expresión Génica/métodos , Centro Germinal/patología , Células Madre Hematopoyéticas/metabolismo , Humanos , Hiperplasia , Linfoma de Células B Grandes Difuso/metabolismo , Linfoma de Células B Grandes Difuso/patología , Ratones Noqueados , Ratones Transgénicos , Mutación , Células Plasmáticas/patología , Factor 1 de Unión al Dominio 1 de Regulación Positiva/genética , Factor 1 de Unión al Dominio 1 de Regulación Positiva/metabolismo , Proteínas Proto-Oncogénicas/metabolismoRESUMEN
The TET2 gene encodes an α-ketoglutarate-dependent dioxygenase able to oxidize 5-methylcytosine into 5-hydroxymethylcytosine, which is a step toward active DNA demethylation. TET2 is frequently mutated in myeloid malignancies but also in B- and T-cell malignancies. TET2 somatic mutations are also identified in healthy elderly individuals with clonal hematopoiesis. Tet2-deficient mouse models showed widespread hematological differentiation abnormalities, including myeloid, T-cell, and B-cell malignancies. We show here that, similar to what is observed with constitutive Tet2-deficient mice, B-cell-specific Tet2 knockout leads to abnormalities in the B1-cell subset and a development of B-cell malignancies after long latency. Aging Tet2-deficient mice accumulate clonal CD19+ B220low immunoglobulin M+ B-cell populations with transplantable ability showing similarities to human chronic lymphocytic leukemia, including CD5 expression and sensitivity to ibrutinib-mediated B-cell receptor (BCR) signaling inhibition. Exome sequencing of Tet2-/- malignant B cells reveals C-to-T and G-to-A mutations that lie within single-stranded DNA-specific activation-induced deaminase (AID)/APOBEC (apolipoprotein B messenger RNA editing enzyme, catalytic polypeptide-like) cytidine deaminases targeted motif, as confirmed by the lack of a B-cell tumor in compound Tet2-Aicda-deficient mice. Finally, we show that Tet2 deficiency accelerates and exacerbates T-cell leukemia/lymphoma 1A-induced leukemogenesis. Together, our data establish that Tet2 deficiency predisposes to mature B-cell malignancies, which development might be attributed in part to AID-mediated accumulating mutations and BCR-mediated signaling.
Asunto(s)
Proteínas de Unión al ADN/deficiencia , Estudios de Asociación Genética , Predisposición Genética a la Enfermedad , Leucemia de Células B/genética , Linfoma de Células B/genética , Proteínas Proto-Oncogénicas/deficiencia , Alelos , Animales , Linfocitos B , Biomarcadores , Supervivencia Celular , Dioxigenasas , Citometría de Flujo , Genotipo , Leucemia de Células B/metabolismo , Leucemia de Células B/patología , Linfoma de Células B/metabolismo , Linfoma de Células B/patología , Ratones , Ratones Noqueados , Mutación , Receptores de Antígenos de Linfocitos B/metabolismoRESUMEN
Primary Ovarian Insufficiency (POI) affects ~1% of women under forty. Exome sequencing of two Finnish sisters with non-syndromic POI revealed a homozygous mutation in FANCM, leading to a truncated protein (p.Gln1701*). FANCM is a DNA-damage response gene whose heterozygous mutations predispose to breast cancer. Compared to the mother's cells, the patients' lymphocytes displayed higher levels of basal and mitomycin C (MMC)-induced chromosomal abnormalities. Their lymphoblasts were hypersensitive to MMC and MMC-induced monoubiquitination of FANCD2 was impaired. Genetic complementation of patient's cells with wild-type FANCM improved their resistance to MMC re-establishing FANCD2 monoubiquitination. FANCM was more strongly expressed in human fetal germ cells than in somatic cells. FANCM protein was preferentially expressed along the chromosomes in pachytene cells, which undergo meiotic recombination. This mutation may provoke meiotic defects leading to a depleted follicular stock, as in Fancm-/- mice. Our findings document the first Mendelian phenotype due to a biallelic FANCM mutation.
Asunto(s)
ADN Helicasas/genética , Homocigoto , Mutación , Ovario/fisiopatología , Insuficiencia Ovárica Primaria/genética , Adulto , Aberraciones Cromosómicas , Proteína del Grupo de Complementación D2 de la Anemia de Fanconi/genética , Proteína del Grupo de Complementación D2 de la Anemia de Fanconi/metabolismo , Femenino , Predisposición Genética a la Enfermedad , Genotipo , Recombinación Homóloga , Humanos , Masculino , Persona de Mediana Edad , Linaje , Fenotipo , Insuficiencia Ovárica Primaria/patología , Ubiquitinación , Secuenciación del Exoma , Adulto JovenRESUMEN
Proteins involved in genetic stability maintenance and safeguarding DNA replication act not only against cancer initiation but could also play a major role in sustaining cancer progression. Here, we report that the FANC pathway is highly expressed in metastatic melanoma harboring the oncogenic microphthalmia-associated transcription factor (MiTF). We show that MiTF downregulation in melanoma cells lowers the expression of several FANC genes and proteins. Moreover, we observe that, similarly to the consequence of MiTF downregulation, FANC pathway silencing alters proliferation, migration and senescence of human melanoma cells. We demonstrate that the FANC pathway acts downstream MiTF and establish the existence of an epistatic relationship between MiTF and the FANC pathway. Our findings point to a central role of the FANC pathway in cellular and chromosomal resistance to both DNA damage and targeted therapies in melanoma cells. Thus, the FANC pathway is a promising new therapeutic target in melanoma treatment.
Asunto(s)
Proliferación Celular , Supervivencia Celular , Proteína del Grupo de Complementación D2 de la Anemia de Fanconi/fisiología , Melanoma/patología , Factor de Transcripción Asociado a Microftalmía/metabolismo , Animales , Línea Celular Tumoral , Resistencia a Antineoplásicos , Proteína del Grupo de Complementación D2 de la Anemia de Fanconi/genética , Silenciador del Gen , Humanos , Indoles/uso terapéutico , Melanoma/tratamiento farmacológico , Melanoma/metabolismo , Ratones , Ratones Desnudos , Factor de Transcripción Asociado a Microftalmía/genética , Oxidación-Reducción , Especies Reactivas de Oxígeno/metabolismo , Sulfonamidas/uso terapéutico , VemurafenibRESUMEN
B-lymphocytes in the bone marrow (BM) must generate a functional B-cell receptor and overcome the negative selection induced by reactivity with autoantigens. Two rounds of DNA recombination are required for the production of functional immunoglobulin heavy (Ig-HCs) and light (LCs) chains necessary for the continuation of B-lymphocyte development in the BM. Both rounds depend on the joint action of recombination activating gene-1 (RAG-1) and RAG-2 endonucleases with the DNA non-homologous end-joining pathway. Loss of the FANC gene leads to the chromosome breakage and cancer predisposition syndrome Fanconi anemia. Because the FANC proteins are involved in certain aspects of the recombination process, we sought to determine the impact of the FANC pathway on the Ig diversification process using Fanca-/- mice. In this work we demonstrated that Fanca-/- animals have a mild B-cell differentiation defect characterized by a specific alteration of the IgM- to IgM+ transition of the B220low B-cell population. Pre-B cells from Fanca-/- mice show evidence of impaired kLC rearrangement at the level of the Vk-Jk junction. Furthermore, Fanca-/- mice showed a skewed Vκ gene usage during formation of the LCs Vk-Jk junctions. Therefore, the Fanca protein appears as a yet unidentified factor involved in the primary diversification of Ig.
Asunto(s)
Linfocitos B/inmunología , Proteína del Grupo de Complementación A de la Anemia de Fanconi/inmunología , Células Precursoras de Linfocitos B/inmunología , Recombinación V(D)J/inmunología , Animales , Reparación del ADN por Unión de Extremidades/inmunología , Proteínas de Unión al ADN/inmunología , Anemia de Fanconi/inmunología , Proteínas del Grupo de Complementación de la Anemia de Fanconi/inmunología , Proteínas de Homeodominio/inmunología , Cadenas Pesadas de Inmunoglobulina/inmunología , Cadenas Ligeras de Inmunoglobulina/inmunología , Ratones , Receptores de Antígenos de Linfocitos B/inmunologíaRESUMEN
Fanconi anemia (FA) is an inherited chromosomal instability syndrome that is characterized by progressive bone marrow failure. One of the main causes of morbidity and mortality in FA is a bleeding tendency, resulting from low platelet counts. Platelets are the final products of megakaryocyte (MK) maturation. Here, we describe a previously unappreciated role of Fanconi anemia group A protein (Fanca) during the endomitotic process of MK differentiation. Fanca deficiency leads to the accumulation of MKs with low nuclear ploidy and to decreased platelet production. We show, for the first time, that Fanca(-/-) mice are characterized by limited number and proliferative capacity of MK progenitors. Defective megakaryopoiesis of Fanca(-/-) cells is associated with the formation of nucleoplasmic bridges and increased chromosomal instability, indicating that inaccurate endoreplication and karyokinesis occur during MK polyploidization. Sustained DNA damage forces Fanca(-/-) MKs to enter a senescence-like state. Furthermore, inhibition of the Rho-associated kinase, a regulator of cytokinesis, improves the polyploidization of Fanca(-/-) MKs but greatly increases their genomic instability and diminishes their differentiation potential, supporting the notion that accumulation of DNA damage through endomitotic cycles affects MK maturation. Our study indicates that Fanca expression during endomitosis is crucial for normal megakaryopoiesis and platelet production.
Asunto(s)
Proteína del Grupo de Complementación A de la Anemia de Fanconi , Regulación de la Expresión Génica/genética , Megacariocitos/metabolismo , Trombocitopenia , Trombopoyesis/genética , Animales , Senescencia Celular/genética , Inestabilidad Cromosómica/genética , Proteína del Grupo de Complementación A de la Anemia de Fanconi/biosíntesis , Proteína del Grupo de Complementación A de la Anemia de Fanconi/genética , Megacariocitos/patología , Ratones , Ratones Noqueados , Mitosis , Trombocitopenia/genética , Trombocitopenia/metabolismo , Trombocitopenia/patologíaRESUMEN
Loss of hematopoietic stem cell (HSC) function and increased risk of developing hematopoietic malignancies are severe and concerning complications of anticancer radiotherapy and chemotherapy. We have previously shown that thrombopoietin (TPO), a critical HSC regulator, ensures HSC chromosomal integrity and function in response to γ-irradiation by regulating their DNA-damage response. TPO directly affects the double-strand break (DSB) repair machinery through increased DNA-protein kinase (DNA-PK) phosphorylation and nonhomologous end-joining (NHEJ) repair efficiency and fidelity. This effect is not shared by other HSC growth factors, suggesting that TPO triggers a specific signal in HSCs facilitating DNA-PK activation upon DNA damage. The discovery of these unique signaling pathways will provide a means of enhancing TPO-desirable effects on HSCs and improving the safety of anticancer DNA agents. We show here that TPO specifically triggers Erk and nuclear factor κB (NF-κB) pathways in mouse hematopoietic stem and progenitor cells (HSPCs). Both of these pathways are required for a TPO-mediated increase in DSB repair. They cooperate to induce and activate the early stress-response gene, Iex-1 (ier3), upon DNA damage. Iex-1 forms a complex with pERK and the catalytic subunit of DNA-PK, which is necessary and sufficient to promote TPO-increased DNA-PK activation and NHEJ DSB repair in both mouse and human HSPCs.
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Reparación del ADN , Quinasas MAP Reguladas por Señal Extracelular/metabolismo , Regulación Enzimológica de la Expresión Génica , Células Madre Hematopoyéticas/citología , Proteínas Inmediatas-Precoces/metabolismo , FN-kappa B/metabolismo , Trombopoyetina/metabolismo , Transporte Activo de Núcleo Celular , Animales , Antineoplásicos/química , Dominio Catalítico , Roturas del ADN de Doble Cadena , Daño del ADN , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Fosforilación , Transducción de Señal , Células Madre/citologíaRESUMEN
DNA double-strand breaks (DSBs) represent a serious threat for hematopoietic stem cells (HSCs). How cytokines and environmental signals integrate the DNA damage response and contribute to HSC-intrinsic DNA repair processes remains unknown. Thrombopoietin (TPO) and its receptor, Mpl, are critical factors supporting HSC self-renewal and expansion. Here, we uncover an unknown function for TPO-Mpl in the regulation of DNA damage response. We show that DNA repair following γ-irradiation (γ-IR) or the action of topoisomerase-II inhibitors is defective in Mpl(-/-) and in wild-type mouse or human hematopoietic stem and progenitor cells treated in the absence of TPO. TPO stimulates DNA repair in vitro and in vivo by increasing DNA-PK-dependent nonhomologous end-joining efficiency. This ensures HSC chromosomal integrity and limits their long-term injury in response to IR. This shows that niche factors can modulate the HSC DSB repair machinery and opens new avenues for administration of TPO agonists for minimizing radiotherapy-induced HSC injury and mutagenesis.
Asunto(s)
Daño del ADN/fisiología , Células Madre Hematopoyéticas/metabolismo , Mutagénesis/fisiología , Células Madre/metabolismo , Trombopoyetina/metabolismo , Animales , Ciclo Celular , Ensayo Cometa , Daño del ADN/genética , Femenino , Técnica del Anticuerpo Fluorescente , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Mutantes , Mutagénesis/genética , Trombopoyetina/genéticaRESUMEN
Serum erythropoietin level less than 100U/L and a transfusion requirement of less than 2 units per month are the best predictive factors for response to treatment by erythropoiesis-stimulating agents in low/int-1 myelodysplastic syndromes. To investigate the factors influencing the response to erythropoiesis-stimulating agents, we enrolled 127 low/int-1 myelodysplastic syndrome patients at diagnosis in a biological study of erythropoiesis. The 54 non-responders had a significantly lower number of burst-forming unit-erythroid and colony-forming unit-erythroid than responders. Erythropoietin-dependent proliferation and survival, and phospho (p)-ERK1/2 expression in steady state and after erythropoietin stimulation were defective in cultured erythroblasts. By flow cytometry, p-ERK1/2 was significantly lower in bone marrow CD45(-)/CD71(+)/GPA(-)cells from non-responders compared to responders or controls. Receiver Operator Characteristic curve analysis showed that this flow cytometry test was a sensitive biomarker for predicting the response to erythropoiesis-stimulating agents.
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Eritroblastos/enzimología , Regulación Enzimológica de la Expresión Génica , Hematínicos/uso terapéutico , Proteína Quinasa 1 Activada por Mitógenos/biosíntesis , Proteína Quinasa 3 Activada por Mitógenos/biosíntesis , Síndromes Mielodisplásicos/enzimología , Anciano , Anciano de 80 o más Años , Biomarcadores/metabolismo , Proliferación Celular/efectos de los fármacos , Células Cultivadas , Eritroblastos/patología , Eritropoyesis/efectos de los fármacos , Eritropoyetina/sangre , Eritropoyetina/farmacología , Femenino , Citometría de Flujo , Humanos , Masculino , Síndromes Mielodisplásicos/tratamiento farmacológico , Síndromes Mielodisplásicos/patologíaRESUMEN
Viability and myogenesis from C2C12 muscle cells and L6 rat myoblasts were dose-dependently stimulated by insulin. The metabolic inhibitors of phosphatidyl-inositol-3-kinase (PI-3K, LY294002) and of MAPKK/ERK kinase (MEK, PD98059) differently affected insulin-stimulated myogenesis of the cells. After LY294002 and PD98059 treatment, viability deteriorated and apparently an additive effect of both metabolic inhibitors was observed, irrespective of the method of measurement (neutral red or MTT assay). These inhibitors were antagonistic in myogenesis. Our results confirm that insulin regulates cell viability by at least two distinct pathways, namely by PI-3K- and MEK-dependent signalling cascades. Both pathways are agonistic in cell viability, whereas PI-3K rather than MEK supports insulin-mediated myogenicity. Accordingly, inhibition of insulin action by LY294002, but not PD98059, was accompanied with a reduced level of Ser473-phosphorylated Akt with additional loss of myogenin protein. Besides, repression of insulin signalling by either PI-3K or MEK inhibitor diminished expression of selected subunits of the mitochondrial oxidative phosphorylation enzymes (OXPHOS). In turn, insulin raised and accelerated protein expression of subunits I and IV of mitochondrial cytochrome-c oxidase (COX). In addition, the level of myogenin, the molecular marker of terminal and general muscle differentiation indices decreased if selected OXPHOS enzymes were individually blocked by rotenone, myxothiazol or oligomycin. Summing up, our results pointed to mitochondria as an essential organelle for insulin-dependent myogenesis. Insulin positively affects mitochondrial function by induction of OXPHOS enzymes, which provide energy indispensable for the anabolic effect of insulin.
Asunto(s)
Insulina/fisiología , Mitocondrias/fisiología , Células Musculares/fisiología , Desarrollo de Músculos , Animales , Línea Celular , Supervivencia Celular , Cromonas/farmacología , Flavonoides/farmacología , Insulina/farmacología , Metacrilatos/farmacología , Mitocondrias/ultraestructura , Quinasas de Proteína Quinasa Activadas por Mitógenos/antagonistas & inhibidores , Quinasas de Proteína Quinasa Activadas por Mitógenos/metabolismo , Morfolinas/farmacología , Células Musculares/ultraestructura , Músculo Esquelético/citología , Miogenina/metabolismo , Oligomicinas/farmacología , Fosfatidilinositol 3-Quinasas/metabolismo , Inhibidores de las Quinasa Fosfoinosítidos-3 , Fosforilación , Proteínas Proto-Oncogénicas c-akt/metabolismo , Ratas , Rotenona/farmacología , Transducción de Señal , Tiazoles/farmacología , Desacopladores/farmacologíaRESUMEN
Previously, we reported that mitogenicity in L6 muscle cells was stimulated by insulin but inhibited by reactive oxygen/nitrogen species (ROS/RNS; []) and that preincubation with sodium ascorbate (ASC) protected from either the impaired DNA synthesis and/or loss of cell viability. Now, we addressed the question how ascorbate (AA) rescued DNA synthesis in L6 muscle cells being challenged with ROS/RNS. We assumed that AA might be able to influence insulin signaling. We found that insulin elevated the protein levels of both PKB/Akt kinase phosphorylated at Serine(473) (pS473-Akt), and c-Jun phosphorylated at Serine63, Serine73 (pS63, pS73-c-Jun) residues, respectively. A short-term treatment experiment (0 - 45 min) revealed that either insulin (0.1 muM) or hydrogen peroxide (0.1, 0.5 mM; H2O2) increased the pS473-Akt and pS63, pS73-c-Jun protein levels, although the effect of ROS/RNS peaked earlier (5 min) than that of insulin (45 min). Astonishingly, the elevated levels of both pS473-Akt and pS63, pS73-c-Jun in response to insulin were reduced by the concomitant treatment with H2O2 in a dose-dependent fashion. In contrast, a 4-hour preincubation with ASC (1 mM) augmented the signal from pS473-Akt and pS63, pS73-c-Jun, when both insulin and H2O2 were added. Moreover, a 24 h preincubation with ASC also elevated the pS473-Akt and pS63, pS73-c-Jun levels in response to insulin irrespective to ROS/RNS co-treatment. During chronic treatment studies, ROS/RNS stimulated neither phosphorylation of Akt nor c-Jun, indicating that ROS/RNS-dependent activation of the above-mentioned proteins was short-term and transient. Furthermore, higher levels of pS473 Akt and pS63, pS73-c-Jun after preincubation with ASC suggest that by this route AA could protect insulin-induced mitogenicity. Basal levels of Akt and its target p70(S6K) remained constant regardless of treatment. These results suggest that AA defends the insulin-stimulated mitogenicity hampered by ROS/RNS most likely by the amplification of insulin signal at the level of pS473-Akt and pS63, pS73-c-Jun, respectively.