RESUMO
Germinal centers (GCs) that form in mucosal sites are exposed to gut-derived factors that have the potential to influence homeostasis independent of antigen receptor-driven selective processes. The G-protein Gα13 confines B cells to the GC and limits the development of GC-derived lymphoma. We discovered that Gα13-deficiency fuels the GC reaction via increased mTORC1 signaling and Myc protein expression specifically in the mesenteric lymph node (mLN). The competitive advantage of Gα13-deficient GC B cells (GCBs) in mLN was not dependent on T cell help or gut microbiota. Instead, Gα13-deficient GCBs were selectively dependent on dietary nutrients likely due to greater access to gut lymphatics. Specifically, we found that diet-derived glutamine supported proliferation and Myc expression in Gα13-deficient GCBs in the mLN. Thus, GC confinement limits the effects of dietary glutamine on GC dynamics in mucosal tissues. Gα13 pathway mutations coopt these processes to promote the gut tropism of aggressive lymphoma.
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B cell receptor (BCR) signalling has emerged as a therapeutic target in B cell lymphomas, but inhibiting this pathway in diffuse large B cell lymphoma (DLBCL) has benefited only a subset of patients1. Gene expression profiling identified two major subtypes of DLBCL, known as germinal centre B cell-like and activated B cell-like (ABC)2,3, that show poor outcomes after immunochemotherapy in ABC. Autoantigens drive BCR-dependent activation of NF-κB in ABC DLBCL through a kinase signalling cascade of SYK, BTK and PKCß to promote the assembly of the CARD11-BCL10-MALT1 adaptor complex, which recruits and activates IκB kinase4-6. Genome sequencing revealed gain-of-function mutations that target the CD79A and CD79B BCR subunits and the Toll-like receptor signalling adaptor MYD885,7, with MYD88(L265P) being the most prevalent isoform. In a clinical trial, the BTK inhibitor ibrutinib produced responses in 37% of cases of ABC1. The most striking response rate (80%) was observed in tumours with both CD79B and MYD88(L265P) mutations, but how these mutations cooperate to promote dependence on BCR signalling remains unclear. Here we used genome-wide CRISPR-Cas9 screening and functional proteomics to determine the molecular basis of exceptional clinical responses to ibrutinib. We discovered a new mode of oncogenic BCR signalling in ibrutinib-responsive cell lines and biopsies, coordinated by a multiprotein supercomplex formed by MYD88, TLR9 and the BCR (hereafter termed the My-T-BCR supercomplex). The My-T-BCR supercomplex co-localizes with mTOR on endolysosomes, where it drives pro-survival NF-κB and mTOR signalling. Inhibitors of BCR and mTOR signalling cooperatively decreased the formation and function of the My-T-BCR supercomplex, providing mechanistic insight into their synergistic toxicity for My-T-BCR+ DLBCL cells. My-T-BCR supercomplexes characterized ibrutinib-responsive malignancies and distinguished ibrutinib responders from non-responders. Our data provide a framework for the rational design of oncogenic signalling inhibitors in molecularly defined subsets of DLBCL.
Assuntos
Carcinogênese , Linfoma Difuso de Grandes Células B/metabolismo , Linfoma Difuso de Grandes Células B/patologia , Complexos Multiproteicos/metabolismo , Transdução de Sinais , Adenina/análogos & derivados , Animais , Biópsia , Sistemas CRISPR-Cas/genética , Carcinogênese/genética , Desenho de Fármacos , Feminino , Humanos , Linfoma Difuso de Grandes Células B/genética , Camundongos , Complexos Multiproteicos/química , Mutação , Fator 88 de Diferenciação Mieloide/genética , Fator 88 de Diferenciação Mieloide/metabolismo , NF-kappa B/metabolismo , Piperidinas , Proteômica , Pirazóis/farmacologia , Pirazóis/uso terapêutico , Pirimidinas/farmacologia , Pirimidinas/uso terapêutico , Receptores de Antígenos de Linfócitos B/antagonistas & inibidores , Receptores de Antígenos de Linfócitos B/genética , Receptores de Antígenos de Linfócitos B/metabolismo , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/genética , Serina-Treonina Quinases TOR/antagonistas & inibidores , Serina-Treonina Quinases TOR/metabolismo , Receptor Toll-Like 9/genética , Receptor Toll-Like 9/metabolismo , Células Tumorais Cultivadas , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
BACKGROUND: Diffuse large B-cell lymphomas (DLBCLs) are phenotypically and genetically heterogeneous. Gene-expression profiling has identified subgroups of DLBCL (activated B-cell-like [ABC], germinal-center B-cell-like [GCB], and unclassified) according to cell of origin that are associated with a differential response to chemotherapy and targeted agents. We sought to extend these findings by identifying genetic subtypes of DLBCL based on shared genomic abnormalities and to uncover therapeutic vulnerabilities based on tumor genetics. METHODS: We studied 574 DLBCL biopsy samples using exome and transcriptome sequencing, array-based DNA copy-number analysis, and targeted amplicon resequencing of 372 genes to identify genes with recurrent aberrations. We developed and implemented an algorithm to discover genetic subtypes based on the co-occurrence of genetic alterations. RESULTS: We identified four prominent genetic subtypes in DLBCL, termed MCD (based on the co-occurrence of MYD88L265P and CD79B mutations), BN2 (based on BCL6 fusions and NOTCH2 mutations), N1 (based on NOTCH1 mutations), and EZB (based on EZH2 mutations and BCL2 translocations). Genetic aberrations in multiple genes distinguished each genetic subtype from other DLBCLs. These subtypes differed phenotypically, as judged by differences in gene-expression signatures and responses to immunochemotherapy, with favorable survival in the BN2 and EZB subtypes and inferior outcomes in the MCD and N1 subtypes. Analysis of genetic pathways suggested that MCD and BN2 DLBCLs rely on "chronic active" B-cell receptor signaling that is amenable to therapeutic inhibition. CONCLUSIONS: We uncovered genetic subtypes of DLBCL with distinct genotypic, epigenetic, and clinical characteristics, providing a potential nosology for precision-medicine strategies in DLBCL. (Funded by the Intramural Research Program of the National Institutes of Health and others.).
Assuntos
Perfilação da Expressão Gênica , Heterogeneidade Genética , Linfoma Difuso de Grandes Células B/genética , Mutação , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Biópsia , Epigênese Genética , Exoma , Genótipo , Humanos , Estimativa de Kaplan-Meier , Linfoma Difuso de Grandes Células B/classificação , Linfoma Difuso de Grandes Células B/tratamento farmacológico , Linfoma Difuso de Grandes Células B/mortalidade , Prognóstico , Análise de Sequência de DNA , TranscriptomaRESUMO
The impact of treatment on the risk of lymphoma in patients with rheumatoid arthritis (RA) is unclear. Here, we aimed to assess if the risk of lymphoma differs according to the type of tumor necrosis factor inhibitor (TNFi), comparing monoclonal anti-TNF antibodies to the soluble TNF receptor. We used B cell activating factor belonging to the TNF family (BAFF)-transgenic (Tg) mice as a model of autoimmunity-associated lymphoma. Six-month-old BAFF-Tg mice were treated with TNFi for 12 months. Histological examination of the spleen, assessment of the cellular composition of the spleen by flow cytometry and assessment of B cell clonality were performed at euthanasia. Crude mortality and incidence of lymphoma were significantly higher in mice treated with monoclonal anti-TNF antibodies compared to both controls and mice treated with the soluble TNF receptor, even at a high dose. Flow cytometry analysis revealed decreased splenic macrophage infiltration in mice treated with monoclonal anti-TNF antibodies. Overall, this study demonstrates, for the first time, that a very prolonged treatment with monoclonal anti-TNF antibodies increase the risk of lymphoma in B cell-driven autoimmunity. These data suggest a closer monitoring for lymphoma development in patients suffering from B cell-driven autoimmune disease with long-term exposure to monoclonal anti-TNF antibodies.
Assuntos
Anticorpos Monoclonais/imunologia , Artrite Reumatoide/imunologia , Fator Ativador de Células B/imunologia , Linfoma/imunologia , Camundongos Transgênicos/imunologia , Inibidores do Fator de Necrose Tumoral/imunologia , Fator de Necrose Tumoral alfa/imunologia , Animais , Doenças Autoimunes/imunologia , Autoimunidade/imunologia , Linfócitos B/imunologia , Linhagem Celular , Camundongos , Camundongos Endogâmicos C57BL , Baço/imunologiaRESUMO
Insulin-like growth factor (IGF)-I has cancer promoting activities. However, the hypothesis that circulating IGF-I concentration is related to risk of lymphoma overall or its subtypes has not been examined prospectively. IGF-I concentration was measured in pre-diagnostic plasma samples from a nested case-control study of 1,072 cases of lymphoid malignancies and 1,072 individually matched controls from the European Prospective Investigation into Cancer and Nutrition. Odds ratios (ORs) and confidence intervals (CIs) for lymphoma were calculated using conditional logistic regression. IGF-I concentration was not associated with overall lymphoma risk (multivariable-adjusted OR for highest versus lowest third = 0.77 [95% CI = 0.57-1.03], ptrend = 0.06). There was no statistical evidence of heterogeneity in this association with IGF-I by sex, age at blood collection, time between blood collection and diagnosis, age at diagnosis, or body mass index (pheterogeneity for all ≥ 0.05). There were no associations between IGF-I concentration and risk for specific BCL subtypes, T-cell lymphoma or Hodgkin lymphoma, although number of cases were small. In this European population, IGF-I concentration was not associated with risk of overall lymphoma. This study provides the first prospective evidence on circulating IGF-I concentrations and risk of lymphoma. Further prospective data are required to examine associations of IGF-I concentrations with lymphoma subtypes.
Assuntos
Fator de Crescimento Insulin-Like I/análise , Linfoma/sangue , Adulto , Idoso , Idoso de 80 Anos ou mais , Estudos de Casos e Controles , Europa (Continente)/epidemiologia , Feminino , Seguimentos , Humanos , Linfoma/epidemiologia , Masculino , Pessoa de Meia-Idade , Inquéritos Nutricionais , Razão de Chances , Risco , Fatores de Risco , Fatores SocioeconômicosAssuntos
Evolução Clonal , Linfoma Folicular , Proteínas de Fusão bcr-abl/genética , Glicosilação , Humanos , AçúcaresRESUMO
Follicular lymphoma (FL) is a B-cell neoplasm resulting from the transformation of germinal center (GC) B cells. Although t(14;18) and ectopic B-cell lymphoma 2 (BCL2) expression constitute the genetic hallmark of FL, t(14;18)(pos) B cells bearing genotypic and phenotypic features of FL cells can be found in the blood of most healthy individuals. Nevertheless, the localization of these FL-like cells (FLLCs) in nonmalignant GC-rich tissues and the functional consequences of BCL2 overexpression have not been evaluated thus far. Among 85 reactive lymph node (RLN) samples, 14% were found to contain high levels of t(14;18) by quantitative polymerase chain reaction. In t(14;18)(hi) RLNs, CD20(pos)BCL2(pos)CD10(pos) FLLCs consistently accumulated within the GC, essentially as nonproliferative CXCR4(neg) centrocytes. Moreover, they displayed a reduced response to proliferative stimuli in vitro. Altogether, our findings provide new insights into in situ FLLC functional properties and suggest that these cells have not acquired the ultimate genetic events leading to FL transformation.
Assuntos
Cromossomos Humanos Par 14 , Cromossomos Humanos Par 18 , Linfoma de Células B/genética , Linfoma Folicular/genética , Translocação Genética , Adulto , Idoso , Antígenos CD20/genética , Antígenos CD20/metabolismo , Transformação Celular Neoplásica/genética , Feminino , Centro Germinativo/metabolismo , Centro Germinativo/patologia , Humanos , Masculino , Pessoa de Meia-Idade , Neprilisina/genética , Neprilisina/metabolismo , Proteínas Proto-Oncogênicas c-bcl-2/genética , Proteínas Proto-Oncogênicas c-bcl-2/metabolismoRESUMO
PURPOSE OF REVIEW: Follicular lymphoma and chronic lymphocytic leukemia (CLL) are indolent B-cell malignancies characterized by a long preclinical phase and frequent relapses once treatment is initiated. The present review gathers recent findings on the occurrence, relevance, and dynamics of premalignant cells in the development of follicular lymphoma and CLL. RECENT FINDINGS: The frequency of circulating cells bearing the follicular lymphoma hallmark translocation t(14;18) in healthy persons is correlated to the risk of developing follicular lymphoma later in life. Chronic B-cell receptor stimulation induces cyclic re-entries of BCL2 B cells into germinal centers that propagate clonal evolution and early follicular lymphoma progression. The lymph node microenvironment is a key activation/proliferation niche for malignant cells in CLL, also active in its preclinical antecedent monoclonal B-cell lymphocytosis. SUMMARY: Considering recent studies of premalignant cells in both diseases and of their putative normal cell counterparts, we propose different models of premalignant evolution for the two pathologies. Before overt follicular lymphoma, t(14;18) B cells exploit the dynamics of memory B cells to re-enter multiple times into local or distant germinal centers, gather activation/proliferation signals, and gain additional mutations to progress to malignant lymphoma. In monoclonal B-cell lymphocytosis, CLL-like activated/memory B cells follow cycles of germinal center-independent activation/proliferation in lymph node. Finally, we discuss the next level genetic and functional analyses that should result in a better understanding of the origins and mechanisms of frequent relapses in follicular lymphoma and CLL.
Assuntos
Linfócitos B/metabolismo , Carcinogênese/genética , Regulação Neoplásica da Expressão Gênica , Leucemia Linfocítica Crônica de Células B/genética , Linfoma Folicular/genética , Linfócitos B/patologia , Carcinogênese/metabolismo , Carcinogênese/patologia , Proliferação de Células , Cromossomos Humanos Par 14 , Cromossomos Humanos Par 18 , Centro Germinativo/metabolismo , Centro Germinativo/patologia , Humanos , Leucemia Linfocítica Crônica de Células B/metabolismo , Leucemia Linfocítica Crônica de Células B/patologia , Linfoma Folicular/metabolismo , Linfoma Folicular/patologia , Células Neoplásicas Circulantes , Proteínas Proto-Oncogênicas c-bcl-2/genética , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Transdução de Sinais , Translocação Genética , Microambiente TumoralRESUMO
PURPOSE: The strong association between t(14;18) translocation and follicular lymphoma (FL) is well known. However, the determinants of this chromosomal aberration and their role in t(14;18) associated FL remain to be established. METHODS: t(14;18) frequency within the B cell lymphoma 2 major breakpoint region was determined for 135 incident FL cases and 251 healthy controls as part of a nested case-control study within the European Prospective Investigation into Cancer cohort. Quantitative real-time PCR was performed in DNA extracted from blood samples taken at recruitment. The relationship between prevalence and frequency of the translocation with baseline anthropometric, lifestyle, and dietary factors in cases and controls was determined. Unconditional logistic regression was used to explore whether the risk of FL associated with these factors differed in t(14;18)(+) as compared to t(14;18)(-) cases. RESULTS: Among incident FL cases, educational level (χ(2) p = 0.021) and height (χ(2) p = 0.025) were positively associated with t(14;18) prevalence, and cases with high frequencies [t(14;18)(HF)] were significantly taller (t test p value = 0.006). These findings were not replicated in the control population, although there were a number of significant associations with dietary variables. Further analyses revealed that height was a significant risk factor for t(14;18)(+) FL [OR 6.31 (95% CI 2.11, 18.9) in the tallest versus the shortest quartile], but not t(14;18)(-) cases. CONCLUSIONS: These findings suggest a potential role for lifestyle factors in the prevalence and frequency of the t(14;18) translocation. The observation that the etiology of FL may differ by t(14;18) status, particularly with regard to height, supports the subdivision of FL by translocation status.
Assuntos
Cromossomos Humanos Par 14 , Cromossomos Humanos Par 18 , Linfoma Folicular/genética , Translocação Genética , Adulto , Idoso , Estudos de Casos e Controles , Feminino , Humanos , Linfoma de Células B/genética , Linfoma de Células B/patologia , Linfoma Folicular/patologia , Masculino , Pessoa de Meia-Idade , Prevalência , Estudos ProspectivosRESUMO
The pathogenesis of follicular lymphoma is a multi-hit process progressing over many years through the accumulation of numerous genetic alterations. Besides the hallmark t(14;18), it is still unclear which other oncogenic hits contribute to the early steps of transformation and in which precursor stages these occur. To address this issue, we performed high-resolution comparative genomic hybridization microarrays on laser-capture micro-dissected cases of follicular lymphoma in situ (n=4), partial involvement by follicular lymphoma (n=4), and duodenal follicular lymphoma (n=4), assumed to represent, potentially, the earliest stages in the evolution of follicular lymphoma. Cases of reactive follicular hyperplasia (n=2), uninvolved areas from follicular lymphoma in situ lymph nodes, follicular lymphoma grade 1-2 (n=5) and follicular lymphoma grade 3A (n=5) were used as controls. Surprisingly, alterations involving several relevant (onco)genes were found in all entities, but at significantly lower proportions than in overt follicular lymphoma. While the number of alterations clearly assigns all these entities as precursors, the pattern of partial involvement by follicular lymphoma alterations was quantitatively and qualitatively closer to that of follicular lymphoma, indicating significant selective pressure in line with its faster rate of progression. Among the most notable alterations, we observed and validated deletions of 1p36 and gains of the 7p and 12q chromosomes and related oncogenes, which include some of the most recurrent oncogenic alterations in overt follicular lymphoma (TNFRSF14, EZH2, MLL2). By further delineating distinctive and hierarchical molecular and genetic features of early follicular lymphoma entities, our analysis underlines the importance of applying appropriate criteria for the differential diagnosis. It also provides a first set of candidates likely to be involved in the cascade of hits that pave the path of the various progression phases to follicular lymphoma development.
Assuntos
Transformação Celular Neoplásica/genética , Linfoma Folicular/genética , Linfoma Folicular/patologia , Carcinoma in Situ/genética , Carcinoma in Situ/patologia , Hibridização Genômica Comparativa , Progressão da Doença , Instabilidade Genômica , Centro Germinativo/patologia , Humanos , Gradação de Tumores , Estadiamento de NeoplasiasRESUMO
Cumulative evidence indicates that MYC, one of the major downstream effectors of NOTCH1, is a critical component of T-cell acute lymphoblastic leukemia (T-ALL) oncogenesis and a potential candidate for targeted therapy. However, MYC is a complex oncogene, involving both fine protein dosage and cell-context dependency, and detailed understanding of MYC-mediated oncogenesis in T-ALL is still lacking. To better understand how MYC is interspersed in the complex T-ALL oncogenic networks, we performed a thorough molecular and biochemical analysis of MYC activation in a comprehensive collection of primary adult and pediatric patient samples. We find that MYC expression is highly variable, and that high MYC expression levels can be generated in a large number of cases in absence of NOTCH1/FBXW7 mutations, suggesting the occurrence of multiple activation pathways in addition to NOTCH1. Furthermore, we show that posttranscriptional deregulation of MYC constitutes a major alternative pathway of MYC activation in T-ALL, operating partly via the PI3K/AKT axis through down-regulation of PTEN, and that NOTCH1(m) might play a dual transcriptional and posttranscriptional role in this process. Altogether, our data lend further support to the significance of therapeutic targeting of MYC and/or the PTEN/AKT pathways, both in GSI-resistant and identified NOTCH1-independent/MYC-mediated T-ALL patients.
Assuntos
Genes myc , PTEN Fosfo-Hidrolase/fisiologia , Leucemia-Linfoma Linfoblástico de Células T Precursoras/genética , Adulto , Células Cultivadas , Criança , Regulação Leucêmica da Expressão Gênica , Humanos , Células Jurkat , PTEN Fosfo-Hidrolase/genética , PTEN Fosfo-Hidrolase/metabolismo , Leucemia-Linfoma Linfoblástico de Células T Precursoras/metabolismo , Leucemia-Linfoma Linfoblástico de Células T Precursoras/patologia , Processamento Pós-Transcricional do RNA/genética , Processamento Pós-Transcricional do RNA/fisiologia , Transdução de Sinais/genética , Ativação Transcricional/genética , TransfecçãoRESUMO
Transformation to diffuse large B-cell lymphoma (DLBCL) is a recognized, but unpredictable, clinical inflection point in the natural history of indolent lymphomas. Large retrospective studies highlight a wide variability in the incidence of transformation across the indolent lymphomas and the adverse outcomes associated with transformed lymphomas. Opportunities to dissect the biology of transformed indolent lymphomas have arisen with evolving technologies and unique tissue collections enabling a growing appreciation, particularly, of their genetic basis, how they relate to the preceding indolent lymphomas and the comparative biology with de novo DLBCL. This review summarizes our current understanding of both the clinical and biological aspects of transformed lymphomas and the outstanding questions that remain.
Assuntos
Linfoma Difuso de Grandes Células B , Linfoma não Hodgkin , Humanos , Estudos Retrospectivos , Recidiva Local de Neoplasia , Linfoma Difuso de Grandes Células B/genética , Linfoma Difuso de Grandes Células B/patologia , Linfoma não Hodgkin/genética , Linfoma não Hodgkin/patologiaRESUMO
Follicular lymphomas (FL) are characterized by BCL2 translocations, often detectable in blood years before FL diagnosis, but also observed in aging healthy individuals, suggesting additional lesions are required for lymphomagenesis. We directly characterized early cooperating mutations by ultradeep sequencing of prediagnostic blood and tissue specimens from 48 subjects who ultimately developed FL. Strikingly, CREBBP lysine acetyltransferase (KAT) domain mutations were the most commonly observed precursor lesions, and largely distinguished patients developing FL (14/48, 29%) from healthy adults with or without detected BCL2 rearrangements (0/13, P = 0.03 and 0/20, P = 0.007, respectively). CREBBP variants were detectable a median of 5.8 years before FL diagnosis, were clonally selected in FL tumors, and appeared restricted to the committed B-cell lineage. These results suggest that mutations affecting the CREBBP KAT domain are common lesions in FL cancer precursor cells (CPC), with the potential for discriminating subjects at risk of developing FL or monitoring residual disease. SIGNIFICANCE: Our study provides direct evidence for recurrent genetic aberrations preceding FL diagnosis, revealing the combination of BCL2 translocation with CREBBP KAT domain mutations as characteristic committed lesions of FL CPCs. Such prediagnostic mutations are detectable years before clinical diagnosis and may help discriminate individuals at risk for lymphoma development. This article is highlighted in the In This Issue feature, p. 1275.
Assuntos
Linfoma Folicular , Adulto , Humanos , Linfoma Folicular/genética , Linfoma Folicular/patologia , Linfócitos B , Mutação , Rearranjo Gênico , Proteínas Proto-Oncogênicas c-bcl-2/genética , Translocação GenéticaRESUMO
Aggressive tumors often display mitochondrial dysfunction. Upon oxidative stress, mitochondria undergo fission through OMA1-mediated cleavage of the fusion effector OPA1. In yeast, a redox-sensing switch participates in OMA1 activation. 3D modeling of OMA1 comforted the notion that cysteine 403 might participate in a similar sensor in mammalian cells. Using prime editing, we developed a mouse sarcoma cell line in which OMA1 cysteine 403 was mutated in alanine. Mutant cells showed impaired mitochondrial responses to stress including ATP production, reduced fission, resistance to apoptosis, and enhanced mitochondrial DNA release. This mutation prevented tumor development in immunocompetent, but not nude or cDC1 dendritic cell-deficient, mice. These cells prime CD8+ lymphocytes that accumulate in mutant tumors, whereas their depletion delays tumor control. Thus, OMA1 inactivation increased the development of anti-tumor immunity. Patients with complex genomic soft tissue sarcoma showed variations in the level of OMA1 and OPA1 transcripts. High expression of OPA1 in primary tumors was associated with shorter metastasis-free survival after surgery, and low expression of OPA1, with anti-tumor immune signatures. Targeting OMA1 activity may enhance sarcoma immunogenicity.
Assuntos
GTP Fosfo-Hidrolases , Sarcoma , Camundongos , Animais , GTP Fosfo-Hidrolases/genética , GTP Fosfo-Hidrolases/metabolismo , Cisteína/metabolismo , Proteínas Mitocondriais/genética , Proteínas Mitocondriais/metabolismo , Mitocôndrias/metabolismo , Sarcoma/genética , Sarcoma/metabolismo , Mamíferos/metabolismo , Metaloproteases/genética , Metaloproteases/metabolismoRESUMO
Follicular lymphoma is one of the most common adult lymphoma, and remains virtually incurable despite its relatively indolent nature. t(14;18)(q32;q21) translocation, the genetic hallmark and early initiating event of follicular lymphoma (FL) pathogenesis, is also present at low frequency in the peripheral blood of healthy individuals. It has long been assumed that in healthy individuals t(14;18) is carried by circulating quiescent naive B cells, where its oncogenic potential would be restrained. Here, we question this current view and demonstrate that in healthy individuals, t(14;18) is actually carried by an expanding population of atypical B cells issued from germinal centers, displaying genotypic and phenotypic features of FL, and prone to constitute potent premalignant FL niches. These findings strongly impact both on the current understanding of disease progression and on the proper handling of t(14;18) frequency in blood as a potential early biomarker for lymphoma.
Assuntos
Subpopulações de Linfócitos B/patologia , Transformação Celular Neoplásica/patologia , Linfoma Folicular/imunologia , Linfoma Folicular/patologia , Subpopulações de Linfócitos B/imunologia , Subpopulações de Linfócitos B/metabolismo , Transformação Celular Neoplásica/genética , Transformação Celular Neoplásica/imunologia , Cromossomos Humanos Par 14 , Cromossomos Humanos Par 18 , Células Clonais , Humanos , Memória Imunológica , Linfoma Folicular/genética , Fase de Repouso do Ciclo Celular/imunologia , Translocação GenéticaRESUMO
Lymphomas are cancers deriving from lymphocytes, arising preferentially in secondary lymphoid organs, and represent the 6th cancer worldwide and the most frequent blood cancer. The majority of B cell Non-Hodgkin lymphomas (B-NHL) develop from germinal center (GC) experienced mature B cells. GCs are transient structures that form in lymphoid organs in response to antigen exposure of naive B cells, and where B cell receptor (BCR) affinity maturation occurs to promote B cell differentiation into memory B and plasma cells producing high-affinity antibodies. Genomic instability associated with the somatic hypermutation (SHM) and class-switch recombination (CSR) processes during GC transit enhance susceptibility to malignant transformation. Most B cell differentiation steps in the GC are at the origin of frequent B cell malignant entities, namely Follicular Lymphoma (FL) and GCB diffuse large B cell lymphomas (GCB-DLBCL). Over the past decade, large sequencing efforts have provided a great boost in the identification of candidate oncogenes and tumor suppressors involved in FL and DLBCL oncogenesis. Mouse models have been instrumental to accurately mimic in vivo lymphoma-specific mutations and interrogate their normal function in the GC context and their oncogenic function leading to lymphoma onset. The limited access of biopsies during the initiating steps of the disease, the cellular and (epi)genetic heterogeneity of individual tumors across and within patients linked to perturbed dynamics of GC ecosystems make the development of genetically engineered mouse models crucial to decipher lymphomagenesis and disease progression and eventually to test the effects of novel targeted therapies. In this review, we provide an overview of some of the important genetically engineered mouse models that have been developed to recapitulate lymphoma-associated (epi)genetic alterations of two frequent GC-derived lymphoma entities: FL and GCB-DLCBL and describe how those mouse models have improved our knowledge of the molecular processes supporting GC B cell transformation.
Assuntos
Modelos Animais de Doenças , Suscetibilidade a Doenças , Linfoma de Células B/etiologia , Camundongos Transgênicos , Animais , Linfócitos B/imunologia , Linfócitos B/metabolismo , Linfócitos B/patologia , Biomarcadores Tumorais , Epigênese Genética , Regulação Neoplásica da Expressão Gênica , Predisposição Genética para Doença , Centro Germinativo/imunologia , Centro Germinativo/metabolismo , Centro Germinativo/patologia , Humanos , Linfoma de Células B/metabolismo , Linfoma de Células B/patologia , Camundongos , Monitorização Imunológica , Translocação GenéticaRESUMO
Follicular lymphoma (FL) is an indolent yet challenging disease. Despite a generally favorable response to immunochemotherapy regimens, a fraction of patients does not respond or relapses early with unfavorable prognosis. For the vast majority of those who initially respond, relapses will repeatedly occur with increasing refractoriness to available treatments. Addressing the clinical challenges in FL warrants deep understanding of the nature of treatment-resistant FL cells seeding relapses, and of the biological basis of early disease progression. Great progress has been made in the last decade in the description and interrogation of the (epi)genomic landscape of FL cells, of their major dependency to the tumor microenvironment (TME), and of the stepwise lymphomagenesis process, from healthy to subclinical disease and to overt FL. A new picture is emerging, in which an ever-evolving tumor-TME duo sparks a complex and multilayered clonal and functional heterogeneity, blurring the discovery of prognostic biomarkers, patient stratification and reliable designs of risk-adapted treatments. Novel technological approaches allowing to decipher both tumor and TME heterogeneity at the single-cell level are beginning to unravel unsuspected cell dynamics and plasticity of FL cells. The upcoming drawing of a comprehensive functional picture of FL within its ecosystem holds great promise to address the unmet medical needs of this complex lymphoma.
Assuntos
Linfoma Folicular , Ecossistema , Humanos , Imunoterapia , Linfoma Folicular/terapia , Prognóstico , Microambiente TumoralRESUMO
In cancer cells, enhancer hijacking mediated by chromosomal alterations and/or increased deposition of acetylated histone H3 lysine 27 (H3K27ac) can support oncogene expression. However, how the chromatin conformation of enhancer-promoter interactions is affected by these events is unclear. In the present study, by comparing chromatin structure and H3K27ac levels in normal and lymphoma B cells, we show that enhancer-promoter-interacting regions assume different conformations according to the local abundance of H3K27ac. Genetic or pharmacological depletion of H3K27ac decreases the frequency and the spreading of these interactions, altering oncogene expression. Moreover, enhancer hijacking mediated by chromosomal translocations influences the epigenetic status of the regions flanking the breakpoint, prompting the formation of distinct intrachromosomal interactions in the two homologous chromosomes. These interactions are accompanied by allele-specific gene expression changes. Overall, our work indicates that H3K27ac dynamics modulates interaction frequency between regulatory regions and can lead to allele-specific chromatin configurations to sustain oncogene expression.
Assuntos
Alelos , Cromatina/química , Loci Gênicos , Histonas/metabolismo , Conformação de Ácido Nucleico , Oncogenes , Acetilação , Pareamento de Bases/genética , Linhagem Celular Tumoral , Elementos Facilitadores Genéticos , Epigênese Genética , Dosagem de Genes , Humanos , Lisina/metabolismo , Regiões Promotoras GenéticasRESUMO
Blood cell analysis is a major pillar of biomedical research and healthcare. These analyses are performed in central laboratories. Rapid shipment from collection site to the central laboratories is currently needed because cells and biomarkers degrade rapidly. The dried blood spot from a fingerstick allows the preservation of cellular molecules for months but entire cells are never recovered. Here leucocyte elution is optimized from dried blood spots. Flow cytometry and mRNA expression profiling are used to analyze the recovered cells. 50-70% of the leucocytes that are dried on a polyester solid support via elution after shaking the support with buffer are recovered. While red blood cells lyse upon drying, it is found that the majority of leucocytes are preserved. Leucocytes have an altered structure that is improved by adding fixative in the elution buffer. Leucocytes are permeabilized, allowing an easy staining of all cellular compartments. Common immunophenotyping and mRNAs are preserved. The ability of a new biomarker (CD169) to discriminate between patients with and without Severe Acute Respiratory Syndrome induced by Coronavirus 2 (SARS-CoV-2) infections is also preserved. Leucocytes from blood can be dried, shipped, and/or stored for at least 1 month, then recovered for a wide variety of analyses, potentially facilitating biomedical applications worldwide.
Assuntos
Doenças Transmissíveis/diagnóstico , Testes Diagnósticos de Rotina/métodos , Teste em Amostras de Sangue Seco/métodos , Hematologia/métodos , Imunofenotipagem/métodos , Anticorpos Antivirais/sangue , Biomarcadores/sangue , Coleta de Amostras Sanguíneas/métodos , COVID-19/diagnóstico , Separação Celular/métodos , Doenças Transmissíveis/virologia , Eritrócitos/virologia , Citometria de Fluxo/métodos , Humanos , Leucócitos/virologia , RNA Mensageiro/sangue , SARS-CoV-2/genéticaRESUMO
Glioblastoma stem cells (GSCs) resist current glioblastoma (GBM) therapies. GSCs rely highly on oxidative phosphorylation (OXPHOS), whose function requires mitochondrial translation. Here we explore the therapeutic potential of targeting mitochondrial translation and report the results of high-content screening with putative blockers of mitochondrial ribosomes. We identify the bacterial antibiotic quinupristin/dalfopristin (Q/D) as an effective suppressor of GSC growth. Q/D also decreases the clonogenicity of GSCs in vitro, consequently dysregulating the cell cycle and inducing apoptosis. Cryoelectron microscopy (cryo-EM) reveals that Q/D binds to the large mitoribosomal subunit, inhibiting mitochondrial protein synthesis and functionally dysregulating OXPHOS complexes. These data suggest that targeting mitochondrial translation could be explored to therapeutically suppress GSC growth in GBM and that Q/D could potentially be repurposed for cancer treatment.