RESUMEN
Peripheral immune cell infiltration into the brain is a prominent feature in aging and various neurodegenerative diseases such as Alzheimer's disease (AD). As AD progresses, CD8+ T cells infiltrate into the brain parenchyma, where they tightly associate with neurons and microglia. The functional properties of CD8+ T cells in the brain are largely unknown. To gain further insights into the putative functions of CD8+ T cells in the brain, we explored and compared the transcriptomic profile of CD8+ T cells isolated from the brain and blood of transgenic AD (APPswe/PSEN1dE9, line 85 [APP-PS1]) and age-matched wild-type (WT) mice. Brain CD8+ T cells of APP-PS1 and WT animals had similar transcriptomic profiles and substantially differed from blood circulating CD8+ T cells. The gene signature of brain CD8+ T cells identified them as tissue-resident memory (Trm) T cells. Gene Ontology enrichment and Kyoto Encyclopedia of Genes and Genomes pathway analysis on the significantly upregulated genes revealed overrepresentation of biological processes involved in IFN-ß signaling and the response to viral infections. Furthermore, brain CD8+ T cells of APP-PS1 and aged WT mice showed similar differentially regulated genes as brain Trm CD8+ T cells in mouse models with acute virus infection, chronic parasite infection, and tumor growth. In conclusion, our profiling of brain CD8+ T cells suggests that in AD, these cells exhibit similar adaptive immune responses as in other inflammatory diseases of the CNS, potentially opening the door for immunotherapy in AD.
Asunto(s)
Enfermedad de Alzheimer , Enfermedad de Alzheimer/metabolismo , Precursor de Proteína beta-Amiloide/genética , Precursor de Proteína beta-Amiloide/metabolismo , Animales , Encéfalo , Linfocitos T CD8-positivos , Modelos Animales de Enfermedad , Células T de Memoria , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Presenilina-1/genética , TranscriptomaRESUMEN
Chronic lymphocytic leukemia (CLL) is a heterogenous disease that is highly dependent on a cross talk of CLL cells with the microenvironment, in particular with T cells. T cells derived from CLL patients or murine CLL models are skewed to an antigen-experienced T-cell subset, indicating a certain degree of antitumor recognition, but they are also exhausted, preventing an effective antitumor immune response. Here we describe a novel mechanism of CLL tumor immune evasion that is independent of T-cell exhaustion, using B-cell-specific deletion of the transcription factor IRF4 (interferon regulatory factor 4) in Tcl-1 transgenic mice developing a murine CLL highly similar to the human disease. We show enhanced CLL disease progression in IRF4-deficient Tcl-1 tg mice, associated with a severe downregulation of genes involved in T-cell activation, including genes involved in antigen processing/presentation and T-cell costimulation, which massively reduced T-cell subset skewing and exhaustion. We found a strong analogy in the human disease, with inferior prognosis of CLL patients with low IRF4 expression in independent CLL patient cohorts, failed T-cell skewing to antigen-experienced subsets, decreased costimulation capacity, and downregulation of genes involved in T-cell activation. These results have therapeutic relevance because our findings on molecular mechanisms of immune privilege may be responsible for the failure of immune-therapeutic strategies in CLL and may lead to improved targeting in the future.
Asunto(s)
Linfocitos B/inmunología , Eliminación de Gen , Factores Reguladores del Interferón/genética , Leucemia Linfocítica Crónica de Células B/inmunología , Escape del Tumor , Animales , Linfocitos B/metabolismo , Regulación Leucémica de la Expresión Génica , Humanos , Factores Reguladores del Interferón/inmunología , Leucemia Linfocítica Crónica de Células B/genética , Ratones Endogámicos C57BL , Ratones SCID , Ratones TransgénicosRESUMEN
Chronic lymphocytic leukemia (CLL) outgrowth depends on signals from the microenvironment. We have previously found that in vitro reconstitution of this microenvironment induces specific variant isoforms of the adhesion molecule CD44, which confer human CLL with high affinity to hyaluronan (HA). Here, we determined the in vivo contribution of standard CD44 and its variants to leukemic B-cell homing and proliferation in Tcl1 transgenic mice with a B-cell-specific CD44 deficiency. In these mice, leukemia onset was delayed and leukemic infiltration of spleen, liver, and lungs, but not of bone marrow, was decreased. Competitive transplantation revealed that CLL homing to spleen and bone marrow required functional CD44. Notably, enrichment of CD44v6 variants particularly in spleen enhanced CLL engraftment and proliferation, along with increased HA binding. We recapitulated CD44v6 induction in the human disease and revealed the involvement of MAPK and NF-κB signaling upon CD40 ligand and B-cell receptor stimulation by in vitro inhibition experiments and chromatin immunoprecipitation assays. The investigation of downstream signaling after CD44v6-HA engagement uncovered the activation of extracellular signal-regulated kinase and p65. Consequently, anti-CD44v6 treatment reduced leukemic cell proliferation in vitro in human and mouse, confirming the general nature of the findings. In summary, we propose a CD44-NF-κB-CD44v6 circuit in CLL, allowing tumor cells to gain HA binding capacity and supporting their proliferation.
Asunto(s)
Proliferación Celular , Receptores de Hialuranos/metabolismo , Leucemia Linfocítica Crónica de Células B/metabolismo , Sistema de Señalización de MAP Quinasas , Proteínas de Neoplasias/metabolismo , Microambiente Tumoral , Animales , Humanos , Receptores de Hialuranos/genética , Ácido Hialurónico/genética , Ácido Hialurónico/metabolismo , Leucemia Linfocítica Crónica de Células B/genética , Leucemia Linfocítica Crónica de Células B/patología , Ratones , Ratones Transgénicos , FN-kappa B/genética , FN-kappa B/metabolismo , Proteínas de Neoplasias/genética , Receptores de Antígenos de Linfocitos B/genética , Receptores de Antígenos de Linfocitos B/metabolismo , Bazo/metabolismo , Bazo/patologíaRESUMEN
Signals from the tumor microenvironment promote the migration, survival, and proliferation of chronic lymphocytic leukemia (CLL) cells. Rho GTPases control various signaling pathways downstream of microenvironmental cues. Here, we analyze the function of Rac1 in the motility and proliferation of CLL cells. We found decreased transcription of the Rac guanine nucleotide exchange factors Tiam1 and Vav1 in unstimulated peripheral blood CLL cells with almost complete loss of Tiam1 but increased transcription of the potential Rac antagonist RhoH. Consistently, stimulation of CLL cells with the chemokine CXCL12 induced RhoA but not Rac1 activation, whereas chemokine-induced CLL cell motility was Rac1-independent. Coculture of CLL cells with activated T cells induced their activation and subsequent proliferation. Here, Tiam1 expression was induced in the malignant cells in line with increased Ki-67 and c-Myc expression. Rac1 or Tiam1 knockdown using siRNA or treatment with the Tiam1/Rac inhibitor NSC-23766 attenuated c-Myc transcription. Furthermore, treatment of CLL cells with NSC-23766 reduced their proliferation. Rac inhibition also antagonized the chemoresistance of activated CLL cells toward fludarabine. Collectively, our data suggest a dynamic regulation of Rac1 function in the CLL microenvironment. Rac inhibition could be of clinical use by selectively interfering with CLL cell proliferation and chemoresistance.
Asunto(s)
Antineoplásicos/farmacología , Proliferación Celular , Resistencia a Antineoplásicos/genética , Factores de Intercambio de Guanina Nucleótido/fisiología , Leucemia Linfocítica Crónica de Células B/genética , Leucemia Linfocítica Crónica de Células B/patología , Proteína de Unión al GTP rac1/fisiología , Aminoquinolinas/farmacología , Animales , Movimiento Celular/genética , Células Cultivadas , Regulación Leucémica de la Expresión Génica/efectos de los fármacos , Factores de Intercambio de Guanina Nucleótido/antagonistas & inhibidores , Humanos , Leucemia Linfocítica Crónica de Células B/tratamiento farmacológico , Ratones , Células 3T3 NIH , Pirimidinas/farmacología , ARN Interferente Pequeño/genética , Transducción de Señal/fisiología , Proteína 1 de Invasión e Inducción de Metástasis del Linfoma-T , Proteína de Unión al GTP rac1/antagonistas & inhibidoresRESUMEN
In chronic lymphocytic leukemia (B-CLL), aberrations along the p53 axis lead to decreased overall survival and therapy resistance. Recent studies identified microRNA-34a (miR-34a) as a major downstream target of p53. We monitored the expression of miR-34a during disease development in a murine B-CLL model. miR-34a was up-regulated more than 20-fold during the leukemic but not during the preleukemic phase. In the human system, B-CLL cells also had 4.6-fold higher miR-34a expression compared with B cells of healthy controls. In B-CLL cells of patients with p53 aberrations, miR-34a expression was consistently low. The broad distribution of miR-34a levels in p53 wild-type patients prompted us to study the correlation between single nucleotide polymorphism 309 (SNP309) in the intronic promoter of MDM2 and miR-34a expression. B-CLL cells of patients with the SNP309 GG genotype had significantly lower miR-34a expression levels compared with patients with the TT genotype (P = .002). Low miR-34a levels were able to predict shorter time to treatment (P = .003) and were associated with an abbreviated lymphocyte doubling time. Further, overexpression of miR-34a in primary B-CLL cells induced apoptosis. These findings suggest miR-34a as a possible therapeutic avenue and a sensitive indicator of the activity of the p53 axis in B-CLL.
Asunto(s)
Leucemia Linfocítica Crónica de Células B/genética , MicroARNs/genética , Polimorfismo de Nucleótido Simple , Proteínas Proto-Oncogénicas c-mdm2/genética , ARN Neoplásico/genética , Anciano , Anciano de 80 o más Años , Animales , Apoptosis , Estudios de Casos y Controles , Supervivencia sin Enfermedad , Femenino , Regulación Leucémica de la Expresión Génica , Genes p53 , Genotipo , Humanos , Intrones , Leucemia Experimental/etiología , Leucemia Experimental/genética , Leucemia Linfocítica Crónica de Células B/patología , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Persona de Mediana Edad , Regiones Promotoras Genéticas , Células Tumorales CultivadasAsunto(s)
Linfocitos T CD4-Positivos/inmunología , Linfocitos T CD4-Positivos/metabolismo , Antígenos CD40/inmunología , Evolución Clonal , Leucemia Linfocítica Crónica de Células B/inmunología , Leucemia Linfocítica Crónica de Células B/metabolismo , Receptores de Antígenos de Linfocitos B/metabolismo , Evolución Clonal/genética , Evolución Clonal/inmunología , Regiones Determinantes de Complementariedad/genética , Humanos , Cadenas Pesadas de Inmunoglobulina/genética , Leucemia Linfocítica Crónica de Células B/genética , Mutación , Receptores de Antígenos de Linfocitos B/genéticaRESUMEN
The clinical decisions made when treating patients with metastatic cancer require knowledge of the current tumor extent and response to therapy. For the majority of solid tumors, a response assessment, which is based on imaging, is used to guide these decisions. However, measuring serum protein biomarkers (i.e. tumor markers) may be of additional use. Furthermore, tumor markers exhibit variable specificity and sensitivity and cannot therefore be solely relied upon when making decisions regarding cancer treatment. Therefore, there is a clinical requirement for the identification of specific, sensitive and quantitative biomarkers. In recent years, circulating cell-free DNA (cfDNA) and mutation-specific circulating cell-free tumor DNA (cftDNA) have been identified as novel potential biomarkers. In the current study, cfDNA and cftDNA were compared using imaging-based staging and current tumor markers in 15 patients with metastatic colorectal, pancreatic or breast cancer. These patients were treated at the Third Medical Department of Paracelsus Medical University Salzburg (Austria). The results of the current study demonstrated a statistically significant correlation between the concentration changes of cfDNA and cftDNA and response to treatment, which was assessed by imaging. A correlation was not indicated with current clinically used tumor markers, including carcinoembryonic antigen, carcinoma antigen 15-3 and carcinoma antigen 19-9. The present study also indicated a correlation between cfDNA and cftDNA and the tumor volume of metastatic lesions, which was not observed with the current clinically used tumor markers. In conclusion, cfDNA and cftDNA exhibit the potential to become novel biomarkers for the response assessment following cancer treatment, and may serve as a tool for the estimation of tumor volume. The current study further supports the increasingly important role of cfDNA and cftDNA as new monitoring tools for use during cancer therapy.
RESUMEN
In the last decade, arsenic trioxide (As2O3) has been used very successfully to treat acute promyelocytic leukaemia (APL). Much less is known about the effectiveness of As2O3 in other neoplastic disorders. In this paper, we report that after 18 h in vitro treatment with 4 microM As2O3, 75+/-18% of B cell chronic lymphocytic leukaemia (B-CLL) cells (n=52) underwent apoptosis. It is important to note that B-CLL cells harboring a deletion of chromosome 17p13, which predisposes to fludarabine resistance and has been identified as an important negative predictor of clinical outcome, were more susceptible to As2O3 toxicity than cells lacking this aberration. Furthermore, unfavourable risk profiles such as unmutated IgVH status, high CD38 expression and prior treatment were associated with significantly higher sensitivity of B-CLL cells to As2O3. As2O3 also preferentially killed B-CLL cells compared to B cells from healthy age-matched controls. Molecular analysis revealed that basal superoxide dismutase activity was positively correlated with the pro-apoptotic activity of As2O3 pointing to a role of reactive oxygen species in cell death induction. The high activity of As2O3 in B-CLL cells from high-risk patients makes it a promising drug for high-risk and/or fludarabine-refractory B-CLL patients.
Asunto(s)
Apoptosis/efectos de los fármacos , Arsenicales/farmacología , Deleción Cromosómica , Cromosomas Humanos Par 17/genética , Leucemia Linfocítica Crónica de Células B/diagnóstico , Leucemia Linfocítica Crónica de Células B/patología , Óxidos/farmacología , Trióxido de Arsénico , Caspasas/metabolismo , Resistencia a Antineoplásicos/efectos de los fármacos , Activación Enzimática/efectos de los fármacos , Femenino , Depuradores de Radicales Libres/farmacología , Humanos , Leucemia Linfocítica Crónica de Células B/enzimología , Masculino , Estrés Oxidativo/efectos de los fármacos , Óxidos/toxicidad , Poli(ADP-Ribosa) Polimerasas/metabolismo , Pronóstico , Especies Reactivas de Oxígeno/metabolismo , Superóxido Dismutasa/metabolismo , Vidarabina/análogos & derivados , Vidarabina/farmacologíaRESUMEN
PURPOSE: Chronic lymphocytic leukemia (CLL) pathophysiology is characterized by a complex crosstalk of tumor cells with the microenvironment. In this regard, NF-κB signaling is considered as important signaling axis, with a variety of key molecules aberrantly expressed or genetically altered in patients with CLL. One of these molecules is BIRC3 (cIAP2), a central regulator of noncanonical NF-κB signaling that serves as pathway brake in the absence of microenvironmental signals. However, the contribution of BIRC3 expression to CLL progression and potential therapeutic implications is unknown.Experimental Design: We analyzed the role of BIRC3 mRNA expression in primary CLL samples in correlation to clinical datasets and used ex vivo assays to investigate functional consequences on the level of NF-κB signaling and downstream target gene regulation. For proof-of-principle experiments, we used genetically modified cell lines. RESULTS: We demonstrate that patients with CLL with low BIRC3 expression experience a more rapid disease progression, which coincides with an enhanced activation of canonical NF-κB target genes evidenced by an increased p65/Rel-B nuclear translocation ratio. As a consequence of enhanced canonical NF-κB target gene activation, both anti- and proapoptotic Bcl-2 family members were upregulated in BIRC3low primary CLL cells, which was associated with higher sensitivity to venetoclax treatment in vitro. CONCLUSIONS: Here we show the impact of BIRC3 expression in CLL disease progression in the absence of BIRC3 mutations and show altered canonical NF-κB target gene activation with therapeutic implications.
Asunto(s)
Proteína 3 que Contiene Repeticiones IAP de Baculovirus/metabolismo , Compuestos Bicíclicos Heterocíclicos con Puentes/farmacología , Resistencia a Antineoplásicos/genética , Leucemia Linfocítica Crónica de Células B/patología , FN-kappa B/metabolismo , Sulfonamidas/farmacología , Adulto , Anciano , Anciano de 80 o más Años , Animales , Apoptosis/genética , Proteína 3 que Contiene Repeticiones IAP de Baculovirus/genética , Compuestos Bicíclicos Heterocíclicos con Puentes/uso terapéutico , Línea Celular Tumoral , Núcleo Celular/metabolismo , Supervivencia Celular/genética , Técnicas de Cocultivo , Conjuntos de Datos como Asunto , Progresión de la Enfermedad , Femenino , Regulación Leucémica de la Expresión Génica , Técnicas de Silenciamiento del Gen , Humanos , Leucemia Linfocítica Crónica de Células B/tratamiento farmacológico , Leucemia Linfocítica Crónica de Células B/genética , Masculino , Ratones , Persona de Mediana Edad , Células 3T3 NIH , Prueba de Estudio Conceptual , Proteínas Proto-Oncogénicas c-bcl-2/metabolismo , Transducción de Señal/genética , Sulfonamidas/uso terapéutico , Resultado del Tratamiento , Regulación hacia ArribaRESUMEN
The TCL1 mouse model is widely used to study pathophysiology, clonal evolution, and drug sensitivity or resistance of chronic lymphocytic leukemia (CLL). By performing whole exome sequencing, we present the genetic landscape of primary tumors from TCL1 mice and of TCL1 tumors serially transplanted into wild-type recipients to mimic clonal evolution. We show that similar to CLL patients, mutations in mice are frequently subclonal and heterogenous among different primary TCL1 mice. We further describe that this molecular heterogeneity mirrors heterogenous disease characteristics such as organ infiltration or CLL dependent T cell skewing. Similar to human CLL, we further observed the occurrence of novel mutations and structural variations during clonal evolution and found plasticity in the expansion of B cell receptor specific subclones. Thus, our results uncover that the genetic complexity, pathway dependence and clonal dynamics in mouse CLL are in relevant agreement to human CLL, and they are important to consider in future research using the TCL1 mouse for studying CLL.
Asunto(s)
Evolución Clonal , Modelos Animales de Enfermedad , Secuenciación del Exoma/métodos , Heterogeneidad Genética , Leucemia Linfocítica Crónica de Células B/genética , Leucemia Linfocítica Crónica de Células B/patología , Proteínas Proto-Oncogénicas/fisiología , Animales , Progresión de la Enfermedad , Exoma , Humanos , Ratones , Ratones Transgénicos , MutaciónAsunto(s)
Leucemia Linfocítica Crónica de Células B/patología , Microambiente Tumoral , Linfocitos T CD4-Positivos/patología , Ligando de CD40/inmunología , División Celular , Separación Celular , Técnicas de Cocultivo , Humanos , Inmunofenotipificación , Activación de Linfocitos , Proteínas Recombinantes/inmunología , Proteínas Recombinantes/farmacología , Células Tumorales Cultivadas/patologíaRESUMEN
The proliferation of chronic lymphocytic leukemia (CLL) cells requires communication with the lymphoid organ microenvironment. Integrin-linked kinase (ILK) is a multifunctional intracellular adaptor protein that transmits extracellular signals to regulate malignant cell motility, metastasis, and cell-cycle progression, but is poorly characterized in hematologic malignancies. In this study, we investigated the role of ILK in the context of CLL and observed high ILK expression in patient samples, particularly in tumor cells harboring prognostic high-risk markers such as unmutated IGHV genes, high Zap70, or CD38 expression, or a signature of recent proliferation. We also found increased numbers of Ki67 (MKI67)-positive cells in regions of enhanced ILK expression in lymph nodes from CLL patients. Using coculture conditions mimicking the proliferative lymph node microenvironment, we detected a parallel induction of ILK and cyclin D1 (CCND1) expression in CLL cells that was dependent on the activation of NF-κB signaling by soluble TNFα. The newly synthesized ILK protein colocalized to centrosomal structures and was required for correct centrosome clustering and mitotic spindle organization. Furthermore, we established a mouse model of CLL in which B-cell-specific genetic ablation of ILK resulted in decelerated leukemia development due to reduced organ infiltration and proliferation of CLL cells. Collectively, our findings describe a TNFα-NF-κB-mediated mechanism by which ILK expression is induced in the lymph node microenvironment and propose that ILK promotes leukemogenesis by enabling CLL cells to cope with centrosomal defects acquired during malignant transformation. Cancer Res; 76(8); 2186-96. ©2016 AACR.
Asunto(s)
Leucemia Linfocítica Crónica de Células B/patología , Tejido Linfoide/enzimología , FN-kappa B/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Factor de Necrosis Tumoral alfa/metabolismo , Animales , Proliferación Celular , Humanos , Leucemia Linfocítica Crónica de Células B/enzimología , Leucemia Linfocítica Crónica de Células B/metabolismo , Tejido Linfoide/patología , Ratones , Ratones Transgénicos , Pronóstico , Proteínas Serina-Treonina Quinasas/genética , Transducción de SeñalRESUMEN
Chronic lymphocytic leukemia develops within a complex network driven by genetic mutations and microenvironmental interactions. Among the latter a complex interplay with the immune system is established by the clone. Next to a proposed recruitment of support from T and myeloid cells, potential anti-CLL immune reactions need to be subverted. By using TCL1 mice as a CLL model, we show that TCR-Vß7+ NK1.1+ T cells are overrepresented in this disease model and constitute a main subset of peripheral CD3+ cells with biased TCR usage, showing that these cells account for a major part for T cell skewing in TCL1 mice. Moreover, we show that overrepresentation is dependent on CD1d expression in TCL1 mice, implicating that these cells belong to a NKT-like cell fraction which are restricted to antigen presented by the MHC-like surface marker CD1d. Accordingly, we observed a high fraction of CD161+ cells within overrepresented T cells in CLL patients and we found downregulation of CD1d on the surface of CLL cells, both in TCL1 mice and patients. Finally, we show that in TCL1 mice, CD1d deficiency resulted in shortened overall survival. Our results point to an interaction between CLL and CD161+ T cells that may represent a novel therapeutic target for immune modulation.
Asunto(s)
Antígenos CD1d/metabolismo , Linfocitos T CD8-positivos/citología , Leucemia Linfocítica Crónica de Células B/metabolismo , Células T Asesinas Naturales/citología , Anciano , Anciano de 80 o más Años , Animales , Complejo CD3/metabolismo , Progresión de la Enfermedad , Femenino , Humanos , Leucemia Linfocítica Crónica de Células B/genética , Masculino , Ratones , Ratones Noqueados , Persona de Mediana Edad , Mutación , Subfamilia B de Receptores Similares a Lectina de Células NK/metabolismo , Receptores de Antígenos de Linfocitos T/metabolismoRESUMEN
Homing to distinct lymphoid organs enables chronic lymphocytic leukemia (CLL) cells to receive pro-survival and proliferative signals. Cytogenetic aberrations can significantly affect CLL cell compartmentalization. Trisomy 12 (tri12) defines a CLL subgroup with specific clinical features and increased levels of the negative prognostic marker CD49d, the α4-subunit of the integrin VLA-4, which is a key regulator of CLL cell homing to bone marrow (BM). Chemokine-induced inside-out VLA-4 activation, particularly via the CXCL12-CXCR4 axis, increases the arrest of various cell types on VCAM-1 presenting endothelium. Here, we demonstrate that high CD49d expression in tri12 CLL is accompanied by decreased CXCR4 expression. Dissecting functional consequences of these alterations, we observed that tri12 CLL cell homing to murine BM is not affected by CXCR4-CXCL12 blockage using AMD3100 or olaptesed pegol/NOX-A12. In line, CCL21-CCR7 rather than CXCL12-CXCR4 interactions triggered VLA-4-mediated arrests of tri12 CLL cells to VCAM-1 under blood flow conditions. Concordantly, in real-time kinetic analyses we found CCL21 but not CXCL12 being capable to induce inside-out VLA-4 conformational changes in this CLL subgroup. Our results provide novel insights into the peculiar clinico-biological behaviour of tri12 CLL and emphasize its specific chemokine and integrin utilization during pathophysiologically and therapeutically relevant interactions with the microenvironment.
Asunto(s)
Quimiocina CCL21/genética , Quimiocina CCL21/metabolismo , Quimiocina CXCL12/genética , Quimiocina CXCL12/metabolismo , Leucemia Linfocítica Crónica de Células B/genética , Receptores CXCR4/genética , Receptores CXCR4/metabolismo , Animales , Humanos , Ratones , Transducción de SeñalRESUMEN
Microenvironmental interactions are crucial for the survival and proliferation of chronic lymphocytic leukemia (CLL) cells. CD4+ T cells that express CD40 ligand (CD40L), along with other accessory immune and stromal cells within CLL lymph nodes, provide signals needed for activation and outgrowth of the tumor clone. Furthermore, correct positioning of CLL cells within lymphoid subcompartments is essential for the transmission of these supportive signals. Thereby, interstitial cell migration and adhesion events, influenced by activational stimuli, determine CLL cell localization. CD44 has been implicated in cell activation, migration, and tissue retention via binding to its extracellular matrix ligand hyaluronan (HA). In this study, we investigated the role of CD44-HA interactions for CLL positioning and interaction with supportive microenvironments in peripheral lymph nodes, focusing on its regulation via CD40L-dependent, T-cell-mediated activation of CLL cells. We found that hyaluronan triggered a robust CCL21-induced motility of resting CLL cells. However, CD40L stimulation promoted the firm, CD44-mediated adhesion of CLL cells to hyaluronan, antagonizing their motile behavior. N-linked glycosylations of CD44, particularly associated with the variant isoform CD44v6 after CD40L activation, seemed to facilitate hyaluronan recognition by CD44. We propose that the CD40L-CD40 signaling axis provides a stop signal to motile CLL cells within lymph node compartments by inducing high avidity CD44-HA adhesion. This might retain CLL cells close to T-cell stimuli and facilitate essential interactions with hyaluronan-bearing stromal cells, collectively promoting CLL cell proliferation and survival.
Asunto(s)
Antígenos CD40/inmunología , Quimiocina CCL21/inmunología , Ácido Hialurónico/metabolismo , Leucemia Linfocítica Crónica de Células B/inmunología , Antígenos CD40/metabolismo , Ligando de CD40/inmunología , Movimiento Celular/inmunología , Humanos , Ganglios Linfáticos/inmunología , Activación de Linfocitos/inmunología , Células Tumorales CultivadasRESUMEN
Chronic lymphocytic leukemia (CLL) has an incidence 4/1,00,000 people in the western world and is one of the first cancers reported to be associated with deregulated miRNA expression. microRNAs are small non coding RNAs that are important regulators of protein expression through binding to their untranslated 3'-UTR region. The miR-34 family was demonstrated to be induced by the tumor suppressor p53 and to elicit p53-like responses like senescence, cell cycle arrest and apoptosis depending on the cell type. We have shown in a recent paper that miR-34a is severely increased in the TCL1-mouse model of CLL. This finding was reflected in human CLL. Moreover, it is demonstrated that its expression is dependent on the presence of the SNP309 in the intronic promoter of the MDM2 gene. In addition, low miR-34a expression was associated with shorter time to treatment (log-rank p = 0.003) in CLL. When reintroduced into CLL cells, miR-34a was able to induce apoptosis. Interestingly, this was dependent on an intact p53 pathway. Here, we present data showing that knockdown of p53 in HCT-116 cells severely reduces miR-34a induced apoptosis. In conclusion, miR-34a is proposed as a marker for the activity of the p53 pathway in CLL.