RESUMEN
Precursor B cell acute lymphoblastic leukemia (BCP-ALL) constitutes the leading cause of cancer-related death in children. While chromosomal alterations contribute to BCP-ALL pathogenesis, they are insufficient for leukemia development. Epidemiological data and evidence from a mouse model suggest that immune responses to infections may trigger the emergence of leukemia, but the mechanisms remain unclear. Here, we show that T helper (Th) cells from bone marrow of pediatric BCP-ALL patients can be attracted and activated by autologous BCP-ALL cells. Bone-marrow Th cells supportively interacted with BCP-ALL cells, inducing upregulation of important surface molecules and BCP-ALL cell proliferation. These Th cells displayed a Th1-like phenotype and produced high levels of IFN-γ. IFN-γ was responsible for the upregulation of CD38 in BCP-ALL cells, a molecule which we found to be associated with early relapse, and accountable for the production of IP-10, a chemokine involved in BCP-ALL migration and drug resistance. Thus, our data provide mechanistic support for an involvement of Th cell immune responses in the propagation of BCP-ALL and suggest that BCP-ALL cell-supportive Th cells may serve as therapeutic target.
Asunto(s)
Linfocitos B/inmunología , Médula Ósea/inmunología , Proliferación Celular/fisiología , Leucemia-Linfoma Linfoblástico de Células Precursoras B/inmunología , Leucemia-Linfoma Linfoblástico de Células Precursoras/inmunología , Linfocitos T Colaboradores-Inductores/inmunología , Células TH1/inmunología , ADP-Ribosil Ciclasa 1/metabolismo , Linfocitos B/metabolismo , Médula Ósea/metabolismo , Células de la Médula Ósea/inmunología , Células de la Médula Ósea/metabolismo , Humanos , Interferón gamma/metabolismo , Fenotipo , Leucemia-Linfoma Linfoblástico de Células Precursoras B/metabolismo , Leucemia-Linfoma Linfoblástico de Células Precursoras/metabolismo , Linfocitos T Colaboradores-Inductores/metabolismo , Células TH1/metabolismo , Regulación hacia Arriba/inmunologíaRESUMEN
Burkitt's lymphoma (BL) is the most common childhood cancer in equatorial Africa, and is endemic to areas where people are chronically co-infected with Epstein-Barr virus (EBV) and the malaria pathogen Plasmodium falciparum. The contribution of these pathogens in the oncogenic process remains poorly understood. We showed earlier that the activation of Toll-like receptor (TLR) 9 by hemozoin, a disposal product formed from the digestion of blood by P. falciparum, suppresses the lytic reactivation of EBV in BL cells. EBV lytic reactivation is regulated by the expression of transcription factor Zta (ZEBRA), encoded by the EBV gene BZLF1. Here, we explore in the BL cell line Akata, the mechanism involved in repression by TLR9 of expression of BZLF1. We show that BZLF1 repression is mediated upon TLR9 engagement by a mechanism that is largely independent of de novo protein synthesis. By CRISPR/Cas9-induced inactivation of TLR9, MyD88, IRAK4 and IRAK1 we confirm that BZLF1 repression is dependent on functional TLR9 and MyD88 signaling, and identify IRAK4 as an essential element for TLR9-induced repression of BZLF1 expression upon BCR cross-linking. Our results unprecedentedly show that TLR9-mediated inhibition of lytic EBV is largely independent of new protein synthesis and demonstrate the central roles of MyD88 and IRAK4 in this process contributing to EBV's persistence in the host's B-cell pool.
Asunto(s)
Linfoma de Burkitt/patología , Herpesvirus Humano 4/genética , Quinasas Asociadas a Receptores de Interleucina-1/fisiología , Receptor Toll-Like 9/fisiología , Transactivadores/genética , Linfoma de Burkitt/virología , Línea Celular Tumoral , Repeticiones Palindrómicas Cortas Agrupadas y Regularmente Espaciadas , Herpesvirus Humano 4/fisiología , Humanos , Quinasas Asociadas a Receptores de Interleucina-1/metabolismo , Factor 88 de Diferenciación Mieloide/metabolismo , Activación ViralRESUMEN
Primary infection of the immunocompromised host with the oncovirus Epstein-Barr virus (EBV) that targets mainly B-cells is associated with an increased risk for EBV-associated tumors. The early events subsequent to primary infection with potential for B-cell transformation are poorly studied. Here, we modeled in vitro the primary infection by using B-cells isolated from tonsils, the portal of entry of EBV, since species specificity of EBV hampers modeling in experimental animals. Increasing evidence indicates that the host DNA damage response (DDR) can influence and be influenced by EBV infection. Thus, we inoculated tonsillar B-cells (TBCs) with EBV-B95.8 and investigated cell proliferation and the DDR during the first 96 hours thereafter. We identified for the first time that EBV infection of TBCs induces a period of hyperproliferation 48-96 hours post infection characterized by the activation of ataxia telangiectasia and Rad3-releated (ATR) and checkpoint kinase-1 (Chk1). Whereas inhibition of Chk1 did not affect B-cell transformation, the specific inhibition of ATR robustly decreased the transformation efficiency of EBV. Our results suggest that activation of ATR is key for EBV-induced B-cell transformation. Thus, targeting the interaction between ATR/Chk1 and EBV could offer new options for the treatment of EBV-associated malignancies.
Asunto(s)
Linfocitos B/virología , Transformación Celular Viral , Quinasa 1 Reguladora del Ciclo Celular (Checkpoint 1)/metabolismo , Infecciones por Virus de Epstein-Barr/virología , Herpesvirus Humano 4/patogenicidad , Tonsila Palatina/enzimología , Tonsila Palatina/virología , Antígenos CD19/metabolismo , Proteínas de la Ataxia Telangiectasia Mutada/análisis , Proteínas de la Ataxia Telangiectasia Mutada/metabolismo , Linfocitos B/efectos de los fármacos , Linfocitos B/enzimología , Linfocitos B/inmunología , Ligando de CD40/metabolismo , Proliferación Celular , Células Cultivadas , Quinasa 1 Reguladora del Ciclo Celular (Checkpoint 1)/análisis , Daño del ADN , Reparación del ADN , Activación Enzimática , Infecciones por Virus de Epstein-Barr/enzimología , Infecciones por Virus de Epstein-Barr/inmunología , Infecciones por Virus de Epstein-Barr/patología , Herpesvirus Humano 4/inmunología , Interacciones Huésped-Patógeno , Humanos , Tonsila Palatina/efectos de los fármacos , Tonsila Palatina/inmunología , Inhibidores de Proteínas Quinasas/farmacología , Transducción de Señal , Factores de TiempoRESUMEN
Langerhans cell histiocytosis (LCH) is a rare disease caused by the clonal accumulation of dendritic Langerhans cells, which is often accompanied by osteolytic lesions. It has been reported that osteoclast-like cells play a major role in the pathogenic bone destruction seen in patients with LCH and these cells are postulated to originate from the fusion of DCs. However, due to the lack of reliable animal models the pathogenesis of LCH is still poorly understood. In this study, we have established a mouse model of histiocytosis- recapitulating human disease for osteolytic lesions seen in LCH patients. At 12 weeks after birth, severe bone lesions were observed in our multisystem histiocytosis (Mushi) model, when CD8α conventional dendritic cells (DCs) are transformed (MuTuDC) and accumulate. Most importantly, our study demonstrates that bone loss in LCH can be accounted for the transdifferentiation of MuTuDCs into functional osteoclasts both in vivo and in vitro. Moreover, we have shown that injected MuTuDCs reverse the osteopetrotic phenotype of oc/oc mice in vivo. In conclusion, our results support a crucial role of DCs in bone lesions in histiocytosis patients. Furthermore, our new model of LCH based on adoptive transfer of MuTuDC lines, leading to bone lesions within 1-2 weeks, will be an important tool for investigating the pathophysiology of this disease and ultimately for evaluating the potential of anti-resorptive drugs for the treatment of bone lesions.