RESUMO
Neurodegenerative diseases (ND) are characterized by progressive loss of neuronal function. Mechanisms of ND pathogenesis are incompletely understood, hampering the development of effective therapies. Langerhans cell histiocytosis (LCH) is an inflammatory neoplastic disorder caused by hematopoietic progenitors expressing mitogen-activated protein kinase (MAPK)-activating mutations that differentiate into senescent myeloid cells that drive lesion formation. Some individuals with LCH subsequently develop progressive and incurable neurodegeneration (LCH-ND). Here, we showed that LCH-ND was caused by myeloid cells that were clonal with peripheral LCH cells. Circulating BRAFV600E+ myeloid cells caused the breakdown of the blood-brain barrier (BBB), enhancing migration into the brain parenchyma where they differentiated into senescent, inflammatory CD11a+ macrophages that accumulated in the brainstem and cerebellum. Blocking MAPK activity and senescence programs reduced peripheral inflammation, brain parenchymal infiltration, neuroinflammation, neuronal damage and improved neurological outcome in preclinical LCH-ND. MAPK activation and senescence programs in circulating myeloid cells represent targetable mechanisms of LCH-ND.
Assuntos
Histiocitose de Células de Langerhans , Proteínas Proto-Oncogênicas B-raf , Humanos , Proteínas Proto-Oncogênicas B-raf/genética , Proteínas Proto-Oncogênicas B-raf/metabolismo , Histiocitose de Células de Langerhans/genética , Histiocitose de Células de Langerhans/patologia , Histiocitose de Células de Langerhans/terapia , Encéfalo/metabolismo , Células Mieloides/metabolismo , Diferenciação CelularRESUMO
Neurodegenerative diseases (ND) are characterized by progressive loss of neuronal function. Mechanisms of ND pathogenesis are incompletely understood, hampering the development of effective therapies. Langerhans cell histiocytosis (LCH) is an inflammatory neoplastic disorder caused by hematopoietic progenitors expressing MAPK activating mutations that differentiate into senescent myeloid cells that drive lesion formation. Some patients with LCH subsequently develop progressive and incurable neurodegeneration (LCH-ND). Here, we show that LCH-ND is caused by myeloid cells that are clonal with peripheral LCH cells. We discovered that circulating BRAF V600E + myeloid cells cause the breakdown of the blood-brain barrier (BBB), enhancing migration into the brain parenchyma where they differentiate into senescent, inflammatory CD11a + macrophages that accumulate in the brainstem and cerebellum. Blocking MAPK activity and senescence programs reduced parenchymal infiltration, neuroinflammation, neuronal damage and improved neurological outcome in preclinical LCH-ND. MAPK activation and senescence programs in circulating myeloid cells represent novel and targetable mechanisms of ND.
RESUMO
Hemophagocytic lymphohistiocytosis (HLH) is a syndrome characterized by pathologic immune activation in which prompt recognition and initiation of immune suppression is essential for survival. Children with HLH have many overlapping clinical features with critically ill children with sepsis and systemic inflammatory response syndrome (SIRS) in whom alternative therapies are indicated. To determine whether plasma biomarkers could differentiate HLH from other inflammatory conditions and to better define a core inflammatory signature of HLH, concentrations of inflammatory plasma proteins were compared in 40 patients with HLH to 47 pediatric patients with severe sepsis or SIRS. Fifteen of 135 analytes were significantly different in HLH plasma compared with SIRS/sepsis, including increased interferon-γ (IFN-γ)-regulated chemokines CXCL9, CXCL10, and CXCL11. Furthermore, a 2-analyte plasma protein classifier including CXCL9 and interleukin-6 was able to differentiate HLH from SIRS/sepsis. Gene expression in CD8+ T cells and activated monocytes from blood were also enriched for IFN-γ pathway signatures in peripheral blood cells from patients with HLH compared with SIRS/sepsis. This study identifies differential expression of inflammatory proteins as a diagnostic strategy to identify critically ill children with HLH, and comprehensive unbiased analysis of inflammatory plasma proteins and global gene expression demonstrates that IFN-γ signaling is uniquely elevated in HLH. In addition to demonstrating the ability of diagnostic criteria for HLH and sepsis or SIRS to identify groups with distinct inflammatory patterns, results from this study support the potential for prospective evaluation of inflammatory biomarkers to aid in diagnosis of and optimizing therapeutic strategies for children with distinctive hyperinflammatory syndromes.
Assuntos
Linfo-Histiocitose Hemofagocítica , Sepse , Criança , Diagnóstico Diferencial , Humanos , Interferon gama , Linfo-Histiocitose Hemofagocítica/diagnóstico , Proteoma , Sepse/diagnóstico , Síndrome de Resposta Inflamatória Sistêmica/diagnósticoRESUMO
Hodgkin lymphoma (HL) histopathology is characterized by rare malignant Reed-Sternberg cells among an inflammatory infiltrate. We hypothesized that characteristics of inflammation in pediatric HL lesions would be reflected by the levels of inflammatory cytokines or chemokines in pre-therapy plasma of children with HL. The study objectives were to better define the inflammatory pre-therapy plasma proteome and identify plasma biomarkers associated with extent of disease and clinical outcomes in pediatric HL. Pre-therapy plasma samples were obtained from pediatric subjects with newly diagnosed HL and healthy pediatric controls. Plasma concentrations of 135 cytokines/chemokines were measured with the Luminex platform. Associations between protein concentration and disease characteristics were determined using multivariate permutation tests with false discovery control. Fifty-six subjects with HL (mean age: 13 years, range 3-18) and 47 controls were analyzed. The cytokine/chemokine profiles of subjects with HL were distinct from controls, and unique cytokines/chemokines were associated with high-risk disease (IL-10, TNF-α, IFN-γ, IL-8) and slow early response (CCL13, IFN-λ1, IL-8). TNFSF10 was significantly elevated among those who ultimately relapsed and was significantly associated with worse event-free survival. These biomarkers could be incorporated into biologically based risk stratification to optimize outcomes and minimize toxicities in pediatric HL.
RESUMO
Cytokine storm syndromes (CSS) are severe hyperinflammatory conditions characterized by excessive immune system activation leading to organ damage and death. Hemophagocytic lymphohistiocytosis (HLH), a disease often associated with inherited defects in cell-mediated cytotoxicity, serves as a prototypical CSS for which the 5-year survival is only 60%. Frontline therapy for HLH consists of the glucocorticoid dexamethasone (DEX) and the chemotherapeutic agent etoposide. Many patients, however, are refractory to this treatment or relapse after an initial response. Notably, many cytokines that are elevated in HLH activate the JAK/STAT pathway, and the JAK1/2 inhibitor ruxolitinib (RUX) has shown efficacy in murine HLH models and humans with refractory disease. We recently reported that cytokine-induced JAK/STAT signaling mediates DEX resistance in T cell acute lymphoblastic leukemia (T-ALL) cells, and that this could be effectively reversed by RUX. On the basis of these findings, we hypothesized that cytokine-mediated JAK/STAT signaling might similarly contribute to DEX resistance in HLH, and that RUX treatment would overcome this phenomenon. Using ex vivo assays, a murine model of HLH, and primary patient samples, we demonstrate that the hypercytokinemia of HLH reduces the apoptotic potential of CD8 T cells leading to relative DEX resistance. Upon exposure to RUX, this apoptotic potential is restored, thereby sensitizing CD8 T cells to DEX-induced apoptosis in vitro and significantly reducing tissue immunopathology and HLH disease manifestations in vivo. Our findings provide rationale for combining DEX and RUX to enhance the lymphotoxic effects of DEX and thus improve the outcomes for patients with HLH and related CSS.
Assuntos
Apoptose/efeitos dos fármacos , Linfócitos T CD8-Positivos/efeitos dos fármacos , Síndrome da Liberação de Citocina/tratamento farmacológico , Dexametasona/uso terapêutico , Inibidores de Janus Quinases/uso terapêutico , Linfo-Histiocitose Hemofagocítica/tratamento farmacológico , Pirazóis/uso terapêutico , Transdução de Sinais/efeitos dos fármacos , Animais , Linfócitos T CD8-Positivos/imunologia , Síndrome da Liberação de Citocina/etiologia , Síndrome da Liberação de Citocina/fisiopatologia , Citocinas/fisiologia , Dexametasona/administração & dosagem , Dexametasona/farmacologia , Modelos Animais de Doenças , Resistência a Medicamentos/efeitos dos fármacos , Quimioterapia Combinada , Humanos , Interleucina-2/farmacologia , Inibidores de Janus Quinases/administração & dosagem , Inibidores de Janus Quinases/farmacologia , Janus Quinases , Coriomeningite Linfocítica/complicações , Coriomeningite Linfocítica/fisiopatologia , Linfo-Histiocitose Hemofagocítica/complicações , Linfo-Histiocitose Hemofagocítica/enzimologia , Linfo-Histiocitose Hemofagocítica/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Nitrilas , Perforina/deficiência , Pirazóis/administração & dosagem , Pirazóis/farmacologia , Pirimidinas , Fator de Transcrição STAT5/fisiologia , Organismos Livres de Patógenos EspecíficosRESUMO
Accurate and high-throughput technologies are needed for identification of new therapeutic targets and for optimizing therapy in inflammatory bowel disease. Our aim was to assess multi-analyte protein-based assays of cytokines/chemokines using Luminex technology. We have reported that Luminex-based profiling was useful in assessing response to L-arginine therapy in the mouse model of dextran sulfate sodium colitis. Therefore, we studied prospectively collected samples from ulcerative colitis (UC) patients and control subjects. Serum, colon biopsies, and clinical information were obtained from subjects undergoing colonoscopy for evaluation of UC or for non-UC indications. In total, 38 normal controls and 137 UC cases completed the study. Histologic disease severity and the Mayo Disease Activity Index (DAI) were assessed. Serum and colonic tissue cytokine/chemokine profiles were measured by Luminex-based multiplex testing of 42 analytes. Only eotaxin-1 and G-CSF were increased in serum of patients with histologically active UC vs. controls. While 13 cytokines/chemokines were increased in active UC vs. controls in tissues, only eotaxin-1 was increased in all levels of active disease in both serum and tissue. In tissues, eotaxin-1 correlated with the DAI and with eosinophil counts. Increased eotaxin-1 levels were confirmed by real-time PCR. Tissue eotaxin-1 levels were also increased in experimental murine colitis induced by dextran sulfate sodium, oxazolone, or Citrobacter rodentium, but not in murine Helicobacter pylori infection. Our data implicate eotaxin-1 as an etiologic factor and therapeutic target in UC, and indicate that Luminex-based assays may be useful to assess IBD pathogenesis and to select patients for anti-cytokine/chemokine therapies.
Assuntos
Quimiocina CCL11/metabolismo , Colite Ulcerativa/metabolismo , Adulto , Animais , Colite Ulcerativa/sangue , Colite Ulcerativa/induzido quimicamente , Feminino , Gastrite/sangue , Gastrite/metabolismo , Gastrite/microbiologia , Helicobacter pylori/patogenicidade , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Pessoa de Meia-Idade , Oxazolona/toxicidade , Estudos ProspectivosRESUMO
L-Arginine (L-Arg) is a semiessential amino acid that has altered availability in human ulcerative colitis (UC), a form of inflammatory bowel disease, and is beneficial in murine colitis induced by dextran sulfate sodium (DSS), a model with similarity to UC. We assessed the role of cationic amino acid transporter 2 (CAT2), the inducible transporter of L-Arg, in DSS colitis. Expression of CAT2 was upregulated in tissues from colitic mice and localized predominantly to colonic macrophages. CAT2-deficient (CAT2-/-) mice exposed to DSS exhibited worsening of survival, body weight loss, colon weight, and histological injury. These effects were associated with increased serum L-Arg and decreased tissue L-Arg uptake and inducible nitric oxide synthase protein expression. Clinical benefits of L-Arg supplementation in wild-type mice were lost in CAT2-/- mice. There was increased infiltration of macrophages, dendritic cells, granulocytes, and T cells in colitic CAT2-/- compared with wild-type mice. Cytokine profiling revealed increases in proinflammatory granulocyte colony-stimulating factor, macrophage inflammatory protein-1α, IL-15, and regulated and normal T cell-expressed and -secreted and a shift from an IFN-γ- to an IL-17-predominant T cell response, as well as an increase in IL-13, in tissues from colitic CAT2-/- mice. However, there were no increases in other T helper cell type 2 cytokines, nor was there a global increase in macrophage-derived proinflammatory cytokines. The increase in IL-17 derived from both CD4 and γδ T cells and was associated with colonic IL-6 expression. Thus CAT2 plays an important role in controlling inflammation and IL-17 activation in an injury model of colitis, and impaired L-Arg availability may contribute to UC pathogenesis.
Assuntos
Transportador 2 de Aminoácidos Catiônicos/deficiência , Colite/induzido quimicamente , Colite/imunologia , Sulfato de Dextrana , Interleucina-17/metabolismo , Linfócitos T/imunologia , Animais , Arginina/metabolismo , Transportador 2 de Aminoácidos Catiônicos/genética , Transportador 2 de Aminoácidos Catiônicos/fisiologia , Colite/fisiopatologia , Interleucina-17/genética , Interleucina-23/genética , Interleucina-6/genética , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , RNA Mensageiro/análise , Regulação para CimaRESUMO
Inflammatory bowel disease (IBD), consisting of Crohn's disease and ulcerative colitis (UC), results in substantial morbidity and is difficult to treat. New strategies for adjunct therapies are needed. One candidate is the semi-essential amino acid, L-arginine (L-Arg), a complementary medicine purported to be an enhancer of immunity and vitality in the lay media. Using dextran sulfate sodium (DSS) as a murine colonic injury and repair model with similarities to human UC, we assessed the effect of L-Arg, as DSS induced increases in colonic expression of the y(+) cationic amino acid transporter 2 (CAT2) and L-Arg uptake. L-Arg supplementation improved the clinical parameters of survival, body weight loss, and colon weight, and reduced colonic permeability and the number of myeloperoxidase-positive neutrophils in DSS colitis. Luminex-based multi-analyte profiling demonstrated that there was a marked reduction in proinflammatory cytokine and chemokine expression with L-Arg treatment. Genomic analysis by microarray demonstrated that DSS-treated mice supplemented with L-Arg clustered more closely with mice not exposed to DSS than to those receiving DSS alone, and revealed that multiple genes that were upregulated or downregulated with DSS alone exhibited normalization of expression with L-Arg supplementation. Additionally, L-Arg treatment of mice with DSS colitis resulted in increased ex vivo migration of colonic epithelial cells, suggestive of increased capacity for wound repair. Because CAT2 induction was sustained during L-Arg treatment and inducible nitric oxide (NO) synthase (iNOS) requires uptake of L-Arg for generation of NO, we tested the effect of L-Arg in iNOS(-/-) mice and found that its benefits in DSS colitis were eliminated. These preclinical studies indicate that L-Arg supplementation could be a potential therapy for IBD, and that one mechanism of action may be functional enhancement of iNOS activity.
Assuntos
Arginina/farmacologia , Arginina/farmacocinética , Colite Ulcerativa/induzido quimicamente , Colite Ulcerativa/tratamento farmacológico , Sulfato de Dextrana/toxicidade , Regulação da Expressão Gênica/efeitos dos fármacos , Aminoácidos/sangue , Aminoácidos/metabolismo , Animais , Arginina/uso terapêutico , Western Blotting , Transportador 2 de Aminoácidos Catiônicos/metabolismo , Movimento Celular/efeitos dos fármacos , Quimiocinas/metabolismo , Colite Ulcerativa/patologia , Citocinas/metabolismo , Primers do DNA/genética , Suplementos Nutricionais , Células Epiteliais/efeitos dos fármacos , Regulação da Expressão Gênica/fisiologia , Imuno-Histoquímica , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Análise em Microsséries , Neutrófilos/efeitos dos fármacos , Óxido Nítrico Sintase Tipo II/genética , Tamanho do Órgão/efeitos dos fármacos , Permeabilidade/efeitos dos fármacos , Redução de Peso/efeitos dos fármacosRESUMO
Recent identification of intestinal epithelial stem cell (ISC) markers and development of ISC reporter mice permit visualization and isolation of regenerating ISCs after radiation to define their functional and molecular phenotypes. Previous studies in uninjured intestine of Sox9-EGFP reporter mice demonstrate that ISCs express low levels of Sox9-EGFP (Sox9-EGFP Low), whereas enteroendocrine cells (EEC) express high levels of Sox9-EGFP (Sox9-EGFP High). We hypothesized that Sox9-EGFP Low ISCs would expand after radiation, exhibit enhanced proliferative capacities, and adopt a distinct gene expression profile associated with rapid proliferation. Sox9-EGFP mice were given 14 Gy abdominal radiation and studied between days 3 and 9 postradiation. Radiation-induced changes in number, growth, and transcriptome of the different Sox9-EGFP cell populations were determined by histology, flow cytometry, in vitro culture assays, and microarray. Microarray confirmed that nonirradiated Sox9-EGFP Low cells are enriched for Lgr5 mRNA and mRNAs enriched in Lgr5-ISCs and identified additional putative ISC markers. Sox9-EGFP High cells were enriched for EEC markers, as well as Bmi1 and Hopx, which are putative markers of quiescent ISCs. Irradiation caused complete crypt loss, followed by expansion and hyperproliferation of Sox9-EGFP Low cells. From nonirradiated intestine, only Sox9-EGFP Low cells exhibited ISC characteristics of forming organoids in culture, whereas during regeneration both Sox9-EGFP Low and High cells formed organoids. Microarray demonstrated that regenerating Sox9-EGFP High cells exhibited transcriptomic changes linked to p53-signaling and ISC-like functions including DNA repair and reduced oxidative metabolism. These findings support a model in which Sox9-EGFP Low cells represent active ISCs, Sox9-EGFP High cells contain radiation-activatable cells with ISC characteristics, and both participate in crypt regeneration.
Assuntos
Proteínas de Fluorescência Verde/biossíntese , Jejuno/efeitos da radiação , Fatores de Transcrição SOX9/biossíntese , Células-Tronco/efeitos da radiação , Animais , Proliferação de Células/efeitos da radiação , Células Cultivadas , Expressão Gênica/efeitos da radiação , Proteínas de Homeodomínio/biossíntese , Jejuno/metabolismo , Camundongos , Camundongos Transgênicos , Proteínas Nucleares/biossíntese , Complexo Repressor Polycomb 1 , Proteínas Proto-Oncogênicas/biossíntese , Receptores Acoplados a Proteínas G/biossíntese , Regeneração/efeitos da radiação , Proteínas Repressoras/biossínteseRESUMO
Once acquired, Helicobacter pylori infection is lifelong due to an inadequate innate and adaptive immune response. Our previous studies indicate that interactions among the various pathways of arginine metabolism in the host are critical determinants of outcomes following infection. Cationic amino acid transporter 2 (CAT2) is essential for transport of L-arginine (L-Arg) into monocytic immune cells during H. pylori infection. Once within the cell, this amino acid is utilized by opposing pathways that lead to elaboration of either bactericidal nitric oxide (NO) produced from inducible NO synthase (iNOS), or hydrogen peroxide, which causes macrophage apoptosis, via arginase and the polyamine pathway. Because of its central role in controlling L-Arg availability in macrophages, we investigated the importance of CAT2 in vivo during H. pylori infection. CAT2(-/-) mice infected for 4 months exhibited decreased gastritis and increased levels of colonization compared to wild type mice. We observed suppression of gastric macrophage levels, macrophage expression of iNOS, dendritic cell activation, and expression of granulocyte-colony stimulating factor in CAT2(-/-) mice suggesting that CAT2 is involved in enhancing the innate immune response. In addition, cytokine expression in CAT2(-/-) mice was altered from an antimicrobial Th1 response to a Th2 response, indicating that the transporter has downstream effects on adaptive immunity as well. These findings demonstrate that CAT2 is an important regulator of the immune response during H. pylori infection.
Assuntos
Sistemas de Transporte de Aminoácidos Básicos/metabolismo , Infecções por Helicobacter/imunologia , Infecções por Helicobacter/microbiologia , Helicobacter pylori/imunologia , Imunidade Inata/imunologia , Doença Aguda , Animais , Contagem de Células , Doença Crônica , Contagem de Colônia Microbiana , Células Dendríticas/patologia , Gastrite/imunologia , Gastrite/microbiologia , Gastrite/patologia , Infecções por Helicobacter/patologia , Helicobacter pylori/crescimento & desenvolvimento , Interleucina-12/metabolismo , Macrófagos/enzimologia , Macrófagos/patologia , Camundongos , Óxido Nítrico Sintase Tipo II/metabolismo , Estômago/microbiologia , Estômago/patologia , Células Th1/imunologia , Células Th2/imunologiaRESUMO
BACKGROUND: Obesity induced by high fat (HF) diet is associated with inflammation which contributes to development of insulin resistance. Most prior studies have focused on adipose tissue as the source of obesity-associated inflammation. Increasing evidence links intestinal bacteria to development of diet-induced obesity (DIO). This study tested the hypothesis that HF western diet and gut bacteria interact to promote intestinal inflammation, which contributes to the progression of obesity and insulin resistance. METHODOLOGY/PRINCIPAL FINDINGS: Conventionally raised specific-pathogen free (CONV) and germ-free (GF) mice were given HF or low fat (LF) diet for 2-16 weeks. Body weight and adiposity were measured. Intestinal inflammation was assessed by evaluation of TNF-alpha mRNA and activation of a NF-kappaB(EGFP) reporter gene. In CONV but not GF mice, HF diet induced increases in body weight and adiposity. HF diet induced ileal TNF-alpha mRNA in CONV but not GF mice and this increase preceded obesity and strongly and significantly correlated with diet induced weight gain, adiposity, plasma insulin and glucose. In CONV mice HF diet also resulted in activation of NF-kappaB(EGFP) in epithelial cells, immune cells and endothelial cells of small intestine. Further experiments demonstrated that fecal slurries from CONV mice fed HF diet are sufficient to activate NF-kappaB(EGFP) in GF NF-kappaB(EGFP) mice. CONCLUSIONS/SIGNIFICANCE: Bacteria and HF diet interact to promote proinflammatory changes in the small intestine, which precede weight gain and obesity and show strong and significant associations with progression of obesity and development of insulin resistance. To our knowledge, this is the first evidence that intestinal inflammation is an early consequence of HF diet which may contribute to obesity and associated insulin resistance. Interventions which limit intestinal inflammation induced by HF diet and bacteria may protect against obesity and insulin resistance.
Assuntos
Bactérias , Gorduras na Dieta , Resistência à Insulina , Intestinos/microbiologia , Obesidade/complicações , Tecido Adiposo/metabolismo , Animais , Biomarcadores/metabolismo , Peso Corporal , Regulação da Expressão Gênica , Inflamação/complicações , Inflamação/metabolismo , Inflamação/microbiologia , Inflamação/patologia , Mucosa Intestinal/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , NF-kappa B/metabolismo , Obesidade/metabolismo , Obesidade/microbiologia , Obesidade/patologia , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Organismos Livres de Patógenos Específicos , Fator de Necrose Tumoral alfa/genéticaRESUMO
Epigenetic in vitro and in vivo studies suggest that suppressor of cytokine signaling-2 (SOCS2) may normally limit tumorigenesis in the intestine; however, this theory has not been directly tested. We hypothesized that SOCS2 deficiency promotes spontaneous intestinal tumorigenesis in Apc(Min/+) mice. Therefore, we quantified tumor number, size, and load in the small intestine and colon using SOCS2(+/+)/Apc(Min/+), SOCS2(+/-)/Apc(Min/+), and SOCS2(-/-)/Apc(Min/+) mice and assayed hematocrit as an indirect marker of disease severity. Biochemical and histological assays were used to assess mechanisms. Heterozygous and homozygous disruption of SOCS2 alleles promoted 166 and 441% increases in tumor load in the small intestine, respectively, accelerated development of colon tumors, and caused severe anemia. SOCS2 deletion promoted significant increases in intestinal insulin-like growth factor-I mRNA but did not affect plasma insulin-like growth factor-I. Western blots and immunohistochemical analysis demonstrated that tumor and nontumor intestinal tissue of SOCS2(-/-)/Apc(Min/+) mice had increased serine 727 phosphorylation of signal transducer and activator of transcription 3 compared with SOCS2(+/+)/Apc(Min/+) mice. Moreover, electromobility shift assays showed that SOCS2 deletion did not alter signal transducer and activator of transcription 3 DNA binding. However, tumors and small intestine from SOCS2(-/-)/Apc(Min/+) showed dramatic increases in activator protein-1 (AP-1) DNA binding, and SOCS2 overexpression in vitro reduced levels of AP-1. These studies indicate that SOCS2 deletion promotes the spontaneous development of intestinal tumors driven by mutations in the adenomatous polyposis coli/beta-catenin pathway and activates AP-1. Therefore, reduced expression or epigenetic silencing of SOCS2 may serve as a useful biomarker for colorectal cancer risk.
Assuntos
Regulação Neoplásica da Expressão Gênica , Genes APC , Proteínas Supressoras da Sinalização de Citocina/metabolismo , Fator de Transcrição AP-1/metabolismo , Alelos , Animais , Biomarcadores Tumorais , Epigênese Genética , Deleção de Genes , Inativação Gênica , Homozigoto , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos TransgênicosRESUMO
Reduced apoptosis of crypt stem/progenitor cells and elevated insulin and IGFs are linked to colon cancer risk. Insulin receptor substrate-1 (IRS-1) mediates the actions of insulin, IGF-I, and IGF-II, but the role of endogenous IRS-1 in crypt apoptosis and cancer is undefined. Using IRS-1(-/-), IRS-1(+/-), and IRS-1(+/+) mice, we tested the hypothesis that reduced IRS-1 expression increases apoptosis of intestinal crypt cells and protects against Apc(min/+) (Min)/beta-catenin-driven intestinal tumors. Expression of Sox9, a transcriptional target of Tcf/beta-catenin and putative biomarker of crypt stem cells, was assessed in intestine of different IRS-1 genotypes and cell lines. Irradiation-induced apoptosis was significantly increased in the crypts and crypt stem cell region of IRS-1-deficient mice. Tumor load was significantly reduced by 31.2 +/- 14.6% in IRS-1(+/-)/Min and by 64.1 +/- 7.6% in IRS-1(-/-)/Min mice, with more prominent reductions in tumor number than size. Compared with IRS-1(+/+)/Min, IRS-1(-/-)/Min mice had fewer Sox9-positive cells in intestinal crypts and reduced Sox9 mRNA in intestine. IRS-1 overexpression increased Sox9 expression in an intestinal epithelial cell line. We conclude that even small reductions in endogenous IRS-1 increase apoptosis of crypt stem or progenitor cells, protect against beta-catenin-driven intestinal tumors, and reduce Sox9, a Tcf/beta-catenin target and putative stem/progenitor cell biomarker.