RESUMEN
Caspase-8 is the initiator caspase of extrinsic apoptosis1,2 and inhibits necroptosis mediated by RIPK3 and MLKL. Accordingly, caspase-8 deficiency in mice causes embryonic lethality3, which can be rescued by deletion of either Ripk3 or Mlkl4-6. Here we show that the expression of enzymatically inactive CASP8(C362S) causes embryonic lethality in mice by inducing necroptosis and pyroptosis. Similar to Casp8-/- mice3,7, Casp8C362S/C362S mouse embryos died after endothelial cell necroptosis leading to cardiovascular defects. MLKL deficiency rescued the cardiovascular phenotype but unexpectedly caused perinatal lethality in Casp8C362S/C362S mice, indicating that CASP8(C362S) causes necroptosis-independent death at later stages of embryonic development. Specific loss of the catalytic activity of caspase-8 in intestinal epithelial cells induced intestinal inflammation similar to intestinal epithelial cell-specific Casp8 knockout mice8. Inhibition of necroptosis by additional deletion of Mlkl severely aggravated intestinal inflammation and caused premature lethality in Mlkl knockout mice with specific loss of caspase-8 catalytic activity in intestinal epithelial cells. Expression of CASP8(C362S) triggered the formation of ASC specks, activation of caspase-1 and secretion of IL-1ß. Both embryonic lethality and premature death were completely rescued in Casp8C362S/C362SMlkl-/-Asc-/- or Casp8C362S/C362SMlkl-/-Casp1-/- mice, indicating that the activation of the inflammasome promotes CASP8(C362S)-mediated tissue pathology when necroptosis is blocked. Therefore, caspase-8 represents the molecular switch that controls apoptosis, necroptosis and pyroptosis, and prevents tissue damage during embryonic development and adulthood.
Asunto(s)
Apoptosis/genética , Caspasa 8/genética , Caspasa 8/metabolismo , Necroptosis/genética , Piroptosis/genética , Animales , Línea Celular , Células Cultivadas , Activación Enzimática/genética , Perfilación de la Expresión Génica , Técnicas de Inactivación de Genes , Células HEK293 , Humanos , Inflamasomas/metabolismo , Mucosa Intestinal/citología , Mucosa Intestinal/enzimología , Queratinocitos/citología , Queratinocitos/patología , Ratones , Mutación , Receptor TIE-2/genética , Receptor TIE-2/metabolismoRESUMEN
BACKGROUND: Immune infiltration is implicated in the development of acquired resistance to anti-angiogenic cancer therapy. We therefore investigated the correlation between neutrophil infiltration in metastasis of colorectal cancer (CRC) patients and survival after treatment with bevacizumab. Our study identifies CD177+ tumour neutrophil infiltration as an adverse prognostic factor for bevacizumab treatment. We further demonstrate that a novel anti-VEGF/anti-Ang2 compound (BI-880) can overcome resistance to VEGF inhibition in experimental tumour models. METHODS: A total of 85 metastatic CRC patients were stratified into cohorts that had either received chemotherapy alone (n = 39) or combined with bevacizumab (n = 46). Tumour CD177+ neutrophil infiltration was correlated to clinical outcome. The impact of neutrophil infiltration on anti-VEGF or anti-VEGF/anti-Ang2 therapy was studied in both xenograft and syngeneic tumour models by immunohistochemistry. RESULTS: The survival of bevacizumab-treated CRC patients in the presence of CD177+ infiltrates was significantly reduced compared to patients harbouring CD177- metastases. BI-880 treatment reduced the development of hypoxia associated with bevacizumab treatment and improved vascular normalisation in xenografts. Furthermore, neutrophil depletion or BI-880 treatment restored treatment sensitivity in a syngeneic tumour model of anti-VEGF resistance. CONCLUSIONS: Our findings implicate CD177 as a biomarker for bevacizumab and suggest VEGF/Ang2 inhibition as a strategy to overcome neutrophil associated resistance to anti-angiogenic treatment.
Asunto(s)
Neoplasias Colorrectales/tratamiento farmacológico , Isoantígenos/genética , Neovascularización Patológica/tratamiento farmacológico , Receptores de Superficie Celular/genética , Factor A de Crecimiento Endotelial Vascular/genética , Proteínas de Transporte Vesicular/genética , Anciano , Inhibidores de la Angiogénesis/administración & dosificación , Animales , Anticuerpos Monoclonales Humanizados/administración & dosificación , Bevacizumab/administración & dosificación , Biomarcadores de Tumor/genética , Neoplasias Colorrectales/genética , Neoplasias Colorrectales/patología , Resistencia a Antineoplásicos/genética , Femenino , Proteínas Ligadas a GPI/genética , Humanos , Masculino , Ratones , Persona de Mediana Edad , Metástasis de la Neoplasia , Células Madre Neoplásicas/efectos de los fármacos , Neovascularización Patológica/genética , Neovascularización Patológica/patología , Neutrófilos/efectos de los fármacos , Factor A de Crecimiento Endotelial Vascular/antagonistas & inhibidores , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
Short-chain fatty acids (SCFAs) are immunomodulatory compounds produced by the microbiome through dietary fiber fermentation. Although generally considered beneficial for gut health, patients suffering from inflammatory bowel disease (IBD) display poor tolerance to fiber-rich diets, suggesting that SCFAs may have contrary effects under inflammatory conditions. To investigate this, we examined the effect of SCFAs on human macrophages in the presence of Toll-like receptor (TLR) agonists. In contrast to anti-inflammatory effects under steady-state conditions, we found that butyrate and propionate activated the NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome in the presence of TLR agonists. Mechanistically, these SCFAs prevented transcription of FLICE-like inhibitory protein (cFLIP) and interleukin-10 (IL-10) through histone deacetylase (HDAC) inhibition, triggering caspase-8-dependent NLRP3 inflammasome activation. SCFA-driven NLRP3 activation was potassium efflux independent and did not result in cell death but rather triggered hyperactivation and IL-1ß release. Our findings demonstrate that butyrate and propionate are bacterially derived danger signals that regulate NLRP3 inflammasome activation through epigenetic modulation of the inflammatory response.