RESUMO
In this study, we show for the first time that the therapeutic antagonization of inhibitor of apoptosis proteins (IAPs) inhibits B16 melanoma growth by disrupting tumor vasculature. Specifically, the treatment of mice bearing B16 melanoma with an IAP antagonist compound A (Comp A) inhibits tumor growth not by inducing direct cytotoxicity against B16 cells but rather by a hitherto unrecognized antiangiogenic activity against tumor vessels. Our detailed analysis showed that Comp A treatment induces NF-κB activity in B16 tumor cells and facilitates the production of TNF. In the presence of Comp A, endothelial cells (ECs) become highly susceptible to TNF and undergo apoptotic cell death. Accordingly, the antiangiogenic and growth-attenuating effects of Comp A treatment were completely abolished in TNF-R knockout mice. This novel targeting approach could be of clinical value in controlling pathological neoangiogenesis under inflammatory condition while sparing blood vessels under normal condition.
Assuntos
Inibidores da Angiogênese/farmacologia , Endotélio Vascular/patologia , Proteínas Inibidoras de Apoptose/antagonistas & inibidores , Melanoma Experimental/irrigação sanguínea , Melanoma Experimental/tratamento farmacológico , Animais , Apoptose/efeitos dos fármacos , Inflamação/fisiopatologia , Melanoma Experimental/metabolismo , Melanoma Experimental/patologia , Camundongos , Camundongos Knockout , NF-kappa B/metabolismo , Neovascularização Patológica , Receptores do Fator de Necrose Tumoral/genética , Fator de Necrose Tumoral alfa/metabolismoRESUMO
The X-linked inhibitor of apoptosis protein (XIAP) is a potent caspase inhibitor, best known for its anti-apoptotic function in cancer. During apoptosis, XIAP is antagonized by SMAC, which is released from the mitochondria upon caspase-mediated activation of BID. Recent studies suggest that XIAP is involved in immune signaling. Here, we explore XIAP as an important mediator of an immune response against the enteroinvasive bacterium Shigella flexneri, both in vitro and in vivo. Our data demonstrate for the first time that Shigella evades the XIAP-mediated immune response by inducing the BID-dependent release of SMAC from the mitochondria. Unlike apoptotic stimuli, Shigella activates the calpain-dependent cleavage of BID to trigger the release of SMAC, which antagonizes the inflammatory action of XIAP without inducing apoptosis. Our results demonstrate how the cellular death machinery can be subverted by an invasive pathogen to ensure bacterial colonization.
Assuntos
Proteína Agonista de Morte Celular de Domínio Interatuante com BH3/fisiologia , Proteínas de Transporte/metabolismo , Disenteria Bacilar/imunologia , Mitocôndrias/imunologia , Proteínas Mitocondriais/metabolismo , Shigella/imunologia , Proteínas Inibidoras de Apoptose Ligadas ao Cromossomo X/fisiologia , Animais , Apoptose , Proteínas Reguladoras de Apoptose , Western Blotting , Caspases/metabolismo , Proliferação de Células , Células Cultivadas , Disenteria Bacilar/microbiologia , Disenteria Bacilar/patologia , Feminino , Hepatócitos/imunologia , Hepatócitos/metabolismo , Hepatócitos/patologia , Técnicas Imunoenzimáticas , Integrases/metabolismo , Masculino , Potencial da Membrana Mitocondrial , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Mitocôndrias/metabolismo , Mitocôndrias/patologia , Proteínas Mitocondriais/imunologia , RNA Mensageiro/genética , Reação em Cadeia da Polimerase em Tempo Real , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Shigella/patogenicidade , Transdução de Sinais , Espectrometria de Massas por Ionização por Electrospray , Espectrometria de Massas em TandemRESUMO
The BH3-only protein NOXA represents one of the critical mediators of DNA-damage-induced cell death. In particular, its involvement in cellular responses to cancer chemotherapy is increasingly evident. Here, we identify a strategy of cancer cells to escape genotoxic chemotherapy by increasing proteasomal degradation of NOXA. We show that the deubiquitylating enzyme UCH-L1 is a key regulator of NOXA turnover, which protects NOXA from proteasomal degradation by removing Lys(48)-linked polyubiquitin chains. In the majority of tumors from patients with melanoma or colorectal cancer suffering from high rates of chemoresistance, NOXA fails to accumulate because UCH-L1 expression is epigenetically silenced. Whereas UCH-L1/NOXA-positive tumor samples exhibit increased sensitivity to genotoxic chemotherapy, downregulation of UCH-L1 or inhibition of its deubiquitylase activity resulted in reduced NOXA stability and resistance to genotoxic chemotherapy in both human and C. elegans cells. Our data identify the UCH-L1/NOXA interaction as a therapeutic target for overcoming cancer chemoresistance.