Assuntos
Glicoproteínas/metabolismo , Hipóxia-Isquemia Encefálica/metabolismo , Hipóxia-Isquemia Encefálica/patologia , Chaperonas Moleculares/metabolismo , Animais , Encéfalo/patologia , Caspase 3 , Caspases/metabolismo , Morte Celular , Clusterina , Glicoproteínas/genética , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Chaperonas Moleculares/genéticaRESUMO
FLIP (FLICE Inhibitory Protein) is a recently identified intracellular inhibitor of caspase-8 activation that potently inhibits cell death mediated by all death receptors including Fas and TRAIL. FLIP has recently been shown to favor tumor growth and immune escape in mouse tumor models. We analyzed FLIP expression by immunohistochemistry in a panel of 61 benign and malignant human melanocytic skin lesions. FLIP expression was undetectable in all but one benign melanocytic lesion (31/32, 97%). In contrast, FLIP was strongly expressed in most melanomas (24/29 = 83%). Overexpression of FLIP by transfection in a Fas- and TRAIL-sensitive human melanoma cell line rendered this cell line more resistant to death mediated by both TRAIL and FasL. Selective expression of FLIP by human melanomas may confer in vivo resistance to FasL and TRAIL, thus representing an additional mechanism by which melanoma cells escape immune destruction.
Assuntos
Apoptose , Proteínas de Transporte/genética , Regulação Neoplásica da Expressão Gênica , Peptídeos e Proteínas de Sinalização Intracelular , Melanoma/fisiopatologia , Neoplasias Cutâneas/fisiopatologia , Especificidade de Anticorpos , Proteínas Reguladoras de Apoptose , Proteína Reguladora de Apoptosis Semelhante a CASP8 e FADD , Proteínas de Transporte/análise , Proteínas de Transporte/imunologia , Proteína Ligante Fas , Humanos , Imuno-Histoquímica , Glicoproteínas de Membrana/análise , Glicoproteínas de Membrana/genética , Nevo , Ligante Indutor de Apoptose Relacionado a TNF , Transfecção , Células Tumorais Cultivadas , Fator de Necrose Tumoral alfa/análise , Fator de Necrose Tumoral alfa/genéticaRESUMO
Membrane-bound Fas ligand (FasL, Apo-1L, CD95L) induces rapid apoptosis of Fas (CD95)-sensitive cells on interaction with Fas, and is an important effector molecule of cytolytic T lymphocytes (CTLs). Melanomas are immunogenic and induce the production of specific CTLs, but are usually able to escape immune destruction. We investigated Fas expression and function in 53 cutaneous melanocytic lesions and 13 melanoma cell lines grown in vitro. Immunohistochemical analysis of Fas expression in cutaneous melanocytic lesions showed moderate to high levels of Fas in common benign melanocytic naevi, but low to undetectable levels in atypical naevi, primary (superficial spreading melanoma, nodular melanoma) and cutaneous melanoma metastases. Fluorescence-activated cell sorting (FACS) analysis of Fas expression in melanoma cell lines revealed undetectable or low levels of cell surface Fas expression in five of the 13 melanoma cell lines. Analysis of Fas signalling by quantification of cell death following exposure to recombinant FasL showed that a reduction in Fas expression results in resistance to FasL-mediated cell death. Furthermore, two of the 13 melanoma cell lines were found to be resistant to FasL-mediated cell death despite conserved Fas expression. Thus seven of the 13 melanoma cell lines were found to have impaired Fas signalling. Taken together, our results indicate that downregulation of Fas expression and resistance to Fas-mediated apoptosis are frequent in melanoma.