%0 Journal Article
%A Rodríguez, Teresa
%A Méndez, Rosa
%A Campo, Ana Del
%A Jiménez, Pilar
%A Aptsiauri, Natalia
%A Garrido, Federico
%A Ruiz-Cabello, Francisco
%T Distinct mechanisms of loss of IFN-gamma mediated HLA class I inducibility in two melanoma cell lines
%D 2007
%U http://hdl.handle.net/10668/616
%X BACKGROUNDThe inability of cancer cells to present antigen on the cell surface via MHC class I molecules is one of the mechanisms by which tumor cells evade anti-tumor immunity. Alterations of Jak-STAT components of interferon (IFN)-mediated signaling can contribute to the mechanism of cell resistance to IFN, leading to lack of MHC class I inducibility. Hence, the identification of IFN-gamma-resistant tumors may have prognostic and/or therapeutic relevance. In the present study, we investigated a mechanism of MHC class I inducibility in response to IFN-gamma treatment in human melanoma cell lines.METHODSBasal and IFN-induced expression of HLA class I antigens was analyzed by means of indirect immunofluorescence flow cytometry, Western Blot, RT-PCR, and quantitative real-time RT-PCR (TaqMan(R) Gene Expression Assays). In demethylation studies cells were cultured with 5-aza-2'-deoxycytidine. Electrophoretic Mobility Shift Assay (EMSA) was used to assay whether IRF-1 promoter binding activity is induced in IFN-gamma-treated cells.RESULTSAltered IFN-gamma mediated HLA-class I induction was observed in two melanoma cells lines (ESTDAB-004 and ESTDAB-159) out of 57 studied, while treatment of these two cell lines with IFN-alpha led to normal induction of HLA class I antigen expression. Examination of STAT-1 in ESTDAB-004 after IFN-gamma treatment demonstrated that the STAT-1 protein was expressed but not phosphorylated. Interestingly, IFN-alpha treatment induced normal STAT-1 phosphorylation and HLA class I expression. In contrast, the absence of response to IFN-gamma in ESTDAB-159 was found to be associated with alterations in downstream components of the IFN-gamma signaling pathway.CONCLUSIONWe observed two distinct mechanisms of loss of IFN-gamma inducibility of HLA class I antigens in two melanoma cell lines. Our findings suggest that loss of HLA class I induction in ESTDAB-004 cells results from a defect in the earliest steps of the IFN-gamma signaling pathway due to absence of STAT-1 tyrosine-phosphorylation, while absence of IFN-gamma-mediated HLA class I expression in ESTDAB-159 cells is due to epigenetic blocking of IFN-regulatory factor 1 (IRF-1) transactivation.
%K HLA Antigens
%K IRF1 protein, human
%K Interferon Regulatory Factor-1
%K STAT1 Transcription Factor
%K STAT1 protein, human
%K Interferon-gamma
%K Interferón gamma
%K Melanoma
%K Fosforilación Oxidativa
%K Factor de Transcripción STAT1
%K Transducción de Señal
%K Neoplasias Cutáneas
%K Activación Transcripcional
%K Células Tumorales Cultivadas
%K Antineoplastic Agents
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