Distinct mechanisms of loss of IFN-gamma mediated HLA class I inducibility in two melanoma cell lines

BACKGROUND The 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. METHODS Basal 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. RESULTS Altered 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. CONCLUSION We 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.

Reseccion intestinal masiva. Proceso de adaptacion nutricional

INTRODUCTION Massive small bowel resection (MSBR) with a remnant jejunum shorter than 60 cm produces severe water, electrolytes, vitamins and protein-caloric depletion. While waiting for a viable intestinal transplantation, most of MSBR patients depend on total parenteral nutrition (TPN). CLINICAL CASE 32 years old male, with MSBR due to sectioning trauma of the superior mesenteric artery root. First surgical intervention: jejunostomy with small bowel, right colon, and spleen resection. Six months later: jejunocolic anastomosis with 12-cm long jejunum remnant and prophylactic cholecystectomy. NUTRITIONAL INTERVENTION: 1st phase. Hemodynamic stabilization and enteral stimulation (6 months): TPN + enteral nutrition with elemental formula + oral glucohydroelectrolitic solution (OGHS) + 15 g/d of oral glutamine + omeprazol. Clinical course indicators: biochemistry, I/L balance. 2a phase. Digestive adaptation with colonic integration (8 months): replacement of TPN by part-time peripheral PN. Progressive cooked diet complemented with pancreatic poly-enzyme preparation, omeprazol, OGHS, glutamine, elemental formula. Clinical course indicators: biochemistry, diuresis, weight and feces. 3a phase. Auto-sufficiency without parenteral dependence: fragmented free oral diet supplemented with pancreatic poly-enzyme preparation, mineralized beverages, enteral formula supplement, Ca and Mg oral supplements, oral multivitamin and mineral preparation, monthly IM vitamin B12. Current situation actual (52 months): slight ponderal gain, diuresis > liter/day, 2-3 normal feces, no clinical signs of any deficiency and normal blood levels of micronutrients. CONCLUSION It may be possible to withdraw from PN in MSBR considering, as in this case, favorable age and etiology and early implementation of an appropriate protocol of remnant adaptation.

Resección intestinal masiva: Proceso de adaptación intestinal.

Carta al Director de J. M. Moreno Villares, sobre el artículo: Leyva Martínez S, Fernández Lloret S, Martín Ruiz JL. Resección intestinal masiva. Proceso de adaptación intestinal. Nutr Hosp 2007; 22:616-20; y réplica de los autores (Leyva Martínez S).