ABSTRACT
Cross-presentation is one of the main features of dendritic cells (DCs), which is critically important for the development of spontaneous and therapy-inducible antitumor immune responses. Patients, at early stages of cancer, have normal presence of DCs. However, the difficulties in the development of antitumor responses in patients with low tumor burden raised the question of the mechanisms of DC dysfunction. In this study, we found that, in differentiated DCs, tumor-derived factors blocked the cross-presentation of exogenous Ags without inhibiting the Ag presentation of endogenous protein or peptides. This effect was caused by intracellular accumulation of different types of oxidized neutral lipids: triglycerides, cholesterol esters, and fatty acids. In contrast, the accumulation of nonoxidized lipids did not affect cross-presentation. Oxidized lipids blocked cross-presentation by reducing the expression of peptide-MHC class I complexes on the cell surface. Thus, this study suggests the novel role of oxidized lipids in the regulation of cross-presentation.
Subject(s)
Antigen Presentation/immunology , Cross-Priming/immunology , Dendritic Cells/immunology , Lipids/immunology , Neoplasms/immunology , Acetylcysteine/analogs & derivatives , Acetylcysteine/pharmacology , Animals , Cell Line, Tumor , Cells, Cultured , Culture Media, Conditioned/metabolism , Culture Media, Conditioned/pharmacology , Cysteine Proteinase Inhibitors/pharmacology , Dendritic Cells/drug effects , Dendritic Cells/metabolism , Flow Cytometry , Histocompatibility Antigens Class I/immunology , Histocompatibility Antigens Class II/immunology , Humans , Interferon-gamma/pharmacology , Lipids/chemistry , Mice , Mice, Inbred BALB C , Mice, Inbred C57BL , Mice, Transgenic , Microscopy, Confocal , Neoplasms/metabolism , Neoplasms/pathology , Ovalbumin/immunology , Oxidation-Reduction , Peptide Fragments/immunologyABSTRACT
Stabilization of p53 in erythroid precursors in response to nucleosomal stress underlies the hypoplastic anemia in myelodysplastic syndromes (MDS) with chromosome 5q deletion [del(5q)]. We investigated whether cenersen, a clinically active 20-mer antisense oligonucleotide complementary to TP53 exon10, could suppress p53 expression and restore erythropoiesis in del(5q) MDS. Cenersen treatment of ribosomal protein S-14-deficient erythroblasts significantly reduced cellular p53 and p53-up-regulated modulator of apoptosis expression compared with controls, accompanied by a significant reduction in apoptosis and increased cell proliferation. In a two-stage erythroid differentiation assay, cenersen significantly suppressed nuclear p53 in bone marrow CD34+ cells isolated from patients with del(5q) MDS, whereas erythroid burst recovery increased proportionally to the magnitude of p53 suppression without evidence of del(5q) clonal suppression (r = -0.6; P = 0.005). To explore the effect of p53 suppression on erythropoiesis in vivo, dexamethasone, a glucocorticoid receptor-dependent p53 antagonist, was added to lenalidomide treatment in eight lower-risk, transfusion-dependent, del(5q) MDS patients with acquired drug resistance. Transfusion independence was restored in five patients accompanied by expansion of erythroid precursors and decreased cellular p53 expression. We conclude that targeted suppression of p53 could support effective erythropoiesis in lenalidomide-resistant del(5q) MDS.