These findings demonstrated that DLBCL tumors cells express GILT and that GILT maintains the same intracellular localization as in benign B cells. == Physique 5. survival. In contrast, low expression of a classical MHC class II gene, HLA-DRA, was associated with poor survival in one of four cohorts. The association of low GILT expression with poor survival was impartial of established clinical and molecular prognostic factors, the International Prognostic Index and the cell of origin classification, respectively. Immunohistochemical analysis of GILT expression in 96 DLBCL cases exhibited variation in GILT protein expression within tumor cells which correlated strongly with GILT mRNA expression. These studies identify a novel association between GILT expression and clinical outcome in lymphoma. Our findings underscore the role of antigen processing in DLBCL and suggest that molecules targeting this pathway warrant investigation as potential therapeutics. Keywords:GILT, MHC class II, antigen processing and presentation, diffuse large B cell lymphoma, tumor immunology == Introduction == The major histocompatibility complex (MHC) Costunolide class II-restricted antigen processing pathway generates cell-surface peptide-MHC class II complexes essential for the activation of CD4+T cells (1). The three classical MHC class II proteins, HLA-DP, HLA-DQ, and HLA-DR, are heterodimers composed of an and chain encoded by A and B genes, respectively (e.g., HLA-DRA and HLA-DRB) (2). MHC class II molecules assemble with invariant chain (Ii) in the endoplasmic reticulum. Ii is responsible for trafficking the class II-Ii complex to the endocytic pathway and protecting the peptide binding groove from prematurely acquiring a peptide. Gamma-interferon-inducible lysosomal thiol reductase (GILT) catalyzes the reduction of protein disulfide bonds in the late endosomes and lysosomes, thereby exposing buried peptide epitopes for binding to MHC class II and enhancing the MHC class II-restricted presentation of a number of epitopes (39). In the lysosomes, proteases degrade endocytosed and endogenous proteins to form class II-binding peptides. A non-classical MHC class II protein HLA-DM mediates loading MHC class II with a high affinity peptide. Peptide-MHC class II complexes are then directed to the Costunolide Dicer1 cell surface for recognition by and activation of CD4+T cells. CD4+T cells augment anti-tumor immunity, in part through promoting the differentiation and maintenance of CD8+cytotoxic T cells (1012). MHC class II molecules are expressed by professional antigen presenting cells (APCs), such as dendritic cells (DCs) and B cells, as well as cancers derived from these Costunolide cell types. In addition, ectopic expression of MHC class II has been described on multiple cancers, including melanoma, breast, colon, thyroid, and cervical (6,1316). Therefore, MHC class II-restricted processing and presentation by tumor cells may exert a major influence over T cell responses and play a critical role in anti-tumor immunity. Diffuse large B-cell lymphoma (DLBCL) is the most common type of aggressive lymphoid neoplasm, accounting for 30% of adult non-Hodgkin lymphomas (17). DLBCL is a heterogeneous disease with large variations in clinical outcome (17). Prognostic stratification is based on clinical risk factors used to determine the International Prognostic Index (IPI), which incorporates patient Costunolide age at diagnosis, tumor stage, serum lactate dehydrogenase level, performance status, and number of extra-nodal sites (18). The combination of cyclophosphamide, hydroxydaunorubicin (doxorubicin), Oncovin(vincristine), and prednisone (CHOP) had been the standard chemotherapy regimen for decades. The recent addition of rituximab, a monoclonal antibody (mAb) to CD20, to Costunolide the treatment protocol (R-CHOP) has significantly improved patient survival (19,20). Gene expression profiling (GEP) studies have demonstrated molecular heterogeneity in histologically similar DLBCL tumors and identified gene expression signatures which could offer more accurate prognostic stratification compared to the IPI (2129). Alizadeh et al. demonstrated distinct molecular subgroups based on the cell of origin (COO) or differentiation state of the tumor (21). Patients with germinal center B cell-like (GCB) DLBCL have significantly improved survival compared to activated B cell-like (ABC) DLBCL (21). Subsequent GEP studies have identified that the immune response plays a favorable role in prognosis (22,27,28). In particular, low expression of genes involved in MHC class II-restricted antigen presentation is associated with poor survival in DLBCL (22,27,3032). Gamma-interferon-inducible lysosomal thiol reductase is a key component of the MHC class II-restricted antigen processing and presentation pathway. However, unlike other members of this pathway including HLA-DR, HLA-DP, HLA-DQ, HLA-DM, and li, GILT is not regulated by transcription factor class II transactivator (CIITA) (3335). Therefore, we sought to determine whether GILT expression levels may provide further prognostic value. Although GILT mRNA expression was previously identified as part.
