Cutting edge: induction of the antigen-processing enzyme IFN-gamma-inducible lysosomal thiol reductase in melanoma cells Is STAT1-dependent but CIITA-independent

Molecular mechanisms of IFN-gamma to up-regulate MHC class I antigen processing and presentation

IFN-gamma up-regulates MHC class I expression and antigen processing and presentation on cells, since IFN-gamma can induce multiple gene expressions that are related to MHC class I antigen processing and presentation. MHC class I antigen presentation-associated gene expression is initiated by IRF-1. IRF-1 expression is initiated by phosphorylated STAT1. IFN-gamma binds to IFN receptors, and then activates JAK1/JAK2/STAT1 signal transduction via phosphorylation of JAK and STAT1 in cells. IFN-gamma up-regulates MHC class I antigen presentation via activation of JAK/STAT1 signal transduction pathway. Mechanisms of IFN-gamma to enhance MHC class I antigen processing and presentation were summarized in this literature review.

Insights into the Role of GILT in HLA Class II Antigen Processing and Presentation by Melanoma

Metastatic melanoma is one of the deadliest of skin cancers and is increasing in incidence. Since current treatment regimens are ineffective at controlling and/or curing the disease, novel approaches, such as immunotherapy, for treating this malignant disease are being explored. In this review, we discuss potential melanoma antigens (Ags) and their role in utilizing the HLA class II pathway to elicit tumor Ag-specific CD4+ T cell responses in order to effectively induce long-lasting CD8+ antitumor memory. We also discuss the role of endolysosomal cathepsins and Gamma-Interferon-inducible Lysosomal Thiol reductase (GILT) in Ag processing and presentation, and at enhancing CD4+ T cell recognition of melanoma cells. This review also summarizes our current knowledge on GILT and highlights a novel mechanism of GILT-mediated immune responses against melanoma cells. At the end, we propose a strategy employing GILT in the development of a potential whole cell vaccine for combating metastatic melanoma.

Gamma-IFN-inducible-lysosomal thiol reductase modulates acidic proteases and HLA class II antigen processing in melanoma

HLA class II-restricted antigen (Ag) processing and presentation are important for the activation of CD4+ T cells, which are the central orchestrating cells of immune responses. The majority of melanoma cells either expresses, or can be induced to express, HLA class II proteins. Thus, they are prime targets for immune mediated elimination by class II-restricted CD4+ T cells. We have previously shown that human melanoma cells lack an important enzyme, gamma interferon-inducible lysosomal thiol-reductase (GILT), capable of perturbing immune recognition of these tumors. Here, we show that GILT expression in human melanoma cells enhances Ag processing and presentation via HLA class II molecules. We also show that GILT expression influences the generation of active forms of cysteinyl proteases, cathepsins B, L and S, as well as an aspartyl protease cathepsin D in melanoma cells. Mechanistic studies revealed that GILT does not regulate acidic cathepsins at the transcriptional level; rather it colocalizes with the cathepsins and influences HLA class II Ag processing. GILT expression in melanoma cells also elevated HLA-DM molecules, which favor epitope loading onto class II in the endolysosomal compartments, enhancing CD4+ T cell recognition. These data suggest that GILT-expressing melanoma cells could prove to be very promising for direct antigen presentation and CD4+ T cell recognition, and may have direct implications for the design of cancer vaccines.

Neuromyelitis optica/Devic's disease: gene expression profiling of brain lesions

Neuromyelitis optica (NMO), also known as Devic's disease, is an inflammatory demyelinating disease that affects selectively the optic nerves and the spinal cord, possibly mediated by an immune mechanism distinct from that of multiple sclerosis (MS). Recent studies indicate that NMO also involves the brain. Here, we studied gene expression profile of brain lesions of a patient with NMO by using DNA microarray, along with gene expression profile of the brains of Parkinson disease and amyotrophic lateral sclerosis patients. We identified more than 200 genes up-regulated in NMO brain lesions. The top 20 genes were composed of the molecules closely associated with immune regulation, among which marked up-regulation of interferon gamma-inducible protein 30 (IFI30), CD163, and secreted phosphoprotein 1 (SPP1, osteopontin) was validated by real time RT-PCR, Northern blot and Western blot analysis. Pathologically, CD68(+) macrophages and microglia expressed intense immunoreactivities for IFI30 and CD163 in NMO lesions, consisting of inflammatory demyelination, axonal loss, necrosis, cavity formation, and vascular fibrosis. KeyMolnet, a bioinformatics tool for analyzing molecular interaction on the curated knowledge database, suggested that the molecular network of up-regulated genes in NMO brain lesions involves transcriptional regulation by the nuclear factor-kappaB (NF-kappaB) and B-lymphocyte-induced maturation protein-1 (Blimp-1). These results suggest that profound activation of the macrophage-mediated proinflammatory immune mechanism plays a pivotal role in development of NMO brain lesions.

Structure-related clustering of gene expression fingerprints of thp-1 cells exposed to smaller polycyclic aromatic hydrocarbons

This study was undertaken to test the hypothesis that structurally similar PAHs induce similar gene expression profiles. THP-1 cells were exposed to a series of 12 selected PAHs at 50 microM for 24 hours and gene expressions profiles were analyzed using both unsupervised and supervised methods. Clustering analysis of gene expression profiles revealed that the 12 tested chemicals were grouped into five clusters. Within each cluster, the gene expression profiles are more similar to each other than to the ones outside the cluster. One-methylanthracene and 1-methylfluorene were found to have the most similar profiles; dibenzothiophene and dibenzofuran were found to share common profiles with fluorine. As expression pattern comparisons were expanded, similarity in genomic fingerprint dropped off dramatically. Prediction analysis of microarrays (PAM) based on the clustering pattern generated 49 predictor genes that can be used for sample discrimination. Moreover, a significant analysis of Microarrays (SAM) identified 598 genes being modulated by tested chemicals with a variety of biological processes, such as cell cycle, metabolism, and protein binding and KEGG pathways being significantly (p < 0.05) affected. It is feasible to distinguish structurally different PAHs based on their genomic fingerprints, which are mechanism based.

Molecular cloning and expression analysis of interferon-gamma-inducible-lysosomal thiol reductase gene in orange-spotted grouper, Epinephelus coioides

In mammals, interferon-gamma-inducible-lysosomal thiol reductase (GILT) has been demonstrated to play a key role in the processing and presentation of MHC class II-restricted antigen (Ag) by catalyzing disulfide bond reduction, thus unfolding native protein Ag and facilitating subsequent cleavage by proteases. In this study a cDNA containing the orange-spotted grouper GILT (OsgGILT) coding sequence has been cloned and its complete sequence determined. The full-length cDNA of OsgGILT gene is 1066 bp nucleotides (nt) encoding a protein of 260 amino acids (aa), with a putative molecular weight of 28.7 kDa. The deduced OsgGILT possesses the typical structural feature of mammalian GILT, including an active-site CXXC motif, a GILT signature sequence CQHGX(2)ECX(2)NX(4)C, and 10 conserved cysteines. The result of real-time PCR showed that OsgGILT mRNA was expressed in heart, liver, brain, gill, kidney and muscle and more highly expressed in spleen. The OsgGILT expression is obviously up-regulated in spleen and kidney after induction with LPS, these results suggest that OsgGILT may be involved in the immune response to LPS challenge in orange-spotted grouper.

Emerging Role of Combination of All-trans Retinoic Acid and Interferon-gamma as Chemoimmunotherapy in the Management of Human Glioblastoma

Glioblastoma is the most malignant and common type of brain tumor with devastating outcome. Because current treatment modalities are mostly ineffective in controlling and curing glioblastoma, new and innovative therapeutic strategies must be developed. This article describes recent advances in chemoimmunotherapy, which is combination of chemotherapy and immunotherapy, against glioblastoma. We provide an overview of available treatment options for glioblastomas, gaps in our knowledge of immune recognition of these malignant tumors, and chemotherapeutic and immunotherapeutic agents that need to be further explored for designing novel chemoimmunotherapeutic strategy for the management of human glioblastomas. Our recent study demonstrated that combination of the chemotherapeutic agent all-trans retinoic acid (ATRA) and the immunotherapeutic agent interferon-gamma (IFN-gamma) could concurrently induce differentiation, apoptotic death, and immune components in two different human glioblastoma cell lines. We propose that combination of ATRA and IFN-gamma can become an efficacious chemoimmunotherapy for the treatment of human glioblastoma.

Induction of apoptosis and immune response by all-trans retinoic acid plus interferon-gamma in human malignant glioblastoma T98G and U87MG cells

Glioblastoma is the most common and highly malignant brain tumor. It is also one among the most therapy-resistant human neoplasias. Patients die within a year of diagnosis despite the use of available treatment strategies such as surgery, radiotherapy, and chemotherapy. Thus, there is a critical need to find a novel therapeutic strategy for treating this disease. Here, we have investigated the molecular mechanisms for induction of apoptosis as well as for activation of immune components in human malignant glioblastoma T98G and U87MG cells following treatment with all-trans retinoic acid (ATRA) plus interferon-gamma (IFN-gamma). Treatment of glioblastoma cells with ATRA alone prevented cell proliferation and induced astrocytic differentiation, while IFN-gamma alone induced apoptosis and modulated expression of human leukocyte antigen (HLA) class II molecules such as HLA-DRalpha, HLA-DR complex, invariant chain (Ii), HLA-DM (an important catalyst of the class II-peptide loading), and gamma interferon-inducible lysosomal thiol-reductase (GILT). Interestingly, both T98G and U87MG cells showed more increase in apoptosis with expression of the HLA class II components for an effective immune response following treatment with ATRA plus IFN-gamma than with IFN-gamma alone. Apoptotic mode of cell death was confirmed morphologically by Wright staining and biochemically by measuring an increase in caspase-3 activity. While conversion of tumor cells into HLA class II+/Ii- cells by stimulation with the helper CD4+ T cells is thought to be challenging, this study reports for the first time that treatment of glioblastoma cells with ATRA plus IFN-gamma can simultaneously enhance apoptosis and expression of the HLA class II immune components with a marked suppression of Ii expression. Taken together, this study suggests that induction of apoptosis and immune components of the HLA class II pathway by ATRA plus IFN-gamma may be a promising chemoimmunotherapeutic strategy for treatment of human malignant glioblastoma.

Characterization and expression of gamma-interferon-inducible lysosomal thiol reductase (GILT) gene in amphioxus Branchiostoma belcheri with implications for GILT in innate immune response

An amphioxus cDNA, AmphiGILT, encoding GILT protein was isolated from the gut cDNA library of Branchiostoma belcheri. It codes for a deduced protein of 254 amino acids, which has all the main features typical of GILT proteins including the signature sequence CQHGX(2)CX(2)NX(4)C, CXXC motif and 11 conserved cysteines. Phylogenetic analysis showed that AmphiGILT and sea urchin GILT clubbed together and positioned at the base of vertebrate GILT clade, suggesting that both AmphiGILT and sea urchin GILT might share some characteristics of the archetype of vertebrate GILT proteins. The genomic DNA sequence of B. floridae contains seven exons and six introns, which is similar to vertebrate GILT exon-intron organization. AmphiGILT was expressed in a tissue-specific manner with the most abundant mRNA in the digestive system including hepatic caecum and hind-gut. It was also found that mammalian IFN-gamma only exerted a slight effect on the expression of GILT gene in amphioxus, forming a contrast to the marked induction of human and mouse GILT expression by IFN-gamma. Taken the absence of the adaptive immune system including MHC class II molecules and lymphocytes into consideration, these results suggest that AmphiGILT is highly likely to play a role in the innate immune responses in amphioxus.

Exposure of the Promonocytic Cell Line THP-1 to Escherichia coli Induces IFN-γ-Inducible Lysosomal Thiol Reductase Expression by Inflammatory Cytokines

IFN-gamma-inducible lysosomal thiol reductase (GILT), which plays a role in MHC class II-restricted processing and presentation of Ags containing disulfide bonds, can be induced in various cell types by the cytokine IFN-gamma. APCs, including circulating macrophages, constitutively express high levels of GILT, although the pathways regulating its expression in these cells have not been characterized. In this study, we used the promonocytic cell line THP-1, an established model for monocyte to macrophage differentiation, to investigate the induction of GILT upon exposure to bacteria. We show that contact with LPS or intact Escherichia coli causes THP-1 cells to undergo programmed differentiation, characterized by adhesion, cytokine secretion, and up-regulation of Ag processing and presentation components, including GILT. Unlike GILT induction in response to IFN-gamma treatment, induction by bacteria is dependent on new protein synthesis, NF-kappaB signaling, and secretion of the inflammatory cytokines TNF and IL-1beta. Furthermore, we show that both cytokines are sufficient for GILT induction in the absence of a microbial stimulus. The majority of GILT synthesized by differentiated THP-1 cells is secreted as the precursor form rather than being transported to, and maturing in, lysosomes, suggesting a novel role for GILT in cells of the macrophage lineage.

Cloning and expression analysis of interferon-gamma-inducible-lysosomal thiol reductase gene in large yellow croaker (Pseudosciaena crocea)

In mammals, interferon-gamma-inducible-lysosomal thiol reductase (GILT) has been demonstrated to play a key role in the processing and presentation of MHC class II-restricted antigen (Ag) by catalyzing disulfide bond reduction, thus unfolding native protein Ag and facilitating subsequent cleavage by proteases. Here, we reported the cloning of a GILT gene homologue from the spleen of large yellow croaker, a marine fish (LycGILT). The full-length cDNA of LycGILT gene is 1033 nucleotides (nt) encoding a protein of 256 amino acids (aa), with a putative molecular weight of 28.9 kDa. The deduced protein is highly homologous to that of mammalian and zebrafish GILTs and shares 54.1% sequence identity to that of zebrafish and 43.2-39.2% sequence identity to that of various mammals. The deduced LycGILT possesses the typical structural feature of mammalian GILT, including an active-site CXXC motif, a GILT signature sequence CQHGX2ECX2NX4C, and other six cysteines responsible for the formation of disulfide bonds in the C-terminus. Genomic analysis revealed that LycGILT gene, spanning a 3159nt fragment, contained seven exons interrupted by six introns and exhibited a similar exon-intron organization to human and mouse GILT genes except for a slightly more compact intron arrangement. The LycGILT expression is obviously up-regulated in spleen and kidney after immunization with inactivated trivalent bacterial vaccine consisting of Vibrio alginolyticus, V. paraphaemolyticus, and Aeromonas hydrophila although it also is constitutively expressed in liver, gills, brain, and heart, suggesting that LycGILT may be involved in the immune response to bacterial challenge in large yellow croaker. A search of NCBI sequence data with LycGILT cDNA identified a pufferfish (fugu rubrides) GILT homologue cDNA and its genomic DNA sequence, where two putative interferon-gamma activation sites (GAS) were found within the promoter region. This provided evidence that a fish GILT homologue like mammalian GILT, may also be regulated by interferon-gamma (IFN-gamma) through the JAK-STAT signal pathway. These results indicate that the bony fish GILT is a functional homologue of mammalian GILT.

Differential MHC class II component expression in HPV-positive cervical cancer cells: implication for immune surveillance

Effective eradication of human papillomavirus (HPV)-positive tumors may require CD8+ and CD4+ T-cell-mediated immune responses. Ectopic expression of MHC class II surface molecules has been described in the context of cervical cancer, but coexpression with other components of the MHC class II antigen presentation pathway has not been addressed. We have evaluated the MHC class II antigen presentation pathway in malignant squamous epithelium of HPV+ cervical cancer lesions by in situ costaining HLA-DR with CLIP or DMA/DMB. Cervical cancer cells exhibit 3 MHC class II phenotypes: (i) DR+/CLIP+ or DM+; (ii) DR+/CLIP- or DM-; and (iii) DR-/CLIP+ or DM+. The identical profile has been identified in HPV+ ME180 cells, which serve as a target for HLA-DR4-restricted and HPV68, E7-specific CD4+ T cells. IFN-gamma pretreatment of ME180 cells, associated with differential trafficking of MHC class II molecules, is necessary for effective T-cell recognition. Although proinflammatory cytokines may facilitate MHC class II-restricted antigen recognition in tumor cells, different phenotypes of the MHC class II antigen presentation pathway may be associated with evasion from CD4+-mediated cellular immune responses.

Compartmentalization of class II antigen presentation: contribution of cytoplasmic and endosomal processing

During antigen processing, peptides are generated and displayed in the context of major histocompatibility complex (MHC) class II molecules on the surface of antigen-presenting cells (APCs) to modulate immune responses to foreign antigens and guide self-tolerance. Exogenous and cytoplasmic antigens are processed by distinct routes within APCs to yield class II ligands. Exogenous antigens are internalized, processed, and bound to class II molecules within endosomal and lysosomal compartments of APCs. Studies reviewed here demonstrate the importance of reduction in regulating exogenous antigen presentation. The differential expression of a gamma-interferon-inducible lysosomal thiol reductase in professional APCs and melanomas is discussed in the context of tumor immune evasion. Cytoplasmic autoantigens, by contrast, are degraded by the proteasome and other enzymes in the cytosol, with the resulting peptides translocating to endosomal and lysosomal compartments for intersection with class II molecules. Processing and editing of these antigenic peptides within endosomes and lysosomes may be critical in regulating their display via class II proteins. Multiple pathways may regulate the transit of cytosolic peptides to class II molecules. The role of lysosome-associated membrane protein-2a and heat-shock cognate protein 70 in promoting cytoplasmic peptide presentation by MHC class II molecules is discussed.