Class II Major Histocompatibility Complex Transactivator (CIITA): A Master MHC-II Regulator Impacting Cancer and Beyond.

Breast cancer remains a major global health burden, necessitating improved prognostic markers and therapeutic strategies. This study investigates the role of class II major histocompatibility complex transactivator (CIITA), a master regulator of major histocompatibility complex class II(MHC-II) gene expression, in breast cancer. Although CIITA is well recognized for its role in antigen presentation in immune cells, its function in tumor immunity and prognosis remains underexplored. Through integrative bioinformatics analyses using The Cancer Genome Atlas (TCGA) and other datasets, we demonstrate that high CIITA expression is associated with favorable clinical outcomes and enhanced immune activation in breast cancer. CIITA levels correlate with increased infiltration of antitumor immune cells, elevated expression of immune checkpoint genes, and enrichment of immune-related pathways. Immunohistochemical staining of breast cancer tissues further confirms CIITA protein expression patterns. Moreover, functional enrichment analyses suggest that CIITA may influence tumor-immune interactions by modulating immune response pathways. A prognostic nomogram incorporating CIITA expression shows robust predictive value for overall survival, offering potential clinical utility. These findings highlight CIITA as a promising prognostic biomarker and immunomodulatory target in breast cancer, shedding light on its role in shaping the tumor immune microenvironment.

To determine the regulation of class II major histocompatibility complex (MHC) expression in fibroblast-like synoviocytes (FLS) in order to investigate their role as nonprofessional antigen-presenting cells in collagen-induced arthritis (CIA). Expression of class II MHC, class II MHC transactivator (CIITA), and Ciita isoforms PI, PIII, and PIV was examined by real-time quantitative polymerase chain reaction, immunohistochemistry, and flow cytometry in human synovial tissues, arthritic mouse joints, and human and murine FLS. CIA was induced in mice in which isoform PIV of Ciita was knocked out (PIV(-/-) ), in PIV(-/-) mice transgenic for CIITA in the thymus (K14 CIITA), and in their control littermates. HLA-DRA, total CIITA, and CIITA PIII messenger RNA levels were significantly increased in synovial tissue samples from patients with rheumatoid arthritis compared with the levels in tissue from patients with osteoarthritis. Human FLS expressed surface class II MHC via CIITA PIII and PIV, while class II MHC expression in murine FLS was entirely mediated by PIV. Mice with a targeted deletion of CIITA PIV lack CD4+ T cells and were protected against CIA. The expression of CIITA was restored in the thymus of PIV(-/-) K14 CIITA-transgenic mice, which had a normal CD4+ T cell repertoire and normal surface levels of class II MHC on professional antigen-presenting cells, but did not induce class II MHC on FLS. Synovial inflammation and immune responses against type II collagen were similar in PIV(-/-) K14 CIITA-transgenic mice and control mice with CIA, but bone erosion was significantly reduced in the absence of PIV. Overexpression of class II MHC is tightly correlated with CIITA expression in arthritic synovium and in FLS. Selective targeting of Ciita PIV in peripheral tissues abrogates class II MHC expression by murine FLS but does not protect against inflammation and autoimmune responses in CIA.

BackgroundAntigen presentation on monocyte surface to T-cells by Major Histocompatibility Complex, Class II (MHC-II) molecules is fundamental for pathogen recognition and efficient host response. Accordingly, loss of Major Histocompatibility Complex, Class II, DR (HLA-DR) surface expression indicates impaired monocyte functionality in patients suffering from sepsis-induced immunosuppression. Besides the impact of Class II Major Histocompatibility Complex Transactivator (CIITA) on MHC-II gene expression, X box-like (XL) sequences have been proposed as further regulatory elements. These elements are bound by the DNA-binding protein CCCTC-Binding Factor (CTCF), a superordinate modulator of gene transcription. Here, we hypothesized a differential interaction of CTCF with the MHC-II locus contributing to an altered monocyte response in immunocompromised septic patients.MethodsWe collected blood from six patients diagnosed with sepsis and six healthy controls. Flow cytometric analysis was used to identify sepsis-induced immune suppression, while inflammatory cytokine levels in blood were determined via ELISA. Isolation of CD14++ CD16—monocytes was followed by (i) RNA extraction for gene expression analysis and (ii) chromatin immunoprecipitation to assess the distribution of CTCF and chromatin modifications in selected MHC-II regions.ResultsCompared to healthy controls, CD14++ CD16—monocytes from septic patients with immune suppression displayed an increased binding of CTCF within the MHC-II locus combined with decreased transcription of CIITA gene. In detail, enhanced CTCF enrichment was detected on the intergenic sequence XL9 separating two subregions coding for MHC-II genes. Depending on the relative localisation to XL9, gene expression of both regions was differentially affected in patients with sepsis.ConclusionOur experiments demonstrate for the first time that differential CTCF binding at XL9 is accompanied by uncoupled MHC-II expression as well as transcriptional and epigenetic alterations of the MHC-II regulator CIITA in septic patients. Overall, our findings indicate a sepsis-induced enhancer blockade mediated by variation of CTCF at the intergenic sequence XL9 in altered monocytes during immunosuppression.

NLRs are a large family belonging to pattern recognition receptors which could recognize pathogen associated molecular patterns. Class II, major histocompatibility complex, transactivator (CIITA) is a member of NLR family. It is a critical transcription factor which could regulate the expression of MHC class II. In this study, a full-length cDNA of CIITA was cloned from channel catfish according to ten sequenced ESTs. This cDNA contains a 5'-UTR of 71bp, a 3'-UTR of 238bp and an ORF of 3,210bp encoding 1,069 amino acids. Phylogenetic analysis showed that catfish CIITA was conserved with other CIITAs. Quantitative real-time PCR was conducted to detect the expression profiles of CIITA in normal tissues and responding to different pathogens (Edwardsiella tarda, Streptococcus iniae and channel catfish Hemorrhage Reovirus (CCRV)). The expression profile in blood was the highest (53.879-fold) in normal tissues. E. tarda and S. iniae could induce catfish CIITA in head kidney, liver and spleen. CCRV virus could also induce CIITA in head kidney and liver but reduce it in spleen. And S. iniae could induce the expression of CIITA to the highest extent and contrarily CCRV virus to the lowest extent. The expression data showed the tissue-specific and pathogen-specific expression patterns of CIITA responding to different pathogens. These expression data indicated the immune-related functions of CIITA. The data obtained in this study provide a basis for further research aimed at explore the precise immune-related molecular mechanism of CIITA in catfish.

IFNh and IRF9 influence the transcription of MHCII mediated by IFNγ to maintain immune balance in sea perch lateolabrax japonicus

Nasal polyps are abnormal lesions arising mainly from the nasal mucosa and paranasal sinuses. Since the human classII, major histocompatibility complex, transactivator (CIITA) is a positive regulator of classII, major histocompatibility complex gene transcription, the CIITA gene is thought to be involved in the presence of nasal polyps in asthma and aspirin hypersensitive patients. To investigate the association between CIITA and nasal polyposis, 18single nucleotide polymorphisms (SNPs) were genotyped in 467asthmatics who were classified into 158aspirin-exacerbated respiratory disease (AERD) and 309aspirin-tolerant asthma (ATA) subgroups. Differences in the frequency distribution of CIITA variations between polyp-positive cases and polyp-negative controls were determined using logistic analyses. Initially, a total of 9CIITA variants were significantly associated with the presence of nasal polyps in the overall asthma, AERD and ATA groups [P=0.001-0.05, odds ratio (OR)=0.53-2.35 in the overall asthma group; P=0.01-0.02, OR=2.45-2.66 in the AERD group; P=0.001‑0.05, OR=0.45-2.61 in the ATA group using various modes of genetic inheritance]. One the variations (rs12932187) retained this association after multiple testing corrections (Pcorr=0.01) in the overall asthma group. In addition, two variations (rs12932187 and rs11074938) were associated with the presence of nasal polyps following multiple testing corrections (Pcorr=0.02and0.04, respectively) in the ATA group. These novel findings suggest that rs12932187 and rs11074938 may constitute susceptibility markers of inflammation of the nasal passages in asthma patients.

IFN-γ and CIITA modulate IL-6 expression in skeletal muscle

Impact of VHSV on CIITA-mediated MHCII expression and antigen presentation in largemouth bass.

BackgroundPostoperative abdominal infections belong to the most common triggers of sepsis and septic shock in intensive care units worldwide. While monocytes play a central role in mediating the initial host response to infections, sepsis-induced immune dysregulation is characterized by a defective antigen presentation to T-cells via loss of Major Histocompatibility Complex Class II DR (HLA-DR) surface expression. Here, we hypothesized a sepsis-induced differential occupancy of the CCCTC-Binding Factor (CTCF), an architectural protein and superordinate regulator of transcription, inside the Major Histocompatibility Complex Class II (MHC-II) region in patients with postoperative sepsis, contributing to an altered monocytic transcriptional response during critical illness.ResultsCompared to a matched surgical control cohort, postoperative sepsis was associated with selective and enduring increase in CTCF binding within the MHC-II. In detail, increased CTCF binding was detected at four sites adjacent to classical HLA class II genes coding for proteins expressed on monocyte surface. Gene expression analysis revealed a sepsis-associated decreased transcription of (i) the classical HLA genes HLA-DRA, HLA-DRB1, HLA-DPA1 and HLA-DPB1 and (ii) the gene of the MHC-II master regulator, CIITA (Class II Major Histocompatibility Complex Transactivator). Increased CTCF binding persisted in all sepsis patients, while transcriptional recovery CIITA was exclusively found in long-term survivors.ConclusionOur experiments demonstrate differential and persisting alterations of CTCF occupancy within the MHC-II, accompanied by selective changes in the expression of spatially related HLA class II genes, indicating an important role of CTCF in modulating the transcriptional response of immunocompromised human monocytes during critical illness.

The nucleotide-binding and oligomerization domain-like receptors (NLRs) NLR family CARD domain-containing protein 5 (NLRC5) and Class II Major Histocompatibility Complex Transactivator (CIITA) are transcriptional regulators of major histocompatibility complex (MHC) class I and class II genes, respectively. MHC molecules are central players in our immune system, allowing the detection of hazardous 'non-self' antigens and, thus, the recognition and elimination of infected or transformed cells from the organism. Recently, CIITA and NLRC5 have emerged as regulators of selected genes of the butyrophilin (BTN) family that interestingly are located in the extended MHC locus. BTNs are transmembrane proteins exhibiting structural similarities to B7 family co-modulatory molecules. The family member BTN2A2, which indeed contributes to the control of T cell activation, was found to be transcriptionally regulated by CIITA. NLRC5 emerged instead as an important regulator of the BTN3A1, BTN3A2, and BTN3A3 genes. Together with BTN2A1, BTN3As regulate non-conventional Vγ9Vδ2 T cell responses triggered by selected metabolites of microbial origin or accumulating in hematologic cancer cells. Even if endogenous metabolites conform to the canonical definition of 'self', metabolically abnormal cells can represent a danger for the organism and should be recognized and controlled by immune system cells. Collectively, new data on the role of NLRC5 in the expression of BTN3As link the mechanisms regulating canonical 'non-self' presentation and those marking cells with abnormal metabolic configurations for immune recognition, an evolutionary parallel that we discuss in this perspective review.

Matrix metalloproteinases (MMPs) are a family of structurally related proteins with the collective capability to degrade all components of the extracellular matrix. Although MMP-mediated degradation of the extracellular matrix occurs physiologically, numerous pathological conditions exhibit increased MMP levels and excessive matrix degradation. Previous work from our laboratory has shown that interferon-gamma inhibits MMP-9 expression in a manner dependent upon STAT-1alpha. Here we extend our previous observations and show that the class II major histocompatibility complex transactivator (CIITA), a transcriptional target of STAT-1alpha, is also capable of inhibiting MMP-9 expression. By using stable cell lines that inducibly express CIITA or various mutant forms of CIITA, we show that CIITA requires the ability to bind the CREB-binding protein (CBP) to effectively inhibit MMP-9 expression. Furthermore, we show that CIITA-mediated inhibition of the MMP-9 gene does not rely on the transcriptional capability of CIITA. These findings support a model wherein CIITA inhibits MMP-9 expression by binding to and sequestering CBP, which reduces the levels of CBP at the MMP-9 promoter, inhibits levels of acetylated histone 3 at the MMP-9 promoter, and subsequently inhibits MMP-9 expression.

Osteoarthritis (OA) involves progressive extracellular matrix (ECM) degradation in articular cartilage. We previously revealed that the m6A demethylase ALKBH5 stabilizes Runx2 mRNA in chondrocytes via YTHDF1, thereby increasing MMP and ADAMTS expression, causing ECM degradation. However, the transcriptional co-regulators of Runx2 remain unidentified. OA was induced in mice via injection of sodium monoiodoacetate (MIA). The histological architecture and proteoglycan content of the articular cartilage were evaluated using H&E and Safranin O-Fast Green staining, while subchondral bone microarchitecture was assessed by micro-computed tomography. Circulating proinflammatory cytokine levels were determined by ELISA. Immunoprecipitation and mass spectrometry analyses of articular cartilage from MIA-induced OA mice identified the transcriptional coactivator EYA1 (Eyes Absent Homolog 1) and CIITA (Class II Major Histocompatibility Complex Transactivator) as novel Runx2-interacting proteins. In vitro and in vivo experiments demonstrated that EYA1, CIITA, and Runx2 form a functional EYA1-CIITA-Runx2 complex that binds to the promoters of MMP and ADAMTS genes and activates their expression. Silencing any member of the complex significantly reduced transcription of these matrix-degrading enzymes. Furthermore, we identified EYA1 as a phosphatase that dephosphorylates CIITA at serine 782, a phosphorylation site targeted by Pim3 (provirus integration site for Moloney murine leukemia virus 3) under inflammatory conditions. Our findings uncover a previously unrecognized transcriptional mechanism in OA pathogenesis, in which EYA1 promotes ECM degradation by regulating CIITA dephosphorylation and assembling a transcriptional complex with CIITA and Runx2. Targeting this pathway may provide a promising therapeutic strategy for OA.

Smoking is considered as the major risk factor for the progression of atherosclerosis (AS), whereas the underlying immunological mechanism remains unclear. ApoEKO mice were treated with cigarette tar via inhalation in vivo, mouse arterial endothelial cells (MAECs) and human coronary artery endothelial cells (HCAECs) were treated with cigarette tar in vitro. Single cell RNA sequencing (scRNA-seq) was utilized to explore the molecular mechanism of CD4+ Granzyme A (Gzma+) T cells activation in smoke-related atherosclerotic progression. Cigarette tar significantly aggravated the development of atherosclerotic lesion in ApoEKO mice. Results of scRNA-seq and validation experiments further indicated that cigarette tar inhalation significantly increased the proportion of CD4+Gzma+ T cells, a T cell subset which could lead to endothelial cells (ECs) damage. Concurrently, a significant reduction in the proportion of ECs was observed. Of note, cigarette tar enhanced interaction of ECs and CD4+Gzma+ T cells via mediating major histocompatibility complex II (MHC II) signaling pathway activation rather than other antigen-presenting cell types. Mechanistically, class II major histocompatibility complex transactivator (CIITA), a key transcriptional regulator of MHC II genes expression, was identified to connect with protein arginine methyltransferases-5 (PRMT5), scoring highest via utilizing mass spectrometry analysis, which triggered symmetrical dimethylation modification of H3R2 and promoted MHC II expression. Meanwhile, CIITA knockout/knockdown, and PRMT5 inhibition/knockdown inhibited the infiltration of CD4+Gzma+ T cells and MHC II expression of ECs, alleviating the atherosclerotic lesion severity. Additionally, findings from the in vitro co-culture experiment provided additional confirmation that activated CD4+Gzma+ T cells possessed the capability to induce cytotoxicity in ECs. Cigarette tar augments the expression of MHC II in ECs via promoting CIITA nuclear translocation and PRMT5-mediated methylation modification. This process activates CD4+Gzma+ T cells, which subsequently mediate ECs injury in turn, thereby contributing to the progression of AS. Therefore, CIITA and PRMT5 represent potential therapeutic targets for interventions aimed at mitigating smoke-related AS.

Purpose: To evaluate whether patients with metastatic gastrointestinal adenocarcinomas refractory to chemotherapy harbor tumor-reactive CD4+ T cells. Experimental Design: Expansion of CD4+ tumor-infiltrating lymphocytes (TIL) and cancer cell lines was performed from gastrointestinal cancer metastases in 5 patients for the study of antitumor immune recognition. Retroviral transduction of genes encoding the class II, major histocompatibility complex, transactivator (CIITA) was used to induce the expression of major histocompatibility complex (MHC) class II in tumor cell lines. Recognition of autologous tumor cell lines by TIL was evaluated by up-regulation of 4-1BB and OX40 by flow cytometry, and/or secretion of IFNg by ELISA. Results: TIL were expanded from metastases, and new tumor cell lines were generated in 5 patients. Retroviral transduction of CIITA in tumor cell lines effectively induced expression of MHC class II in >80% of cells. Autologous tumor recognition was found in CD4+ TIL from 2 of these 5 patients. In a patient with gastric cancer liver metastases, tumor-reactive CD4+OX40+ TIL were cell-sorted from a TIL cell line. These cells up-regulated OX40 in the presence of all 4 autologous cancer cell lines albeit at different levels, but they did not produce IFNg. This recognition was specifically abolished by pan-MHC class II blocking antibodies. CD4+ TIL clones have been isolated and are being further characterised. Interestingly, tumor-reactive CD8+ TIL were previously identified and characterized in this patient. In a second patient with colon cancer abdominal wall metastases, tumor-reactive CD4+OX40+ TIL were cell-sorted from a TIL cell line. These cells were reactive to all 4 autologous cancer cell lines as they up-regulated OX40 and secreted IFNg. Recognition was blocked by anti-HLA-DR blocking antibodies. CD4+ TIL clones have been isolated and are being further characterized. In the near future, we expect to identify the TCR and HLA restriction element for both patients. We will also determine if CD4+ TIL clones have cross-reactivity against allogeneic HLA-matched gastrointestinal tumor cell lines. Conclusions: This study provides a basis for the development of immunotherapy for patients with advanced gastrointestinal malignancies by first establishing the presence of naturally occurring tumor-reactive CD4+ TIL at the molecular level. Citation Format: Sandy Pelletier, Simon Turcotte. Tumor-reactive CD4+ T cells in metastatic gastrointestinal cancer refractory to chemotherapy. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr B074.

Cis-element dependence and occupancy of the human invariant chain promoter in CIITA-dependent and -independent transcription