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Tetraspanin CD81, a modulator of immune suppression in cancer and metastasis
OncoImmunology
Abstract
Cancer cells can escape the antitumor immune response by recruiting immune suppressor cells. However, although innate myeloid-derived suppressor cells (MDSCs) and T regulatory (Treg) cells accumulate normally in tumor-bearing CD81-deficient mice, both populations are impaired in their ability to suppress the antitumor immune response.
... Remarkably, several upregulated LR interactions from microglia to astrocytes were identified, including C3-CD81 and LR interactions with ligands encoded by APOE and PSAP. Particularly, complement component 3 (C3) and its receptor CD81 molecule (CD81) are recognized for their neuroinflammatory function between microglia and astrocytes, suggesting potential implications in AD pathophysiology (Fig. 2c, Additional file 1: Fig. S2c) [52,53]. ...
... LRP1 expression is known to decrease in endothelial cells due to normal aging and in AD. C3 interacts and can bind with low-density LRP1 to regulate immune response and participate in several cellular processes [44,[64][65][66][67]. Ligand C3 and receptor CD81 play an inhibitory role in the control of immune responses [52]. We also identified alpha-2-macroglobulin (A2M) as a ligand in the A2M-LRP1 pair, which was upregulated in microglia in the discovery dataset. ...
Background
Recently, single-nucleus RNA-seq (snRNA-seq) analyses have revealed important cellular and functional features of Alzheimer's disease (AD), a prevalent neurodegenerative disease. However, our knowledge regarding intercellular communication mediated by dysregulated ligand-receptor (LR) interactions remains very limited in AD brains.
Methods
We systematically assessed the intercellular communication networks by using a discovery snRNA-seq dataset comprising 69,499 nuclei from 48 human postmortem prefrontal cortex (PFC) samples. We replicated the findings using an independent snRNA-seq dataset of 56,440 nuclei from 18 PFC samples. By integrating genetic signals from AD genome-wide association studies (GWAS) summary statistics and whole genome sequencing (WGS) data, we prioritized AD-associated Gene Ontology (GO) terms containing dysregulated LR interactions. We further explored drug repurposing for the prioritized LR pairs using the Therapeutic Targets Database.
Results
We identified 190 dysregulated LR interactions across six major cell types in AD PFC, of which 107 pairs were replicated. Among the replicated LR signals, we found globally downregulated communications in the astrocytes-to-neurons signaling axis, characterized, for instance, by the downregulation of APOE-related and Calmodulin (CALM)-related LR interactions and their potential regulatory connections to target genes. Pathway analyses revealed 44 GO terms significantly linked to AD, highlighting Biological Processes such as ‘amyloid precursor protein processing’ and ‘ion transmembrane transport,’ among others. We prioritized several drug repurposing candidates, such as cromoglicate, targeting the identified dysregulated LR pairs.
Conclusions
Our integrative analysis identified key dysregulated LR interactions in a cell type-specific manner and the associated GO terms in AD, offering novel insights into potential therapeutic targets involved in disrupted cell–cell communication in AD.
... Remarkably, several upregulated LR interactions from microglia to astrocytes were identi ed, including C3-CD81 and LR interactions with ligand encoded by APOE and PSAP. Particularly, complement component 3 (C3) and its receptor CD81 molecule (CD81) are recognized for their neuroin ammatory function between microglia and astrocytes, suggesting potential implication in AD pathophysiology (Fig. 2c, Additional le 1: Fig. S2c) [49,50]. ...
... LRP1 expression is known to decrease in endothelial cells due to normal aging and in AD. C3 interacts and can bind with low-density LRP1 to regulate immune response and participate in several cellular processes [41,[62][63][64][65]. Ligand C3 and receptor CD81 play an inhibitory role in the control of immune responses [49]. We also identi ed alpha-2-macroglobulin (A2M) as a ligand in the A2M-LRP1 pair, which was upregulated in microglia. ...
Background
Recently, single-nucleus RNA-seq (snRNA-seq) analyses have revealed important cellular and functional features of Alzheimer's disease (AD), a prevalent neurodegenerative disease. However, our knowledge regarding intercellular communication mediated by dysregulated ligand-receptor (LR) interactions remains very limited in AD brains.
Methods
We systematically assessed the intercellular communication networks by using a discovery snRNA-seq dataset comprising 69,499 nuclei from 48 human postmortem prefrontal cortex (PFC) samples. We replicated the findings using an independent snRNA-seq dataset of 56,440 nuclei from 18 PFC samples. By integrating genetic signals from AD genome-wide association studies (GWAS) summary statistics and whole genome sequencing (WGS) data, we prioritized AD-associated Gene Ontology (GO) terms containing dysregulated LR interactions. We further explored drug repurposing for the prioritized LR pairs using the Therapeutic Targets Database.
Results
We identified 316 dysregulated LR interactions across six major cell types in AD PFC, of which 210 pairs were replicated. Among the replicated LR signals, we found globally downregulated communications in astrocytes-to-neurons signaling axis, characterized, for instance, by the downregulation of APOE-related and Calmodulin (CALM)-related LR interactions and their potential regulatory connections to target genes. Pathway analyses revealed 60 GO terms significantly linked to AD, highlighting Biological Processes such as ‘amyloid precursor protein processing’ and ‘ion transmembrane transport’, among others. We prioritized several drug repurposing candidates, such as cromoglicate, targeting the identified dysregulated LR pairs.
Conclusions
Our integrative analysis identified key dysregulated LR interactions in a cell type-specific manner and the associated GO terms in AD, offering novel insights into potential therapeutic targets involved in disrupted cell-cell communication in AD.
... CD81 is a member of the tetraspanin family that was originally identified as a target of the antiproliferative antibody TAPA-1 (10). In addition to its important role in the immune system, CD81 has been revealed to be involved in the progression of most types of cancer (11,12). CD81 expression was revealed to be increased in breast cancer and promoted cell migration and proliferation in breast cancer cell lines (13). ...
... Previous studies have revealed differential expression of CD81 in various types of cancers, such as classic vs. variant hairy cell leukemia, breast cancer, and gastric cancer (13,27,28). A study by Vences-Catalan et al indicated that CD81, which is a promoter of tumor growth and metastasis, is widely expressed in most tissues and on the majority of tumor cells (11). In breast cancer, CD81 was also revealed to be upregulated in tumor tissues, associated with poor overall survival, and promoted tumor cell proliferation and migration (13). ...
CD81, a member of the tetraspanin family, has been revealed to be upregulated and associated with prognosis in several types of cancer; however, this relationship has not been explored in prostate cancer. The present study aimed to investigate the prognostic significance and functional role of CD81 in prostate cancer. The expression of CD81 in prostate cancer tissues and cell lines was evaluated using qRT-PCR analysis. Kaplan-Meier survival analysis and Cox regression analysis were conducted to explore the prognostic significance of CD81. Cell experiments were used to explore the effects of CD81 on cell proliferation, migration, and invasion in prostate cell lines in vitro. The expression of CD81 was increased in both prostate cancer tissues and cell lines. Upregulation of CD81 was significantly associated with lymph node metastasis and TNM stage. Moreover, patients with high CD81 levels had poorer overall survival than those with lower levels. Additionally, tumor cell proliferation, migration, and invasion were inhibited by knockdown of CD81. The present results indicated that CD81 plays an oncogenic role in prostate cancer. Overexpression of CD81 may serve as a prognostic biomarker and therapeutic target and is involved in the progression of prostate cancer.
... CD9 also plays a role in cell adhesion by stabilizing intercellular connections, thereby affecting cell-to-cell communication [100,101]. CD81 is additionally involved in the regulation of cellular signaling, particularly in transmitting signals associated with immune responses [102,103]. CD63 is closely linked to MVBs and late endosomes [104,105]. It plays a key role in cargo maturation and sorting and contributes to the removal of damaged proteins through lysosomal degradation [104,106]. ...
Regenerative processes occur at various levels in all organisms, yet their complexity continues to raise new questions about their mechanisms. It has been demonstrated that small extracellular vesicles (sEVs), secreted by all cells and influencing their function, play a significant role in regeneration. In the context of regenerative processes, oral mucosal tissues consistently receive interest, as they are among the most rapidly healing tissues in the human body. In this study, we utilized spatial transcriptomics to map gene expression to specific spatial locations within the gingiva tissue section, using publicly available transcriptomic data. This analysis revealed new insights into this tissue and the biogenesis of sEVs within it. The identified clusters encompassed two main regions—the epithelium and lamina propria—as well as minor niches within them. Using Gene Ontology (GO) analysis, we identified two clusters most enriched in extracellular vesicle-related GO processes. These included the superficial and deeper layers of the sulcular epithelium, one of the most peripheral regions of the gingiva. Of the 43 genes identified in the literature as having a potential or documented role in sEVs biogenesis, 12 were selected for further analysis. MUC1, SDCBP2, and VPS37B showed clear specificity and the highest expression in the superficial layer of the sulcular epithelium. CHMP4C also exhibited high expression in this layer, though its levels were comparable to the outer layer of the oral epithelium. Other well-established sEVs marker genes, such as ANXA2, CD9, CD63, CD81, FLOT1, RAB22A, RAB27B, and RAB5A, were also expressed in the examined tissue; however, their expression was not specifically exclusive to the sulcular epithelium. Our study is the first to perform a meta-analysis of available gingival transcriptomic data in the specific context of sEVs biogenesis. The presented data and conclusions provide new insights into the role of different structures within healthy human gingiva and shed new light on both known and potential markers of sEVs biogenesis. These findings may contribute to the development of regeneration-targeted research, especially on oral tissues.
... This is the case for the specific anti-human CD81 antibody 5A6 which recognizes a conformational epitope on the ectodomain of CD81 and has proved very efficient at inhibiting invasion of TNBC cells and the formation of metastases in xenograft models of TNBC [30]. Several antibodies targeting CD81 are being developed [68]. In contrast, there are no small molecules at present known to efficiently and selectively target CD81. ...
Aim: Harzianoic acids A and B (Hz-A/B) are two rare cyclobutene-containing sesquiterpenes isolated from a marine strain of the sponge-associated fungus Trichoderma harzianum. They display anticancer and antiviral effects, reducing the entry of hepatitis C virus (HCV) into hepatocarcinoma cells. The large extracellular loop (LEL) of the tetraspanin protein CD81 represents a molecular target for both Hz-A and Hz-B. Methods: The interaction of Hz-A/B with CD81 has been modeled, using structures of the cholesterol-bound full-length protein and a truncated protein corresponding to the LEL portion. The models mimicked the closed and open conformations of the LEL. Results: The best ligand Hz-B can form stable complexes with the open LEL structure, whereas binding to the closed form is drastically reduced. Key H-bonds between the acid groups of Hz-B and the CD81-LEL domain stabilize the ligand-protein complex. A comparison of the interaction with the homologous tetraspanin CD9, which also presents a dynamic open/closed equilibrium, underlined the marked selectivity of Hz-A/B for CD81 over CD9. The cyclobutane-containing monoterpene grandisol, an insect pheromone, has been identified as a fragment that could be modulated to improve its modest interaction with CD81-LEL. Conclusions: The modeling docking analysis suggests that Hz-B is a robust CD81 binder, better interacting with the LEL portion of CD81 compared to CD9-LEL. The docking study paves the way to the design of small molecules targeting CD81. The study has implications for a better understanding of CD81 binding properties and the regulation of its activities.
... We previously demonstrated that both T regulatory cells and myeloid-derived suppressor cells are impaired in CD81KO mice (4). Consequently, tumor growth and metastasis are inhibited in CD81KO mice (1,5,6). CD81 belongs to an evolutionarily conserved tetraspanin family, members of which play a role in cell-cell interactions (7,8). ...
Metastases are reduced in CD81KO mice. In addition, a unique anti-CD81 antibody, 5A6, inhibits metastasis in vivo and invasion and migration in vitro. Here, we probed the structural components of CD81 required for the antimetastatic activity induced by 5A6. We found that the removal of either cholesterol or the intracellular domains of CD81 did not affect inhibition by the antibody. We show that the uniqueness of 5A6 is due not to increased affinity but rather to its recognition of a specific epitope on the large extracellular loop of CD81. Finally, we present a number of CD81 membrane-associated partners that may play a role in mediating the 5A6 antimetastatic attributes, including integrins and transferrin receptors.
... In this case, the corresponding KO cell line transplanted in mice exhibited a significantly reduced tumor growth and lung metastasis compared to the control group [116]. Moreover, CD81 KO mice exhibit an impaired immune response due to the altered capacity of CD81 to regulate the secretion of interleukin-10 (IL-10) in T regulatory (Treg) cells [117,118]. ...
Simple Summary
Novel therapeutic targets are needed to improve treatments of aggressive cancers and viral diseases. Tetraspanins represent an emerging class of anticancer targets, notably the transmembrane protein CD81 which has been structurally well characterized. CD81 plays key roles in tumor growth and dissemination, and serves as a co-receptor for a number of viruses. The protein interacts with a variety of protein partners involved in different signaling pathways. Here, we provide an overview of the complementary approaches used to target CD81, with monoclonal antibodies and small molecules, including both natural products and synthetic compounds. Drug design approaches are discussed, as well as the limitations associated with the targeting of this ubiquitous protein. CD81 is considered as a promising anticancer and antiviral target.
Abstract
Tetraspanin CD81 plays major roles in cell-cell interactions and the regulation of cellular trafficking. This cholesterol-embarking transmembrane protein is a co-receptor for several viruses, including HCV, HIV-1 and Chikungunya virus, which exploits the large extracellular loop EC2 for cell entry. CD81 is also an anticancer target implicated in cancer cell proliferation and mobility, and in tumor metastasis. CD81 signaling contributes to the development of solid tumors (notably colorectal, liver and gastric cancers) and has been implicated in the aggressivity of B-cell lymphomas. A variety of protein partners can interact with CD81, either to regulate attachment and uptake of viruses (HCV E2, claudin-1, IFIM1) or to contribute to tumor growth and dissemination (CD19, CD44, EWI-2). CD81-protein interactions can be modulated with molecules targeting the extracellular domain of CD81, investigated as antiviral and/or anticancer agents. Several monoclonal antibodies anti-CD81 have been developed, notably mAb 5A6 active against invasion and metastasis of triple-negative breast cancer cells. CD81-EC2 can also be targeted with natural products (trachelogenin and harzianoic acids A-B) and synthetic compounds (such as benzothiazole-quinoline derivatives). They are weak CD81 binders but offer templates for the design of new compounds targeting the open EC2 loop. There is no anti-CD81 compound in clinical development at present, but this structurally well-characterized tetraspanin warrants more substantial considerations as a drug target.
... Nr3c1 also activates expression of repair gene Areg. Foxp3, Zfp281 and Batf upregulate age-increased Cd81, a receptor important for Treg antitumor responses (Vences-Catalán et al. 2016). Similar to the TfhInt population, cTreg have age-elevated Stat3 activity, which is predicted to suppress interferon-inducible genes and drives Tfh10 core regulator Nfia, in this context as well. ...
Aging profoundly affects immune system function, rendering the elderly more susceptible to pathogens, cancers and chronic inflammation. We previously identified a population of IL-10-producing, T follicular helper-like cells ("Tfh10"), linked to suppressed vaccine responses in aged mice. Here, we use the power of single-cell (sc)genomics and genome-scale modeling to characterize Tfh10 — and the full CD4 ⁺ memory T cell (CD4 ⁺ TM) compartment — in young and old mice. Unprecedented scRNA-seq coverage of the CD4 ⁺ TM compartment and parallel chromatin accessibility measurements (scATAC-seq) enabled identification of 13 CD4 ⁺ TM populations, which we validated as a reference through comprehensive cross-comparison to aging cell atlases and scRNA-seq studies reporting Tfh10 in other contexts. Beyond robust characterization of age- and cell-type-dependent transcriptional landscapes, we used integrative computational modeling to predict the underlying regulatory mechanisms: We inferred gene regulatory networks (GRNs) that describe transcription-factor control of gene expression in each T-cell population and how these circuits change with age. Furthermore, we integrated our data with prior, pan-cell scRNA-seq studies to identify intercellular-signaling networks driving age-dependent changes in CD4 ⁺ TM. Our atlas of finely resolved CD4 ⁺ TM subsets, GRNs and cell-cell communication networks is a critical resource for analysis of biologic processes operative in memory T cells in youth and old age. The resource presents new opportunities to manipulate regulatory circuits in CD4 ⁺ TM, which, long-term, could improve immune responses in the elderly.
... CD81 is identified as an exosomal biomarker and has been found in highly enriched antigens in EVs [221]. Moreover, CD81 has been reported to be involved in the progression of many types of cancers via intracellular communications [227]. Furthermore, CD81 is revealed as a cancer biomarker as higher levels have been reported in BC [188,228]. ...
Exosomes have emerged as natural nanocarriers and are advantageous in the field of nanomedicine due to their lipid bilayer membrane comprising many proteins, nucleic acids and cell debris. Exosomes are secreted from all types of living cells and play a role in cancer diagnosis and therapy because of their biological properties, such as intercellular communication, modulation of immune responses, biocompatibility and target specificity. Many studies have shown that exosomes can be engineered or modified with different therapeutic substances, including nucleic acids, proteins, drugs and other nanomaterials, to improve their specificity, efficiency and safety in nanomedicine. In this review, we summarize the methodologies of exosome biogenesis, purification, the possible mechanisms of cellular uptake and the important role of exosomes in cancer diagnosis, followed by the role of engineered exosomes in cancer therapy. Also, future trends and challenges are discussed. We strongly suggest that a clear articulation of the fundamental principles for the creation of exosome-based theranostic platforms will help reveal the unique powers of exosomes in early cancer diagnosis and therapeutics, including chemotherapy, gene therapy, immunotherapy and phototherapy.
... CD81 is a quadruple transmembrane protein molecule that is widely distributed in living organisms and participates in a variety of physiological responses [15]. CD81 is widely expressed in tumor cells, and its role in malignant cells and the host microenvironment has been preliminarily studied [16]. ...
Background: Bladder cancer (BC) is a highly heterogeneous stem cell disease. Cancer stem cells (CSCs) are the drivers of tumor growth and recurrence, with the ability to self-renew, metastasize, and resist chemotherapy. However, the specific molecular mechanisms of CSCs driving BC recurrence and progression remains unclear.
Objective: To explore the underlying molecular mechanism of CSCs driving BC recurrence and progression.
Methods: Tumor xenograft model in vivo was established after 4-6-week-old male nude mice were subcutaneously injected with 5×10⁶ of T24 and 5637 cells in 0.1 mL 50% Matrigel. Pearson correlation analysis analyzed the correlation between miR-582-5p and CD81, and which was furtherly verified by dual-luciferase reporter gene assay. Sphere formation assay, flow cytometry, immunohistochemistry (IHC), qRT-PCR and Western blot were carried to examine sphere formation, ALDHhigh populations, the level of genes and proteins. Multivariate analysis was carried to explore the factors associated with recurrence free survival of BC patients.
Results: MiR-582-5p was down-regulated in patients with BC, and miR-582-5p overexpression negatively correlated with BC stemness. Mechanically, miR-582-5p negatively targeted to CD81. Functionally, miR-582-5p overexpression inhibited BC stemness and recurrence via targeting CD81.
Conclusion: Our study illustrated that miR-582-5p inhibited cell stemness and recurrence via targeting CD81 in BC. Our findings illustrated the specific molecular mechanism of miR-582-5p inhibiting BC progression. MiR-582-5p may serve as the novel biomarker for BC clinical therapeutics and prognosis.
... BAFF transgenic mice have expanded CD25 + Foxp3 + Tregs with a cell surface phenotype consistent with an increased activation status and enhanced ability to home to inflamed sites [28]. Ccr2, Cd81, and Tnfrsf4 are involved in the trafficking of Tregs to tumors [29,30]. Il1r2, encoding a decoy receptor for IL-1, was highly expressed in activated aged Tregs. ...
Aging is associated with a massive infiltration of T lymphocytes in the lacrimal gland. Here, we aimed to characterize the immune phenotype of aged CD4+ T cells in this tissue as compared with lymphoid organs. To perform this, we sorted regulatory T cells (Tregs, CD4+CD25+GITR+) and non-Tregs (CD4+CD25negGITRneg) in lymphoid organs from female C57BL/6J mice and subjected these cells to an immunology NanoString® panel. These results were confirmed by flow cytometry, live imaging, and tissue immunostaining in the lacrimal gland. Importantly, effector T helper 1 (Th1) genes were highly upregulated on aged Tregs, including the master regulator Tbx21. Among the non-Tregs, we also found a significant increase in the levels of EOMESmed/high, TbetnegIFN-γ+, and CD62L+CD44negCD4+ T cells with aging, which are associated with cell exhaustion, immunopathology, and the generation of tertiary lymphoid tissue. At the functional level, aged Tregs from lymphoid organs are less able to decrease proliferation and IFN-γ production of T responders at any age. More importantly, human lacrimal glands (age range 55-81 years) also showed the presence of CD4+Foxp3+ cells. Further studies are needed to propose potential molecular targets to avoid immune-mediated lacrimal gland dysfunction with aging.
... The above evidence indicates that tetraspanins play important roles in exosome biogenesis via an ESCRT-independent mechanism. In addition to being an exosome marker, CD9 was previously demonstrated to participate in the invasive and metastatic abilities of human breast cancer cells [158,159], whereas CD81 has been reported to modulate immune suppression and promote tumor growth and metastasis [160]. Proteins related to the biogenesis and secretion of exosomes (such as ALIX and TSG101) facilitate exosome formation via the ESCRT mechanism [7]. ...
Exosomes participate in cell–cell communication by transferring molecular components between cells. Previous studies have shown that exosomal molecules derived from cancer cells and liquid biopsies can serve as biomarkers for cancer diagnosis and prognosis. The exploration of the molecules transferred by lung cancer-derived exosomes can advance the understanding of exosome-mediated signaling pathways and mechanisms. However, the molecular characterization and functional indications of exosomal proteins and lipids have not been comprehensively organized. This review thoroughly collected data concerning exosomal proteins and lipids from various lung cancer samples, including cancer cell lines and cancer patients. As potential diagnostic and prognostic biomarkers, exosomal proteins and lipids are available for clinical use in lung cancer. Potential therapeutic targets are mentioned for the future development of lung cancer therapy. Molecular functions implying their possible roles in exosome-mediated signaling are also discussed. Finally, we emphasized the importance and value of lung cancer stem cell-derived exosomes in lung cancer therapy. In summary, this review presents a comprehensive description of the protein and lipid composition and function of lung cancer-derived exosomes for lung cancer diagnosis, prognosis, and treatment.
... CD81 is a four-fold transmembrane protein molecule with multiple biological activities. 18 It is widely distributed in the organism, and it participates in a large number of physiological responses. CD81 plays an important role in multiple cellular processes; it is closely related to the pathogenesis of many human diseases. ...
Yuan H, Zhao J, Yang Y, et al. Cancer Manag Res. 2020;12:13273–13284.
We, the Editors and Publisher of Cancer Management and Research, have retracted the following article.
Following publication of the article, concerns were raised regarding the duplication of images from Figure 2 with images from other unrelated articles. Images for Figure 2F have been duplicated with images for Figure 3F from Zhu Z, Wang H, Pang Y, Hu H, Zhang H, Wang W. Exosomal long non-coding RNA UCA1 functions as growth inhibitor in esophageal cancer. Aging (Albany NY). 2020;12:20523-20539. https://doi.org/10.18632/aging.103911 (RETRACTED) and Figure 4D from Zhong X, Wen X, Chen L, Gu N, Yu X, Sui K. Long non-coding RNA KCNQ1OT1 promotes the progression of gastric cancer via the miR-145-5p/ARF6 axis. J Gene Med. 2021;23:e3330. https://doi.org/10.1002/jgm.3330.
In addition, the images of Figure 2E, LOVO, vector-NC and si-NC, have been duplicated.
The authors responded to our queries but were unable to provide an explanation for the duplicated images or provide data for the study. As verifying the validity of published work is core to the integrity of the scholarly record, we are therefore retracting the article and the authors agree with this decision.
We have been informed in our decision-making by our editorial policies and COPE guidelines.
The retracted article will remain online to maintain the scholarly record, but it will be digitally watermarked on each page as “Retracted”.
... It is widely expressed on many healthy tissues and on the majority of tumor cells. Vences-Catalan et al. demonstrated in comprehensive studies the role of CD81 as a promoter of tumor growth and metastasis with a putatively important role in tumor progression [24,25]. Zhang et al. described that an increased expression of CD81 was significantly associated with reduced overall survival in patients with mammary carcinoma. ...
Malignant germ cell tumors (GCT) are the most common malignant tumors in young men between 18 and 40 years. The correct identification of histological subtypes, in difficult cases supported by immunohistochemistry, is essential for therapeutic management. Furthermore, biomarkers may help to understand pathophysiological processes in these tumor types. Two GCT cell lines, TCam-2 with seminoma-like characteristics, and NTERA-2, an embryonal carcinoma-like cell line, were compared by a quantitative proteomic approach using high-resolution mass spectrometry (MS) in combination with stable isotope labelling by amino acid in cell culture (SILAC). We were able to identify 4856 proteins and quantify the expression of 3936. 347 were significantly differentially expressed between the two cell lines. For further validation, CD81, CBX-3, PHF6, and ENSA were analyzed by western blot analysis. The results confirmed the MS results. Immunohistochemical analysis on 59 formalin-fixed and paraffin-embedded (FFPE) normal and GCT tissue samples (normal testis, GCNIS, seminomas, and embryonal carcinomas) of these proteins demonstrated the ability to distinguish different GCT subtypes, especially seminomas and embryonal carcinomas. In addition, siRNA-mediated knockdown of these proteins resulted in an antiproliferative effect in TCam-2, NTERA-2, and an additional embryonal carcinoma-like cell line, NCCIT. In summary, this study represents a proteomic resource for the discrimination of malignant germ cell tumor subtypes and the observed antiproliferative effect after knockdown of selected proteins paves the way for the identification of new potential drug targets.
... It plays an important role in cell organization, protein trafficking, cellular fusion, and cell-cell interactions, and is associated with cell signaling molecules such as protein kinase C, extracellular signal-regulated kinase (ERK), mitogen-activated protein kinase (MAPK), Ras, and Rac [8]. CD81 is also involved in B and T cell activation in the immune system and affects tumor growth and metastasis through the regulation of T regulatory cell function [9][10][11][12]. In several cancers such as breast and lung cancer, hepatocellular carcinoma, and melanoma, CD81 expression was reported to be associated with cancer progression [13][14][15][16][17]. ...
Purpose:
CD81 is a prognostic biomarker for high-grade bladder cancer (BC). In this study, we aimed to determine the functional mechanisms underlying the role of CD81 in BC progression.
Materials and methods:
In two invasive BC cell lines (T24, J82), CD81 expression was suppressed by the transfection of lentiviral vectors including CD81-specific shRNAs, and then the migration and invasion of BC cells was analyzed. Enzymatic activity of matrix metalloproteinases (MMPs) was also analyzed by collagen-zymography. The expression of MMPs was confirmed by western blotting using culture supernatants from each cell line. Signaling pathways related to MMPs were investigated using various antibodies.
Results:
CD81 was successfully knocked down by shRNAs in T24 and J82 cell lines. While the migration of BC cells was not affected after the knockdown of CD81, the invasive activity was significantly increased in both cell lines. Zymography produced distinct bands using supernatants from CD81-knockdown cells, whereas only faint bands were observed with empty vector-transfected cells. We also observed an increased expression of MMPs, specifically MMP2 and 9, in the conditioned media from CD81-knockdown cells by western blotting. Mechanistically, the phosphorylation of extracellular signal-regulated kinase (ERK) was associated with the invasive activity of BC cells, while U0126 (an ERK inhibitor) reduced the invasive activity of CD81-knockdown BC cells.
Conclusions:
Taken together, CD81 suppression promotes the invasive property of BC cells through MMP signaling via ERK phosphorylation. Our results suggest that the regulation of CD81 expression may have some therapeutic potential in BC.
... Additionally, expression of CD81 in the host contributes to tumor progression; CD81KO mice have fewer metastases of breast and lung tumors in syngeneic mouse models (23). Importantly, expression of CD81 in immune suppressive cells contributes to tumor progression (24). A recent study showed that expression of CD151 in human is associated with a hyper-proliferative T cell phenotype (25), it would be interesting to know if CD151 expressed in mouse immune cells plays a role in tumor progression. ...
Metastasis is the ultimate consequence of cancer progression and the cause of patients’ death across different cancer types. Patients with initial diagnosis of distant disease have a worst 5-year survival compared to patients with localized disease. Therapies that target primary tumors fail to eradicate distant dissemination of cancer. Recently, immunotherapies have improved the survival of patients with metastatic disease, such as melanoma and lung cancer. However, only a fraction of patients responds to immunotherapy modalities that target the host immune system. The need to identify new druggable targets that inhibit or prevent metastasis is, therefore, much needed. Tetraspanins have emerged as key players in regulating cell migration, invasion, and metastasis. By serving as molecular adaptors that cluster adhesion receptors, signaling molecules, and cell surface receptors; tetraspanins are involved in all steps of the metastatic cascade. They regulate cell proliferation, participate in EMT transition, modulate integrin-mediated cell adhesion, and participate in angiogenesis and invasion processes. Tetraspanins have also been shown to modulate metastasis indirectly through exosomes and by regulating cellular interactions in the immune system. Importantly, targeting individual tetraspanin with antibodies has impacted tumor progression. This review will focus on the contribution of tetraspanins to the metastatic process and their potential as therapeutic tumor targets.
The healing of wounds in diabetic patients is a huge challenge issue in clinical medicine due to the disordered immune. Recruiting endogenous cells to play a role in the early stage and timely reducing inflammation to promote healing in the middle or late of injuring are both prerequisites for effective treatment. Here, inspired by natural extracellular matrix, three-dimensional porous polyurethane-hyaluronic acid hybrid hydrogel scaffolds (PUHA) were prepared to repair diabetic wound through activate cell immunity by moderate foreign body reaction, provide cell adhesion growth extracellular matrix of hyaluronic acid (HA) and exhibit anti-inflammatory effect of polyurethane (PU). The interaction between PU and HA alters the compact PU hydrogel into macroporous PUHA hydrogel scaffolds with super-swelling, elastic mechanical properties, and controllable degradation, which are suitable for endogenous cells infiltration, growth and immune activation. Additionally, incorporating with RGD, PUHA hydrogel scaffolds with bioactive physicochemical features can evidently reduce the inflammation and modulate the polarization of macrophage apparently both in vitro and in vivo, mainly through downregulation of cytokine-cytokine receptor interaction genes, leading to reprogramming immune-microenvironment and rapid diabetic wound healing. This method of gathering cells initially and intervening immune-microenvironment in time provides an expected way to design biomaterials for chronic wound healing.
Background
The oncogenic tetraspanins CD9, CD 63, CD 81, CD151, and Tspan 8 have been recognized as critical mediators of cellular functions and malignant molecular mechanisms of human cancers. They support metastasis, drug resistance, and stem cell maintenance by interacting with other tetraspanins, receptors, and signaling molecules. Targeting tetraspanins have been proven to be efficient in destroying cancer cells and in blocking metastasis. Breast, ovarian, and cervical cancers are leading cancers among the top ten cancer in women. Their treatment is highly challenging due to the lack of early diagnostic markers and potential targets of drug resistance mechanisms.
Purpose
To review the recent updates on oncogenic tetraspanin-mediated metastasis, drug resistance, and maintenance of stem cells, as well as their potentiality in the treatment and diagnosis of cancers in females.
Discussion
This review discussed the role of oncogenic tetraspanins in regulating signaling pathways of metastasis. We also discussed their role in maintaining stem cells and drug resistance. Finally, we elaborated on their relevance in treating and diagnosing cancers in females.
Conclusion
This study could help identify promising tetraspanins, which can be implicated in the early diagnosis and treatment of cancers in females.
A case of a young girl diagnosed with an antibody deficiency syndrome serves to highlight the role of CD81 in B cell biology. Moreover, this case illustrates a fundamental function of the tetraspanin family, namely their association with partner proteins. Characterization of the patient's B cells revealed lack of surface CD19 although both of her CD19 alleles were normal. Further analysis determined that her antibody deficiency syndrome was due to a mutation in the CD81 gene, which did not enable expression of CD19 on the surface of the patient's B cells. Actually, the partnership of CD81 with CD19 and the dependency of CD19 for its trafficking to the cell surface expression were first documented in CD81-deficient mice. CD81 is a widely expressed protein, yet the mutation in the antibody-deficient patient impaired mostly her B cell function. CD81 is required for multiple normal physiological functions, which have been subverted by major human pathogens, such as hepatitis C virus. However, this review will focus on the function of CD81 in cells of the adaptive immune system. Specifically, it will highlight studies focusing on the different roles of CD81 in B and T cells and on its function in B-T cell interactions.
Myeloid cells are the most abundant nucleated haematopoietic cells in the human body and are a collection of distinct cell populations with many diverse functions. The three groups of terminally differentiated myeloid cells - macrophages, dendritic cells and granulocytes - are essential for the normal function of both the innate and adaptive immune systems. Mounting evidence indicates that the tumour microenvironment alters myeloid cells and can convert them into potent immunosuppressive cells. Here, we consider myeloid cells as an intricately connected, complex, single system and we focus on how tumours manipulate the myeloid system to evade the host immune response.
Antibody deficiencies constitute the largest group of symptomatic primary immunodeficiency diseases. In several patients, mutations in CD19 have been found to underlie disease, demonstrating the critical role for the protein encoded by this gene in antibody responses; CD19 functions in a complex with CD21, CD81, and CD225 to signal with the B cell receptor upon antigen recognition. We report here a patient with severe nephropathy and profound hypogammaglobulinemia. The immunodeficiency was characterized by decreased memory B cell numbers, impaired specific antibody responses, and an absence of CD19 expression on B cells. The patient had normal CD19 alleles but carried a homozygous CD81 mutation resulting in a complete lack of CD81 expression on blood leukocytes. Retroviral transduction and glycosylation experiments on EBV-transformed B cells from the patient revealed that CD19 membrane expression critically depended on CD81. Similar to CD19-deficient patients, CD81-deficient patients had B cells that showed impaired activation upon stimulation via the B cell antigen receptor but no overt T cell subset or function defects. In this study, we present what we believe to be the first antibody deficiency syndrome caused by a mutation in the CD81 gene and consequent disruption of the CD19 complex on B cells. These findings may contribute to unraveling the genetic basis of antibody deficiency syndromes and the nonredundant functions of CD81 in humans.
Membrane lipids and proteins are non-randomly distributed and are unable to diffuse freely in the plane of the membrane. This is because of multiple constraints imposed both by the cortical cytoskeleton and by the preference of lipids and proteins to cluster into diverse and specialized membrane domains, including tetraspanin-enriched microdomains, glycosylphosphatidyl inositol-linked proteins nanodomains and caveolae, among others. Recent biophysical characterization of tetraspanin-enriched microdomains suggests that they might be specially suited for the regulation of avidity of adhesion receptors and the compartmentalization of enzymatic activities. Moreover, modulation by tetraspanins of the function of adhesion receptors involved in inflammation, lymphocyte activation, cancer and pathogen infection suggests potential as therapeutic targets. This review explores this emerging picture of tetraspanin microdomains and discusses the implications for cell adhesion, proteolysis and pathogenesis.
CD81 is a cell surface molecule expressed on many cell types and associated with the CD19/CD21/Leu13 signal-transducing complex on B cells. A recent report implies that CD81 expression on thymic stromal cells is important in the maturation of thymocytes from CD4-CD8- to CD4+CD8+. However, we have produced CD81-null mice by gene targeting, and find that they undergo normal development of thymocytes and express normal numbers of T cells. B cells are also found in normal numbers in the spleen, blood, and peritoneal cavity of CD81-null mice, but they express a lower level of CD19 compared to heterozygous littermates. Finally, early antibody responses to the protein antigen ovalbumin are weaker in CD81-null mice compared to their heterozygous littermates. This is consistent with the proposed role of the CD19/CD21/CD81-signaling complex in lowering the threshold for B cell responses. These results show that CD81 is not required for maturation of T cells, but is important for optimal expression of CD19 on B cells and optimal stimulation of antibody production.
The tetraspanin CD81 has been involved in T-dependent B cell-mediated immune responses. However, the behavior of CD81 during immune synapse (IS) formation has not been elucidated. We determined herein that CD81 redistributed to the contact area of T cell-B cell and T cell-dendritic cell conjugates in an Ag-dependent manner. Confocal microscopy showed that CD81 colocalized with CD3 at the central supramolecular activation complex. Videomicroscopy studies with APC or T cells transiently expressing CD81-green fluorescent protein (GFP) revealed that in both cells CD81 redistributed toward the central supramolecular activation complex. In T lymphocytes, CD81-GFP rapidly redistributed to the IS, whereas, in the APC, CD81-GFP formed a large accumulation in the contact area that later concentrated in a discrete cluster and waves of CD81 accumulated at the IS periphery. These results suggest a relevant role for CD81 in the topography of the IS that would explain its functional implication in T cell-B cell collaboration.
Tumor cells counteract innate and adaptive antitumor immune responses by recruiting regulatory T cells (Treg) and innate myeloid-derived suppressor cells (MDSC), which facilitate immune escape and metastatic dissemination. Here we report a role in these recruitment processes for CD81, a member of the tetraspanin family of proteins that have been implicated previously in cancer progression. We found that genetic deficiency in CD81 reduced tumor growth and metastasis in two genetic mouse backgrounds and multiple tumor models. Mechanistic investigations revealed that CD81 was not required for normal development of Treg and MDSC but was essential for immunosuppressive functions. Notably, adoptive transfer of wildtype Treg into CD81-deficient mice was sufficient to promote tumor growth and metastasis. Our findings suggested that CD81 modulates adaptive and innate immune responses, warranting further investigation of CD81 in immunomodulation in cancer and its progression.
Copyright © 2015, American Association for Cancer Research.
Immune checkpoint therapy, which targets regulatory pathways in T cells to enhance antitumor immune responses, has led to important clinical advances and provided a new weapon against cancer. This therapy has elicited durable clinical responses and, in a fraction of patients, long-term remissions where patients exhibit no clinical signs of cancer for many years. The way forward for this class of novel agents lies in our ability to understand human immune responses in the tumor microenvironment. This will provide valuable information regarding the dynamic nature of the immune response and regulation of additional pathways that will need to be targeted through combination therapies to provide survival benefit for greater numbers of patients.
Preclinical models have been developed and applied to predict the clinical efficacy of immune checkpoint antibodies. Now these models can be used to dissect the mechanisms by which such immunotherapeutic antibodies work and to build the rationale for combining immune checkpoint-targeting antibodies with potential synergistic activity in cancer patients.
Tumours progress through a cascade of events that enable the formation of metastases. Some of the components that are required for this fatal process are well established. Tetraspanins, however, have only recently received attention as both metastasis suppressors and metastasis promoters. This late appreciation is probably due to their capacity to associate with various molecules, which they recruit into special membrane microdomains, and their abundant presence in tumour-derived small vesicles that aid intercellular communication. It is reasonable to assume that differences in the membrane and vesicular web components that associate with individual tetraspanins account for their differing abilities to promote and suppress metastasis.