Cyclophilin-CD147 interactions: a new target for anti-inflammatory therapeutics

Participation of 3-O-sulfated heparan sulfates in the protection of macrophages by herpes simplex virus-1 glycoprotein D and cyclophilin B against apoptosis

Heparan sulfates (HS) are involved in numerous biological processes, which rely on their ability to interact with a large panel of proteins. Although the reaction of 3‐O‐sulfation can be catalysed by the largest family of HS sulfotransferases, very few mechanisms have been associated with this modification and to date, only glycoprotein D (gD) of herpes simplex virus‐1 (HSV‐1 gD) and cyclophilin B (CyPB) have been well‐described as ligands for 3‐O‐sulfated HS. Here, we hypothesized that both ligands could induce the same responses via a mechanism dependent on 3‐O‐sulfated HS. First, we checked that HSV‐1 gD was as efficient as CyPB to induce the activation of the same signalling events in primary macrophages. We then demonstrated that both ligands efficiently reduced staurosporin‐induced apoptosis and modulated the expression of apoptotic genes. In addition to 3‐O‐sulfated HS, HSV‐1 gD was reported to interact with other receptors, including herpes virus entry mediator (HVEM), nectin‐1 and ‐2. Thus, we decided to identify the contribution of each binding site in the responses triggered by HSV‐1 gD and CyPB. We found that knock‐down of 3‐O‐sulfotransferase 2, which is the main 3‐O‐sulfated HS‐generating enzyme in macrophages, strongly reduced the responses induced by both ligands. Moreover, silencing the expression of HVEM rendered macrophages unresponsive to either HSV‐1 gD and CyPB, thus indicating that both proteins induced the same responses by interacting with a complex formed by 3‐O‐sulfated HS and HVEM. Collectively, our results suggest that HSV‐1 might hijack the binding sites for CyPB in order to protect macrophages against apoptosis for efficient infection.

Melittin inhibits the invasion of MCF-7 cells by downregulating CD147 and MMP-9 expression

Tumor invasion and metastasis are the critical steps in determining the aggressive phenotype of human cancers. Melittin, a major component of bee venom, has been reported to induce apoptosis in several cancer cells. However, the mechanisms of melittin involvement in cancer invasion and metastasis remain unclear. Our previous study indicated that melittin inhibits cyclophilin A (CypA), a ubiquitously distributed peptidylprolyl cis-trans isomerase, in macrophage cells. In the present study, the Transwell assay results showed that melittin may downregulate the invasion level of MCF-7 cells in a dose-dependent manner. Additionally, it was also found, using flow cytometry and reverse transcription-polymerase chain reaction, that melittin decreased the expression of cluster of differentiation (CD)147 and matrix metallopeptidase-9 (MMP-9), whereas CypA upregulated the expression of CD147 and MMP-9. Overall, the present study indicated that melittin decreased the invasion level of MCF-7 cells by downregulating CD147 and MMP-9 by inhibiting CypA expression. The results of the present study provide an evidence for melittin in anticancer therapy and mechanisms.

Inhibition of tumor growth and metastasis by EMMPRIN multiple antigenic peptide (MAP) vaccination is mediated by immune modulation

Previously, we have identified a new epitope in EMMPRIN, a multifunctional protein that mediates tumor cell-macrophage interactions and induces both MMP-9 and VEGF. Here, we synthesized this epitope as an octa-branched multiple antigenic peptide (MAP) to vaccinate mice implanted with subcutaneous syngeneic colon (CT26), prostate (TRAMP-C2) or renal (RENCA) cell line carcinomas. Vaccination inhibited, and sometimes regressed, tumor growth in a dose-dependent manner, reaching 94%, 71% and 72% inhibition, respectively, at a 50 μg dose (p < 0.01). Mice with regressed tumors demonstrated immune memory, preventing tumor recurrence upon re-implantation (p < 0.001). When tumor cells were administered through the tail vein to generate lung metastases, vaccination reduced the number of metastatic foci (by 15- and 23-folds, p < 0.001), and increased the median survival time by 25% and 53% in RENCA and CT26 metastases, respectively (p < 0.01) relative to scrambled-MAP controls. No significant adverse responses were observed in all experiments. We show that the tumor microenvironment was immune modulated, as vaccination induced production of EMMPRIN-specific antibodies, increased CD8⁺ T cells infiltration and cytotoxicity, alleviated immune suppression by decreasing TGFβ concentrations, reduced angiogenesis and cell proliferation, and enhanced apoptosis. Thus, our successful active peptide vaccination strategy differs from previous, unsuccessful attempts, both in the selected target (the EMMPRIN epitope) and in the use of a modified, MAP configuration, and demonstrates that this may be an efficient approach for the treatment and prevention of some types of cancer.

Impact of Minocycline on Extracellular Matrix Metalloproteinase Inducer, a Factor Implicated in Multiple Sclerosis Immunopathogenesis

Extracellular matrix metalloproteinase inducer (EMMPRIN, CD147) is a transmembrane glycoprotein that is upregulated on leukocytes in active lesions in multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). Administration of anti-EMMPRIN Abs reduces the severity of EAE. Minocycline is a tetracycline antibiotic with immune-modulatory properties that decreases the severity of EAE; it was recently found to attenuate the conversion from a first demyelinating event to clinically definite MS in a phase III trial. We investigated whether and how minocycline affects the expression of EMMPRIN on T cells in culture and in mice afflicted with EAE. EMMPRIN expression in cultures of mouse splenocytes or human PBMCs was elevated upon polyclonal T cell activation, and this was reduced by minocycline correspondent with decreased P-Akt levels. An established MS medication, IFN-β, also diminished EMMPRIN levels on human cells whereas this was not readily observed for fingolimod or monomethylfumarate. In EAE-afflicted mice, minocycline treatment significantly reduced EMMPRIN levels on splenic lymphocytes at the presymptomatic (day 7) phase, and prevented the development of disease. Day 7 spleen transcripts from minocycline-treated EAE mice had a significantly lower MMP-9/TIMP-1 ratio, and significantly lower MCT-1 and CD98 levels, factors associated with EMMPRIN function. Day 16 (peak clinical severity) CNS samples from EAE mice had prominent representation of inflammatory perivascular cuffs, inflammatory molecules and EMMPRIN, and these were abrogated by minocycline. Overall, minocycline attenuated the activation-induced elevation of EMMPRIN on T cells in culture and in EAE mice, correspondent with reduced immune function and EAE CNS pathology.

Identification of low abundance cyclophilins in human plasma

Cylophilins (Cyps) belong to the ubiquitously distributed enzyme class of peptidyl prolyl cis/trans isomerases (EC5.2.1.8), which are foldases capable of accelerating slow steps in the refolding of denatured proteins. At least 20 different Cyp isoenzymes are broadly distributed among all organs and cellular compartments in humans. Extracellularly localized Cyps came into the scientific focus recently because of their involvement in the control of inflammatory diseases, as well as viral and bacterial infections. However, detailed insights into Cyp functions are often hampered by the lack of sensitive detection methods. We present an improved method for affinity purification and detection of Cyp in biotic samples in this manuscript. The procedure takes advantage of two novel cyclosporine A derivatives. Derivative 1 was used to capture Cyps from the sample while derivative 2 was applied for selective release from the affinity matrix. Using this approach, eight different Cyp (CypA, CypB, CypC, Cyp40 (PPID), CypE, CypD (PPIF), CypH, and CypL1) were unambiguously detected in healthy human blood plasma. Moreover, extracellular CypA was found to be partially modified by N^ε acetylation on residues Lys44, Lys133, Lys155, as well as N^α  acetylation at the N-terminal Val residue. N^α  acetylation of Ser2 residue was also found for Cyp40.

Xkr8 phospholipid scrambling complex in apoptotic phosphatidylserine exposure

Xk-related protein (Xkr) 8, a protein carrying 10 transmembrane regions, is essential for scrambling phospholipids during apoptosis. Here, we found Xkr8 as a complex with basigin (BSG) or neuroplastin (NPTN), type I membrane proteins in the Ig superfamily. In BSG(-/-)NPTN(-/-) cells, Xkr8 localized intracellularly, and the apoptosis stimuli failed to expose phosphatidylserine, indicating that BSG and NPTN chaperone Xkr8 to the plasma membrane to execute its scrambling activity. Mutational analyses of BSG showed that the atypical glutamic acid in the transmembrane region is required for BSG's association with Xkr8. In cells exposed to apoptotic signals, Xkr8 was cleaved at the C terminus and the Xkr8/BSG complex formed a higher-order complex, likely to be a heterotetramer consisting of two molecules of Xkr8 and two molecules of BSG or NPTN, suggesting that this cleavage causes the formation of a larger complex of Xkr8-BSG/NPTN for phospholipid scrambling.

Peptidyl-Proline Isomerases (PPIases): Targets for Natural Products and Natural Product-Inspired Compounds

Peptidyl-proline isomerases (PPIases) are a chaperone superfamily comprising the FK506-binding proteins (FKBPs), cyclophilins, and parvulins. PPIases catalyze the cis/trans isomerization of proline, acting as a regulatory switch during folding, activation, and/or degradation of many proteins. These "clients" include proteins with key roles in cancer, neurodegeneration, and psychiatric disorders, suggesting that PPIase inhibitors could be important therapeutics. However, the active site of PPIases is shallow, solvent-exposed, and well conserved between family members, making selective inhibitor design challenging. Despite these hurdles, macrocyclic natural products, including FK506, rapamycin, and cyclosporin, bind PPIases with nanomolar or better affinity. De novo attempts to derive new classes of inhibitors have been somewhat less successful, often showcasing the "undruggable" features of PPIases. Interestingly, the most potent of these next-generation molecules tend to integrate features of the natural products, including macrocyclization or proline mimicry strategies. Here, we review recent developments and ongoing challenges in the inhibition of PPIases, with a focus on how natural products might inform the creation of potent and selective inhibitors.

Effect of a quality-controlled fermented nutraceutical on skin aging markers: An antioxidant-control, double-blind study

The aim of the present study was to determine whether oral supplementation with a fermented papaya preparation (FPP-treated group) or an antioxidant cocktail (antioxidant-control group, composed of 10 mg trans-resveratrol, 60 µg selenium, 10 mg vitamin E and 50 mg vitamin C) was able to improve the skin antioxidant capacity and the expression of key skin genes, while promoting skin antiaging effects. The study enrolled 60 healthy non-smoker males and females aged 40-65 years, all of whom showed clinical signs of skin aging. The subjects were randomly divided into two matched groups, and were administered FPP or antioxidant treatment of a 4.5 g/day sachet sublingually twice a day for 90 days in a double-blind fashion. The parameters investigated were: Skin surface, brown spots, skin evenness, skin moisturization, elasticity (face), redox balance, nitric oxide (NO) concentration, and the expression levels of key genes (outer forearm sample). As compared with the baseline (day 0) and antioxidant-control values, FPP-treated subjects showed a significant improvement in skin evenness, moisturization and elasticity. The two treatments improved the MDA and SOD skin concentrations, but only the FPP-treated group showed a higher SOD level and a significant NO increase, along with significant upregulation of acquaporin-3 and downregulation of the potentially pro-aging/carcinogenetic cyclophilin-A and CD147 genes (P<0.05). Progerin was unaffected in both treatment groups. In conclusion, these findings suggest that orally-administered FPP showed a consistent biological and gene-regulatory improvement in the skin, as was also demonstrated in previous experimental and clinical trials testing other tissues, while common oral antioxidants had only a minor effect.

NS-398 promotes pancreatic cancer cell invasion by CD147 and MMP-2 via the activation of P38

The overexpression or abnormal activation of cyclo‑oxygenase‑2 (COX‑2) has been reported in pancreatic cancer cells. NS‑398, a selective inhibitor of COX‑2, is unable to inhibit pancreatic cancer cell proliferation, as determined by a Cell Counting Kit 8 assay. However, it does increase cancer cell invasiveness, and therefore the invasiveness of the PANC‑1 cells was determined, along with the activation of P38, which was assessed by western blotting. In the present study, to evaluate the mechanisms underlying the action of NS‑398 in pancreatic cancer cells, PANC‑1 cells were treated with NS‑398, and the invasion signaling pathways of cluster of differentiation (CD)147‑matrix metalloproteinase (MMP)‑2 and mitogen‑activated protein kinases were evaluated. The results showed that NS‑398‑induced the expression of CD147 and MMP‑2 via the activation of P38, which was involved in antiproliferative activity and induced pancreatic cancer cell invasiveness. The PANC‑1 cells were also co‑treated with CD147 small interfering (si)RNA and NS‑398, and it was found that the NS‑398‑induced activation of P38 was not inhibited by CD147 siRNA, however, the expression of MMP‑2 was inhibited. CD147 siRNA inhibited the invasiveness of the pancreatic cancer cells induced by NS‑398, but also restored NS‑398‑induced antiproliferative activity. These data indicated that P38 in the pancreatic cancer cells was non‑specifically activated by NS‑398. This activation induced the expression of CD147‑MMP‑2, opposed the antiproliferative activity of NS‑398 and increased the invasiveness of the PANC‑1 cells.

Basigin (CD147), a multifunctional transmembrane glycoprotein with various binding partners

Basigin, also called CD147 or EMMPRIN, is a transmembrane glycoprotein that belongs to the immunoglobulin superfamily. Basigin has isoforms; the common form (basigin or basigin-2) has two immunoglobulin domains, and the extended form (basigin-1) has three. Basigin is the receptor for cyclophilins, S100A9 and platelet glycoprotein VI, whereas basigin-1 serves as the receptor for the rod-derived cone viability factor. Basigin tightly associates with monocarboxylate transporters and is essential for their cell surface translocation and activities. In the same membrane plane, basigin also associates with other proteins including GLUT1, CD44 and CD98. The carbohydrate portion of basigin is recognized by lectins, such as galectin-3 and E-selectin. These molecular recognitions form the basis for the role of basigin in the transport of nutrients, migration of inflammatory leukocytes and induction of matrix metalloproteinases. Basigin is important in vision, spermatogenesis and other physiological phenomena, and plays significant roles in the pathogenesis of numerous diseases, including cancer. Basigin is also the receptor for an invasive protein RH5, which is present in malaria parasites.

How, with whom and when: an overview of CD147-mediated regulatory networks influencing matrix metalloproteinase activity

Matrix metalloproteinases (MMPs) comprise a family of 23 zinc-dependent enzymes involved in various pathologic and physiologic processes. In cancer, MMPs contribute to processes from tumour initiation to establishment of distant metastases. Complex signalling and protein transport networks regulate MMP synthesis, cell surface presentation and release. Earlier attempts to disrupt MMP activity in patients have proven to be intolerable and with underwhelming clinical efficacy; thus targeting ancillary proteins that regulate MMP activity may be a useful therapeutic approach. Extracellular matrix metalloproteinase inducer (EMMPRIN) was originally characterized as a factor present on lung cancer cells, which stimulated collagenase (MMP-1) production in fibroblasts. Subsequent studies demonstrated that EMMPRIN was identical with several other protein factors, including basigin (Bsg), all of which are now commonly termed CD147. CD147 modulates the synthesis and activity of soluble and membrane-bound [membrane-type MMPs (MT-MMPs)] in various contexts via homophilic/heterophilic cell interactions, vesicular shedding or cell-autonomous processes. CD147 also participates in inflammation, nutrient and drug transporter activity, microbial pathology and developmental processes. Despite the hundreds of manuscripts demonstrating CD147-mediated MMP regulation, the molecular underpinnings governing this process have not been fully elucidated. The present review summarizes our present knowledge of the complex regulatory systems influencing CD147 biology and provides a framework to understand how CD147 may influence MMP activity.

Knockdown of EMMPRIN improves adverse remodeling mediated by IL-18 in the post-infarcted heart

Interleukin-18 (IL-18) exacerbates cardiac dysfunction following myocardial infarction (MI). Extracellular matrix metalloproteinase inducer (EMMPRIN) has been shown to exacerbate ventricular remodeling via induction of extracellular matrix metalloproteinase (MMP) synthesis. While up-regulation of EMMPRIN expression by IL-18 has been demonstrated in vitro, little is known regarding its in vivo effects. Here, we investigated the role of EMMPRIN in progressive post-infarct ventricular remodeling induced by IL-18. Cardiac function was impaired on echocardiography and organ weight was increased in mice receiving daily intraperitoneal injection of IL-18 following MI. Accompanying these adverse functional effect were increased EMMPRIN levels. Gene silencing of cardiac EMMPRIN by intramyocardial RNA interference rescued IL-18 mediated adverse effects on post-infarct cardiac function. Finally, EMMPRIN silencing reduced MMP-9 expression in the post-infarcted left ventricular myocardium. In conclusion, progressive post-infarct left ventricular remodeling induced by IL-18 can be reversed by gene silencing of EMMPRIN. Knock down of EMMPRIN may be a potential therapeutic strategy to abrogate the adverse effects of IL-18 on post-infarct left ventricular remodeling likely via MMP-9 inhibition.

CD147/basigin limits lupus nephritis and Th17 cell differentiation in mice by inhibiting the interleukin-6/STAT-3 pathway

OBJECTIVE

Interleukin-17 (IL-17)-producing T cells (Th17 cells) play critical roles in the pathogenesis of immune-related diseases, including systemic lupus erythematosus. However, the fundamental mechanism regulating Th17 cell differentiation is not fully understood. Recently, we demonstrated that plasma levels of CD147/basigin (Bsg) in patients with lupus nephritis (LN) were closely associated with disease activity. but the molecular mechanism involving Bsg has been elusive. Here, we addressed the role of Bsg in the pathogenesis of LN.

METHODS

Injections of pristane (2,6,10,14-tetramethylpentadecane [TMPD]) were administered to Bsg(-/-) or Bsg(+/+) mice to induce LN. The mice were killed 6 months after being injected, for histologic and biochemical analyses of the kidneys and spleens.

RESULTS

Pristane induced LN more strikingly in Bsg(-/-) mice than in Bsg(+/+) mice, even though humoral autoimmunity was similarly increased in both genotypes. The increased number of Th17, but not Th1, Treg cells, was augmented in Bsg(-/-) mice. The expression of IL-17 was also increased in the kidneys of Bsg(-/-) mice, in proportion to LN disease activity. Furthermore, treatment with anti-IL-17 antibody reduced LN disease activity in Bsg(-/-) mice. Complementary to these phenotypes of Bsg(-/-) mice, Bsg expression was enhanced in activated CD4+ T cells in vivo and in vitro. Bsg deficiency selectively augmented in vitro differentiation of naive CD4+ T cells to Th17 cells and STAT-3 phosphorylation during this differentiation. Moreover, STAT-3 phosphorylation was suppressed by crosslinking of Bsg with its antibody.

CONCLUSION

Bsg plays an indispensable role in Th17 cell differentiation as a negative regulator by suppressing the IL-6/STAT-3 pathway.

An epitope-specific novel anti-EMMPRIN polyclonal antibody inhibits tumor progression

Extracellular matrix metalloproteinase inducer (EMMPRIN/CD147) mediates tumor cell-macrophage interactions, and has been shown to induce both matrix metalloproteinases (MMPs) and vascular endothelial growth factor (VEGF). However, the epitope responsible for MMP induction is controversial, and the epitope responsible for VEGF induction is yet unknown. We generated a novel anti-EMMPRIN antibody directed against a specific epitope that successfully inhibited the production of both MMP-9 and VEGF in tumor cell-macrophage in vitro co-culture systems, exhibiting a U-shaped dose response. Furthermore, this antibody efficiently inhibited in vivo tumor progression in both the RENCA renal cell carcinoma and CT26 colon carcinoma subcutaneous tumor models, and reduced tumor size and number of metastatic foci in the 4T1 orthotopic model. This was achieved by inhibiting angiogenesis as assessed by immunohistochemical staining for the endothelial marker CD31, by inhibiting tumor cell proliferation as assessed by the staining for Ki-67, and by enhancing tumor cell apoptosis as assessed in the TUNEL assay. Moreover, administration of the antibody recruited more macrophages into the tumor, and skewed the tumor microenvironment for macrophages from TGFβ-dominated anti-inflammatory microenvironment, to a less immunosuppressive one. The antibody improved the ability of stimulated macrophages to perform antibody-dependent cell cytotoxicity (ADCC) and kill tumor cells. Thus, our new antibody maps the epitope capable of inducing both MMPs and VEGF, and places EMMPRIN as a good target for cancer therapy.

CD147 promotes IKK/IκB/NF-κB pathway to resist TNF-induced apoptosis in rheumatoid arthritis synovial fibroblasts

Abstract

TNF is highly expressed in synovial tissue of rheumatoid arthritis (RA) patients, where it induces proinflammatory cytokine secretion. However, in other cases, TNF will cause cell death. Considering the abnormal proliferation and activation of rheumatoid arthritis synovioblasts, the proper rate of synovioblast apoptosis could possibly relieve arthritis. However, the mechanism mediating TNF-induced synovioblast survival versus cell death in RA is not fully understood. Our objective was to study the role of CD147 in TNF downstream pathway preference in RA synovioblasts. We found that overexpressing TNF in synovial tissue did not increase the apoptotic level and, in vitro, TNF-induced mild synovioblast apoptosis and promoted IL-6 secretion. CD147, which was highly expressed in rheumatoid arthritis synovial fibroblasts (RASFs), increased the resistance of synovioblasts to apoptosis under TNF stimulation. Downregulating CD147 both increased the apoptotic rate and inhibited IκB kinase (IKK)/IκB/NF-κB pathway-dependent proinflammatory cytokine secretion. Further, we determined that it was the extracellular portion of CD147 and not the intracellular portion that was responsible for synovioblast apoptosis resistance. CD147 monoclonal antibody inhibited TNF-induced proinflammatory cytokine production but had no effect on apoptotic rates. Thus, our study indicates that CD147 is resistant to TNF-induced apoptosis by promoting IKK/IκB/NF-κB pathway, and the extracellular portion of CD147 is the functional region.

Key messages

CD147 inhibits TNF-stimulated RASF apoptosis.

CD147 knockdown decreases IKK expression and inhibits NF-κB-related cytokine secretion.

CD147’s extracellular portion is responsible for apoptosis resistance.

CD147 antibody inhibits TNF-related cytokine secretion without additional apoptosis.

Targeting Extracellular Cyclophilins Ameliorates Disease Progression in Experimental Biliary Atresia

Biliary atresia (BA) is a devastating liver disease of unknown etiology affecting children generally within the first 3 months of life. The disease is manifested by inflammation and subsequent obstruction of the extrahepatic bile ducts, fibrosis and liver failure. The mechanisms responsible for disease pathogenesis are not fully understood, but a number of factors controlled by the SMAD signaling pathway have been implicated. In this study, we investigated the role of a known proinflammatory factor, extracellular cyclophilin A (CypA), in the pathogenesis of biliary atresia using the rhesus rotavirus (RRV) murine model. We used a unique cyclosporine A derivative, MM284, which does not enter cells and therefore inactivates exclusively extracellular cyclophilins, as a potential treatment. We demonstrated that levels of CypA in plasma of RRV-infected mice were increased significantly, and that treatment of mice with MM284 prior to or one day after disease initiation by RRV infection significantly improved the status of mice with experimental BA: weight gain was restored, bilirubinuria was abrogated, liver infiltration by inflammatory cells was reduced and activation of the SMAD pathway and SMAD-controlled fibrosis mediators and tissue inhibitor of metalloproteinases (TIMP)-4 and matrix metalloproteinase (MMP)-7 was alleviated. Furthermore, treatment of human hepatic stellate cells with recombinant cyclophilin recapitulated SMAD2/3 activation, which was also suppressed by MM284 treatment. Our data provide the first evidence that extracellular cyclophilins activate the SMAD pathway and promote inflammation in experimental BA, and suggest that MM284 may be a promising therapeutic agent for treating BA and possibly other intrahepatic chronic disorders.

Extracellular cyclophilin A possesses chemotaxic activity in cattle

Cyclophilin A (CyPA) was originally discovered in bovine thymocytes as a cytosolic binding protein of the immunosuppressive drug cyclosporine A. Recent studies have revealed that in mice and humans, CyPA is secreted from cells in injured or infected tissues and plays a role in recruiting inflammatory cells in those tissues. Here we found that in cattle abundant level of extracellular CyPA was observed in tissues with inflammation. To aid in investigating the role of extracellular CyPA in cattle, we generated recombinant bovine CyPA (rbCyPA) and tested its biological activity as an inflammatory mediator. When bovine peripheral blood cells were treated with rbCyPA in vitro, we observed that rbCyPA reacts with the membranous surface of granulocytes, monocytes and lymphocytes. Chemotaxis analysis showed that the granulocytes migrate toward rbCyPA and the migration is inhibited by pre-treatment with an anti-bovine CyPA antibody. These results indicate that, as for mice and humans, extracellular CyPA possesses chemotactic activity to recruit inflammatory cells (e.g., granulocytes) in cattle, and could thus be a potential therapeutic target for the treatment of inflammation.

Expression of CD147, PCNA, VEGF, MMPs and their clinical significance in the giant cell tumor of bones

BACKGROUND

Giant cell tumor of bone (GCT) is a potentially malignant tumor. CD147 is a multifunctional protein, which expresses itself in many tumors. In this study, we have investigated the correlation between CD147 and PCNA, VEGF, MMPs expression in giant cell tumor of bones. We have also explored the relationship between its clinical pathology and prognosis.

RESULTS

A significant difference of the expression level of CD147, MMPs was found in cases of GCT with Jaffe grading and prognosis (P<0.05). But, it was not in accordance with the patient's age and sex. An expression of CD147 was positively correlated with MMP-9, VEGF, MVD, PCNA (r=0.271, P=0.025; r=0.411, P=0.000; r=0.872, P=0.000; r=0.394, P=0.001).

CONCLUSION

The expression level of CD147 in giant cell tumors of bones is correlated with the development of cancers and relapse. There was a positive correlation between expressions of CD147 and MMP-9, VEGF, MVD, PCNA, and CD147. This is an important indicator in evaluating the malignant degree and prognosis of giant cell tumors of bone. It may be the new target for ensuring chemopreventive strategies.

The Cyclophilin A-CD147 complex promotes the proliferation and homing of multiple myeloma cells

B cell malignancies frequently colonize the bone marrow. The mechanisms responsible for this preferential homing are incompletely understood. Here we studied multiple myeloma (MM) as a model of a terminally differentiated B cell malignancy that selectively colonizes the bone marrow. We found that extracellular CyPA (eCyPA), secreted by bone marrow endothelial cells (BMECs), promoted the colonization and proliferation of MM cells in an in vivo scaffold system via binding to its receptor, CD147, on MM cells. The expression and secretion of eCyPA by BMECs was enhanced by BCL9, a Wnt-β-catenin transcriptional coactivator that is selectively expressed by these cells. eCyPA levels were higher in bone marrow serum than in peripheral blood in individuals with MM, and eCyPA-CD147 blockade suppressed MM colonization and tumor growth in the in vivo scaffold system. eCyPA also promoted the migration of chronic lymphocytic leukemia and lymphoplasmacytic lymphoma cells, two other B cell malignancies that colonize the bone marrow and express CD147. These findings suggest that eCyPA-CD147 signaling promotes the bone marrow homing of B cell malignancies and offer a compelling rationale for exploring this axis as a therapeutic target for these malignancies.

The role of EMMPRIN in T cell biology and immunological diseases

Review on EMMPRIN in numerous immunological/inflammatory disease conditions and its complex roles in T cell biology.

EMMPRIN (CD147), originally described as an inducer of the expression of MMPs, has gained attention in its involvement in various immunologic diseases, such that anti‐EMMPRIN antibodies are considered as potential therapeutic medications. Given that MMPs are involved in the pathogenesis of various disease states, it is relevant that targeting an upstream inducer would make for an effective therapeutic strategy. Additionally, EMMPRIN is now appreciated to have multiple roles apart from MMP induction, including in cellular functions, such as migration, adhesion, invasion, energy metabolism, as well as T cell activation and proliferation. Here, we review what is known about EMMPRIN in numerous immunologic/inflammatory disease conditions with a particular focus on its complex roles in T cell biology.

Structure and Dynamics of GeoCyp: A Thermophilic Cyclophilin with a Novel Substrate Binding Mechanism That Functions Efficiently at Low Temperatures

Thermophilic proteins have found extensive use in research and industrial applications because of their high stability and functionality at elevated temperatures while simultaneously providing valuable insight into our understanding of protein folding, stability, dynamics, and function. Cyclophilins, constituting a ubiquitously expressed family of peptidyl-prolyl isomerases with a range of biological functions and disease associations, have been utilized both for conferring stress tolerances and in exploring the link between conformational dynamics and enzymatic function. To date, however, no active thermophilic cyclophilin has been fully biophysically characterized. Here, we determine the structure of a thermophilic cyclophilin (GeoCyp) from Geobacillus kaustophilus, characterize its dynamic motions over several time scales using an array of methodologies that include chemical shift-based methods and relaxation experiments over a range of temperatures, and measure catalytic activity over a range of temperatures to compare its structure, dynamics, and function to those of a mesophilic counterpart, human cyclophilin A (CypA). Unlike those of most thermophile/mesophile pairs, GeoCyp catalysis is not substantially impaired at low temperatures as compared to that of CypA, retaining ~70% of the activity of its mesophilic counterpart. Examination of substrate-bound ensembles reveals a mechanism by which the two cyclophilins may have adapted to their environments through altering dynamic loop motions and a critical residue that acts as a clamp to regulate substrate binding differentially in CypA and GeoCyp. Fast time scale (pico- to nanosecond) dynamics are largely conserved between the two proteins, in accordance with the high degree of structural similarity, although differences do exist in their temperature dependencies. Slower (microsecond) time scale motions are likewise localized to similar regions in the two proteins with some variability in their magnitudes yet do not exhibit significant temperature dependencies in either enzyme.

CD147: regulator of hyaluronan signaling in invasiveness and chemoresistance

Major determinants that influence negative outcome in cancer patients are the abilities of cancer cells to resist current therapies and to invade surrounding host tissue, consequently leading to local and metastatic dissemination. Hyaluronan (HA), a prominent constituent of the tumor microenvironment, not only provides structural support but also interacts with cell surface receptors, especially CD44, that influence cooperative signaling pathways leading to chemoresistance and invasiveness. CD147 (emmprin; basigin) is a member of the Ig superfamily that has also been strongly implicated in chemoresistance and invasiveness. CD147 both regulates HA synthesis and interacts with the HA receptors, CD44, and LYVE-1. Increased CD147 expression induces formation of multiprotein complexes containing CD44 (or LYVE-1) as well as members of the membrane-type matrix metalloproteinase, receptor tyrosine kinase, ABC drug transporter, or monocarboxylate transporter families, which become assembled in specialized lipid raft domains along with CD147 itself. In each case, multivalent HA-receptor interactions are essential for formation or stabilization of the lipid raft complexes and for downstream signaling pathways or transporter activities that are driven by these complexes. We conclude that cooperativity between HA, HA receptors, and CD147 may be a major driver of the interconnected pathways of invasiveness and chemoresistance widely critical to malignancy.

CD147 and MMP-9 expressions in type II/III adenocarcinoma of esophagogastric junction and their clinicopathological significances

OBJECTIVES

To investigate CD147 and matrix metalloproteinase-9 (MMP-9) expressions in type II/III adenocarcinoma of esophagogastric junction (AEG), and their clinicopathological significances.

METHODS

Seventy-four patients clinically and pathologically diagnosed with type II/III AEG were analyzed, each undergoing radical total gastrectomy and Roux-en-Y esophagojejunostomy. The avidin streptavidin-perosidase immunohistochemistry technique was used to detect CD147 and MMP-9 in type II/III AEGs and 20 para-tumor controls, and their correlations with clinicopathological data and their reciprocal relationship were then analyzed. Kaplan-Meier survival analysis was conducted to reveal their prognostic significances. SPSS 20.0 was used for data analysis. A difference was statistically significant with P < 0.05, and very significant with P < 0.01.

RESULTS

In type II/III AEG CD147 and MMP-9 were mainly expressed on cellular membrane of in tumor cell cytoplasm. MMP-9 expression was significantly stronger at tumor-stroma junction and front edge of invasion. Their positive rates were significantly higher in malignant tissues than para-tumor tissues (P < 0.01 for both). There existed a significant positive correlation between both expressions (P < 0.05). They were significantly more highly expressed in cancers with lymphatic metastasis (P < 0.01 for both), at TNM III/IV stages (P < 0.01 for both), and with poor differentiation grade (P < 0.05 for both). Higher CD147 and MMP-9 expression rates were correlated with inferior postsurgical survivals (P < 0.05 for both).

CONCLUSIONS

CD147 and MMP-9 could be novel biomarkers for type II/III AEG, and potentially predict tumor progression and prognosis. They are worth further investigation.

The roles of CD147 and/or cyclophilin A in kidney diseases

CD147 is a widely expressed integral plasma membrane glycoprotein and has been involved in a variety of physiological and pathological activities in combination with different partners, including cyclophilins, caveolin-1, monocarboxylate transporters, and integrins. Recent data demonstrate that both CyPA and CD147 significantly contribute to renal inflammation, acute kidney injury, renal fibrosis, and renal cell carcinoma. Here we review the current understanding of cyclophilin A and CD147 expression and functions in kidney diseases and potential implications for treatment of kidney diseases.

Biomarkers of calcineurin inhibitor nephrotoxicity in transplantation

Over 35 years of use has demonstrated the revolutionary therapeutic benefits of calcineurin inhibitors (CNI) in not only preventing transplant rejection, but also the renal and nonrenal toxicity of CNI. Acute reversible and insidious irreversible forms of CNI nephrotoxicity have been identified, with ischemia from an imbalance between vasoconstrictors and vasodilators playing an important role. The ongoing search to define toxicity pathways has been enriched by ‘Omics’ studies. Changes in proteins including those involved in activation of pro-inflammatory responses, oxidative stress, ER stress and the unfolded protein response have been identified, and these may serve as biomarkers of toxicity. However, the current standard of CNI toxicity, histology, lacks specificity, which creates challenges for biomarker validation. This review focuses on progress in nephrotoxic pathway identification of CNI and biomarker validation.

Extracellular cyclophilins in health and disease

BACKGROUND

Extracellular cyclophilins (eCyPs) are pro-inflammatory factors implicated in pathogenesis of a number of inflammatory diseases. Most pathogenic activities of eCyPs are related to their chemotactic action towards leukocytes, which is mediated by eCyP receptor on target cells, CD147, and involves peptidyl-prolyl cis-trans isomerase activity of cyclophilins. This activity is inhibited by cyclosporine A (CsA) and non-immunosuppressive derivatives of this drug. Accumulating evidence for the role of eCyPs in disease pathogenesis stimulated research on the mechanisms of eCyP-initiated events, resulting in identification of multiple signaling pathways, characterization of a variety of effector molecules released from eCyP-treated cells, and synthesis of CsA derivatives specifically blocking eCyPs. However, a number of important questions related to the mode of action of eCyPs remain unanswered.

SCOPE OF REVIEW

In this article, we integrate available information on release and function of extracellular cyclophilins into a unified model, focusing on outstanding issues that need to be clarified.

MAJOR CONCLUSIONS

Extracellular cyclophilins are critical players in pathogenesis of a number of inflammatory diseases. Their mechanism of action involves interaction with the receptor, CD147, and initiation of a poorly characterized signal transduction process culminating in chemotaxis and production of pro-inflammatory factors.

GENERAL SIGNIFICANCE

Extracellular cyclophilins present an attractive target for therapeutic interventions that can be used to alleviate symptoms and consequences of acute and chronic inflammation. This article is part of a Special Issue entitled Proline-directed Foldases: Cell Signaling Catalysts and Drug Targets.

Inhibition of synovitis and joint destruction by a new single domain antibody specific for cyclophilin A in two different mouse models of rheumatoid arthritis

Introduction

Cyclophilin A (CypA) is implicated in rheumatoid arthritis (RA) pathogenesis. We studied whether a novel anti-CypA single domain antibody (sdAb) treatment would modulate the severity of the disease in two different animal models of RA.

Methods

A novel sdAb, named sdAbA1, was screened from an immunized camel sdAb library and found to have a high binding affinity (K_D = 6.9 × 10^-9 M) for CypA. The SCID-HuRAg model and the collagen-induced arthritis (CIA) in mice were used to evaluate the effects of sdAbA1 treatment on inflammation and joint destruction. For in vitro analysis, monocytes/macrophages were purified from synovial fluid and peripheral blood of patients with RA and were tested for the effect of anti-CypA sdAb on metalloproteinase (MMP) production. Human monocyte cell line THP-1 cells were selected and western blot analyses were performed to examine the potential signaling pathways.

Results

In the CIA model of RA, the sdAbA1 treatment resulted in a significant decrease in clinical symptoms as well as of joint damage (P <0.05). In the SCID-HuRAg model, treatment with anti-CypA antibody sdAbA1 significantly reduced cartilage erosion, inflammatory cell numbers and MMP-9 production in the implanted tissues (P <0.05). It also significantly reduced the levels of human inflammatory cytokines IL-6 and IL-8 in mouse serum (P <0.05). No toxic effects were observed in the two animal models. In vitro results showed that sdAbA1 could counteract CypA-dependent MMP-9 secretion and IL-8 production by interfering with the ERK-NF-κB pathway.

Conclusions

Blockade of CypA significantly inhibited synovitis and cartilage/bone erosion in the two tested animal models of RA. Our findings provide evidence that sdAbA1 may be a potential therapeutic agent for RA.

The biological function and clinical utilization of CD147 in human diseases: a review of the current scientific literature

CD147 or EMMPRIN is a member of the immunoglobulin superfamily in humans. It is widely expressed in human tumors and plays a central role in the progression of many cancers by stimulating the secretion of matrix metalloproteinases (MMPs) and cytokines. CD147 regulates cell proliferation, apoptosis, and tumor cell migration, metastasis and differentiation, especially under hypoxic conditions. CD147 is also important to many organ systems. This review will provide a detailed overview of the discovery, characterization, molecular structure, diverse biological functions and regulatory mechanisms of CD147 in human physiological and pathological processes. In particular, recent studies have demonstrated the potential application of CD147 not only as a phenotypic marker of activated regulatory T cells but also as a potential diagnostic marker for early-stage disease. Moreover, CD147 is recognized as an effective therapeutic target for hepatocellular carcinoma (HCC) and other cancers, and exciting clinical progress has been made in HCC treatment using CD147-directed monoclonal antibodies.

CD147 and CD98 complex-mediated homotypic aggregation attenuates the CypA-induced chemotactic effect on Jurkat T cells

Homotypic cell aggregation plays important roles in physiological and pathological processes, including embryogenesis, immune responses, angiogenesis, tumor cell invasion and metastasis. CD147 has been implicated in most of these phenomena, and it was identified as a T cell activation-associated antigen due to its obvious up-regulation in activated T cells. However, the explicit function and mechanism of CD147 in T cells have not been fully elucidated. In this study, large and compact aggregates were observed in Jurkat T cells after treatment with the specific CD147 monoclonal antibody HAb18 or after the expression of CD147 was silenced by RNA interference, which indicated an inhibitory effect of CD147 in T cell homotypic aggregation. Knocking down CD147 expression resulted in a significant decrease in CD98, along with prominent cell aggregation, similar to that treated by CD98 and CD147 monoclonal antibodies. Furthermore, decreased cell chemotactic activity was observed following CD147- and CD98-mediated cell aggregation, and increased aggregation was correlated with a decrease in the chemotactic ability of the Jurkat T cells, suggesting that CD147- and CD98-mediated homotypic cell aggregation plays a negative role in T cell chemotaxis. Our data also showed that p-ERK, p-ZAP70, p-CD3ζ and p-LCK were significantly decreased in the CD147- and CD98-knocked down Jurkat T cells, which suggested that decreased CD147- and/or CD98-induced homotypic T cell aggregation and aggregation-inhibited chemotaxis might be associated with these signaling pathways. A role for CD147 in cell aggregation and chemotaxis was further indicated in primary CD4(+) T cells. Similarly, low expression of CD147 in primary T cells induced prominent cell aggregation and this aggregation attenuated primary T cell chemotactic ability in response to CypA. Our results have demonstrated the correlation between homotypic cell aggregation and the chemotactic response of T cells to CypA, and these data indicate that CD147 and CD98 might play important roles in cyclophilin-induced cell migration.

From chemical tools to clinical medicines: nonimmunosuppressive cyclophilin inhibitors derived from the cyclosporin and sanglifehrin scaffolds

The cyclophilins are widely expressed enzymes that catalyze the interconversion of the cis and trans peptide bonds of prolines. The immunosuppressive natural products cyclosporine A and sanglifehrin A inhibit the enzymatic activity of the cyclophilins. Chemical modification of both the cyclosporine and sanglifehrin scaffolds has produced many analogues that inhibit cyclophilins in vitro but have reduced immunosuppressive properties. Three nonimmunosuppressive cyclophilin inhibitors (alisporivir, SCY-635, and NIM811) have demonstrated clinical efficacy for the treatment of hepatitis C infection. Additional candidates are in various stages of preclinical development for the treatment of hepatitis C or myocardial reperfusion injury. Recent publications suggest that cyclophilin inhibitors may have utility for the treatment of diverse viral infections, inflammatory indications, and cancer. In this review, we document the structure-activity relationships of the nonimmunosuppressive cyclosporins and sanglifehrins in clinical and preclinical development. Aspects of the pharmacokinetic behavior and chemical biology of these drug candidates are also described.

Pathogenic Neisseria meningitidis utilizes CD147 for vascular colonization

Neisseria meningitidis is a cause of meningitis epidemics worldwide and of rapidly progressing fatal septic shock. A crucial step in the pathogenesis of invasive meningococcal infections is the adhesion of bloodborne meningococci to both peripheral and brain endothelia, leading to major vascular dysfunction. Initial adhesion of pathogenic strains to endothelial cells relies on meningococcal type IV pili, but the endothelial receptor for bacterial adhesion remains unknown. Here, we report that the immunoglobulin superfamily member CD147 (also called extracellular matrix metalloproteinase inducer (EMMPRIN) or Basigin) is a critical host receptor for the meningococcal pilus components PilE and PilV. Interfering with this interaction potently inhibited the primary attachment of meningococci to human endothelial cells in vitro and prevented colonization of vessels in human brain tissue explants ex vivo and in humanized mice in vivo. These findings establish the molecular events by which meningococci target human endothelia, and they open new perspectives for treatment and prevention of meningococcus-induced vascular dysfunctions.

Plasma CD147 reflects histological features in patients with lupus nephritis

OBJECTIVE

A glycosylated transmembrane protein, CD147, has been implicated in regulating lymphocyte responsiveness and leukocyte recruitment. As lupus nephritis (LN) often follows a relapsing-remitting disease course, accurate understanding of the disease activity would be extremely helpful in improving prognosis. Unfortunately, neither clinical nor serological data can accurately reflect the histological features of LN. The present study investigated whether CD147 can accurately predict pathological features of LN.

METHODS

Plasma and spot urine samples were collected from 64 patients who underwent renal biopsy between 2008 and 2011. Disease activity for LN tissues was evaluated using the biopsy activity index, and compared to levels of biomarkers including CD147.

RESULTS

In LN tissues, CD147 induction was striking in injured glomeruli and infiltrating inflammatory cells, but not in damaged tubules representing atrophy. Plasma CD147 levels accurately reflected the histological disease activity. However, prediction using a single molecule would be quite difficult because of the complex pathogenesis of LN. The diagnostic accuracy of multiplex parameters indicated that the combination including plasma CD147 might yield excellent diagnostic abilities for guiding ideal LN therapy.

CONCLUSION

Plasma CD147 levels might offer useful insights into disease activity as a crucial biomarker in patients with LN.

Abnormalities in soluble CD147 / MMPs / TIMPs axis in Ankylosing Spondylitis patients with and without a history of Acute Anterior Uveitis / Anomalii ale axei CD147 solubil / MMPs / TIMPs la pacienții cu spondilită anchilozantă cu sau fără uveită acută anterioară

Ankylosing Spondylitis (AS) is the prototype of the axial form of spondyloarthritis. Despite extensive studies, complex mechanisms related to abnormal cellular and molecular processes in AS are not completely understood. Among proinflammatory mediators such as proinflammatory cytokines, NOS-2, chemokines, which lead to inflammation, matrix metalloproteinases (MMPs) play an important role in inflammatory processes that characterize AS. Therefore, we purposed to evaluate whether the disruption of extracellular MMPs inducer (EMMPRIN/CD147), MMPs and tissue inhibitors of MMPs (TIMPs) homeostasis play a role in the evolution of AS especially in patients with a history of Acute Anterior Uveitis (AAU). For this purpose sera from AS patients and from healthy donors (HDs) were assessed for soluble CD147 (sCD147), MMP-3 and TIMP-1 levels using enzyme-linked immunosorbent assay and for the activity of MMP-2 and -9 gelatinases by gelatin zymography. The experimental results showed that the levels of sCD147, MMP-3 and TIMP-1 were significantly increased in AS patients compared to HDs. sCD147 as well as the ratio MMP-2/sCD147 differentiated AS patients with a history of AAU from those without it. The ratios MMP-2/sCD147, MMP-3/sCD147 and MMP-3/TIMP-1 suggested an imbalance between MMPs and their regulators in AS patients. These results suggest that MMPs/sCD147 ratios could be potential biomarkers to strengthen the characterization of AS patients and to predict disease evolution. Positive or negative correlations between some of the experimental and/or clinical features of AS patients and the therapy also highlight the usefulness of the evaluation of these biomarkers to identify an individualized and efficient therapy.

Acetylation of cyclophilin A is required for its secretion and vascular cell activation

AIMS

Cyclophilin A (CyPA) is a pro-inflammatory mediator involved in oxidative stress-related cardiovascular diseases. It is secreted from vascular smooth muscle cell (VSMC) in response to reactive oxygen species (ROS) in a highly regulated manner. Extracellular CyPA activates VSMCs and endothelial cells (ECs) promoting inflammation, cell growth, and cell death. Recently, it was shown that acetylated CyPA (AcK-CyPA) affects its function. We investigated the role of acetylation of CyPA for its secretion and signalling in vascular cells.

METHODS AND RESULTS

We used angiotensin II (Ang II) to create sustained ROS and found significantly increased AcK-CyPA in VSMC. Site-directed mutagenesis showed that lysines K82 and K125 were the predominant CyPA residues acetylated in response to Ang II. Importantly, acetylation of K82 and K125 were required for Ang II-mediated CyPA secretion. ROS inhibitors, Tiron, and N-acetylcysteine inhibited Ang II-induced intracellular CyPA acetylation and also AcK-CyPA secretion. Using secreted CyPA from wild type and K82/125R mutants expressed in transduced VSMC or in vitro acetylated recombinant CyPA, we showed that extracellular AcK-CyPA significantly increased pERK1/2, matrix metalloproteinase-2 activation, and ROS production in VSMC compared with non-acetylated CyPA. Moreover, extracellular AcK-CyPA increased adhesion molecule expression (VCAM-1 and ICAM-1) in EC, which promoted monocyte adhesion.

CONCLUSIONS

ROS-dependent acetylation of CyPA is required for the generation of extracellular CyPA. Acetylated extracellular CyPA regulates VSMC and EC activation, suggesting that inhibition of acetylation of CyPA may prevent the pathogenesis of oxidative stress-related cardiovascular diseases.

Cyclophilin A from Schistosoma japonicum promotes a Th2 response in mice

Background

Schistosomiasis is a chronic infection, where the host immune response to the parasite changes from a predominantly Th1 to Th2 phenotype, when parasite enters the egg stage, restraining the host inflammatory immune responses to achieve a longer survival in the host. On the other hand, the development of Th2 responses causes immunopathological changes such as liver fibrosis. Therefore identification of schistosome-derived Th2 inducing molecules is important in the understanding of pathogenesis of schistosomiasis. A cyclophilin A homologue of Schistosoma japonicum was reported to be an egg-stage specific antigen, but its immunogenicity and immunoregulatory activities remain unknown.

Methods

We cloned and expressed the gene of cyclophilin A from Schistosoma japonicum (AY814078), named as SjCyP18 based on its molecular weight. The expression profiles in different stages of S. japonicum were examined by RT-PCR and immunofluorescence assay. The immunogenicity of SjCyP18 was measured by the presence of IgG in the sera from S. japonicum infected patients and animals, and the Th2-promting activities were examined by the subclass of immunoglobulins against SjCyP18 and by the IL-4 induction in T cells following footpad injection of SjCyP18.

Results

The cloned SjCyP18 has 65% homology with human or mouse cyclophilin A at the amino acid level. In contrast to reports as an egg-stage specific antigen, the gene was found to be expressed in all stages of S. japonicum. IgG responses against SjCyP18 were found in some S. japonicum infected patients and were significantly induced when infection become patent and produce eggs in infected mice. Furthermore, the Th2-promoting subclass of IgG1 was the predominant isotype in S. japonicum infected mice. More importantly, footpad injection of SjCyP18 induced a greater production of IL-4 than that of IFN-γ by lymphocytes compared to responses from PBS injection controls.

Conclusion

The cyclophilin A homologue found in S. japonicum is immunogenic and promotes Th2 responses in vivo which may contribute to the establishment of chronic infection by schistosomes.

Do reciprocal interactions between cell stress proteins and cytokines create a new intra-/extra-cellular signalling nexus?

Cytokine biology began in the 1950s, and by 1988, a large number of cytokines, with a myriad of biological actions, had been discovered. In 1988, the basis of the protein chaperoning function of the heat shock, or cell stress, proteins was identified, and it was assumed that this was their major activity. However, since this time, evidence has accumulated to show that cell stress proteins are secreted by cells and can stimulate cellular cytokine synthesis with the generation of pro- and/or anti-inflammatory cytokine networks. Cell stress can also control cytokine synthesis, and cytokines are able to induce, or even inhibit, the synthesis of selected cell stress proteins and may also promote their release. How cell stress proteins control the formation of cytokines is not understood and how cytokines control cell stress protein synthesis depends on the cellular compartment experiencing stress, with cytoplasmic heat shock factor 1 (HSF1) having a variety of actions on cytokine gene transcription. The endoplasmic reticulum unfolded protein response also exhibits a complex set of behaviours in terms of control of cytokine synthesis. In addition, individual intracellular cell stress proteins, such as Hsp27 and Hsp90, have major roles in controlling cellular responses to cytokines and in controlling cytokine synthesis in response to exogenous factors. While still confusing, the literature supports the hypothesis that cell stress proteins and cytokines may generate complex intra- and extra-cellular networks, which function in the control of cells to external and internal stressors and suggests the cell stress response as a key parameter in cytokine network generation and, as a consequence, in control of immunity.

HAb18G/CD147 promotes pSTAT3-mediated pancreatic cancer development via CD44s

PURPOSE

Signal transducer and activator of transcription 3 (STAT3) plays a critical role in initiation and progression of pancreatic cancer. However, therapeutically targeting STAT3 has failed clinically. We previously identified HAb18G/CD147 as an effective target for cancer treatment. In this study, we aimed to investigate the potential role of HAb18G/CD147 in STAT3-involved pancreatic tumorigenesis in vitro and in vivo.

EXPERIMENTAL DESIGN

The expression of HAb18G/CD147, pSTAT3, and CD44s was determined in tissue microarrays. The tumorigenic function and molecular signaling mechanism of HAb18G/CD147 were assessed by in vitro cellular and clonogenic growth, reporter assay, immunoblot assay, immunofluorescence staining, immunoprecipitation, and in vivo tumor formation using loss or gain-of-function strategies.

RESULTS

Highly expressed HAb18G/CD147 promoted cellular and clonogenic growth in vitro and tumorigenicity in vivo. Cyclophilin A (CyPA), a ligand of CD147, stimulated STAT3 phosphorylation and its downstream genes cyclin D1/survivin through HAb18G/CD147-dependent mechanisms. HAb18G/CD147 was associated and colocalized with cancer stem cell marker CD44s in lipid rafts. The inhibitors of STAT3 and survivin, as well as CD44s neutralizing antibodies suppressed the HAb18G/CD147-induced cell growth. High HAb18G/CD147 expression in pancreatic cancer was significantly correlated with the poor tumor differentiation, and the high coexpression of HAb18G/CD147-CD44s-STAT3 associated with poor survival of patients with pancreatic cancer.

CONCLUSIONS

We identified HAb18G/CD147 as a novel upstream activator of STAT3, which interacts with CD44s and plays a critical role in the development of pancreatic cancer. The data suggest that HAb18G/CD147 could be a promising therapeutic target for highly aggressive pancreatic cancer and a surrogate marker in the STAT3-targeted molecular therapies.

Anti-inflammatory effects of extracellular cyclosporins are exclusively mediated by CD147

Leukocyte trafficking and recruitment is a critical process in host immune surveillance and in inflammatory diseases. Extracellular cyclophilins (eCyps) have been identified as a novel class of chemotactic mediators. The impact of eCyp/CD147 interactions for the recruitment of leukocytes during inflammation was analyzed using a structurally simplified cell-impermeable eCyp inhibitor. This compound was highly effective at inhibiting leukocyte migration toward CypA in vitro as well as in the recruitment of leukocytes during inflammation in a mouse model of experimentally induced peritonitis and delayed-type hypersensitivity reaction. By using CD147-/- mice in combination with the cell-impermeable eCyp inhibitor, we were able to show that the action of eCyps in inflammation is exclusively mediated by interaction with CD147. Our findings suggest that blocking eCyps may be an effective therapeutic target for reducing inflammatory diseases associated with leukocyte recruitment.

Galectin-3 induces clustering of CD147 and integrin-β1 transmembrane glycoprotein receptors on the RPE cell surface

Proliferative vitreoretinopathy (PVR) is a blinding disease frequently occurring after retinal detachment surgery. Adhesion, migration and matrix remodeling of dedifferentiated retinal pigment epithelial (RPE) cells characterize the onset of the disease. Treatment options are still restrained and identification of factors responsible for the abnormal behavior of the RPE cells will facilitate the development of novel therapeutics. Galectin-3, a carbohydrate-binding protein, was previously found to inhibit attachment and spreading of retinal pigment epithelial cells, and thus bares the potential to counteract PVR-associated cellular events. However, the identities of the corresponding cell surface glycoprotein receptor proteins on RPE cells are not known. Here we characterize RPE-specific Gal-3 containing glycoprotein complexes using a proteomic approach. Integrin-β1, integrin-α3 and CD147/EMMPRIN, a transmembrane glycoprotein implicated in regulating matrix metalloproteinase induction, were identified as potential Gal-3 interactors on RPE cell surfaces. In reciprocal immunoprecipitation experiments we confirmed that Gal-3 associated with CD147 and integrin-β1, but not with integrin-α3. Additionally, association of Gal-3 with CD147 and integrin-β1 was observed in co-localization analyses, while integrin-α3 only partially co-localized with Gal-3. Blocking of CD147 and integrin-β1 on RPE cell surfaces inhibited binding of Gal-3, whereas blocking of integrin-α3 failed to do so, suggesting that integrin-α3 is rather an indirect interactor. Importantly, Gal-3 binding promoted pronounced clustering and co-localization of CD147 and integrin-β1, with only partial association of integrin-α3. Finally, we show that RPE derived CD147 and integrin-β1, but not integrin-α3, carry predominantly β-1,6-N-actyl-D-glucosamine-branched glycans, which are high-affinity ligands for Gal-3. We conclude from these data that extracellular Gal-3 triggers clustering of CD147 and integrin-β1 via interaction with β1,6-branched N-glycans on RPE cells and hypothesize that Gal-3 acts as a positive regulator for CD147/integrin-β1 clustering and therefore modifies RPE cell behavior contributing to the pathogenesis of PVR. Further investigations at this pathway may aid in the development of specific therapies for PVR.

CD147, CD44, and the epidermal growth factor receptor (EGFR) signaling pathway cooperate to regulate breast epithelial cell invasiveness

The immunoglobulin superfamily glycoprotein CD147 (emmprin; basigin) is associated with an invasive phenotype in various types of cancers, including malignant breast cancer. We showed recently that up-regulation of CD147 in non-transformed, non-invasive breast epithelial cells is sufficient to induce an invasive phenotype characterized by membrane type-1 matrix metalloproteinase (MT1-MMP)-dependent invadopodia activity (Grass, G. D., Bratoeva, M., and Toole, B. P. (2012) Regulation of invadopodia formation and activity by CD147. J. Cell Sci. 125, 777-788). Here we found that CD147 induces breast epithelial cell invasiveness by promoting epidermal growth factor receptor (EGFR)-Ras-ERK signaling in a manner dependent on hyaluronan-CD44 interaction. Furthermore, CD147 promotes assembly of signaling complexes containing CD147, CD44, and EGFR in lipid raftlike domains. We also found that oncogenic Ras regulates CD147 expression, hyaluronan synthesis, and formation of CD147-CD44-EGFR complexes, thus forming a positive feedback loop that may amplify invasiveness. Last, we showed that malignant breast cancer cells are heterogeneous in their expression of surface-associated CD147 and that high levels of membrane CD147 correlate with cell surface EGFR and CD44 levels, activated EGFR and ERK1, and activated invadopodia. Future studies should evaluate CD147 as a potential therapeutic target and disease stratification marker in breast cancer.