Monoclonal anti-CD44 Antibody Research Articles

A CD44-specific peptide, RP-1, exhibits capacities of assisting diagnosis and predicting prognosis of gastric cancer.

Early diagnosis and evaluation of prognosis are both crucial for preventing poor prognosis of patients with gastric cancer (GC), a leading cause of cancer-related deaths worldwide. Cluster of differentiation 44 (CD44), an indicator of cancer stem cells, can be specifically targeted by molecular probes and detected in tissues of GC in a large quantity. In current study we found that RP-1, a specific peptide binding to CD44 protein, exhibited the potentials of specific binding to CD44 high-expressing cancer cells both in vitro and in vivo, and the capacity of predicting prognosis of human GC in a microarray assay. Results showed that RP-1 was characterized by high affinity, sensitivity and specificity, and low toxicity, suggesting RP-1 could be an ideal bio-probe for accessory diagnosis of GC. Further immunohistochemical studies and statistical analysis of tissue microarray of human GC demonstrated similar sensitivity and specificity of RP-1 with the monoclonal anti-CD44 antibody in the diagnosis of GC, and even proved that positive RP-1 could be an independent risk factor. Therefore, this study suggests RP-1 has the potentials of binding to CD44 protein expressed on the membrane of GC cells, and demonstrates the feasibility and reliability of its further application in molecular diagnosis and prognostic prediction of GC.

Cell-specific perforation using functionalized plasmonic nanoparticles and near-infrared femtosecond laser

Event Abstract Back to Event Cell-specific perforation using functionalized plasmonic nanoparticles and near-infrared femtosecond laser Eric Bergeron1*, Christos Boutopoulos1, 2, Rosalie Martel1*, Alexandre Torres1*, Camille Rodriguez1*, Jukka Niskanen3*, Jean-Jacques Lebrun4*, Françoise M. Winnik3, 5*, Przemyslaw Sapieha6* and Michel Meunier1* 1 Polytechnique Montréal, Department of Engineering Physics, Canada 2 University of St. Andrews, SUPA, School of Physics and Astronomy, United Kingdom 3 Université de Montréal, Faculty of Pharmacy and Department of Chemistry, Canada 4 McGill University Health Centre, Division of Medical Oncology, Department of Medicine, Canada 5 Nanoarchitectonics (MANA) and National Institute for Materials Science (NIMS), World Premier International (WPI) Research Center Initiative, International Center for Materials, Japan 6 Hôpital Maisonneuve-Rosemont Research Center, Université de Montréal, Department of Ophthalmology, Canada Introduction: Gold nanoparticles (AuNPs) have found numerous applications in nanomedicine, in view of their robustness, ease of functionalization and low toxicity[1],[2]. Our group has demonstrated that near-infrared (NIR) femtosecond (fs) laser excitation of 100 nm citrate-capped AuNPs enables high cell membrane perforation, while maintaining high cell viability and enabling transfection of DNA plasmids into cancer cells[3]. Such laser irradiation of AuNPs minimizes the heat absorption from AuNPs and biological tissues since they absorb energy very weakly in the NIR range[4],[5]. The amplification of the electromagnetic field around the irradiated AuNP can cause the generation of nanoplasma leading to a nanobubble, thus inducing cell perforation without AuNP fragmentation[3],[6]-[8]. Since selective targeting of diseased cells can increase therapeutic efficacy and limit off-target adverse effects, the next step for selective cell optoporation is to develop stable AuNPs which labeled targeted cells without affecting surrounding non-targeted cells. Here the receptor CD44 strongly expressed by cancer cells was used as a model for selective targeting and optoporation. Materials: Monoclonal anti-CD44 antibodies (Abs) from abcam. Orthopyridyl-disulfide-poly(ethylene glycol) (5kDa)-N-hydroxysuccinimide (OPSS-PEG-NHS) and HS-PEG (5kDa) from Nanocs. Citrate-capped AuNPs (50 μg/mL, 100 nm in diameter) from Nanopartz. HS-PEG (2kDa), PBS, Lucifer Yellow (LY) and DAPI from Sigma-Aldrich. Tetramethylrhodamine-wheat germ agglutinin (WGA) and Alexa 488-Abs from Life Technologies. Methods: Abs were conjugated to OPSS-PEG-NHS (OPSS-PEG-Ab). AuNPs were functionalized with 0.01 OPSS-PEG-Ab/nm2 and 5 µM HS-PEG[9]. The stability of functionalized AuNPs (fAuNPs) was evaluated by UV-visible spectroscopy and zeta potential measurements. Cells were incubated for 3 h with 8 μg/mL fAuNPs, washed with PBS, incubated with LY and treated with a 45 fs laser at 800 nm (Spitfire, Spectra Physics). Two hours after the laser treatment, the cells were washed with PBS, fixed and stained with DAPI. Results and Discussion: The fAuNPs with HS-PEG (5kDa) were colloidally stable in cell culture medium containing serum proteins, while fAuNPs with HS-PEG (2kDa) were unstable. Selective targeting with stable fAuNPs was confirmed by immunofluorescence, darkfield and fluorescence imaging, flow cytometry and SEM on targeted CD44+ human cells (MDA-MB-231 breast cancer and ARPE-19 retinal pigmented epithelium) and on non-targeted CD44- mouse 661W photoreceptors (Fig. 1). The fAuNPs attached mostly as single particles 115 times more to targeted cells than to non-targeted cells. Selective optoporation of targeted cells was demonstrated with stable fAuNPs enhancing fs laser without affecting surrounding non-targeted cells (Fig. 2 and 3). Perforated cells in the laser-irradiated area were mainly targeted cells which accumulated LY, while untreated cells remained non-perforated[10]. Conclusion: The proposed novel highly versatile treatment paradigm can be adapted to target and perforate other cell populations by adapting to desired biomarkers. Since living biological tissues absorb energy very weakly in the NIR range, the developed non-invasive tool may provide a safe, cost-effective clinically relevant approach to ablate pathologically deregulated cells and limit complications associated with surgical interventions. This work was supported by Le Fonds de recherche du Québec, Consortium québécois sur la découverte du médicament (CQDM), the Natural Science and Engineering Research Council of Canada (NSERC) and Canadian Institutes of Health Research (CIHR). EB received funding from Fonds de recherche du Québec – Santé and CB acknowledges funding from the EU under a Marie Curie Fellowship, FP7-PEOPLE-2013-IOF, project reference 624888. David Rioux, Sergiy Patskovsky, Rémi Lachaine, Alexandra Thibeault-Eybalin, Ariel Wilson, Flavie Lavoie-Cardinal and Yves Drolet are acknowledged for technical assistance and fruitful discussions. The authors also thank Danièle Gagné and Gaël Dulude from the IRIC flow cytometry platform for assistance with flow cytometry.

CD44 in human glioma correlates with histopathological grade and cell migration

Glioblastomas are associated with high mortality due to their aggressive growth and invasiveness. Interactions and functional cross-talk between tumor cells and their microenvironments are mediated by cell surface receptors that are responsible for cell-cell and cell-extracellular matrix adhesion. Central nervous tissues contain plenty of the glycosaminoglycan hyaluronan, and glioma cells express the major cell surface hyaluronan receptor, CD44. In this study, we analyzed the expression and roles of CD44 in human brain tissues. Normal brain tissues showed no or weak CD44 expression, while reactive astrocytes and astrocytoma cells expressed CD44 at variable levels. Immunohistochemically, a higher percentage and intensity of CD44-positive tumor cells were detected in high-grade astrocytomas compared with low-grade astrocytomas. Glioblastoma cells that express CD44 were localized in perivascular and perinecrotic lesions. The human glioma cell lines A172 and KG-1-C expressed CD44 mRNA and protein. Administration of monoclonal anti-human-CD44 antibody inhibited the migration of A172 cells, which are glioblastoma-derived, but did not affect cell growth. In conclusion, CD44 expression levels correlated with the histopathological grade of gliomas, and monoclonal anti-CD44 antibody inhibited the migration of glioblastoma cells. These findings suggest that CD44 is a potential therapeutic target of glioblastomas.

Epigenetic regulation of CD44in Hodgkin and non-Hodgkin lymphoma

BackgroundEpigenetic inactivation of tumor suppressor genes (TSG) by promoter CpG island hypermethylation is a hallmark of cancer. To assay its extent in human lymphoma, methylation of 24 TSG was analyzed in lymphoma-derived cell lines as well as in patient samples.MethodsWe screened for TSG methylation using methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) in 40 lymphoma-derived cell lines representing anaplastic large cell lymphoma, Burkitt lymphoma (BL), diffuse large B-cell lymphoma (DLBCL), follicular lymphoma (FL), Hodgkin lymphoma and mantle cell lymphoma (MCL) as well as in 50 primary lymphoma samples. The methylation status of differentially methylated CD44 was verified by methylation-specific PCR and bisulfite sequencing. Gene expression of CD44 and its reactivation by DNA demethylation was determined by quantitative real-time PCR and on the protein level by flow cytometry. Induction of apoptosis by anti-CD44 antibody was analyzed by annexin-V/PI staining and flow cytometry.ResultsOn average 8 ± 2.8 of 24 TSG were methylated per lymphoma cell line and 2.4 ± 2 of 24 TSG in primary lymphomas, whereas 0/24 TSG were methylated in tonsils and blood mononuclear cells from healthy donors. Notably, we identified that CD44 was hypermethylated and transcriptionally silenced in all BL and most FL and DLBCL cell lines, but was usually unmethylated and expressed in MCL cell lines. Concordant results were obtained from primary lymphoma material: CD44 was not methylated in MCL patients (0/11) whereas CD44 was frequently hypermethylated in BL patients (18/29). In cell lines with CD44 hypermethylation, expression was re-inducible at mRNA and protein levels by treatment with the DNA demethylating agent 5-Aza-2'-deoxycytidine, confirming epigenetic regulation of CD44. CD44 ligation assays with a monoclonal anti-CD44 antibody showed that CD44 can mediate apoptosis in CD44+ lymphoma cells. CD44 hypermethylated, CD44- lymphoma cell lines were consistently resistant towards anti-CD44 induced apoptosis.ConclusionOur data show that CD44 is epigenetically regulated in lymphoma and undergoes de novo methylation in distinct lymphoma subtypes like BL. Thus CD44 may be a promising new epigenetic marker for diagnosis and a potential therapeutic target for the treatment of specific lymphoma subtypes.

Abstract 5120: A6 peptide binds to CD44 and inhibits migration and metastasis of CD44+ cell lines in in vitro and in vivo studies

Abstract Background: CD44 plays a role in many physiological and pathological processes, including cell-cell and cell-extracellular matrix interactions, cell migration, and metastatic spread. A6 (KPSSPPEE) is a synthetic peptide that inhibits migration of human cancer cell lines and has anti-tumor activity in the absence of significant adverse events in tumor models and in a Phase 2 clinical trial in ovarian cancer. The current study was directed at identifying the mechanism of action of A6 through investigation of its effects on cell migration and metastasis. Methods: The effect of A6 on migration was investigated using human ovarian and breast carcinoma cell lines. Effects on cell migration in response to NIH3T3 conditioned media supplemented with VEGF were assessed using the Boyden chamber technique. To demonstrate the potential of A6 to inhibit cancer metastasis in vivo, the number of tumor nodules generated in the lungs of C57BL/6 mice intravenously inoculated with B16-F10 mouse melanoma cells was quantified. To characterize A6 binding and CD44 expression, standard FACS, cross-linking, and immunoprecipitation/blotting techniques were used. Results: A6 inhibited the migration of a subset of ovarian and breast cancer cell lines (e.g. SKOV3, OVCAR3, MDA-MB 361 and MDA-MB 468), exhibiting IC50 values in an in vitro chemotaxis assay in the pM to nM range. The ability of A6 to inhibit cancer cell migration in vitro correlated with CD44 expression: CD44 positive lines (e.g., SKOV3, OVCAR3, murine B16-F10 melanoma) were inhibited by A6 whereas cell lines expressing little or no CD44 (e.g., OVCAR4, OVCAR5, late passage A2780) were refractory to A6. Immunopreciptation studies demonstrate that CD44 binds biotin-tagged A6 peptide cross-linked to the plasma membrane. Although A6 perturbed the binding of a monoclonal anti-CD44 antibody (DF-1485) to SKOV3 cells it did not inhibit hyaluronic acid (HA)-induced adhesion of cancer cells through CD44 suggesting that A6 peptide is not a competitive antagonist of CD44/HA binding. In fact A6 potentiated the HA-induced adhesion of cancer cells. The ability of A6 to agonize the CD44 receptor and desensitize cells to migration signals represents a novel strategy for inhibiting CD44 function. In vivo, A6 (100 mg/kg delivered subcutaneously twice a day for 11 days) reduced the number of lung foci generated from the IV inoculation of 106 B16-F10 melanoma cells by 50% (pvalue= 0.003 in an unpaired t test), in a lung metastasis model dependent on the migration of B16-F10 melanoma cells from the circulation to the lungs. Conclusions: A6 potently blocks of the migration of CD44-positive cells in vitro through a novel mechanism of action. It binds to CD44 on the cell surface and in vivo it blocks the development of metastatic tumors at secondary sites. GOG study 170N is testing the activity of A6 in patients with recurrent ovarian cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5120.

Hyaluronan-CD44 Interaction with Protein Kinase Cϵ Promotes Oncogenic Signaling by the Stem Cell Marker Nanog and the Production of MicroRNA-21, Leading to Down-regulation of the Tumor Suppressor Protein PDCD4, Anti-apoptosis, and Chemotherapy Resistance in Breast Tumor Cells

Multidrug resistance and disease relapse is a challenging clinical problem in the treatment of breast cancer. In this study, we investigated the hyaluronan (HA)-induced interaction between CD44 (a primary HA receptor) and protein kinase Cepsilon (PKCepsilon), which regulates a number of human breast tumor cell functions. Our results indicate that HA binding to CD44 promotes PKCepsilon activation, which, in turn, increases the phosphorylation of the stem cell marker, Nanog, in the breast tumor cell line MCF-7. Phosphorylated Nanog is then translocated from the cytosol to the nucleus and becomes associated with RNase III DROSHA and the RNA helicase p68. This process leads to microRNA-21 (miR-21) production and a tumor suppressor protein (e.g. PDCD4 (program cell death 4)) reduction. All of these events contribute to up-regulation of inhibitors of apoptosis proteins (IAPs) and MDR1 (multidrug-resistant protein), resulting in anti-apoptosis and chemotherapy resistance. Transfection of MCF-7 cells with PKCepsilon or Nanog-specific small interfering RNAs effectively blocks HA-mediated PKCepsilon-Nanog signaling events, abrogates miR-21 production, and increases PDCD4 expression/eIF4A binding. Subsequently, this PKCepsilon-Nanog signaling inhibition causes IAP/MDR1 down-regulation, apoptosis, and chemosensitivity. To further evaluate the role of miR-21 in oncogenesis and chemoresistance, MCF-7 cells were also transfected with a specific anti-miR-21 inhibitor in order to silence miR-21 expression and inhibit its target functions. Our results indicate that anti-miR-21 inhibitor not only enhances PDCD4 expression/eIF4A binding but also blocks HA-CD44-mediated tumor cell behaviors. Thus, this newly discovered HA-CD44 signaling pathway should provide important drug targets for sensitizing tumor cell apoptosis and overcoming chemotherapy resistance in breast cancer cells.

Hyaluronan Mixed Esters of Butyric and Retinoic Acid Drive Cardiac and Endothelial Fate in Term Placenta Human Mesenchymal Stem Cells and Enhance Cardiac Repair in Infarcted Rat Hearts

We have developed a mixed ester of hyaluronan with butyric and retinoic acid (HBR) that acted as a novel cardiogenic/vasculogenic agent in human mesenchymal stem cells isolated from bone marrow, dental pulp, and fetal membranes of term placenta (FMhMSCs). HBR remarkably enhanced vascular endothelial growth factor (VEGF), KDR, and hepatocyte growth factor (HGF) gene expression and the secretion of the angiogenic, mitogenic, and antiapoptotic factors VEGF and HGF, priming stem cell differentiation into endothelial cells. HBR also increased the transcription of the cardiac lineage-promoting genes GATA-4 and Nkx-2.5 and the yield of cardiac markerexpressing cells. These responses were notably more pronounced in FMhMSCs. FMhMSC transplantation into infarcted rat hearts was associated with increased capillary density, normalization of left ventricular function, and significant decrease in scar tissue. Transplantation of HBR-preconditioned FMhM-SCs further enhanced capillary density and the yield of human vWF-expressing cells, additionally decreasing the infarct size. Some engrafted, HBR-pretreated FMhMSCs were also positive for connexin 43 and cardiac troponin I. Thus, the beneficial effects of HBR-exposed FMhMSCs may be mediated by a large supply of angiogenic and antiapoptotic factors, and FMhMSC differentiation into vascular cells. These findings may contribute to further development in cell therapy of heart failure.

Increased Toll-Like Receptor 4 Expression on T Cells May Be a Mechanism for Enhanced T cell Response Late After Burn Injury

Burn injury is associated with a dynamic T cell response. We have previously reported an enhanced functional T cell response 14 days after burn injury. Toll-like receptors (TLR), primarily expressed on innate immune cells, have recently been identified on certain T cell subsets, including activated and memory T cells. Our hypothesis is that increased TLR4 expression on memory T cells may be a mechanism for enhanced T cell response 14 days after burn injury. Splenocytes from wild-type C57Bl/6 mice were harvested 14 days after a 20% total body surface area (TBSA) scald burn or sham injury. Splenocytes ex vivo were surface stained either with monoclonal anti-CD3, anti-CD4, anti-CD8, or anti-CD44 antibodies or a two-step biotin-TLR4 monoclonal antibody-streptavidin-FITC surface stain and results analyzed by flow cytometry. TLR4 expression is successfully detected on CD4 and CD8 T cells. TLR4 expression is significantly (p < 0.05) increased on CD4 T cells and CD8 T cells 14 days after burn injury. There is a significant (p < 0.05) increase in CD44 (memory) CD4 and CD44 (memory) CD8 T cells 14 days after burn injury and this is associated with a significant (p < 0.05) increase of TLR4 expression in both T cell populations. This study demonstrates for the first time the potential role of TLR4 expression on memory T cells generated late after burn injury. Although further analysis is required, these data reiterate the importance of adaptive immunity and the complexity of the immune response to burn injury.

Exogenous hyaluronic acid enhances porcine parthenogenetic embryo development in vitro possibly mediated by CD44

Exogenous hyaluronic acid (HA) has been reported to improve early embryo development in vitro in pigs and cows. Although early embryo development in vitro is improved by exogenous HA, the mechanism mediating the action of HA is not clearly defined. In the present study, two possible HA actions on early embryo development were proposed to understand interactions between HA and the embryos using porcine parthenotes. We hypothesized that improvement of early embryo development mediated by HA would be caused by embryo-derived growth factors due to the high molecular weight of HA or cellular response through its receptor (CD44). We examined the effects of HA molecular weight on parthenogenetic embryo development, permeability of HA into the zona pellucida, expression of CD44 in porcine parthenotes at various stages, and blocking interactions between HA and CD44 by monoclonal anti-CD44 antibody (mCD44Ab). As a result, although development of porcine parthenotes to the blastocyst stage was significantly enhanced by exogenous HA with various molecular weights, there was no difference in blastocyst formation among the various molecular weights ( P < 0.05). Immunofluorescence revealed that exogenous HA was accessible to CD44 through the zona pellucida, irrespective of the oocyte activation and that CD44 was also expressed in both oocytes and parthenotes at all developmental stages. In addition, development of parthenotes was partially blocked by mCD44Ab. In conclusion, we demonstrated that exogenous HA enhanced development of porcine parthenotes in vitro. This improvement mediated by exogenous HA on parthenogenetic embryo development was possibly caused by cellular response via CD44.

Up-regulation of CD44 in rheumatoid chondrocytes

The adhesion molecule CD44 is thought to play an important role in the inflammatory process. To identify the expression of CD44 in articular chondrocytes in rheumatoid arthritis (RA), monoclonal anti-CD44 antibodies were immunohistochemically used to react with articular cartilage specimens of 15 patients with RA, 9 with osteoarthritis (OA), and 6 with femoral neck fracture (FF). The proportion of CD44-positive chondrocytes in RA was 93±2% (N=16), which was significantly higher than that in OA (59±7%, N=9, p<0.001) and FF (46±5%, N=6, p<0.001). Among CD44 isoforms examined, the hemopoietic form was dominant in chondrocytes in RA. Therefore, up-regulation of CD44 on chondrocytes may play a significant role in cartilage degeneration in RA.

Hyaluronic acid (HA) binding to CD44 activates Rac1 and induces lamellipodia outgrowth.

Both cell adhesion protein CD44 and its main ligand hyaluronic acid (HA) are thought to be involved in several processes ultimately requiring cytoskeleton rearrangements. Here, we show that the small guanine nucleotide (GTP)-binding protein, Rac1, can be activated upon HA binding to CD44. When applied locally to a passive cell edge, HA promoted the formation of lamellipodial protrusions in the direction of the stimulus. This process was inhibited by the prior injection of cells with dominant-negative N17Rac recombinant protein or by pretreatment of cells with monoclonal anti-CD44 antibodies, interfering with HA binding, implying the direct involvement of CD44 in signaling to Rac1.

Signal Transduction via CD44: Role of Plasma Membrane Microdomains

CD44 is the principal cell surface receptor for extracellular matrix glycosaminoglycan hyaluronan. CD44-hyaluronan mediated cell adhesion is important in several pathophysiological processes such as inflammation and metastatic spread of cancer cells. It has been recently recognized that CD44 also functions as a signaling receptor in a variety of cell types. Cell stimulation by monoclonal anti-CD44 antibody or natural CD44 ligands activate several signaling pathways that culminate in cell proliferation, cytokine secretion, chemokine gene expression and cytolytic effector functions. One of the earliest signaling events following stimulation via CD44 is tyrosine phosphorylation of intracellular proteins substrates, and CD44 mediated cellular activation could be abolished by protein tyrosine kinase (PTK) inhibitors. The Src-family non-receptor PTKs such as Lck, Fyn, Lyn and Hck were shown to be coupled to CD44 via sphingolipid-rich microdomains (lipid rafts) of the plasma membrane. Studies on T cell receptor and IgE receptor mediated signaling in lymphocytes and mast cells have consolidated the notion that microdomains consist of signaling platforms where components of multiple signaling pathways are assembled. Co-isolation of CD44 with microdomains strongly suggests that CD44 generates cellular activation signals utilizing the signaling machinery of the plasma membrane microdomains.

Requirement for CD44 in proliferation and homing of hematopoietic precursor cells.

The hematopoietic form of the adhesion molecule CD44 is known to be involved in lymphocyte maturation and homing. To define lineage and stage of maturation, which requires expression of CD44, murine long-term bone marrow cultures were established. Stroma formation and proliferation of early as well as committed erythroid, myeloid, and lymphoid progenitors were evaluated under the influence of monoclonal anti-CD44 antibodies. Although the formation of stromal elements was not affected, formation of cobblestone areas was completely abolished. [3H]thymidine suicide confirmed that anti-CD44 treatment interfered with the proliferation of early and committed hematopoietic progenitor cells. In addition, homing and seeding of bone marrow cells was impaired by anti-CD44. The data are indicative of a dual functional mode of CD44 in adhesion and proliferation of hematopoietic progenitors and confirm an essential requirement for the molecule in early stages of hematopoiesis.

A cysteine residue located in the transmembrane domain of CD44 is important in binding of CD44 to hyaluronic acid.

In the transmembrane domain and cytoplasmic domain of human CD44 protein there are two cysteine residues. These two cysteines are conserved in all known mammalian CD44 proteins. The functions of these cysteine residues are not known. Site-specific mutagenesis was used to create CD44 mutant proteins lacking either one or both of these cysteine residues. Wild-type CD44 and mutant CD44 genes were transfected into CD44- Jurkat cells to establish stable transfectants. These transfectants were used to study whether these two cysteine residues are important in the binding of CD44(H) to fluorescein-conjugated hyaluronic acid (F-HA). Jurkat transfectant bearing wild-type CD44 did not bind F-HA, unless they were stimulated in vitro with immobilized anti-CD3 monoclonal antibody. Anti-CD3 antibody also stimulated the binding of F-HA in Jurkat CD44.C295A transfectant in which the cytoplasmic cysteine residue has been replaced with alanine. In contrast, anti-CD3 antibody failed to stimulate the binding of F-HA in Jurkat transfectant (CD44.C286A), in which the transmembrane domain cysteine 286 has been replaced with an alanine, and in Jurkat transfectant CD44.2C2A, in which both of the cysteine residues have been altered. Binding can also be induced with a monoclonal anti-CD44 antibody (F-44-10-2) in Jurkat wild-type CD44 and Jurkat CD44.C295A transfectants but not in CD44. C286A transfectant. These results provide evidence that the transmembrane domain of CD44, more specifically the cysteine residue in the transmembrane domain, is important for both activation-induced and anti-CD44 antibody-induced binding of soluble HA.

Differentiation-Associated Changes in CD44 Isoform Expression During Normal Hematopoiesis and Their Alteration in Chronic Myeloid Leukemia

CD44 is a widely expressed, multifunctional, cell-surface glycoprotein that has been implicated in the regulation of normal hematopoiesis. In addition, expression of particular isoforms of CD44 has been associated with malignant transformation and/or the acquisition of metastatic potential. In this study, we used two recently developed monoclonal anti-CD44 antibodies, one reactive with an epitope shared by many CD44 isoforms and the other with an epitope unique to CD44 isoforms containing amino acids encoded by the alternatively spliced exon v10, to compare the expression of CD44 on primitive hematopoietic cells from the marrow of normal individuals and their neoplastic counterparts present in the peripheral blood of patients with chronic myeloid leukemia (CML). Multiparameter fluorescence-activated cell sorter (FACS) analysis and cell sorting studies showed that CD44 is normally expressed at high to very high levels on both long-term culture-initiating cells (LTC-IC) and granulopoietic colony-forming cells (granulocyte-macrophage colony-forming units [CFU-GM]). In contrast, primitive erythropoietic progenitors (burst-forming units-erythroid [BFU-E]) in normal marrow were more homogeneous in their expression of CD44, and very few (less than 5%) showed the very high levels of CD44 seen on 20% to 25% of LTC-IC and CFU-GM. Antibody staining showed the expression of exon v10-containing CD44 isoforms to be restricted to a small subpopulation (4% to 8%) of morphologically recognizable mature (CD34-) myeloid cells within the light-density fraction of normal marrow cells. Reverse transcription-polymerase chain reaction (RT-PCR) analysis showed the presence of two exon v10-containing mRNA species. In CML, a significantly greater proportion of the circulating neoplastic CFU-GM expressed very high levels of CD44, and these CFU-GM were accompanied by an increased number of light density v10+ cells, including some that coexpressed CD34. Nonmalignant hematopoietic progenitors mobilized by prior chemotherapy and growth factor treatment of patients with Hodgkin's disease or acute myeloid leukemia in remission showed no changes in CD44 expression relative to normal marrow progenitors. These results provide evidence of early differentiation-associated changes in CD44 expression during normal hematopoiesis in vivo that may be deregulated in the neoplastic clone of patients with CML.

Differentiation-associated changes in CD44 isoform expression during normal hematopoiesis and their alteration in chronic myeloid leukemia

CD44 is a widely expressed, multifunctional, cell-surface glycoprotein that has been implicated in the regulation of normal hematopoiesis. In addition, expression of particular isoforms of CD44 has been associated with malignant transformation and/or the acquisition of metastatic potential. In this study, we used two recently developed monoclonal anti-CD44 antibodies, one reactive with an epitope shared by many CD44 isoforms and the other with an epitope unique to CD44 isoforms containing amino acids encoded by the alternatively spliced exon v10, to compare the expression of CD44 on primitive hematopoietic cells from the marrow of normal individuals and their neoplastic counterparts present in the peripheral blood of patients with chronic myeloid leukemia (CML). Multiparameter fluorescence-activated cell sorter (FACS) analysis and cell sorting studies showed that CD44 is normally expressed at high to very high levels on both long-term culture-initiating cells (LTC-IC) and granulopoietic colony-forming cells (granulocyte-macrophage colony-forming units [CFU-GM]). In contrast, primitive erythropoietic progenitors (burst-forming units-erythroid [BFU-E]) in normal marrow were more homogeneous in their expression of CD44, and very few (less than 5%) showed the very high levels of CD44 seen on 20% to 25% of LTC-IC and CFU-GM. Antibody staining showed the expression of exon v10-containing CD44 isoforms to be restricted to a small subpopulation (4% to 8%) of morphologically recognizable mature (CD34-) myeloid cells within the light-density fraction of normal marrow cells. Reverse transcription-polymerase chain reaction (RT-PCR) analysis showed the presence of two exon v10-containing mRNA species. In CML, a significantly greater proportion of the circulating neoplastic CFU-GM expressed very high levels of CD44, and these CFU-GM were accompanied by an increased number of light density v10+ cells, including some that coexpressed CD34. Nonmalignant hematopoietic progenitors mobilized by prior chemotherapy and growth factor treatment of patients with Hodgkin's disease or acute myeloid leukemia in remission showed no changes in CD44 expression relative to normal marrow progenitors. These results provide evidence of early differentiation-associated changes in CD44 expression during normal hematopoiesis in vivo that may be deregulated in the neoplastic clone of patients with CML.

Administration of Antibodies to Hyaluronanreceptor (CD44) Delays the Start and Ameliorates the Severity of Collagen II Arthritis

Hyaluronanreceptor (CD44) has been shown to be involved in lymphocyte homing during normal leucocyte circulation and during leucocyte extravasation into sites of tissue inflammation. In addition, interaction with CD44 molecule induces T-cell activation and production of cytokines, such as interferon-gamma. In this study we have examined what influence interaction with the CD44 receptor would have on collagen II-induced arthritis in mice. Mice were immunized with rat collagen II and administered with injections of a monoclonal anti-CD44 antibody. Seventeen days after the outbreak of the disease, all of the anti-CD44 treated animals remained clinically health, whereas 37% of the controls displayed arthritis (P < 0.001). Ten days later the prevalence of arthritis was 26% and 65% (P < 0.05), respectively. Furthermore, the severity of the arthritis was significantly ameliorated by the anti-CD44 treatment. Serum levels of interferon-gamma were significantly higher in collagen II immunized animals having been treated with anti-CD44, compared to the controls. Delayed-type hypersensitivity (DTH) response was significantly decreased in the anti-CD44 treated animals, indicating a functional suppression of T cells. In contrast, T cell independent experimental inflammation was not affected by the administration of CD44 antibodies. Our results suggest that interaction with CD44 down-regulates T lymphocyte/monocyte mediated inflammatory reaction, possibly by triggering of interferon-gamma release.

A CD44 monoclonal antibody differentially regulates CD11a/CD18 binding to intercellular adhesion molecules CD54, CD102 and CD50

We have made a monoclonal anti-CD44 antibody which is able to activate the leukocyte integrin CD11a/CD18. Activated T cells strongly aggregated, and the aggregation was shown to be intercellular adhesion molecule (ICAM)-1 (CD54) and ICAM-2 (CD102) dependent. Using purified ICAM coated on plastic, only binding to ICAM-1 was increased by the CD44 antibody, whereas activation by phorbol ester increased binding to both ICAM-1 and ICAM-3. The binding to ICAM-2 was not affected by either treatment. These findings show that the CD11a/CD18 integrin can be activated in a ligand-specific manner by engagement of CD44.

Defective phosphorylation and hyaluronate binding of CD44 with point mutations in the cytoplasmic domain.

CD44 is a cell surface adhesion molecule that plays a role in leukocyte extravasation, leukopoiesis, T lymphocyte activation, and tumor metastasis. The principal known ligand for CD44 is the glycosaminoglycan hyaluronate, (HA), a major constituent of extracellular matrices. CD44 expression is required but is not sufficient to confer cellular adhesion to HA, suggesting that the adhesion function of the receptor is regulated. We recently demonstrated that CD44 in primary leukocytes is phosphorylated in a cell type- and activation state-dependent fashion. In this study we demonstrate that serines 325 and 327 within the cytoplasmic domain of CD44 are required for the constitutive phosphorylation of CD44 in T cells. Furthermore, we demonstrate that cells expressing mutated CD44 containing a serine to glycine substitution at position 325 or a serine to alanine substitution at amino acid 327 are defective in HA binding, CD44-mediated adhesion of T cells to smooth muscle cells, as well as ligand-induced receptor modulation. The effect of these mutations can be partially reversed by a monoclonal anti-CD44 antibody that enhances CD44-mediated HA binding.

Palmitoylation of CD44 interferes with CD3-mediated signaling in human T lymphocytes

We studied the interactions between CD44 and four different monoclonal anti-CD44 antibodies. All four monoclonal anti-CD44 antibodies studied (P3H9, Bu52, IM.7, and GKW.A3) act in synergy with human anti-CD2 antibodies in stimulating normal human peripheral blood lymphocytes to proliferate. GKW.A3 and IM.7 but not P3H9 or Bu52 inhibited the proliferation of normal human peripheral blood lymphocytes stimulated by anti-CD3. Interestingly, only GKW.A3 and IM.7 stimulated the incorporation of [3H]palmitic acid and palmitoylation of CD44 molecules by normal human peripheral blood lymphocytes. The two monoclonal anti-CD44 antibodies (P3H9 and Bu52) that failed to inhibit anti-CD3 induced proliferation also failed to induce the incorporation of [3H]palmitic acid. More importantly, the inhibitory effects of GKW.A3 were reversed in the presence of cerulenin, an inhibitor of protein palmitoylation. Therefore, palmitoylation of CD44 may interfere with anti-CD3 mediated signaling pathways. These data support the hypothesis that palmitoylation of cell surface receptors may play an active role in receptor and receptor interactions and signal transduction in normal human T lymphocytes.