Localization of CD44, the hyaluronate receptor, on the plasma membrane of osteocytes and osteoclasts in rat tibiae

CD44 is a multifunctional adhesion molecule that binds to hyaluronic acid, type I collagen, and fibronectin. We have studied the immunohistochemical localization of CD44 in bone cells by confocal laser scanning microscopy and transmission electron microscopy in order to clarify its role in the cell-cell and/or cell-matrix interaction of bone cells. In round osteoblasts attached to bone surfaces, immunoreactivity is restricted to their cytoplasmic processes. On the other hand, osteocytes in bone matrices show intense immunoreactivity on their plasma membrane. Intense immunoreactivity for CD44 can be detected on the basolateral plasma membranes of osteoclasts. There is considerably less reactivity observed in the area of the plasma membrane that is in direct contact with bone. The pre-embedding electron-microscopical method has revealed that CD44 is mainly localized on the basolateral plasma membrane of osteoclasts. However, the ruffled border and clear zone show little immunoreactivity. A CD44-positive reaction can be detected on both plasma membranes in the contact region between osteoclasts and osteocytes. These findings suggest that: 1) cells of the osteoblast lineage express CD44 in accordance with their morphological changes from osteoblasts into osteocytes; 2) osteoclasts express CD44 on their basolateral plasma membrane; 3) CD44 in osteoclasts and osteocytes may play an important role in cell-cell and/or cell-matrix attachment via extracellular matrices.

Regulation of growth and dissemination of a human lymphoma by CD44 splice variants

CD44 is a polymorphic cell surface glycoprotein, currently proposed to be the principal cell surface receptor for hyaluronan. However, different isoforms of CD44, expressed in human lymphoid tumor cells, appear to have distinct effects on the ability of the cells to attach to hyaluronan-coated surfaces and on their capacity to form tumors in vivo. In the present study, we address the mechanisms that may regulate CD44 isoform-dependent adhesion to hyaluronan. We use a human Burkitt lymphoma, stably transfected with six different alternatively spliced human CD44 isoforms, to determine their potential hyaluronan binding and tumor growth promoting roles. We show that transfectants expressing CD44 splice variants that contain variable exons 6–10, 7–10 and 8–10 adhere to hyaluronan-coated surfaces weakly and that corresponding tumor formation in vivo is delayed with respect to CD44-negative parental cell-derived tumors. Abundant shedding of these three isoforms may play a significant role in determining the rate of tumor development. Transfectants expressing variable exon 3, on the other hand, fail to display CD44-mediated adhesion to hyaluronan, but form bone marrow tumors rapidly following intravenous injection. These observations suggest that different mechanisms regulate CD44-mediated adhesion and tumor growth, and provide evidence that expression of exon v3 may confer novel ligand-binding properties.

Changes in CD44 expression during B cell differentiation in the human tonsil

CD44 is a widely distributed cell surface glycoprotein that has been implicated in a number of cellular adhesion processes and signal transduction events. These functional capabilities qualify CD44 as a potential mediator of contact-signaling events underlying the process of antigen-dependent B cell differentiation in secondary lymphoid tissues. We postulated that changes in the expression of CD44 during B cell differentiation reflect the cells' changing requirements for this receptor. It has been reported that germinal center B cells are low to negative for CD44 expression, implying that the receptor is lost upon activation. Correlation of the expression of CD44 with surface immunoglobulin and a number of B cell differentiation markers revealed a trimodal expression pattern. High levels of CD44 are expressed on resting IgD+/IgM+ cells. The receptor is still expressed at the early activation stage defined by the expression of CD23. At the early blast stage, when the blast marker CD38 appears on the cell surface and IgD and CD23 disappear, CD44 is downregulated. The majority of CD38+/IgM+ blasts and CD38+/Ig- centroblasts are CD44 low/negative. The receptor is re-upregulated at the point of transition from the centroblast to the centrocyte level. Centrocytes expressing IgG or IgA comprise CD44high and CD44low fractions. IgG+ or IgA+ cells at the postgerminal center stage express high levels of CD44. The functional implications of this expression pattern are discussed.

CD44 variant exon epitopes in primary breast cancer and length of survival

CD44 designates a group of closely related cell-surface proteins generated by alternative splicing. We have previously shown that splice variants carrying sequences encoded by exon v6 are preferentially expressed in metastatic animal cancer cell lines and that they confer metastatic behaviour on non-metastatic animal tumour cell lines. In this study we set out to assess the expression of CD44 epitopes specific for variant exon sequences in human breast cancer and their potential for determining prognosis. We used affinity-purified polyclonal sera and four monoclonal antibodies raised against the human homologues of CD44 variant exon sequences to investigate the presence of CD44 on 100 primary invasive breast tumours, 12 local recurrences, 18 lymph node metastases, and normal tissue controls. Whereas normal mammary ductal epithelial cells and cells derived from hyperplastic lesions do not express CD44 variant exons, expression of v3, v5, and v6 epitopes was found in most tumour samples. The DIII (exon v6) epitope was present in 84% of the primary tumours and in 100% of axillary lymph node metastases and local recurrences. The presence of these CD44 epitopes is correlated with poor overall survival. 15 patients with exon-v6-negative tumours had good survival compared with 76 patients with exon-v6-positive tumours (p = 0.005; log rank test). Multivariate analysis showed that the CD44 epitope encoded by exon v6 was a good marker for prognosis independent of progesterone receptor, lymph node status, tumour size, and grade.

Intravascular bronchioloalveolar tumor of the lung presenting as pulmonary thromboembolic disease and pulmonary hypertension

Intravascular bronchioloalveolar tumor, the pulmonary counterpart of epithelioid hemangioendothelioma, typically presents as bilateral pulmonary nodules in young women. We report a case of intravascular bronchioloalveolar tumor that clinically mimicked acute pulmonary thromboembolic disease initially and was subsequently proven to have pulmonary hypertension with right ventricular dysfunction by angiography. The diagnosis of intravascular bronchioloalveolar tumor was confirmed by immunohistochemical and ultrastructural studies after it was suspected on routine histologic examination. In addition, the tumor cells expressed glycoprotein cell adhesion molecule CD44, which has been implicated in increased tumor invasiveness and metastasis in various carcinomas and several aggressive non-Hodgkin's lymphomas.

Lymphocytes infiltrating the CNS during inflammation display a distinctive phenotype and bind to VCAM-1 but not to MAdCAM-1

The nature of inflammatory lymphocytes recruited to the CNS has been studied in a model of chronic inflammation. Injection of killed Corynebacterium parvum into the cortex of the mouse brain produces a circumscribed inflammatory cellular infiltrate around the injection site, and recruited mononuclear inflammatory cells (IC) can be isolated for flow cytometric analysis. The majority of IC were T cells. In comparison with the predominant naive population of mesenteric lymph node T cells, IC T cells express much higher levels of CD44, LFA-1 and ICAM-1, and lower levels of CD45RB, features commonly associated with memory (previously activated) cells. In addition, in contrast to the L-selectin+ alpha 6-integrinlow phenotype of naive lymph node T cells, IC T cells lacked L-selectin and were alpha 6-integrin-. Mac-1, recently proposed as another marker of memory T cell differentiation, was not displayed by IC T cells, suggesting that Mac-1 expression may be heterogeneous among memory T cell subsets. A subset of mesenteric lymph node (MLN) T cells, probably representing activated T cells undergoing the naive to memory transition, but not of IC T cells, expressed high levels of alpha 6-, beta 7- and alpha E-integrin. IC and MLN naive T cells expressed comparable levels of alpha 4-integrin, but IC T cells stain poorly with anti-beta 7 mAbs and with mAb DATK 32, specific for the alpha 4 beta 7 heterodimeric lymphocyte homing receptor for the mucosal addressin MAdCAM-1, suggesting that these inflammatory cells express more alpha 4 beta 1 than alpha 4 beta 7. Consistent with this, in in vitro adhesion assays, brain IC bound better than MLN cells to the alpha 4 beta 1 integrin ligand VCAM-1 and the LFA-1 ligand ICAM-1 but adhered very poorly to the alpha 4 beta 7 ligand MAdCAM-1. These findings are consistent with and extend previous immunohistological studies of T cells in murine experimental autoimmune encephalomyelitis, and demonstrate a distinctive phenotype for lymphocytes being present in the chronically inflamed brain.

Comparison of cell adhesion molecule expression between glioblastoma multiforme and autologous normal brain tissue

We investigated glioblastoma multiforme (GBM) for a pattern of consistent alterations in cell adhesion molecules (CAM) expression that might distinguish tumor from normal autologous brain tissue. We used frozen section immunohistochemistry with anti-CAM and computerized image analysis to quantify staining intensity which we expressed as relative intensity units (RIU). Our results showed that normal brain tissue generally did not express alpha 1 beta 1, intercellular CAM-1 (ICAM-1), and sialylated Lewisx, slightly expressed alpha 2, alpha 4, alpha 5, alpha 6 beta 1, alpha v beta 3, lymphocyte function-associated antigen-3 (LFA-3), Lewisx, sialylated LewisLewisx, had a good expression of alpha 3 beta 1 and CD44, and strongly expressed neural CAM (NCAM). GBM expressed alpha 2, alpha 3, alpha 5, alpha 6 beta 1, alpha v beta 3, ICAM-1, LFA-3, CD44, Lewisx, sialylated Lewisx, and sialylated LewisLewisx significantly higher (2-11-fold RIU) than normal brain tissue. ICAM-1 and LFA-3 were the most distinctive markers of GBM. The small blood vessel endothelial cells of the normal brain and the GBM showed a few differences. The tumor endothelium expression of alpha 2 beta 1, alpha 4 beta 1, and LFA-3 RIU appeared twice higher than in normal endothelium and alpha 6 beta 1 showed an average of 40% RIU decrease in comparison to normal. These results show that the expression of several CAM is consistently altered in GBM and its microvasculature when compared with autologous normal brain tissue.

Junctional proteins of keratinocytes in Grover's disease, Hailey-Hailey's disease and Darier's disease

Alterations of junctional structures in non-immune mediated acantholytic diseases (Grover's, Hailey-Hailey's and Darier's diseases) were examined using monoclonal antibodies against desmosomal attachment constituents (desmoplakin I & II and plakoglobin), desmosomal intercellular cement glycoprotein (desmoglein), protein of adherens junction (vinculin), and protein of gap junction (43Kd connexin). Universal cell surface (transmembrane) glycoprotein CD44 was also studied. In acantholytic foci of these diseases, attachment plaque proteins had dissolved and diffused into the acantholytic cells. The normal dotted linear pattern of immunostaining on the cell membrane was totally lost. In contrast, CD44 was well preserved on the cell membranes of acantholytic cells. Adherens junction and gap junction proteins were mostly preserved. Acantholytic cells of pemphigus vulgaris were similarly studied. In these cells, desmosomal attachment plaque proteins were very well preserved, while intercellular cement substance (desmoglein), adherens junctional proteins (vinculin), and gap junction protein (connexin) were totally absent, either on the cell membrane or in the cytoplasm. Electron microscopy confirmed an early dissolution of attachment plaque. Internalized desmosomal structures were seldom found in acantholytic cells of non-immune diseases. It was concluded that the primary event in acantholysis in these three diseases is the dissolution of desmosomal attachment plaque.

Correlation of expression of CD44 isoforms and E-cadherin with differentiation in human urothelial cell lines and transitional cell carcinoma

Using immunostaining, immunoblot, reverse-transcriptase polymerase chain reaction and Southern blot, we found that expressions of CD44 isoforms and E-cadherin were very closely linked and were correlated with the differentiation status in human urothelial cell lines and clinical specimens of transitional cell carcinoma. Normal urothelium, well to moderately differentiated cell lines and surgical samples expressed E-cadherin and large CD44 isoforms containing exon v6, which was pivotal in metastasis of rat pancreatic cell line model. Poorly differentiated cell lines and surgical samples, were E-cadherin-negative and expressed primarily standard form CD44, which did not contain exon v6. We concluded that CD44v6 isoforms and E-cadherin were both down-regulated during the carcinogenesis of urothelium. The large exon v6 containing CD44 isoforms were readily detected in normal urothelium, therefore, were not likely linked to cancer metastasis. E-cadherin and CD44v6 may be used as differentiation markers for human urothelial tumors. Immunohistochemical study solely with antibody against epitopes encoded by exon v6 alone is not informative enough as other alternatively spliced exons may change the function of CD44v6 isoforms.

Comparison of immunohistochemistry and RT-PCR for detection of CD44v-expression, a new prognostic factor in human breast cancer

In different human tumors, splice variants of the surface glycoprotein CD44 (CD44v) are correlated with advanced stages of tumor growth and metastatic potential. In breast cancer and colon cancer, expression of epitopes encoded by exon v6 on primary tumors is an independent prognostic factor for poor patient survival. Two different screening methods for the detection of CD44 variants in tumors have been applied: immunohistochemistry (IHC) and semi-quantitative reverse transcription PCR (RT-PCR). In this study, we have compared the predictive capacity and the applicability of both approaches, using 31 human breast-tissue specimens (normal and neoplastic). IHC reveals lack of expression of CD44v on normal ductal epithelial cells but strong expression on myoepithelial cells. The majority of tumors express CD44 epitopes encoded by several variant exons. RT-PCR detects splice variants in normal epithelium, probably derived from RNA expressed in the myoepithelium. In tumors, RT-PCR reveals expression of a wide range of splice variants, including new ones that are not detected in normal breast tissue, e.g. ones that contain all variant exons. The conclusion of this comparison is that IHC is the better method for breast-tumor sample screening but that the increased sensitivity of RT-PCR can help to distinguish CD44v-positive from CD44v-negative tumors in cases where only a few tumor cells express variants or where epitopes are masked.

Cleaved L-selectin concentrations in meningeal leukaemia

Involvement of the central nervous system has important therapeutic implications in acute leukaemia. Because the identification of blast cells in cerebrospinal fluid (CSF) is often difficult, there is a need for sensitive markers of leukaemic infiltration. Since the shed form of L-selectin (sL-selectin) is frequently increased in acute leukaemia (sL-selectin+ leukaemia), we examined whether assay of sL-selectin in CSF could improve our ability to detect such meningeal involvement. CSF sL-selectin was significantly (p < 0.001) higher in 15 patients with sL-selectin+ meningeal leukaemia (median 60 ng/mL, range 34-150) than in 20 patients with acute leukaemia without meningeal involvement (12 ng/mL, 1-39) or 88 control patients (14 ng/mL, 0-37). Serial measurements of sL-selectin in patients with sL-selectin+ leukaemic meningitis showed increased CSF concentrations of the cleaved receptor in 4 patients with therapy-resistant meningeal leukaemia and sustained normal concentrations in 9 patients in remission. Our results suggest that CSF sL-selectin may be a useful marker in the detection of meningeal involvement by blast cells in patients with sL-selectin+ leukaemia.

Expression of proteoglycans and hyaluronan during wound healing

We investigated the expression of proteoglycans (PGs) and hyaluronan (HA) during healing of human mucosal wounds. Biopsy specimens of experimental wounds were taken 1, 3, and 7 days after wounding. Frozen sections were used for immunolocalization of CD44, syndecan-1, basement membrane-associated heparan sulfate proteoglycan (BM-HSPG), decorin, and biglycan. HA was localized in paraffin sections with a specific HA-binding probe. Epithelium showed first signs of migration on Day 1, more progressive migration on Day 3, and epithelial sheets confronted on Day 7. CD44 surrounded migrating keratinocytes at all stages of wound healing. In epithelium, CD44 and HA remarkably localized to the same region. Expression of syndecan-1 was switched from the suprabasal cell layer of unwounded epithelium to the basal cell layer of the migrating wound epithelium. BM-HSPG was absent under migrating keratinocytes. It started to reappear at the basement membrane zone on Day 7. The area under the wound epithelium containing newly synthesized collagen fibers first became positive for decorin on Day 7, whereas staining of biglycan was negative. Granulation tissue was also strongly positive for CD44 and hyaluronan. Our results indicate that migrating keratinocytes express both CD44 and syndecan-1 but not BM-HSPG. During differentiation of keratinocytes, expression of CD44 preceded that of syndecan-1. The results suggest that different HSPGs have multiple functions in keratinocyte migration and differentiation during reepithelialization.

Expression of cell interaction molecules by immature rat thymocytes during passage through the CD4+8+ compartment: developmental regulation and induction by T cell receptor engagement of CD2, CD5, CD28, CD11a, CD44 and CD53

Rat thymocytes of the T cell receptorlow (TcRlow) CD4+8+ subset which is the target of repertoire selection are heterogeneous with respect to expression of the cell interaction (CI) molecules CD2, CD5, CD11a/CD18 (LFA-1), CD28 and CD44. We show that this heterogeneity is due to the developmental regulation of these CI molecules during passage through the CD4+8+ compartment, and to up-regulation by TcR engagement. Thus, cohorts of CD4+8+ cells differentiating synchronously in vitro from their direct precursors, the immature CD4-8+ cells, were homogeneous with regard to CI molecule expression. Upon entry into the CD4+8+ compartment, they expressed relatively high levels of CD2 and CD44, and moderate levels of CD5, CD28 and CD11a. CD2, CD28 and CD44 were slightly down-regulated during the following 2 days, whereas CD5 slightly increased and CD11a remained constant. TcR stimulation using immobilized monoclonal antibodies resulted in rapid and dramatic up-regulation of CD2, CD5 and CD28 and, to a lesser extent, of CD11a and CD44. Finally CD53, a triggering structure absent from unstimulated CD4+8+ thymocytes was also rapidly induced by TcR stimulation. Inclusion of interleukin (IL)-2, IL-4, or IL-7 in this in vitro differentiation system did not affect the levels of CI molecules studied. Since the high levels of CI molecules induced by TcR-stimulation correspond to those found in vivo on TcRintermediate thymocytes known to be undergoing repertoire selection, these results suggest that upregulation of CI molecules by TcR engagement provides a mechanism by which thymocytes that have entered the selection process gain preferential access to further interactions with stromal and lymphoid cells in the thymus.

VLA-4-dependent adhesion in follicular non-Hodgkin's lymphomas

The cellular contact between B cells and follicular dendritic cells (FDCs) in the germinal center is thought to play a key role in B-cell maturation and proliferation. The adhesion pathway through the very late antigen 4 (VLA-4) on the B cells and the vascular cell adhesion molecule 1 (VCAM-1) on the FDCs support this binding process. The neoplastic follicular centers in follicular non-Hodgkin's lymphomas (FNHLs) have similar structures and cellular components to those of normal germinal centers, but their interaction between B cells and FDCs may be functionally disturbed. In view of this we analyzed the interaction between VLA-4 and VCAM-1 molecules in the germinal center microenvironment, both in neoplastic and normal follicles. The structural characterization of FNHLs and reactive lymph nodes was studied with indirect immunohistochemical stainings using monoclonal antibodies against VLA-4, VCAM-1, and fibronectin, with special reference to the reaction pattern in the normal and neoplastic follicles. In the reactive follicular centers most B cells did not show a positive reaction for VLA-4, except for moderate reaction products in the B cells of the light zone. In FNHLs, on the other hand, most follicular center B cells were positive for VLA-4. The reaction patterns of VCAM-1 and fibronectin in both normal and neoplastic follicular centers were not basically different. To investigate the interaction of VLA-4 with VCAM-1 in both neoplastic and normal follicular centers, we performed a frozen-section binding assay, which found decreased binding between VLA-4 and VCAM-1 in FNHLs. The results of this study indicated that the microenvironment in neoplastic follicular centers is different from that in their normal counterparts, in terms of the characteristic distribution pattern of the VLA-4-positive B cells, and the functional deterioration of the VCAM-1 on FDCs.

Mammary and extramammary Paget's disease: expression of Ca 15-3, Ka-93, Ca 19-9 and CD44 in Paget cells and adjacent normal skin

The histogenesis of mammary Paget's disease (MPD) and extramammary Paget's disease (EMPD) cells remains controversial. The purpose of this study was to investigate MPD and EMPD immunohistochemically with antibodies to some tumour markers (Ca 15-3, KA-93 and Ca 19-9), and a cell surface receptor for hyaluronate (CD44), as these have been shown to be expressed in normal eccrine or apocrine glands and/or the epidermis, as well as some tumours. Surgically excised, formalin-fixed, paraffin-embedded tissues, or frozen tissues, from seven mammary, five vulvar, two scrotal and two axillary lesions were studied. Paget cells stained strongly with antibodies to Ca 15-3 and KA-93, but did not stain with those to Ca 19-9 and CD44. Staining with the antibody to Ca 15-3 was also observed in the ductal and secretory portions of the eccrine and apocrine glands, and in the sebaceous gland cells. Staining with the antibody to KA-93 was also seen in the apocrine secretory coils, lactiferous duct, epidermal dendritic cells, and cells in the dermal inflammatory infiltrate. Staining with the antibody to Ca 19-9 was observed only in the eccrine duct, and that to CD44 was seen in eccrine secretory cells and epidermal keratinocytes. These findings suggest that the origin of Paget cells may be the secretory cells of apocrine sweat glands (in EMPD) or the luminal lactiferous ducts (in MPD). We found that the antibodies to Ca 15-3 and CD44 were useful in differentiating Paget cells from surrounding keratinocytes, by showing positive and negative immunoreactivity, respectively.

The majority of postselection CD4+ single-positive thymocytes requires the thymus to produce long-lived, functional T cells

We have previously isolated, and characterized in vitro, two subsets of CD4hi T cell receptor (TCR)hi single positive (SP) thymocytes: CD8- and CD8lo. In this report, we have analyzed phenotypic, functional, and developmental characteristics of these "late" CD4hi SP thymocyte subsets. The TCRhi phenotype and the elimination of T cells expressing TCR V beta segments reactive with endogenous mouse mammary tumor virus (MMTV) products suggested that both subsets had undergone positive and negative selection. CD8-4hi thymocytes were functional, as judged by their ability to: (a) induce lethal graft versus host disease (GVHD); (b) survive and expand in peripheral lymphoid organs; and (c) proliferate, rather than undergo apoptosis, in response to in vitro TCR cross-linking. By contrast, CD8lo4hi cells could not induce GVHD, were unable to expand (and perhaps even survive) in peripheral organs and underwent apoptosis upon TCR cross-linking. However, when reintroduced into the thymus, these cells matured into functional, long-lived CD8-4hi lymphocytes. These results document an obligatory requirement for the thymic microenvironment in the final maturation of the majority of CD4hi SP postselection thymocytes, and demonstrate the existence of a previously unrecognized control point in T cell development.

Isolation and characteristics of tonsil centroblasts with reference to Ig class switching

Most tonsil B cells have high levels of surface CD44 but this molecule is either expressed at low levels or is absent from germinal centre B cells (GCB). On average 62% of isolated GCB were found to be CD44- and the remainder CD44low. Most CD44- GCB were in cell cycle, indicating that they were centroblasts, while centrocytes, non-dividing GCB, were mainly CD44low. Immunohistological analysis confirms that centrocytes, which are located in the light zone of germinal centres, express low levels of CD44, while centroblasts, cells of the dark zone, are CD44-. While most CD77high GCB are centroblasts and CD77low GCB centrocytes, many centroblasts and centrocytes express intermediate levels of CD77, making this less reliable than CD44 for discriminating between these cells. Most CD44low and CD44- GCB were shown to have undergone Ig switch recombination in vivo. This indicates that switch recombination is independent of the maturation of centroblasts to centrocytes and precedes the signals that induce GCB to differentiate to plasma cells or memory B cells. The average rate of entry of the CD44- GCB fraction to apoptosis on culture at 37 degrees C was faster than that of the total GCB preparation. It is suggested that this may reflect strict stromal-dependence of centroblasts while centrocytes have to survive for long enough to have the chance of receiving antigen-specific selection signals. Inhibition of apoptosis by CD40 mAb with IL-4 or phorbol myristate acetate with ionomycin was similar in the CD44- and CD44low preparations.

New CD44 splice variants associated with human breast cancers

Changes in the CD44 variant (CD44v) isoforms on the cell surface have been correlated with tumor metastasis. In this study we have examined the expression of CD44 variant isoforms in human breast carcinoma samples by a variety of techniques including immunohistochemistry, reverse transcriptase-polymerase chain reaction (RT-PCR), and nucleotide sequencing. Using RT-PCR, we have determined that normal human breast tissue contains primarily the CD44 epithelial (CD44E) form and very little CD44 standard (CD44s) form. However, metastatic breast carcinomas appear to overexpress both the CD44E and CD44s forms and also display multiple new species of CD44 variant isoforms. Histocytochemical staining using anti-CD44 antibody (recognizing a common determinant of the CD44 class of glycoproteins) confirms that the CD44 molecules are overexpressed and preferentially located in metastatic breast cancer tissues. Nucleotide sequencing analyses indicate that at least four new CD44 variant isoforms (i.e., displaying unique splicing via the insertion or the deletion of exons 7, 10, 11, and 14) may be closely associated with human metastatic breast cancers. These newly described CD44 variant isoforms may be useful for monitoring the progression of human breast cancer metastasis.

Preferential expression of the cell adhesion molecule CD44 in papillary thyroid carcinoma

CD44 is a polymorphic family of immunologically related integral membrane glycoproteins associated with cell matrix adhesion, lymphocyte activation and targeting, and tumor growth and metastasis. We studied CD44 expression in 114 formalin-fixed paraffin-embedded thyroid tumors using the A3D8 anti-human CD44 monoclonal antibody. Sixty-five of 67 papillary carcinomas (97%) strongly expressed CD44 with an intense plasma membrane pattern. Thirty-seven of these cases originated from Albany, New York, and 30 cases from Russia. Immunoreactivity was also observed in 9 of 16 follicular adenomas (56%); 4 of 8 Hurthle cell neoplasms (50%); 5 of 15 medullary carcinomas (33%); and 3 of 8 follicular carcinomas (38%). These results show that among thyroid neoplasms, papillary carcinomas preferentially display the CD44 antigen (P < or = 0.001). Nonneoplastic follicular epithelium exhibited a low to moderate level of staining. To further characterize the CD44 isoform, we tested a subset of cases with the 2F10 anti-human CD44 variant 6 monoclonal antibody, which recognizes a CD44 variant exon (CD44v6) implicated in tumor metastasis. Eleven of 11 papillary carcinomas tested were 2F10 positive, and 1 of the follicular carcinomas was positive. These results suggest the hypothesis that deregulated CD44v6 expression on the plasma membrane of papillary carcinoma cells contributes to the ability of those cells to metastasize to regional lymph nodes and then to remain dormant for years. Our results suggest that human papillary thyroid cancer will be an interesting model in which to further study the role of CD44 isoforms, particularly those containing CD44v6, in tumor metastasis and lymphatic invasion.

Cell adhesion molecules: a selective therapeutic target for alleviation of IDDM

Selective homing of autoreactive lymphocytes to the pancreatic islets of Langerhans is essential for triggering the cascade of molecular and cellular interactions which culminate in the specific destruction of the insulin-producing beta-cells. Based upon the sequential multistep model of lymphocyte adhesion to the endothelium, we investigated the possibility of preventing the progression of insulin-dependent diabetes mellitus (IDDM) by selectively blocking L-selectin and alpha 4-integrin homing receptors, which function at different stages of the adhesion process. Treatment of NOD mice with mAb specific for L-selectin or alpha 4-integrin resulted in a significant inhibition of lymphocytic infiltration (insulitis). Both spontaneous development and acute transfer of IDDM were completely prevented by administration of anti-alpha 4-integrin antibody and partially inhibited by anti-L-selectin antibody. The protective effect was of long duration. Interestingly, the autoimmune T cell responses to a panel of beta cell autoantigens and the lymphocytic infiltration of salivary glands (sialadenitis) appeared unaffected by anti-L-selectin or anti-alpha 4-integrin treatment. These data suggest that prevention of lymphocyte homing to the pancreatic islets may provide a selective target for prevention/treatment of IDDM in patients.

Defective pulmonary recruitment of neutrophils in a rat model of endotoxemia

We have characterized a defect in the pulmonary recruitment of neutrophils (PMNs) in rats with experimental endotoxemia. Rats pretreated with intravenous (IV) 0.9% saline (NaCl) showed abundant PMNs in bronchoalveolar lavage (BAL) fluid after intratracheal (IT) lipopolysaccharide (LPS) (5 mg/kg) (54.27 +/- 9.80 x 10(6), n = 7, versus IT saline, 0.73 +/- 0.62 x 10(6), n = 4). In contrast, endotoxemic rats (IV LPS 1.0 mg/kg) failed to show PMN influx after IT LPS (0.40 +/- 0.13 x 10(6) PMNs in BAL fluid, n = 7). Four hours after the IT administration of LPS, the chemotactic activity of BAL fluid from endotoxemic rats (87 +/- 9.92% of maximal chemotaxis toward zymosan-activated serum [ZAS], n = 4) was not significantly different (P > 0.05), from rats pretreated with IV NaCl (61.09 +/- 6.17% of maximal chemotaxis toward ZAS, n = 4). Endotoxemic and control rats showed similar chemotactic gradients in determinations of the BAL/plasma chemotactic activity ratio (BAL/plasma ratio: 2.16 +/- 0.14, n = 4, IV NaCl versus 2.98 +/- 0.14, n = 4, IV LPS, P > 0.05). Serum from untreated rats, rats pretreated with IV NaCl, and endotoxemic rats caused minimal effects on rat PMN chemotaxis in vitro (78.17 +/- 8.16%, 79.29 +/- 7.09%, and 69.28 +/- 9.04% of maximal chemotaxis toward ZAS, respectively, n = 4/group, P > 0.05). Quantitation of PMN adhesion molecules revealed a loss of L-selectin (8 +/- 5% of control group, n = 3), an increase in Mac-1 (776 +/- 82.60% of control group, n = 3), and no change in LFA-1 when normal PMNs were incubated with plasma from rats pretreated with IV LPS (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

The significance of CD44 in human pancreatic cancer: II. The role of CD44 in human pancreatic adenocarcinoma invasion

In our previous report (1), we showed the high expression of CD44 in human pancreatic adenocarcinomas cells. Pancreatic cancer aggressively invades surrounding tissues by penetrating basement membrane barriers. To examine the relation between the biological characteristics of human pancreatic adenocarcinoma cells and CD44 expression, we studied the function of CD44 in cell proliferation and cell invasion using a Matrigel basement membrane. The proliferation of human pancreatic adenocarcinoma cells was not affected by anti-CD44 antibody. On the contrary, invasion of the cells was suppressed by anti-CD44 antibody. This result suggests that the CD44 molecule plays an important role in pancreatic cancer cell invasion of the basement membrane.

Expression of CD44 in normal and rheumatoid synovium and cultured synovial fibroblasts

OBJECTIVE

To determine if expression of CD44, the principal receptor for hyaluronan, was altered in rheumatoid (RA) synovium and cultured rheumatoid synovial fibroblasts.

METHODS

Synovium was obtained from normal adult human joints (n = 4) and from joints of patients with RA (n = 5). Specific monoclonal antibodies to CD44 were used in immunofluorescence of whole synovium and cultured synovial fibroblasts and in quantitative Western blotting and ELISA of CD44 in cultured synovial fibroblasts.

RESULTS

CD44 was restricted to the lining layer in normal synovium but present, in reduced concentrations, throughout rheumatoid synovium. Cultured rheumatoid cells were 19% larger in area and showed far fewer and less extensive CD44-positive cytoplasmic extensions, together with reduced staining intensity compared with normal. Quantitative Western blotting normalised for cell protein showed a 75% reduction (normal = 1754 (835), rheumatoid = 409 (84) mean (SD) arbitrary units) in the amount of CD44 in rheumatoid cells compared with normal, and enzyme linked immunosorbent assay (ELISA) of cultured cell monolayers normalised for cell number indicated a 29% reduction (normal = 0.707 (0.110), rheumatoid = 0.504 (0.103), mean (SD) optical density at 405 nm).

CONCLUSIONS

Rheumatoid synovial cells showed altered morphology and reduced CD44 expression compared with normal cells. CD44, by means of modulated associations with the cytoskeleton, may be involved in cell shape change.