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Biomedical subjects

A Bartolazzi

Publications and source records attributed to A Bartolazzi.

At least 37 records · Page 2Linked to original sources
PubMed1996

Glycosylation of CD44 is implicated in CD44-mediated cell adhesion to hyaluronan.

CD44-mediated cell adhesion to hyaluronate is controlled by mechanisms which are poorly understood. In the present work we examine the role of N-linked glycosylation and Ser-Gly motifs in regulating CD44-hyaluronate interaction. Our results show that treatment of a panel of human cell lines which constitutively express CD44 with the inhibitor of N-linked glycosylation tunicamycin results in the loss of attachment of these cells to hyaluronate-coated substrate. In contrast, treatment of the same cells with deoxymannojirimycin, which inhibits the conversion of high mannose oligosaccharides to complex N-linked carbohydrates, results in either no change or an increase in CD44-mediated adhesion to hyaluronate, suggesting that complex N-linked oligosaccharides may not be required for and may even inhibit CD44-HA interaction. Using human melanoma cells stably transfected with CD44 N-linked glycosylation site-specific mutants, we show that integrity of five potential N-linked glycosylation sites within the hyaluronate recognition domain of CD44 is critical for hyaluronate binding. Mutation of any one of these potential N-linked glycosylation sites abrogates CD44-mediated melanoma cell attachment to hyaluronate-coated surfaces, suggesting that all five sites are necessary to maintain the HA-recognition domain in the appropriate conformation. We also demonstrate that mutation of serine residues which constitute the four Ser-Gly motifs in the membrane proximal domain, and provide potential sites for glycosaminoglycan side chain attachment, impairs hyaluronate binding. Taken together, these observations indicate that changes in glycosylation of CD44 can have profound effects on its interaction with hyaluronic acid and suggest that glycosylation may provide an important regulatory mechanism of CD44 function.

1-Deoxynojirimycin↗
PubMed1995

Expression of alpha 3 beta 1 integrin receptor and its ligands in human lung tumors.

Increasing experimental evidence demonstrates that malignant transformation is associated with changes in the repertoire of expression of the integrin family of molecules, which mediate cell-matrix and cell-cell interactions. We have analyzed immunohistochemically and immunochemically the expression of VLA-3 integrin and its known ligands, namely, laminin (LM), fibronectin (FN), collagen type IV (Coll IV), nicein (NIC), and entactin/nidogen (ENT), in lung tumors of various histological types. alpha 3 beta 1 was detectable in normal bronchial epithelium and along basement membranes of alveolar walls. In non-small cell lung carcinomas (NSCLC) the integrin was expressed in 82% of the cases, independently of histological type and degree of differentiation of the tumors. On the other hand, only 13% of the small cell lung carcinomas (SCLC) displayed a weak and heterogeneous distribution of the alpha 3 beta 1 complex. Our findings were confirmed immunochemically using long-term tumor cell lines. While the expression of both alpha 3 beta 1 and ligands LM, FN, Coll IV, and Ent correlated in NSCLC with the presence of basement membranes, FN was the only ligand detectable in the stroma of SCLCs. A selective loss of nicein in basement membranes was demonstrated in NSCLC indicating an impairment of expression of this glycoprotein following malignant transformation.

Adenocarcinoma↗
PubMed1995

Regulation of CD44 binding to hyaluronan by glycosylation of variably spliced exons.

The hyaluronan (HA)-binding function (lectin function) of the leukocyte homing receptor, CD44, is tightly regulated. Herein we address possible mechanisms that regulate CD44 isoform-specific HA binding. Binding studies with melanoma transfectants expressing CD44H, CD44E, or with soluble immunoglobulin fusions of CD44H and CD44E (CD44H-Rg, CD44E-Rg) showed that although both CD44 isoforms can bind HA, CD44H binds HA more efficiently than CD44E. Using CD44-Rg fusion proteins we show that the variably spliced exons in CD44E, V8-V10, specifically reduce the lectin function of CD44, while replacement of V8-V10 by an ICAM-1 immunoglobulin domain restores binding to a level comparable to that of CD44H. Conversely, CD44 bound HA very weakly when exons V8-V10 were replaced with a CD34 mucin domain, which is heavily modified by O-linked glycans. Production of CD44E-Rg or incubation of CD44E-expressing transfectants in the presence of an O-linked glycosylation inhibitor restored HA binding to CD44H-Rg and to cell surface CD44H levels, respectively. We conclude that differential splicing provides a regulatory mechanism for CD44 lectin function and that this effect is due in part to O-linked carbohydrate moieties which are added to the Ser/Thr rich regions encoded by the variably spliced CD44 exons. Alternative splicing resulting in changes in protein glycosylation provide a novel mechanism for the regulation of lectin activity.

Alternative Splicing↗
PubMed1995

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.

Alternative Splicing↗
PubMed1994

Transformation and tumor progression are frequently associated with expression of the alpha 3/beta 1 heterodimer in solid tumors.

The ability of tumor cells to interact with the extracellular matrix (ECM) is functionally mediated by a variety of receptor molecules among which the integrins are a well-characterized family of mediators. In this study we have investigated immunohistochemically the in vivo expression of the alpha 3/beta 1 promiscuous receptor for ECM constituents in a variety of human solid malignancies. Although the receptor appears to undergo changes in distribution patterns, its expression is maintained in a high percentage of primary (76%) and metastatic (82%) tumors. Furthermore, the comparative immunohistochemical evaluation of alpha 3/beta 1 and its ligands, in a selected number of tumors of different histotypes, demonstrated that the expression of this integrin correlates with the presence of at least one ligand, either around nests of neoplastic cells or at the epithelial-stromal interface. The highly conserved expression of alpha 3/beta 1 shown in this study suggests that this receptor may play a role in tumor growth at the primary as well as at the metastatic site.

Cell Transformation, Neoplastic↗
PubMed1994

Interaction between CD44 and hyaluronate is directly implicated in the regulation of tumor development.

CD44 is implicated in the regulation of tumor growth and metastasis but the mechanism by which expression of different CD44 isoforms determines the rate of primary and secondary tumor growth remains unclear. In the present study we use a human melanoma transfected with wild-type and mutant forms of CD44 to determine which functional property of the CD44 molecule is critical in influencing tumor behavior. We show that expression of a wild-type CD44 isoform that binds hyaluronic acid augments the rapidity of tumor formation by melanoma cells in vivo, whereas expression of a CD44 mutant, which does not mediate cell attachment to hyaluronate, fails to do so. The importance of CD44-hyaluronate interaction in tumor development is underscored by the differential inhibitory effect of soluble wild-type and mutant CD44-Ig fusion proteins on melanoma growth in vivo. Whereas local administration of a mutant, nonhyaluronate binding, CD44-Ig fusion protein has no effect on subcutaneous melanoma growth in mice, infusion of wild-type CD44-Ig is shown to block tumor development. Taken together, these observations suggest that the tumor growth promoting property of CD44 is largely dependent on its ability to mediate cell attachment to hyaluronate.

Animals↗
PubMed1994

Murine monoclonal antibody elicited with antibiotic-exposed Escherichia coli exerts protective capacity in experimental bacterial infections.

Escherichia coli pre-exposed to a sub-minimal inhibitory concentration (sub-MIC) of several antibiotics elicits an enhanced humoral response which is protective against challenges with untreated homologous and heterologous bacteria. To characterise the specificity of this response we produced murine monoclonal antibodies (MAbs) to aztreonam-treated E. coli O6:K-. This resulted in the identification of MAb MT 1F, of isotype IgG1, that recognised a 12-kDa protein component of the untreated bacterial cells. After passive transfer, the MAb displayed protective activity in mice infected with lethal doses of live E. coli O6:K- and E. coli O111:B4. In ELISA experiments the MAb cross-reacted with structures located on whole cells of E. coli O6:K-, E. coli O111:B4, E. coli J5 and Salmonella minnesota Re595 and it also exerted a bactericidal activity against live E. coli O6:K-. The modifications induced by antibiotic treatment may unmask bacterial epitopes that may elicit the production of MAbs endowed with protective capacity.

Animals↗
PubMed1993

Integrin expression in cutaneous malignant melanoma: association of the alpha 3/beta 1 heterodimer with tumor progression.

The cell-surface heterodimers of the integrin family of molecules, which mediate cell-cell and cell-substratum interactions, are likely to be functionally relevant in local and metastatic tumor growth. In the present study we have analyzed whether the alpha 3/beta 1 receptor for collagen, laminin and fibronectin undergoes changes in expression during tumor progression in cutaneous malignant melanoma (CMM). The results of this study have demonstrated that, while low levels of VLA3 expression are detectable in benign lesions, in primary melanomas the heterodimer undergoes progressive increase in expression which correlates with the degree of dermal invasiveness. Metastatic lesions were found VLA3 positive in 82% of cases. Furthermore, the heterodimer is homogeneously expressed in multiple autologous metastases. The presence of VLA3 correlates with detection of at least one of the ligands in 45% of the cases studied. These findings provide additional evidence that tumor progression in CMM is associated with changes in integrin phenotypes which include the alpha 3/beta 1 heterodimer.

Biopsy↗
PubMed1993

Vla-3 distribution in normal and neoplastic non-lymphoid human tissues.

Using monoclonal antibody (mAb) M-Kid 2 to the alpha 3 beta 1 heterodimer, we have evaluated immunohistochemically the in vivo expression of the Vla-3 integrin in normal and transformed non-lymphoid human tissues. In normal tissues the alpha 3 beta 1 complex displays a polarized distribution at the baso-lateral aspect of most keratinizing and glandular epithelia. In addition the integrin is detected in perineurium, basal lamina of smooth muscular fibers, vascular media, podocytes and Bowman's capsule, myoepithelial cells of the parotid and breast, and in pulmonary alveoli. Neoplastic transformation is associated with qualitative and quantitative changes in expression of this integrin. The loss of polarized distribution often occurs in various malignancies. Furthermore, a significant decrease in expression occurs in 13% of the colon-rectum carcinomas, 75% of the ductal invasive, and 40% of the lobular invasive breast carcinomas. Among the lung malignancies tested, the small cell lung carcinomas (SCLC) were found to be consistently unreactive with mAb M-Kid 2. Analysis of Vla-3 expression in established tumor cell lines demonstrated that the integrin is almost invariably expressed by the plastic adherent cell subpopulations.

Antibodies, Monoclonal↗
PubMed1993

Differential effect of human and murine polyclonal and monoclonal antisera on TNF-alpha production by human monocytes.

The capacity of human and murine polyclonal and monoclonal antibodies to inhibit lipopolysaccharide (LPS)-induced tumor necrosis factor-alpha (TNF-alpha) release from human monocytes was investigated. Human pooled immunoglobulin G (IVIG), human IgM monoclonal antibody (HA-1A) directed against the lipid A moiety of LPS, and murine IgG monoclonal antibody (MT-1F) raised in mice against antibiotic-treated Escherichia coli O6:K- were either added simultaneously with LPS to monocytes or preincubated for 1 h at 37 degrees C before being added to monocytes. TNF-alpha content in the monocyte supernatants was then tested. Simultaneous addition of increasing concentrations of IVIG (from 0.3 to 2.5 mg/ml) and 10 micrograms/ml of LPS to monocytes induced an enhanced release of TNF-alpha by monocytes in a dose dependent fashion. Preincubation of IVIG with LPS abolished the additive effect, but did not inhibit LPS-induced TNF-alpha release by monocytes. The simultaneous addition of LPS and HA-1A to monocytes had no additive effect nor did it inhibit TNF-alpha release. On the other hand, inhibition of TNF-alpha release was observed when HA-1A was preincubated with LPS before being added to monocytes. In all instances MT-1F inhibited TNF-alpha release when the monocytes were stimulated with smooth type LPS, but not with LPS isolated from rough mutants.

Animals↗
PubMed1992

Immunocytodiagnosis of atypical hyperplasia and endometrial carcinoma in post-menopausal women.

In the present study we have evaluated whether monoclonal antibodies (MAbs) B72.3 and AR-3 which display, on histological preparations, a differential reactivity with normal and transformed endometrium, could be a useful adjunct to endometrial cytology in the identification of pre-neoplastic and neoplastic conditions. Immunocytochemical (ICC) tests, using the 2 reagents, were performed on normal cycling endometrium and on hyperplastic and malignant lesions collected by the endocyte technique both from 86 surgically resected specimens and from 62 postmenopausal symptomatic and asymptomatic outpatients. The results obtained showed that the combination of the 2 MAbs can complement conventional morphology in the identification of pre-malignant atypical lesions and endometrial carcinoma of unclear cytological features, thus allowing a selection of those patients who are candidates for fractional curettage.

Adenocarcinoma↗
PubMed1991

Expression of CAR-3 and TAG-72 macromolecules in normal and transformed endometrium: potential diagnostic application in postmenopausal patients.

Mass cytoscreening for the early diagnosis of endometrial carcinoma has thus far been hampered by the low diagnostic accuracy of current cytopathology. In this study we have analyzed the reactivity of the two monoclonal antibodies, AR-3 and B72.3, recognizing two distinct glycosylated high molecular weight carcinoma associated antigens on histological specimens from normal, hyperplastic, and transformed endometrium with the aim of establishing their diagnostic potential. Because women with a high risk of endometrial cancer are frequently postmenopausal, where normal endometrium is characterized by atrophy and cystic glandular hyperplasia, the following findings were of interest. Both antibodies reacted with variable and apical staining patterns with a minority of specimens of normal cycling endometrium from premenopausal women. However, they were constantly negative when tested on normal atrophic postmenopausal endometrium, and only monoclonal antibody AR-3 occasionally stained glandular cystic hyperplasia. By contrast, lesions with atypical hyperplasia, which represent a preneoplastic condition, were stained by both antibodies in 89 or 67% of the cases depending on the monoclonal antibody used (100% if used in combination). Furthermore, 98% of the endometrial carcinomas tested were found to react with the combination of two monoclonal antibodies. If these findings are confirmed in a multicentric study, the use of the two reagents could be a valuable adjunct in the cytodiagnosis of endometrial cancer, especially in providing a guideline to selecting patients for endometrial curettage and additional diagnostic procedures.

Antibodies, Monoclonal↗
PubMed1991

Monoclonal antibodies to glutathione S-transferase pi-immunohistochemical analysis of human tissues and cancers.

Mouse monoclonal antibodies (MAb) have been generated against the anionic isozyme of human glutathione S-transferase (GST pi). MAb AGST I can inhibit 50-70% of GST pi enzymatic activity and reacts with a 3-dimensional epitope which includes a putative glutathione binding site on GST pi. A sandwich enzyme-immunoassay established using MAb AGST I and a polyclonal antibody displayed a sensitivity of 0.5 ng/ml. Immunohistochemical analysis of human tissues demonstrated marked increases in GST pi levels in cancers of the brain, cervix, endometrium, colon, rectum and testis and in fibro- and chondrosarcomas.

Antibodies, Monoclonal↗
PubMed1991

Monoclonal antibodies to a soluble metallic radioisotope chelator: development and characterization.

Monoclonal antibodies (MAbs) have been prepared with specificity for diethylenetriaminopentaacetic acid (DTPA) used to chelate metal radioisotopes to immunoglobulins for radioimmunoimaging and radioimmunotherapy. The use of fusion partners of lymph node-derived B cells resulted more frequently in the isolation of IgG secreting hybridomas than with splenocytes. All MAbs have been selected for simultaneous recognition of chelated and unchelated DTPA, and have been characterized in their biochemical, physico-chemical and immunochemical features. In view of the potential use in development of bifunctional MAb, these novel MAbs were also proven to lack detectable cross-reactivity with normal human tissues.

Animals↗
PubMed1991

Generation and characterization of the murine monoclonal antibody M-KID 2 to VLA-3 integrin.

Through the analysis of the antigenic phenotype of a recently established human renal carcinoma cell line (KJ29), we have demonstrated that alpha 3 subunit of the integrin family is selectively expressed by the plastic adherent cell subpopulation. Because of the scanty availability of monoclonal antibodies to this adhesion molecule, we have used KJ29 cell line as immunogen to raise novel murine monoclonal antibodies. We isolated an hybridoma secreting the mAb M-KID 2 of the IGg1k isotype that immunoprecipitates from intrinsically [35S]-Methionine labeled KJ29 cells, an heterodimer of 130/130 and 110/150 Kd, in reducing and nonreducing conditions respectively. This reactivity was completely abolished by immunodepletion of the cell extract with a polyclonal anti alpha 3 chain antiserum. Treatment of M-KID 2 immunoprecipitates with various solutions of pH ranging from 2 to 10.5, to dissociate alpha 3 from beta 1 chains, showed a retention of both alpha 3 beta 1 chains thus indicating that the epitope identified by mAb M-Kid 2 is likely to be constituted by the alpha 3 beta 1 heterodimer. Furthermore immunohistochemical studies on selected frozen and paraffin embedded tissues with mAb M-Kid 2 have provided staining pattern indicating the recognition of Vla-3. These findings demonstrate that mAb M-KID 2 can represent a valuable reagent for the study of Vla-3 integrin in normal and pathologic conditions.

Animals↗
PubMed1990

Expression and production of tenascin in benign and malignant lesions of melanocyte lineage.

The distribution of the extracellular matrix (ECM) glyco-protein tenascin (TN) has been evaluated immunohistochemically in benign and malignant lesions of the melanocytic lineage. Results of our study show that TN is detectable in a variety of benign and malignant lesions. In primary melanomas, TN displays a heterogeneous distribution, and a higher degree of expression of this glycoprotein is seen in lesions of greater dermal invasiveness. TN expression does not correlate with that of other ECM glycoproteins such as fibronectin. In vivo and in vitro experiments have also demonstrated that melanoma cells are capable of producing and releasing TN in the extracellular milieu.

Antibodies, Monoclonal↗