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O Segatto

Publications and source records attributed to O Segatto.

30 records · Page 2Linked to original sources
PubMed1989

Analysis of the antigenic profile of uveal melanoma lesions with anti-cutaneous melanoma-associated antigen and anti-HLA monoclonal antibodies.

The reactivity of 12 surgically removed uveal melanoma lesions with monoclonal antibodies (MoAb) to 14 membrane-bound and 2 cytoplasmic cutaneous melanoma-associated antigens (MAA), to the 2 subunits of HLA Class I antigens and to the gene products of the HLA-D region was compared with that of cutaneous melanoma lesions and correlated with their histiotype. The membrane-bound determinants defined by the anti-Mr 92,000 and 45,000 MAA MoAb TP39.1, anti-Mr 110,000 MAA MoAb M111, anti-Mr 118,000 MAA MoAb TP36.1, anti-Mr 115,000 MAA MoAb 345.134, anti-ICAM-1 MoAb CL203.4 and anti-Mr 31,000 MAA MoAb M2590, and the cytoplasmic determinants defined by the anti-MAA MoAb 465.12 and 2G-10 display a distribution in uveal melanoma lesions similar to that in cutaneous melanoma lesions. On the other hand, membrane-bound determinants defined by the anti-Mr 100,000 MAA MoAb 376.96, anti-9-O-acetyl-GD3 ganglioside MoAb ME311 and anti-GD2-GD3 ganglioside MoAb ME361 were not detected in the uveal melanoma lesions tested. Furthermore, the membrane-bound determinants defined by the anti-GD3 MoAb R24, anti-nerve growth factor receptor MoAb ME20.4, anti-Mr 97,000 MAA MoAb 140.240, anti-carcinoembryonic antigen MoAb B1.1 and anti-HMW-MAA 149.53, 225.28, and 763.74 have a markedly lower expression in uveal than in cutaneous melanoma lesions. Incubation of uveal melanoma lesions with the pool of the MoAb 149.53, 225.28, and 763.74 recognizing distinct and spatially distant determinants of the HMW-MAA increased the intensity of staining of six lesions and stained four lesions which were not stained by the individual monoclonal antibodies. The distribution of HLA Class I antigens in uveal melanoma lesions resembles that in cutaneous melanoma lesions, since they are expressed in all the lesions of the mixed and epithelioid type but were not detected in those of the spindle type, i.e., the counterparts of nevocellular nevi. HLA Class II antigens are expressed with a lower frequency in uveal than in cutaneous melanoma lesions, since they were detected only in 2 of the 12 lesions. One of them is of the mixed type and the other one of the epithelioid type. Besides HLA antigens the determinants defined by the anti-carcinoembryonic MoAb B1.1, anti-ICAM-1 MoAb CL203.4, and anti-GD3 MoAb R24 displayed a differential distribution in the different histiotypes of uveal melanoma, since they are preferentially expressed in lesions of the mixed and epithelioid type.

Animals↗
PubMed1988

Different structural alterations upregulate in vitro tyrosine kinase activity and transforming potency of the erbB-2 gene.

Compared with normal erbB-2 gp185, mutant erbB-2 proteins generated by mutations either in the transmembrane domain or by NH2-terminal deletion are able to transform NIH 3T3 cells at a 10- to 100-fold greater efficiency. Mutant proteins of both classes show increased tyrosine kinase activity, suggesting that an abnormal level of receptor-associated tyrosine kinase activity is a major determinant of erbB-2 oncogenic potential.

Animals↗
PubMed1987

erbB-2 is a potent oncogene when overexpressed in NIH/3T3 cells.

A wide variety of human tumors contain an amplified or overexpressed erbB-2 gene, which encodes a growth factor receptor-like protein. When erbB-2 complementary DNA was expressed in NIH/3T3 cells under the control of the SV40 promoter, the gene lacked transforming activity despite expression of detectable levels of the erbB-2 protein. A further five- to tenfold increase in its expression under influence of the long terminal repeat of Moloney murine leukemia virus was associated with activation of erbB-2 as a potent oncogene. The high levels of the erbB-2 product associated with malignant transformation of NIH/3T3 cells were observed in human mammary tumor cells that overexpressed this gene. These findings demonstrate a new mechanism for acquisition of oncogenic properties by genes encoding growth factor receptor-like proteins and provide a functional basis for the role of their overexpression in the development of human malignancies.

Animals↗
PubMed1987

Multiple epitope recognition: an approach to improved radioimmunodetection of tumor-associated antigens.

Three MAbs endowed with comparable affinity for 3 distinct epitopes of a HMW-MAA have been employed to study whether the use of combinations of MAbs might improve the sensitivity of methods for the quantitation of TAAs both on the cell surface and in soluble form. To this end, different combinations and sequences of application of the 3 MAbs were used both in cell-surface binding experiments and in solid-phase radioimmunoassays. Results of this study show that only selected combinations of MAbs are capable of significantly improving the sensitivity of methods for HMW-MAA detection, and that such improvements depend on the order and mode of addition of the 3 reagents. Thus, mixtures of MAbs to distinct epitopes carried by a single TAA molecule are likely to increase the sensitivity of tests for tumor detection both in vitro (i.e. radioimmunoassays) and in vivo (i.e. immunoscintigraphy). However, because the binding properties of such mixtures do not simply reflect those of the individual reagents, protocols for the use of MAb cocktails should be critically evaluated before clinical use.

Animals↗
PubMed1987

Analysis with monoclonal antibodies of the molecular and cellular heterogeneity of human high molecular weight melanoma associated antigen.

Monoclonal antibodies (MoAbs) 225.28, 657.9, and 902.5 recognizing distinct epitopes of the human high molecular weight melanoma associated antigen (HMW-MAA) were used to investigate the molecular and cellular heterogeneity of the HMW-MAA synthesized by human melanoma cells. Sequential immunodepletion and immunoprecipitation experiments showed that not all HMW-MAA molecules synthesized by a melanoma cell line express the antigenic determinants recognized by the three monoclonal antibodies. The majority of the HMW-MAA molecules expressed the epitope defined by MoAb 657.9 since this monoclonal antibody depleted the melanoma cell lysate of all antigen molecules recognized by the other two monoclonal antibodies. Depletion with MoAb 902.5 resulted in the removal of a large proportion of the HMW-MAA molecules precipitated by MoAb 657.9. The MoAb 225.28 depleted the cell lysate of only a fraction of the HMW-MAA molecules recognized by MoAb 657.9 and 902.5. Two-dimensional gel electrophoresis and peptide mapping analysis did not detect any significant difference among the HMW-MAA immunoprecipitated by the three monoclonal antibodies. The heterogeneity of the epitopes recognized by the three monoclonal antibodies is, at least partly, due to glycosylation of the antigen molecule, since treatment of melanoma cells with glycosidases differentially affects their ability to bind the three anti-HMW-MAA monoclonal antibodies. Fluorescent activated cell sorting analysis of the melanoma cells showed that the heterogeneity exhibited by the HMW-MAA is not due to the presence of different cell clones in the culture but reflects a differential distribution of epitopes on the HMW-MAA expressed on the surface of individual cells. Immunohistochemical staining of surgically removed benign and malignant lesions of melanocytic origin, of normal tissues, and of malignant lesions has shown a differential tissue distribution of the determinants recognized by the three monoclonal antibodies. Staining of melanoma cell lines and of surgically removed melanoma lesions with combinations of the three monoclonal antibodies did not cause any significant change of the percentage of stained cells but markedly increased the intensity of staining. These results indicate that combinations of monoclonal antibodies to distinct determinants of HMW-MAA can markedly increase the sensitivity of immunohistochemical techniques to detect melanoma cells.

Antibodies, Monoclonal↗
PubMed1987

The human transforming growth factor type alpha coding sequence is not a direct-acting oncogene when overexpressed in NIH 3T3 cells.

A peptide secreted by some tumor cells in vitro imparts anchorage-independent growth to normal rat kidney (NRK) cells and has been termed transforming growth factor type alpha (TGF-alpha). To directly investigate the transforming properties of this factor, the human sequence coding for TGF-alpha was placed under the control of either a metallothionein promoter or a retroviral long terminal repeat. These constructs failed to induce morphological transformation upon transfection of NIH 3T3 cells, whereas viral oncogenes encoding a truncated form of its cognate receptor, the EGF receptor, or another growth factor, sis/platelet-derived growth factor 2, efficiently induced transformed foci. When NIH 3T3 clonal sublines were selected by transfection of TGF-alpha expression vectors in the presence of a dominant selectable marker, they were shown to secrete large amounts of TGF-alpha into the medium, to have downregulated EGF receptors, and to be inhibited in growth by TGF-alpha monoclonal antibody. These results indicated that secreted TGF-alpha interacts with its receptor at a cell surface location. Single cell-derived TGF-alpha-expressing sublines grew to high saturation density in culture. However, when plated as single cells on contact-inhibited monolayers of NIH 3T3 cells, they failed to form colonies, whereas v-sis- and v-erbB-transfected cells formed transformed colonies under the same conditions. Moreover, TGF-alpha-expressing sublines were not tumorigenic in nude mice. These and other results imply that TGF-alpha exerts a growth-promoting effect on the entire NIH 3T3 cell population after secretion into the medium but little, if any, effect on the individual cell synthesizing this factor. It is concluded that the normal coding sequence for TGF-alpha is not a direct-acting oncogene when overexpressed in NIH 3T3 cells.

Base Sequence↗
PubMed1986

Thy 1.2 antigen inducing capacity of a calf thymus acid hydrolysate and its fractions.

Splenic null cells of normal mice have been shown to undergo phenotypic induction of Thy 1.2 antigen by various thymic extracts. This experimental model has been employed in characterizing the Thy 1.2 inducing ability of an acid lysate from calf thymus and its various fractions. Incubation of splenocytes from C3H/He mice with unfractionated Thymomodulin induces a dose-response percent increase in the Thy 1.2 antigen bearing cells (9.28 +/- 2.6%, p less than 0.05). Comparable increase appears in fractions 5B (9.46 +/- 0.55%, p less than 0.001) and 5C (8.09 +/- 3%, p less than 0.005), obtained by ultrafiltration and containing peptides of m.w. 600-10,000 d and less than 600 d, respectively. The activity is confined to the acid fraction (6.61 +/- 0.54%, p less than 0.001) isolated by isoelectrofocusing. Control lysate from pig duodenal mucosa was devoid of Thy 1.2 inducing activity. The present findings indicate that Thymomodulin possesses Thy 1.2 inducing capacity on murine null cells and that such activity is maintained and enhanced after various fractionation procedures.

Animals↗
PubMed1986

Role of genes for normal growth factors in human malignancy.

The human homologue of the v-sis oncogene encodes one chain of human platelet-derived growth factor (PDGF-2). Previous studies have shown that expression of the coding sequence for this growth factor induces malignant transformation of NIH/3T3 cells. We demonstrate the detection of sis/PDGF-2 products indistinguishable from functional PDGF-2 homodimers in human tumor cells. These findings support the concept that expression of the sis/PDGF-2 product in human cells responsive to its proliferative actions can be an important step in the processes leading to malignancy. Unlike sis/PDGF-2, which remains tightly cell-associated, another growth factor, termed transforming growth factor alpha (TGF alpha), is actively secreted. Expression vectors for the TGF alpha coding sequence failed to induce primary transformed foci upon transfection of NIH/3T3 cells despite high levels of TGF alpha synthesized by these cells. Moreover, transfectants selected for secretion of high levels of TGF alpha failed to form colonies on contact inhibited NIH/3T3 monolayers or to induce tumors upon inoculation of nude mice. Thus, the ability of a growth factor to induce autonomous in vitro or in vivo growth is dependent upon more than expression of cognate receptors by the cell in which it is synthesized.

Growth Substances↗
PubMed1985

Lymphoid stroma of Warthin's tumor: phenotypic analogies with gut-associated lymphoid tissue.

Lymphocytes in cell suspensions and cryostat sections of Warthin's tumors (WT) have been phenotypically characterized using a battery of monoclonal and polyclonal antisera to lymphoid cell-associated antigens. The present study shows that in the WT lymphoid stroma, B cells are more numerous than T lymphocytes and include a significant percentage of surface immunoglobulin A-bearing cells. Of the T cells, the Leu 3a+ and OKT4+ lymphocytes are present in higher percentages than the OKT8+ ones. Both T-cell subsets present a topographic distribution which is similar to that found in human tonsils and gut tunica propria. Intraepithelial lymphocytes displaying an OKT8+, Leu 3a-, OKT3- phenotype are also present. These data, together with previous findings which have demonstrated that Warthin's tumor epithelium synthesizes IgA secretory piece, suggest that these cells may modulate the organization of the surrounding lymphoid stroma toward that of a mature lymphatic tissue phenotipically resembling gut-associated lymphoid tissue.

Adenolymphoma↗
PubMed1984

Differential tissue distribution and ontogeny of DC-1 and HLA-DR antigens.

The tissue distribution and the ontogeny of DC-1 antigens have been investigated and compared with those of HLA-DR antigens. Indirect immunofluorescence (IIF) staining of surgically removed normal tissues from adults with the monoclonal antibody (MoAb) BT3.4 has detected DC-1 antigens in tissues of various embryologic origin. The tissue distribution of DC-1 antigens is more restricted than that of HLA-DR antigens, as the former are not detected in duodenal epithelium, colon mucosa, and ductal mammary gland epithelium. In fetuses up to 26 weeks of age, DC-1 antigens were detected only on cortical and medullary thymic dendritic cells with an anatomic distribution similar to that of reticuloepithelial cells and in endothelial cells of the small intestine. At this stage of intrauterine life, HLA-DR antigens have already reached their full tissue distribution. The tissue distribution and the ontogeny of DC-1 antigens resemble those of their murine counterparts, i.e., the I-A antigens.

Adult↗
PubMed1983

Isolation of viable melanoma cells from surgically removed lesions using dishes coated with monoclonal antibody to a high molecular weight melanoma associated antigen.

The panning methodology has been applied to isolate viable human melanoma cells from surgically removed lesions. In this procedure a monocellular suspension mechanically prepared from a biopsy is incubated in plastic dishes coated with the monoclonal antibody (MoAb) 225.28S to a membrane bound high molecular weight-melanoma associated antigen (HMW-MAA). The melanoma nature of the cells growing in MoAb 225.28S coated dishes is indicated by the specific reactivity with anti-HMW-MAA MoAb, by its detection in spent culture medium and by morphological criteria. The specificity of the procedure is proven by the lack of growth of cells seeded in fetal calf serum (FCS) coated dishes, as well as of cells lacking the HMW-MAA in MoAb 225.28S coated dishes. The adherence of melanoma cells to plastic dishes is influenced by the concentration of the plastic bound MoAb 225.28S and by the incubation time. Melanoma cells isolated by adherence to MoAb 225.28S coated plates do not display any detectable change in their growth curve and colony forming ability. The ready availability of melanoma cells isolated from surgically removed lesions will greatly facilitate the characterization of the interaction between host's immune system and tumor cells and the screening of anti-tumor agents in preclinical tests.

Antibodies, Monoclonal↗