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Biomedical subjects

M J Embleton

Publications and source records attributed to M J Embleton.

At least 55 records · Page 3Linked to original sources
PubMed1983

Preparation and properties of a drug-carrier-antibody conjugate showing selective antibody-directed cytotoxicity in vitro.

The preparation and properties of a drug-carrier-antibody preparation are reported. The antifolate chemotherapeutic agent methotrexate was covalently coupled to human serum albumin as a carrier. The carrier-drug preparation was then chemically linked to a monoclonal antibody, raised originally against a human osteogenic sarcoma cell line, 791T, in a manner permitting retention of antibody-binding activity. The cytotoxic properties of the conjugate were tested in vitro in comparison with carrier-methotrexate and free methotrexate against a panel of tumour cell lines containing both antigenically cross-reactive cell lines and cell lines having low antigenic cross-reactivity with the monoclonal antibody. The cytotoxicity tests demonstrated that coupling of methotrexate to carrier caused a loss of some drug activity but that coupling of the antibody to the carrier-drug preparation permitted full expression of drug cytotoxicity against antibody-reactive cell lines. It was further demonstrated that the conjugate was selective in its action and was preferentially cytotoxic towards antibody-reactive cell types. The cytotoxicity against antibody-reactive cell lines was shown by competitive inhibition by free antibody to be entirely dependent on antibody binding. A clonogenic assay showed that the conjugate was capable of killing greater than 99% of 791T target cells. These results indicate that a drug-carrier antibody conjugate can be synthesized which has all the in vitro properties theoretically necessary for a successful antibody-targeted cytotoxic agent.

Animals↗
PubMed1983

A monoclonal antibody against human colonic adenoma recognizes difucosylated Type-2-blood-group chains.

A monoclonal antibody C14/1/46/10 showing preferential binding to membranes of human colorectal carcinomas over normal colon mucosae was obtained by immunization of mice with extra-nuclear membranes of a human colonic adenoma. Binding and inhibition of binding assays using blood cells or glycoproteins with known blood-group activities indicated that the antibody recognizes a carbohydrate antigen co-existing with the blood-group-H determinant: Fuc alpha 1 leads to 2 Gal. Inhibition assays with structurally defined oligosaccharides showed that the antigenic determinant involves difucosylated Type-2-blood-group chains with the structure: (formula; see text)

Adenoma↗
PubMed1983

Selective cytotoxicity against human tumour cells by a vindesine-monoclonal antibody conjugate.

The anti-mitotic drug vindesine was coupled chemically to a monoclonal antibody raised originally against the human osteogenic sarcoma cell line, 791T. The cytotoxicity of the conjugate in vitro was tested, in comparison with free vindesine, against sarcoma 791T and other antigenically cross-reactive osteogenic sarcoma-cell lines, and also against tumour cell lines which have no detectable reaction with the monoclonal antibody. Continuous exposure of cultured 791T cells indicated that the vindesine was partially inactivated following conjugation since the conjugate was less toxic than the free drug. However, antibody-binding activity was essentially preserved following conjugation. Despite diminished drug activity in the conjugate, assays designed to mimic antibody binding to tumour in which target cells were treated with conjugate and washed before culture, showed selective cytotoxicity for osteogenic sarcoma lines with little or no effect on non-cross reactive control cells. In comparison, free vindesine was toxic equally for all cell lines and free antibody was non-toxic. These studies indicate that conjugation of a cytotoxic agent to a monoclonal antibody can confer on that agent selectivity for a particular target cell type which is recognised by the antibody.

Animals↗
PubMed1983

A monoclonal antibody reactive with human hepatocytes.

A monoclonal antibody, RL23/36, reacting preferentially with a determinant expressed on normal human hepatocytes is described. Use of an immunohistochemical technique on frozen sections from a range of 75 human liver biopsy specimens revealed that the determinant detected by RL23/36 was not expressed on hepatocytes from a number of patients with biopsy-proven liver disease. Although a normal staining pattern was observed in 28 of 29 biopsy specimens from patients with no evidence of liver disease, the antibody did not bind to hepatocytes in some cases of chronic active hepatitis (2/13), alcoholic liver disease (2/9), haemochromatosis (1/1), cirrhosis (1/2) and liver metastases (2/8). Furthermore, as in a previous study undertaken in the rat, the antibody failed to bind to tumour cells in the single human hepatoma observed in this study. These results suggest that further studies using RL23/36 may shed light on the pathogenesis of a number of liver diseases, including primary hepatocellular carcinoma.

Animals↗
PubMed1983

Monoclonal antibodies for radioimmunodetection of tumours and for targeting.

A monoclonal antibody 791T/36 prepared against human osteogenic sarcoma has been used to detect primary and metastatic colorectal carcinomas by external imaging of patients following injection of 131I-labelled antibody. In 10 of 11 patients radiolabelled 791T/36 antibody localized in tumours, the tumour: non tumour ratio of radioactivity ranging from 1.5:1 to 8.1. 791T/36 antibody was also evaluated for its potential for targeting anti-tumour agents including cytotoxic drugs (Vindesine) and immunomodulating agents (interferon0. Vindesine-791T/36 conjugates were preferentially cytotoxic in vitro for target cells expressing the 791T/36 antibody defined antigen. Also interferon conjugated to 791T/36 antibody, like free interferon activated peripheral blood natural killer cell activity. These in vitro tests together with related studies on antibody localization in vivo indicate the potential of monoclonal antibody targeting of anti-tumour agents.

Animals↗
PubMed1982

Radioimmunodetection of human colorectal cancers by an anti-tumour monoclonal antibody.

In 10 out of 11 patients with colorectal cancer radiolabelled antitumour monoclonal antibody (791T/36) was localised to the tumour. The mean tumour to non-tumour uptake ratio of antibody demonstrated by imaging with a gamma camera was 4.4/1 after subtraction of background radioactivity. The antibody did not localise in one patient who had received radiotherapy to his tumour two weeks previously. In 5 patients with primary neoplasms localisation of the antibody was confirmed by further imaging of the resected specimens and in-vitro radioactivity counting of the tumour and comparison with the activity in adjacent normal colon.

Adult↗
PubMed1982

Expression of a monoclonal antibody-defined liver-associated antigen in normal rat hepatocytes and hepatocellular carcinoma cells.

In order to examine changes in the expression of normal cellular antigens during hepatocarcinogenesis, we have developed and characterized a monoclonal antibody detecting an antigen which is particularly associated with adult rat hepatocytes. The antibody showed no reactivity with a range of freshly-prepared normal syngeneic adult rat cell types, but showed strong reactivity with hepatocytes derived from several rat strains in antibody binding tests. Immunoperoxidase staining of sections of normal rat liver showed that the antigen was distributed throughout hepatocytes within the liver, but did not stain cells other than hepatocytes. The antigen detected by this monoclonal antibody was not detectable on a number of transplanted and primary dimethylaminoazobenzene-induced hepatomas. Preliminary data indicated that this monoclonal antibody may be suitable for use in flow cytofluorimetric sorting of mixed populations of normal and tumour cells, allowing the investigation of cell phenotypes during hepatocarcinogenesis.

Animals↗
PubMed1981

Antitumour antibodies induced by rat embryo cells and spontaneous mammary carcinoma cells treated with 3-methylcholanthrene.

It has previously been shown that rat embryo cells treated in vitro with 3-methylcholanthrene (MCA) elicit antibodies in syngeneic rats which react specifically against established MCA-induced sarcomas. To examine the possibility that clonal amplification of one or a few antigenic, preneoplastic clones is responsible for the previously observed specific antibody responses, MCA-treated rat embryo cells have been subjected to 150 Gy of gamma-irradiation before injection into host animals. The resulting antisera were screened for reactivity against a panel of established syngeneic tumours by membrane immunofluorescence and an isotopic antiglobulin test. A positive reaction was observed between an antiserum pool raised against gamma-irradiated MCA-treated cells and the cells of an immunogenic spontaneous mammary carcinoma. Antiserum to gamma-irradiated control (acetone-treated) cells was negative. Thus gamma-irradiation of carcinogen-treated cells before injection failed to abolish specific antibody responses in immunized rats. To investigate further the relationships between cell-carcinogen interaction, neoantigen induction and malignancy, the cells of a non-immunogenic, spontaneous mammary carcinoma were treated with MCA in vitro, and antisera against treated and untreated cells were tested against a panel of established tumours. A positive membrane-immunofluorescence reaction was obtained with an antiserum to MCA-treated cells, but not to untreated cells against an aminoazodye-induced hepatoma, indicating that the previously non-immunogenic mammary carcinoma cells had acquired new antigenic specificities as a consequence of carcinogen treatment.

Animals↗
PubMed1981

Immune responses to naturally occurring rat sarcomas.

Attempts were made to induce immunity to 5 spontaneous rat sarcomas transplanted into syngeneic recipients. Rats were immunized by surgical removal of growing tumour transplants or by treatment with attenuated tumour, followed by challenge with tumour cells in suspension. Two tumours wee apparently not immunogenic, but a low level of immunity was induced against 2, and weak evidence of immunity was observed with another. Induced immunity was individually specific rather than cross-reactive. It is concluded that, contrary to some reports, some spontaneous animal tumours are immunogenic in the strain of origin.

Animals↗
PubMed1981

Antitumour reactions of monoclonal antibody against a human osteogenic-sarcoma cell line.

Monoclonal antibody against an osteogenic-sarcoma cell line (791T) was prepared by production and cloning of a somatic-cell hybrid between the mouse myeloma P3-NS1 and spleen cells from 791T-immunized mice. Three clones of hybridoma producing antibody against 791T, as detected by 125I-labelled Protein A binding, were tested against a range of normal and tumour cell targets to determine the pattern of expression of the antigen detected. The 3 clones had identical activity. They reacted strongly against 791T cells and another osteogenic sarcoma, 788T, and more weakly against a further 2 from a total panel of 10 osteogenic-sarcoma lines. The antibody was negative for fibroblasts from the donor of 791T, and for other fibroblasts, human red blood cells, human peripheral mononuclear cells and sheep red blood cells. When tested against a panel of unrelated tumours, they reacted against individual cell lines derived from carcinomas of colon, lung, bladder and cervix. These cross-reactions were not observed with other colon or lung carcinomas, and it is suggested that the antibody was reacting with a tumour-associated antigen expressed randomly on different tumour types, rather than specifically on osteogenic sarcomas.

Animals↗
PubMed1981

Naturally arising tumors of the inbred WAB/Not rat strain. I. Classification, age and sex distribution, and transplantation behavior.

During a 3-year period, 97 naturally arising tumors were collected from an inbred colony of WAB/Not rats. These tumors were largely confined to the breeding groups of approximately 5,300 female and 2,700 male rats retained up to 2 years of age. The tumors included 39 nephroblastomas and 41 mammary tumors (24 of which were histologically benign); the remaining tumors were mainly connective tissue sarcomas and skin tumors with 1 lymphoma and 2 gastrointestinal lesions. With the exception of the incidence of mammary tumors, males and females had similar tumor incidence, although nephroblastomas in female rats had a marked preference for growth in the left kidney. Most tumors occurred in the first year of life, especially the histologically malignant mammary tumors and the nephroblastomas. Of the tumors investigated, 31 were transplantable. Poor correlation between histologic malignancy and transplantation was seen with the mammary tumors. Only 50% of the nephroblastomas were transplantable. Although most transplanted tumors retained histologic characteristics of the primary tumor, 1 mammary tumor, 1 gastrointestinal tumor, and 1 nephroblastoma deviated from this general finding. In the case of this nephroblastoma, separate transplant lines from opposite poles of the primary tumor also showed differences in histology.

Age Factors↗
PubMed1981

Naturally arising tumors of the inbred WAB/Not rat strain. II. Immunogenicity of transplanted tumors.

The immunogenicity of 28 transplanted naturally arising tumors of the inbred WAB/Not rat was investigated at early passages in strictly syngeneic, contemporary animals. Included were nephroblastomas, histologically benign and malignant mammary tumors, soft tissue and skin tumors, 1 lymphoid tumor, and 2 gastrointestinal lesions. In no case was evidence of immunogenicity observed when animals were treated with multiple grafts of irradiated (15,000 rad) tissue or by excision of a growing tumor. A few of these tumors were further investigated by other methods of immunization, including injection at various sites of irradiated cells followed by challenge at different sites and multiple injections of mitomycin C- or Formalin-treated cells. Again no evidence of immunogenicity was seen. Attempts to immunize with viable cells mixed with BCG or Corynebacterium parvum failed due to lack of tumor suppression by these agents. Limited concomitant immunity experiments yielded similarly negative results, except in one case of a fibrosarcoma for which a slight reduction in second tumor growth was observed when primary implants were very large. Some alterations in biologic properties during transplant passage and the incidence of postexcision recurrence and metastatic spread of some of the tumors are described.

Animals↗
PubMed1981

Characteristics of two anti-tumour monoclonal antibody preparations.

Monoclonal antibodies directed against one spontaneously arising rat mammary carcinoma and a human osteogenic sarcoma have been prepared following the fusion of spleen cells from appropriately immunised donors with mouse myeloma cells. The characteristics of these antibodies have been analysed and methods for their purification have been developed using immunoadsorption chromatography or by utilising their affinity for Sepharose-linked Protein A. The use of these antibodies for the identification, characterisation and isolation of their target tumour antigenic structures is described.

Animals↗
PubMed1980

Monoclonal antibody against a naturally occurring rat mammary carcinoma.

Inbred rats were hyper-immunised against a syngeneic transplanted mammary carcinoma, Sp4, which originally arose spontaneously in a breeding female. Spleen cells from Sp4-immune rats were fused with P3-NSI-Ag4 mouse myeloma cells, and supernatants from the hybrid progeny were screened for antibody reacting with Sp4 cells using an isotopic antiglobulin assay. One hybrid culture was reactive with Sp4 cells but not against other target cells, and this hybrid was cloned in soft agar. Many Sp4-positive clones were isolated and one (Sp4/A4) was chosen for detailed study. Clone Sp4/A4 was positive only with Sp4 cells and failed to react with cells of other tumours or normal tissues. It contained much higher titres of antibody than detected in immune sera, and it is suggested that this approach offers a practical method for producing highly active tumour-specific antibodies.

Animals↗