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Biomedical subjects

L G Durrant

Publications and source records attributed to L G Durrant.

At least 73 records · Page 4Linked to original sources
PubMed1989

The influence of syngeneic anti-idiotypic antibody on the biodistribution of an anti-tumour monoclonal antibody in BALB/c mice.

BALB/c mice were immunized against syngeneic murine 791T/36 monoclonal antibody (MAb) by intraperitoneal (i.p.) injection of the antibody conjugated to ricin toxin A chain. Subsequently, in these and control mice, the biodistribution of radioiodinated 791T/36 antibody and isotype-matched (IgG2b) control immunoglobulin was examined. Pre-treated mice showed marked perturbation of biodistribution of the 791T/36 antibody but not of control IgG2b. This was manifest as rapid hepatic clearance of the antibody which was followed by accelerated catabolism and excretion of the radiolabel. Anti-idiotypic antibodies were identified in immunotoxin pretreated mice by their ability to inhibit the binding of FITC-labelled 791T/36 antibody to tumour target cells. These studies show that antibody responses, even to only the idiotype of a MAb, may produce marked perturbation of its biodistribution. This has implications for the clinical use of human or chimeric MAbs for tumour imaging or targeting of therapeutic agents since, if anti-idiotypic antibodies are evoked, they could still prevent tumour localization of antibody or conjugate.

Animals↗
PubMed1989

Abrogation of antibody responses in rats to murine monoclonal antibody 791T/36 by treatment with daunomycin-cis-aconityl-791T/36 conjugates.

The majority of monoclonal antibodies in clinical use are of murine origin. It is now well-established that patients generate an antibody response to the mouse immunoglobulin which restricts repeated administration. Pre-sensitization of patients to mouse antibody is screened by hypersensitivity to i.d. administered antibody. This study shows that low doses of mouse antibody administered either i.d. or s.c. are highly immunogenic and suggests that a serological assay would be a safer method of screening for anti-mouse antibodies. Rats treated with monoclonal antibody linked via an acid labile cis-aconityl bond to daunomycin failed to produce a primary response to this conjugate. They were also rendered immunologically unresponsive to subsequent challenges with the unconjugated monoclonal antibody. The induced state of immunological unresponsiveness to free antibody persisted in the rats for 18 weeks and although antibody-cis-aconityl-daunomycin pre-treated animals eventually responded to the fourth challenge with free antibody, at week 25, the response was still significantly less than in the free antibody-pre-treated and challenged animals. These studies show that the use of antibody-cis-aconityl-daunomycin conjugates may provide an approach for the control of human responses to mouse immunoglobulin.

Animals↗
PubMed1989

Influence of circulating antigen on the biodistribution and tumour localization of radiolabelled monoclonal antibody in a human tumour: nude mouse xenograft model.

A monoclonal antibody, against a colorectal carcinoma tumour-associated antigen, was radioiodinated and its biodistribution studied in comparison with that of control immunoglobulin in nude mice with colon carcinoma xenografts. Tumour localization of the antibody in comparison with normal tissues was poor, and in absolute terms more control IgG than antibody was present per gram of tumour. This failure to achieve localization could not be ascribed to poor immunoreactivity of the antibody nor to the failure of the xenografts to express the appropriate antigen. Analysis of serum from mice with xenografts showed the presence of circulating tumour-derived antigen. This serum-borne antigen was found to form immune complexes both in vitro and in vivo with the monoclonal antibody, and this complex formation is probably the limiting factor in tumour localization of the antibody. This is one of only few examples where mice with human tumour xenografts have levels of circulating antigen sufficient to perturb biodistribution of antibody. These findings are relevant to the biodistribution of monoclonal antibodies in the clinical situation, since circulating antigen is often found in cancer patients.

Animals↗
PubMed1989

Development of an ELISA to detect early local relapse of colorectal cancer.

The Y haptenic blood group determinant is expressed on the cells of malignant gastrointestinal tumours and on the normal gastrointestinal epithelium of individuals who can secrete blood group antigens. an enzyme-linked immunosorbent assay incorporating the high affinity biotin-avidin interaction was developed to measure the serum levels of antigens bearing the Y hapten in patients with colorectal cancer. The specificity of the assays was between 88 and 93% and the sensitivity in detecting extensive disease was between 24 and 34%. However, up to 67% of patients with local or abdominal recurrent disease secreted antigens expressing the Y hapten, whereas only 30% of patients with overt hepatic metastases secreted a similar antigen. Recognition of antigens bearing the Y hapten may therefore be useful in detecting early local relapse of colorectal cancer when a second operation to excise the recurrence may be possible.

Antibodies, Monoclonal↗
PubMed1989

Enhanced recognition of human colorectal tumour cells using combinations of monoclonal antibodies.

Murine monoclonal antibodies directed against tumour associated antigens are potentially useful in tumour diagnosis and therapy. However, all the antigens they recognise may be heterogeneously expressed on tumours and this may allow escape of cells from therapy if a single monoclonal antibody is used. One approach is to use combinations of monoclonal antibodies recognising complementary cell surface antigens. A flow cytometric method which allows accurate quantitation of the intensity of staining and the percentage of fresh primary tumour cells binding a series of monoclonal antibodies has therefore been developed. This allows calculations as the number of drug molecules which could be potentially delivered by each monoclonal antibody and the optimal combination of antibodies which should be used. Monoclonal antibodies recognising Y hapten (C14), CEA (228, 161) and 791T-p72 antigen (791T/36) have been screened as a possible combination for colorectal cancer. There was inter-tumour variation in the binding of all the monoclonal antibodies although combinations could reduce or abrogate this problem. A combination of the monoclonal antibodies C14, 228, 791T/36 and 161 would recognise 100% of tumours. Sixty per cent of tumours bound all four antibodies, 78% any three, 90% any two and 100% any one antibody. There was also intra-tumour variation in the number of tumour cells per lesion that were recognised, the best monoclonal antibody, 161, stained a mean of 59% of cells per tumour whereas the anti-cytokeratin monoclonal antibody stained a mean of 74% of cells per tumour. An increased intensity of staining of tumour membranes was observed when a combination of C14 and 228 was used compared to binding of individual antibodies. Furthermore there was still no significant binding to normal colon membranes. Combinations of monoclonal antibodies which recognise a high percentage of tumours are likely to be necessary for monoclonal antibody drug targeting to prevent tumour recurrence and/or metastases.

Antibodies, Monoclonal↗
PubMed1989

Humoral immune responses to XMMCO-791-RTA immunotoxin in colorectal cancer patients.

Monoclonal antibody 791 (XMMCO-791) recognizes a colorectal tumour-associated antigen. Antibody 791-ricin A chain immunotoxin (XMMCO-791-RTA) inhibits growth of human tumour xenografts and it is therefore being evaluated for the treatment of colorectal cancer. One of the problems with therapy with mouse monoclonal antibodies is they stimulate humoral responses in patients. However antigens linked to ricin are cytotoxic for B cells and therefore XMMCO-791-RTA may not be immunogenic. The humoral antibody response to murine monoclonal antibody XMMCO-791 (IgG2b) conjugated to the plant toxin, ricin A chain (RTA), was measured in colorectal cancer patients in a phase I clinical trial. All patients produced strong responses to the XMMCO-791 immunoglobulin and to RTA. The predominant response to the antibody was against the idiotypic determinant although anti-subclass and anti-mouse antibodies were also detected. A component of the anti-idiotypic immunoglobulin response in the colorectal cancer patients was directed against the combining site of XMMCO-791. These antibodies inhibited in-vitro binding of XMMCO-791 to target 791 cells and so may be inhibitors of repeated immunotoxin therapy. Immunotoxins do not abrogate the immune response to mouse immunoglobulin in vivo but instead are highly immunogenic.

Adult↗
PubMed1989

Human monoclonal anti-idiotypic antibody to the tumour-associated antibody 791T/36.

A human monoclonal antibody, 105AD7, was produced by fusion of a mouse/human heteromyeloma cell line with lymphocytes from a patient previously injected with mouse monoclonal antibody 791T/36 for tumour immunoscintigraphy. The 105AD7 hybridoma has been in continuous culture for more than 12 months, producing a human monoclonal IgG1 which binds to 791T/36 (IgG2b) and its IgG2a class switch variant, but not a range of other monoclonal mouse immunoglobulins. In quantitative flow cytometric assays, 105AD7 was shown to block the binding of fluorescein-labelled 791T/36 to its target gp72 antigen at the surface of tumour cells, but not the binding of 228, an anti-carcinoembryonic antigen (CEA) monoclonal antibody to CEA. Tests with purified 105AD7 antibody demonstrated a stoichiometric high-affinity interaction between 105AD7 and 791T/36. Thus 105AD7 is a human anti-idiotypic antibody which binds at or very close to the binding site of 791T/36, and as such is a candidate for anti-idiotypic immunization of cancer patients.

Antibodies, Anti-Idiotypic↗
PubMed1988

Growth-promoting action of gastrin on human colonic and gastric tumour cells cultured in vitro.

The gastrointestinal hormone, gastrin, was examined for its trophic effect on the growth of colorectal and gastric tumour cells. All of the freshly disaggregated colorectal and gastric human adenocarcinomas responded to pentagastrin in 24 h cultures in vitro. Two newly established adenocarcinoma cell lines showed a response to pentagastrin at passage 2 but not at passage 6. Long-established cell lines did not respond to pentagastrin; however, upon synchronization of the human gastric cell line, MKN45, a trophic growth response with gastrin-17 was observed. This response was enhanced when the same cell line was grown as a xenograft in nude mice and then examined in vitro for gastrin dependence; this dependence was gradually reduced on further in vitro passaging. These results indicate that trophic responses to gastrin are lost during in vitro culture and may be underestimated by using long-established tumour cell lines. However, as all of the early cultures of colorectal and gastric tumours respond trophically to gastrin, perhaps gastrin-receptor blockers may be an important therapeutic modality for these patients.

Adenocarcinoma↗
PubMed1988

A rat model for imaging the effect of anti mouse antibody responses on the biodistribution of radiolabelled mouse monoclonal antibodies.

Rats were injected both intradermally and intravenously with an IgG2b mouse monoclonal antibody (791T/36) and subsequently the biodistribution of intravenously injected 111In labelled antibody was examined by gamma camera imaging in these and control rats. The majority of pretreated rats showed a marked perturbation of the biodistribution of the radiolabelled antibody with a marked increase of the tracer in the liver. There was similar perturbation of the biodistribution of subsequently administered 111In labelled Fab fragment of the 791T/36 antibody and of another IgG2b monoclonal antibody. In contrast, there was little influence on the biodistribution of IgG2a or IgG1 monoclonal antibodies, indicating that the response in the rats was predominantly against the IgG2b isotype. This rat model system is amenable to examination of a number of aspects of the biological consequences of immune responses to foreign immunoglobulins relevant to their use for clinical imaging.

Animals↗
PubMed1987

Quantitation of MHC antigen expression on colorectal tumours and its association with tumour progression.

A flow cytometric technique has been established for accurately quantitating the cell surface density of MHC antigens and the percentage of cells expressing MHC antigens in 38 colorectal tumours. Thirty-four percent of tumours were partially or completely negative for HLA-ABC antigen expression. Although the quantity of HLA-ABC antigens varied widely, there was no correlation between the density of HLA-ABC antigens, or the percentage of cells expressing these antigens and clinicopathological stage. Fifty percent of the colorectal tumours expressed HLA-DR with varying antigen densities. All of the poorly differentiated tumours expressed HLA-DR but there was no correlation between expression of HLA-DR and clinicopathological stage. The aneuploid tumours expressed more HLA-ABC and HLA-DR antigens on a higher percentage of cells than the diploid tumours. Abnormal expression of the tumour associated antigens CEA, Y haptenic blood group and 791T p72 also correlated with expression of HLA-ABC and HLA-DR antigens on colorectal tumours. The majority of early derived in vitro dividing cells failed to express both HLA-ABC and HLA-DR antigens although they expressed high levels of tumour associated antigens. If there is a correlation between in vitro and in vivo growth perhaps tumours are maintained and seeded by MHC antigen negative cells.

Antigens, Neoplasm↗
PubMed1987

Sensitivity of newly established colorectal cell lines to cytotoxic drugs and monoclonal antibody drug conjugates.

A major problem in the chemotherapy of colorectal cancers is their resistance to most cytotoxic drugs which may be due to insufficient cellular transport. Drugs conjugated to monoclonal antibodies recognising tumour antigens may overcome these difficulties by providing access of active agents to the tumour cells. The anti-tumour monoclonal antibody shown to localise in patients with colorectal cancer, 791T/36, has been investigated as a potential targeting antibody. Eight cell lines were established from surgically resected material and were shown to bind 791T/36 antibody. They were screened for their sensitivity to methotrexate, 5-fluorouracil and daunomycin. Although 5-fluorouracil is the drug of choice for chemotherapy of colorectal cancer it was the most cytotoxic drug in only 2 of the 8 cell lines. Only the 4 cell lines which were resistant to methotrexate showed less cytotoxicity with methotrexate than 5-fluorouracil. The cell lines which were resistant to methotrexate were more sensitive to 791T/36-methotrexate conjugates. Daunomycin was the most cytotoxic drug in 4 of the 8 cell lines. However, a similar cytotoxicity was observed for free drug and 791T/36 daunomycin in the two lines tested. Selective monoclonal antibody drug conjugates may offer a solution to treatment of tumours which are resistant to classical chemotherapeutic agents. This is the first report to show that newly established cell lines that are resistant to classical chemotherapeutic agents are rendered sensitive when the drug enters the cell as a drug monoclonal antibody carrier.

Antibodies, Monoclonal↗
PubMed1987

Genetic evidence for nucleotide excision repair of O6-alkylguanine in mammalian cells.

Human cells that lack O6-alkylguanine DNA alkyltransferase (AT) activity can remove O6-butylguanine (O6-nBuG) produced in cellular DNA by exposure to N-n-butyl-N-nitrosourea as determined by radioimmunoassay of enzyme digests of DNA. Fibroblasts from xeroderma pigmentosum (XP) complementation groups A and G that show less than 5% unscheduled DNA synthesis following exposure to UVC failed to remove O6-nBuG. Hence it appears that O6-alkylguanine is repaired in cells that lack AT by a process that is defective in XP cells, presumably nucleotide excision repair. Neither V79 nor V79/79 Chinese hamster cell lines have AT activity and both are able to remove O6-nBuG from DNA. However, only V79/79 is able to remove O6MeG, suggesting some substrate specificity of the excision repair process. Comparison of relative levels of O6-alkylation by N-methyl-, N-ethyl-, N-propyl- and N-n-butyl-nitrosourea indicate that approximately equal levels of O6-alkylation are produced by equitoxic doses of these agents.

Alkylation↗
PubMed1987

Imaging of primary and metastatic colorectal carcinoma with monoclonal antibody 791T/36 and the therapeutic potential of antibody-drug conjugates.

Monoclonal antibody 791T/36, prepared against a tumour-associated 72,000 dalton glycoprotein, reacted with cells from primary and metastatic colorectal carcinomas. I-131 or In-111-labelled antibody localized in xenografts of colorectal carcinomas established from in vitro clonogenic populations. Clinically, with I-131-labelled antibody, 8/11 colonic tumours imaged positively. Imaging was negative in four patients with benign colon disease. 5/11 rectal tumours were positively imaged, but excreted I-131 in the bladder obscured tumours in several studies. In-111-labelled antibody gave superior images and positively imaged primary and metastatic sites in 13/14 patients. Prospectively in the detection of recurrent disease, I-131 or In-111-antibody detected 29/33 separate sites in 24 patients. Seven negative patients remain disease free. There were 3 false positives; overall sensitivity was 88%, with 70% specificity. Specific localization of radiolabel was confirmed immunochemically and by counting radioactivity in resected specimens. Antibody conjugates with methotrexate, vindesine and daunomycin retained drug activity and antibody function, including xenograft localization and conjugates were therapeutically effective against xenografts. 791T/36 antibody has potential for immunodetection of primary and recurrent colorectal carcinoma and for targeting of therapeutic agents.

Animals↗
PubMed1986

In vitro binding and in vivo localization in colorectal cancer of a high affinity monoclonal antibody to carcinoembryonic antigen.

A monoclonal antibody to carcinoembryonic antigen (CEA) (C46) was tested for its binding properties to colorectal cancer cells in vitro and for its localization in patients with primary colorectal cancer. Strong binding was found to disaggregated primary colorectal cancer cells, with a median of 66 per cent of the cells in the tumour gate binding the antibody. There was a median binding ratio of 8.6:1 compared with normal immunoglobulin. The pattern of immunohistological staining was typical of that for an antibody to CEA. All seven patients with primary colorectal cancer imaged pre-operatively using 111In-labelled C46 gave positive images. The median tumour:non-tumour antibody uptake ratio from resected specimens (n = 8) was 5.8:1. (1.7-7.6:1). Eight of 11 sites of secondary colorectal cancer gave positive images. The high affinity and good tumour localization of C46 have improved clinical imaging and increase the possibilities for targetting of antitumour agents.

Aged↗
PubMed1986

Antigenicity of newly established colorectal carcinoma cell lines.

Cells from two adenocarcinomas, an adenoma and a metastatic node were isolated in soft agar. Expression of antigens, CEA, Y haptenic blood group and 791T-p72, defined by a range of candidate antibodies for tumour targeting was assessed. All of the cells expressed low levels of CEA but high levels of the Y haptenic blood group antigen although there was enormous inter and intraclonal variation. Of particular interest was the membrane expression of 791T-p72 antigen on all of the dividing tumour cells as previous studies had shown that 791T/36 antibody reacted with tumour stromal elements rather than malignant cell surfaces. The DNA content was abnormal in all of the cells whether they were derived from diploid or aneuploid primary tumours. They all grew readily in athymic mice and at least one monoclonal antibody, 791T/36, localised efficiently within these xenografts. Clonogenic cells therefore expressed the three tumour-associated antigens, several at higher levels than observed in the primary tumour. Monoclonal antibody 'cocktails' should therefore allow antibody mediated drug cytotoxicity to be effective at eradicating rapidly dividing tumour cells.

Adenocarcinoma↗
PubMed1986

Association of antigen expression and DNA ploidy in human colorectal tumors.

Fifty colorectal tumors were screened by indirect immunofluorescence and flow cytometry for antigen expression using a panel of monoclonal antibodies that recognize determinants preferentially expressed on tumor cells (carcinoembryonic antigen, Y haptenic blood group, 791T/36 defined antigen 791T-P72). Fifty % of the tumors expressed all three antigens, 41%, two, and 9%, one. Over a third reacted strongly with at least one monoclonal antibody, although the majority of tumors stained with a moderate intensity. Extranuclear membranes from tumors showed similar antigen expression to disaggregated tumor cells and were particularly useful for providing the relative tumor:normal tissue binding ratios. The carcinoembryonic antigen specific monoclonal antibody showed the strongest tumor selectivity with a tumor:normal tissue ratio of 24 +/- 7:1. Lack of correlation between expression of the three antigens suggested that the monoclonal antibodies recognizing them may have potential as a "cocktail." One-third of the tumors contained cells with an aneuploid DNA content and expressed elevated levels of carcinoembryonic antigen and Y haptenic blood group antigen when compared to tumors with diploid DNA content. Aneuploid cells within a tumor were also preferentially stained with all of the monoclonal antibodies.

Adenocarcinoma↗
PubMed1984

Characterization of a human X mouse T cell hybridoma and identification of a clone secreting and binding interleukin-2.

Human lymphocytes stimulated with phytohaemagglutinin (PHA) were fused with an HGPRT- murine lymphoma, BW5147, and a hybridoma BwFc93-1 was isolated and cloned in agarose. This human X mouse hybrid and nine clones derived from it were characterized by chromosome analysis, phenotypic and functional assays. Karyotyping and isoenzyme studies showed the presence of five human chromosomes in BwFc93-1 with preferential retention of three chromosomes--6, X and 15--in the clones. Membrane immunofluorescence analysis revealed that all the clones expressed human and mouse class 1 MHC antigens and the mouse T cell antigens Thy-1 and T200, but were devoid of human OKT3, OKT8 and mouse Lyt-2. Human OKT4 and OKM1 phenotypes were transiently expressed by one clone and mouse Lyt 1 by two other clones. Several T4-, Lyt-1- clones produced and bound human interleukin-2 (IL-2) indicating a lack of correlation between human T cell phenotype and function in those hybrids. There was also evidence of dichotomy in the secretion of IL-2 and expression of the IL-2 receptor since clones were identified which either bound or secreted IL-2. One clone expressing IL-2 receptors could be induced to produce human IL-2 by simultaneously stimulating with PHA and phorbol myristate acetate (PMA).

Animals↗