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R A Robins

Publications and source records attributed to R A Robins.

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

c-myc oncogene product expression and prognosis in operable breast cancer.

The 62 kDa protein product of the c-myc oncogene (p62 c-myc) is thought to be involved in the control of normal cellular proliferation and differentiation. We have measured oncoprotein levels using a flow cytometric assay in 141 operable breast cancers and have correlated levels with prognostic variables, patient survival and disease free intervals. High levels of p62 c-myc were associated with well differentiated tumours. There was no correlation with tumour DNA index, lymph node or oestrogen receptor status. C-myc oncoprotein levels were not predictive of patient survival or disease free interval. This relationship of oncoprotein levels with tumour histological grade is in keeping with the suggestion that the c-myc oncogene is important in the control of cellular differentiation. The other findings imply that measurement of c-myc oncoprotein levels does not yield useful prognostic information.

Breast Neoplasms↗
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

Potentiation of anti-carcinoembryonic antigen immunotoxin cytotoxicity by monoclonal antibodies reacting with co-expressed carcinoembryonic antigen epitopes.

The initial step in ricin A-chain (RTA)-immunotoxin-mediated cell cytotoxicity involves binding to the target cell Ag through the antibody moiety. One of the factors influencing this is the affinity of the antibody component for the target cell Ag. Multiple epitopes on carcinoembryonic Ag have been mapped providing a range of mAb of known specificity. These have been used to show that the cytotoxicity of an immunotoxin containing RTA conjugated to an anti-carcinoembryonic Ag mAb (228-RTA) is potentiated by mAb recognizing different epitopes. The potentiating antibodies also increased the level of target cell binding of antibody 228. Cross-linking of cell bound antibody was not involved because monovalent fragments of a potentiating antibody were effective. The potentiating antibodies modified the binding affinity of 228 antibody increasing the t1/2 of antibody at the tumor cell surface. This increased the dwell time of cell bound antibody and using conjugates of 228 linked to albumin-tetramethylrhodamine it was shown to enhance conjugate endocytosis. These investigations indicate that enhanced antibody affinity leads to increased endocytosis of bound immunoconjugate and potentiates cytotoxicity.

Adjuvants, Immunologic↗
PubMed1988

Transferrin receptor expression of AML blasts is related to their proliferative potential.

Expression of the transferrin receptor (TfR) was studied on peripheral blood blast cells from 11 patients with acute myeloid leukaemia (AML). Using a monoclonal anti-TfR antibody (OKT9) and a polyclonal antibody against surface membrane-bound transferrin, a proportion of blasts from all the patients was found to express receptors for transferrin. Further analysis of OKT9 expression using a fluorescent activated cell sorter (FACS) showed that the TfR was heterogeneously distributed in the blast cell population. In five out of six samples studied, stimulation of DNA synthesis following short-term culture induced a several-fold increase in TfR display as analysed by flow cytometry using OKT9 or FITC-conjugated transferrin. Blasts from seven patients stained with OKT9 were separated on the FACS into positive and negative or weakly positive fractions. Culture of the TfR negative population in a blast cell colony assay produced no colonies in either of two patients. In a further five patients the colony forming cells were predominantly associated with the TfR strongly positive fraction (52 +/- 25 colonies/10(4) cells) rather than the TfR weakly positive fraction (12 +/- 11 colonies/10(4) cells). Analysis of colony size showed that clones derived from the weakly positive fraction were smaller than clones from the TfR strongly positive fraction. These results suggest that TfR display by AML blasts is related to their proliferative capacity and is expressed by the leukaemic stem cell fraction.

Antibodies, Monoclonal↗
PubMed1988

The effect of interferon-gamma treatment of rat tumour cells on their susceptibility to natural killer cell, macrophage and cytotoxic T-cell killing.

The effect of exposing tumour cells to interferon-gamma (IFN-gamma) has been studied investigating changes in MHC antigen expression and susceptibility to a variety of cellular effector mechanisms. Treatment of rat tumour cell lines with rat recombinant IFN-gamma increased their expression of class I MHC molecules, as monitored by quantitative immunofluorescence. Reduced sensitivity to lysis by NK cells was observed, although cold-target competition assays indicated NK cells were bound equally well by both interferon-treated and control cells. Decreased susceptibility to NK lysis was not a general effect of IFN-gamma treatment of tumour cells, as the sensitivity to lysis by activated macrophages was unaffected. Furthermore, both allogeneic CTL and CTL from syngeneic tumour-immune rats were able to kill IFN-gamma-treated tumour cells more effectively than untreated control target cells. These studies show that IFN changes the balance of sensitivity to different cytolytic effector mechanisms, increasing T-cell mediated effects, decreasing NK killing, but leaving macrophage cytotoxicity unaffected. The impact of these changes on tumour rejection will depend on the relative contribution of these mechanisms to target-cell destruction.

Animals↗
PubMed1987

Identification of a monoclonal antibody-defined breast carcinoma antigen in body fluids.

The monoclonal antibody NCRC-11 defines antigens associated with secretory glandular epithelia as well as most epithelial malignancies. These components have been identified in, and isolated from, normal body fluids including urine and skim milk. The immunoadsorbent purified antigens from urine and milk were very similar to those purified from breast and ovarian carcinomas; by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS PAGE) and immunoblotting, NCRC-11 antibody-binding antigens from all sources were of high apparent molecular weight (greater than 400 kD) with the major component(s) present as a single band or a doublet. Also, by analysing epitope profiles, all purified antigen preparations were shown to react in a characteristic manner with a panel of monoclonal antibodies which were originally produced against human milk products or materials from tumours. Since it was shown that NCRC-11 antigens were released from tissues in a soluble form, the possibility that these antigens might represent a diagnostic marker for breast cancer was evaluated. The findings obtained indicated that NCRC-11 antigens were elevated in the serum of advanced breast cancer patients in comparison to healthy control females, so that access to the circulation was available to these products released from the tumour but not to those released from normal epithelia.

Aged↗
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

Tumour aneuploidy, prognostic parameters and survival in primary breast cancer.

Cellular DNA content of primary tumours from 280 patients with operable breast cancer was determined by flow cytometry using nuclei from paraffin sections stained with DAPI, and 199 of these patients were followed for 8-13 years after surgery. Tumours from 67 patients have also been analyzed for their DNA content using single cell suspensions from fresh tumour tissue stained with mithramycin and ethidium bromide, and the results compared with those obtained from paraffin blocks of the same tumours. Overall 60% of the tumours contained cells with abnormal DNA content (DNA-aneuploid populations). Survival and disease free interval were not significantly different in patients with DNA-diploid and DNA-aneuploid tumours when analysed by Mantel's life table method. There was however, an early advantage for patients with DNA-diploid tumours: during the first 30 months after surgery DNA-aneuploidy was associated with higher rate of recurrence and shorter survival. DNA-aneuploidy was strongly related to histological grade. Thus 11/49 (22%) grade I, 60/102 (59%) grade II, and 96/129 (74%) grade III tumours were DNA-aneuploid. Although there was no significant difference in survival of patients with DNA-diploid and DNA-aneuploid tumours overall, there appears to be an unexpected association between DNA-aneuploidy and better survival in grade II patients (P less than 0.01); a similar trend was observed for grade I patients. Although the proportion of DNA-aneuploid tumours was similar in oestrogen receptor positive and negative tumours, DNA-aneuploidy was associated with lower levels of oestrogen receptors in comparison to DNA-diploid tumours. Comparison between the modal DNA values of fresh and paraffin embedded samples showed high rate of comparability (64/67, P less than 0.0001).

Aneuploidy↗
PubMed1986

T-cell responses at the host: tumour interface.

The evidence considered here reinforces the conclusion that T-cell responses to tumours involve complex cellular interactions. An attempt to summarize some of these interactions is shown. This emphasizes that not only are the interactions between the effector cell populations complicated, but that the target cell surface is also subject to variation and modification as a result of the immune response. A feature that also emerges from these studies is that most cells apparently responding to or infiltrating a tumour do not necessarily participate in its destruction, and it is in this area that experimental tumour systems have particular value. This also perhaps explains the preoccupation of experimentalists with the identification of 'the' effector cell crucial to tumour rejection. However, there is heterogeneity between systems in terms of the type of rejection response induced, but a logical basis for this heterogeneity is not established. If experimental studies could define the nature of the immune response generated by a tumour in the context of the biological features of the tumour itself, this could lead to the prediction of the immunogenicity and potential for induction of a rejection response for that tumor. Clearly, experimental tumour systems do not provide an exact reflection of the situation with human tumours. However, they may provide systems that illuminate particular aspects of the human response, and give precedents to guide the interpretation of data derived from human systems. This form of assessment is still at an early stage, but developments in the experimental field should provide a framework for the development and exploitation of T-cell responses to tumours.

Animals↗
PubMed1986

Measurement of tumour reactive antibody and antibody conjugate by competition, quantitated by flow cytofluorimetry.

Binding of unlabelled monoclonal antibody preparations has been assessed by competition at saturation with fluorochrome labelled homologous antibody for binding to antigen bearing target cells. The extent of competition was measured by quantitative flow cytofluorimetry, and simple mathematical procedures have been developed to allow the interpretation of competition data in terms of antibody binding activity. In the system studied, non-specific (non-competitive) fluorescence was minimal, but an iterative method to calculate its contribution to the measured signal is given. This approach has the advantage that the antibody preparation to be tested does not need to be labelled or modified; this is particularly important when evaluating the binding activity of therapeutic antibody conjugates. Comparison with a well characterized standard antibody preparation provides a rapid, sensitive and accurate quality control procedure. This test is also simple to perform, requiring only the mixing of labelled and unlabelled antibodies with target cells, a single incubation, followed by analysis without washing of the target cells.

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↗