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Biomedical subjects

A C Morgan

Publications and source records attributed to A C Morgan.

At least 55 records · Page 3Linked to original sources
PubMed1986

Detection of the intracellular ras p21 oncogene product by flow cytometry.

Rapid identification of the expression of oncogene products in specific cell types could potentially be useful in the diagnosis and treatment of human malignancy. We have now observed that through the use of lysolecithin permeabilization and fluorescence-activated flow cytometry, cells expressing high levels of the v-Ha-ras oncogene product, p21, can readily be distinguished from the nontransformed parent cells in a rapid and quantitative manner.

Animals↗
PubMed1986

Human melanoma-associated antigens: analysis of antigenic heterogeneity by molecular, serologic and flow-cytometric approaches.

The relationship of antigenic heterogeneity to the epitope recognized by an antibody was examined with monoclonal antibodies to human melanoma-associated antigens. Expression of the human melanoma-associated antigens, 250-Kd glycoprotein/proteoglycan and p97, was examined quantitatively by flow cytometry on fresh cell suspensions of human melanoma. Percent positive cells and mean fluorescence intensity were consistently higher with antibody 9.2.27 to the 250-Kd glycoprotein/proteoglycan than with antibody to p97. In addition, assessment of percent positive cells in multiple skin lesions biopsied from individual patients indicated that in 26 of 30 lesions, greater than 90% of the cells stained positively with 9.2.27. This relative lack of antigenic heterogeneity with antibody 9.2.27 contrasted with previous reports which showed considerable antigenic heterogeneity with other antibodies to the 250-Kd glycoprotein/proteoglycan. The explanation for this distinction was sought by quantitative flow cytometric and sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) techniques. Comparison by flow cytometry and immunoperoxidase of three antibodies, which recognized distinct epitopes of the 250-Kd glycoprotein/proteoglycan, indicated that 9.2.27 reacted more intensely with cultured cells and tissue sections than other antibodies to the same antigen. Examination by SDS-PAGE indicated that 9.2.27 could immunoprecipitate a larger proportion of 250-Kd glycoprotein molecules than other antibodies. In addition, immunodepletion experiments in gels indicated that the 9.2.27 determinant was present on a higher proportion of 250-Kd glycoprotein molecules than PG-2 antibody to a separate determinant. It is likely that 9.2.27 antibody displays less antigenic heterogeneity because its epitope is represented on a higher proportion of the antigen molecules. Thus, not only the nature of the antigen but also the epitope recognized by an antibody influences the degree of antigenic heterogeneity.

Antibodies, Monoclonal↗
PubMed1986

Dynamic interaction of 111indium-labeled monoclonal antibodies with surface antigens of solid tumors visualized in vivo by external scintigraphy.

Two 111indium-labeled murine monoclonal antibodies (MoAb), D3 and 9.2.27, directed to tumor antigens of L-10 hepatocarcinoma and human melanoma, respectively, selectively localized antigen-positive target cells in guinea pigs and nude mice. The fate of MoAb differed in the two antigen-antibody systems after reacting with their corresponding tumor antigens in vivo as reflected by patterns of distribution and turnover in vivo. The 9.2.27 localized in melanoma xenograft in nude mice after intravenous administration with slow loss from tumor but more rapid loss from normal tissues and thus demonstrated optimal imaging of small tumors (approximately equal to 5 mm) between 3 and 6 days after injection of the radiolabeled antibody. In contrast, D3 demonstrated a biphasic localization in guinea pig L-10 hepatocarcinoma with a maximal activity on the 2d day after administration and showed rapid loss from both tumor and normal tissues. Nonspecific localization of antibodies in liver and in kidney was found both in syngeneic (nude mice) and xenogeneic (guinea pig) hosts but was more pronounced in the xenogeneic species. These results indicate that the nature of the antigen-antibody interaction may be of importance in selecting MoAb for both diagnosis and therapy of malignant diseases.

Animals↗
PubMed1986

Human melanoma cell lines showing striking inherent differences in sensitivity to immunotoxins containing holotoxins.

The in vitro sensitivity of human melanoma cell lines to conjugates of whole abrin or ricin linked through disulfide bonds to the monoclonal antimelanoma antibody 9.2.27 was studied. After passage of the conjugates through a Sepharose 4B column to remove molecular species with exposed binding sites on their B-chains, toxicity of the conjugates to different melanoma cell lines and nonmelanoma tumor lines was assessed by measuring their ability to inhibit cellular protein synthesis. The abrin conjugate was far more toxic to the target cells than the corresponding ricin conjugate. The 8 melanoma cell lines studied differed widely in their sensitivities to the abrin conjugate. The differences were associated with concomitant large differences in the sensitivities of the cells to the native toxins, and the significance of the level of the antigen expression became apparent only when the sensitivities of the different cell lines were normalized with respect to their sensitivity to native abrin. The observed relationship could not be accounted for by unspecific binding via the B-chain binding site of the immunotoxin. The differential sensitivity of the melanoma cell lines to the immunotoxin seems to be related to inherent differences between the cells in their ability to internalize and to process immunotoxins and toxins. The findings may have considerable practical implications.

Abrin↗
PubMed1985

Quantification of soluble E-receptor in the serum of patients with various diseases and its accompanying in vitro immunosuppression in neoplasia.

Evidence in the literature indicates that soluble E-receptor in the serum may modulate T-dependent immune response. We have developed a solid-phase radioimmunoassay to measure the soluble form of E-receptor from various sources. The assay detects solubilized antigens derived from E-receptor-bearing T lymphocytes and not with non-E-receptor-bearing B lymphocytes. The sensitivity limit of the assay is 0.1 ng/ml of purified E-receptor antigen. Using this assay, one can show that the T-cell mitogen phytohaemagglutinin stimulated both lymphocytes and cells of the resting human T-cell lymphoma cell line Jurkat to shed or secrete E-receptor into the culture medium. Results of the radioimmunoassay performed on human sera indicated that some patients with Hodgkin's disease, melanoma, sarcoma, or acute or chronic lymphocytic leukaemia had elevated levels of this antigen in their serum, whereas normal human sera registered lower levels. Elevated levels of the soluble form of E-receptor in the serum were suggestive of an in vitro assessment of their immunosuppressive activity. These results indicate that activation of T-cell immunity in vivo may result in humoral immunosuppression.

Animals↗
PubMed1985

Human anti-murine immunoglobulin responses in patients receiving monoclonal antibody therapy.

Human anti-murine immunoglobulin responses were assessed in serum from three groups of patients receiving murine monoclonal antibody therapy. Each of the three patient groups responded differently. Chronic lymphocytic leukemia patients demonstrated little or no preexisting murine immunoglobulin G-reactive antiglobulin prior to treatment, while the cutaneous T-cell lymphoma and melanoma patients demonstrated preexisting antiglobulin levels in the same range as those demonstrated in healthy controls. None of 11 chronic lymphocytic leukemia patients receiving the T101 monoclonal antibody demonstrated an antiglobulin response, whereas all four of the cutaneous T-cell lymphoma patients receiving the same antibody developed increased levels of antiglobulins. Three of nine malignant melanoma patients receiving the 9.2.27 monoclonal antibody showed an increase in antiglobulin titers. In patients developing antiglobulin responses, the response was rapid, typically being detectable within 2 weeks. The antiglobulins were primarily immunoglobulin G and, with the exception of a single melanoma patient in whom the response appeared to have a substantial 9.2.27-specific component (i.e., antiidiotype), were cross-reactive with most murine immunoglobulin G preparations tested. This pattern of results suggested that the antiglobulin was a secondary immune reaction with elevation of the levels of preexisting antiglobulin which was cross-reactive with the mouse antibody administered. While the presence of serum antiglobulin would be expected to present major complications to monoclonal antibody therapy, no clinical toxicity related to antiglobulin responses was observed in these patients, and no inhibition of antibody localization on tumor cells was seen.

Antibodies, Anti-Idiotypic↗
PubMed1985

The generation of monoclonal anti-idiotype antibodies to human B cell-derived leukemias and lymphomas.

We developed murine anti-idiotype monoclonal antibodies for each of four patients with B cell-derived leukemias and lymphomas. Idiotypic immunoglobulin was isolated from mouse X human tumor-cell hybridomas or from patients' serum and was used to immunize mice for the development of murine anti-idiotype monoclonal antibodies. Each patient's anti-idiotype antibodies demonstrated reactivity restricted to the immunizing immunoglobulin, thereby limiting their therapeutic utility to a single individual. In addition, we isolated isotype switch variants of hybridomas producing monoclonal anti-idiotypic antibody. The restricted specificity of these antibodies was found to be of value for the analysis of the extent of malignant B cell infiltration in a variety of tissues from several patients. Large populations of idiotype-bearing cells were detectable in biopsy specimens from patients K.T. and L.H. In contrast, although bone marrow specimens from patient G.D. were apparently devoid of morphologically abnormal cells, a small, highly fluorescent population of cells was demonstrable underscoring the potential utility of these antibodies for posttreatment evaluation as well as for therapy. In a fourth patient, H.M., anti-idiotype antibodies developed against the circulating macroglobulin isolated from his plasma failed to react with either his circulating or bone marrow hairy cell leukemia cells. However, examination of an enlarged inguinal lymph node revealed the presence of a large number of idiotype-bearing cells. Thus, the presence of two distinct malignant B cell clones were discovered in this individual through the use of anti-idiotype monoclonal antibodies. Anti-idiotype antibodies, therefore, represent a highly specific tool for the evaluation and potential therapy of B cell malignancies in individual patients.

Adult↗
PubMed1985

Intratumor localization of monoclonal antibody in patients with melanoma treated with antibody to a 250,000-dalton melanoma-associated antigen.

Antibody localization at the tumor site was assessed in melanoma patients who received the murine monoclonal antibody 9.2.27. Antibody was administered twice weekly in escalating doses from 1 to 500 mg. Localization was assessed by biopsies of cutaneous and lymph node lesions obtained 24-96 hours following therapy. The percentage of tumor cells that bound the antibody in vivo was dose dependent, with similar findings obtained by either flow cytometry or immunoperoxidase staining techniques. Little or no in vivo binding of the 9.2.27 antibody to tumor cells was found following 1- and 10-mg doses, whereas all specimens demonstrated in vivo binding of the antibody following 200- and 500-mg doses. Fluorescence staining intensity, as quantitated by flow cytometry, was employed to determine the degree of in vivo saturation of antibody binding sites following therapy. The degree of saturation was found to vary substantially among patients: Some patients demonstrated nearly 100% saturation after 200-mg doses of 9.2.27 antibody, whereas others demonstrated only half maximal saturation after doses of 500 mg. Although immunoperoxidase staining provided important qualitative information regarding the distribution of antigen and antibody within the tumor, these studies demonstrated the usefulness of immunofluorescent flow cytometry for quantitative assessment of antibody localization in solid tumors and provided information necessary for the design of further trials of monoclonal antibodies and immunoconjugates.

Antibodies, Monoclonal↗
PubMed1985

Immunohistochemical detection of the Ca antigen in normal and tumor tissues of humans by use of Ca1 monoclonal antibody.

The Ca1 monoclonal antibody was used to detect Ca antigen in paraffin sections with the use of a two-stage indirect immunoperoxidase technique. A range of normal and malignant human tissues was examined. The antibody reacted with squamous cell carcinomas, small cell carcinomas, adenocarcinomas, ductal carcinomas, and anaplastic carcinomas from gastrointestinal, lung, and breast tissues. Melanomas were negative. Reactivity was also observed against normal tissues: urinary transitional epithelium, fallopian tube epithelium, breast ducts, sweat glands, sebaceous glands, alveolar epithelium, bile duct, gallbladder, kidney tubules, and some digestive tract epithelial cells. Although the study confirms earlier reports that Ca1 is a marker for some normal, nonciliated epithelial cells and for epithelial and some other cancers, a more widespread distribution for normal tissues was found.

Antibodies, Monoclonal↗
PubMed1985

Radiolocalization of xenografted human malignant melanoma by a monoclonal antibody (9.2.27) to a melanoma-associated antigen in nude mice.

A murine monoclonal antibody (9.2.27), directed to a Mr 250,000 glycoprotein-chondroitan sulfate proteoglycan complex, was radiolabeled with 125I and assessed for radiolocalization in tumor and normal tissues of normal and tumor-bearing nude mice. The 125I-9.2.27 localized in vivo preferentially in Mr 250,000 antigen-expressing human melanomas (FMX-Met, SESX) but not in low antigen-expressing tumors (LOX-L) xenografted in nude mice. The imaging index of tumor cells was positively correlated with the antigen density of the various melanoma cell lines as measured by flow cytometry. The nonspecific immunoglobulin RPC-5 of the same IgG2a subclass as 9.2.27 did not specifically localize to xenografts of melanoma. The total amount of 125I-9.2.27 accumulated in the tumor was directly correlated with tumor size. However, the specific radioactivity (cpm/g) in smaller tumors was higher than that in larger tumors. Nonspecific uptake and circulating antibody levels differed between normals and tumor-bearers. The organs of the reticuloendothelial system of normal mice accumulated more labeled antibody than did those of tumor bearers, and conversely, tumor bearers had higher levels of circulating labeled antibody in the blood than normals. The circulating labeled antibody in tumor bearers was still monomeric but had no detectable antigen-binding capacity.

Animals↗
PubMed1984

Stable quantitative differences of antigen expression in human melanoma cells isolated by flow cytometric cell sorting.

The stability of expression of a membrane antigen on human FME melanoma cells was investigated by means of flow cytometric cell sorting and analysis. The melanoma-associated 250 kd antigen was strongly expressed on all cells, as recognized by binding of the monoclonal antibody 9.2.27. By flow cytometric cell sorting, cells of high and low antigen expression were isolated, and the difference in antigen expression between the two populations was examined as a function of time in culture. Immediately after sorting, the median fluorescence intensities of the two populations differed by a factor of 2.7. After the first few days in culture, much of the range in antigen expression of the parent population was regenerated. However, a lasting difference in antigen expression was established, corresponding to 50% higher density of antigen on the cells sorted for high fluorescence intensity, compared to those sorted for low intensity. After trypsin treatment, which removed the antigen from the cell surface, normal antigen expression was regained after 2-3 days in culture, with the same difference between the two populations as before the trypsin treatment. The stability of the established difference in antigen expression between the two sorted subpopulations indicates that expression of this antigen is a precisely controlled, heritable characteristic of the FME melanoma cells.

Antibodies, Monoclonal↗
PubMed1984

Detection of intracytoplasmic antigens by flow cytometry.

A new technique is described for the detection of intracellular antigens by immunofluorescence and flow cytometry. The technique utilizes lysolecithin (lysophosphatidylcholine), a naturally occurring phospholipid, to permeabilize cell membranes and allow antibodies to reach intracellular antigens. The technique is rapid and sensitive, and retains sufficient integrity of the cells being treated to enable differentiation of cell types on the basis of light scatter (e.g., lymphocytes from monocytes). Permeabilization of cells following lysolecithin was assessed using standard techniques including trypan blue exclusion, propidium iodide staining, and hydrolysis of fluorescein diacetate. Lysolecithin treatment was accompanied by only minimal increases in non-specific background fluorescence, and no increase in autofluorescence. Our studies have demonstrated that lysolecithin treatment of human mononuclear cell populations permits flow cytometric analysis of cytoskeletal structures, including intermediate filaments, as well as cytoplasmic immunoglobulin. Studies currently in progress in our laboratory have demonstrated broad intracellular reactivity with some monoclonal antibodies identifying leukocyte differentiation and tumor-associated antigens. These findings contrast with the more restricted expression of these antigens on the cell surface and demonstrate not only the value of the lysolecithin technique but also the importance of the study of intracellular antigens in our overall understanding of the specificity, distribution, synthesis, and function of cellular antigens.

Antigens↗
PubMed1984

Monoclonal antibodies in the treatment of cancer: preliminary observations and future prospects.

The need for improved specificity in cancer therapy is apparent. With the advent of monoclonal antibodies, the possibility of specifically targeted therapy is here. Early trials with monoclonal antibody in experimental animals and in man have demonstrated antibody can travel to specific tumor sites and localize on or around the tumor cells displaying antigens to which the antibody is directed. This evidence of specific targeting, along with early evidence of therapeutic efficacy for monoclonal antibodies and antibody immunoconjugates with drugs, toxins and isotopes, is encouraging. Some preliminary clinical observations from two monoclonal antibody trials are presented and the current status of clinical trials with monoclonal antibodies is reviewed.

Animals↗
PubMed1984

Monoclonal antibodies to human colorectal tumor-associated antigens: improved elicitation and subclass restriction.

Monoclonal antibodies to tumor-associated antigens (TAA) of human colorectal cancer were elicited using immunosorbents of lectins combined with peripheral protein extracts of xenografted colon adenocarcinoma. This method of immunization was compared with whole cells from surgical specimens and to crude membranes from xenografted tumors. The immunosorbent immunogens were superior to the other immunogens in three ways: (1) the number of hybrids reactive with colon tumor cells or extracts, but not with lymphoid cells or extracts, (2) the number of stable hybrids after cloning, and (3) the number of hybridoma clones reactive with tissue sections of colon tumors, but not normal colonic mucosa. In addition, lectin immunosorbents elicited primarily IgG antibodies, especially IgG3, with almost 50% of the clones of interest reacting to seemingly less immunogenic glycoproteins. The improved elicitation of monoclonal antibodies to TAA by the use of lectin immunosorbents and peripheral protein extracts has considerable potential for generating reagents useful in diagnosis and therapy of human tumors.

Animals↗
PubMed1984

Monoclonal antibody therapy of malignant melanoma: in vivo localization in cutaneous metastasis after intravenous administration.

The murine antimelanoma monoclonal antibody, 9.2.27, was administered intravenously to eight patients with metastatic malignant melanoma. Biopsies of metastatic nodules clearly demonstrate the selective localization of this antibody on the melanoma cell surface with a dose-response relationship to the quantity of administered antibody. The antibody infusions were clinically well tolerated and the pharmacokinetics of the antibody and the antiglobulin responses are described. This study indicates that murine monoclonal antibodies have potential as selective targeting agents in the design of future therapeutic trials using monoclonal antibodies or conjugates thereof in the treatment of cancer.

Adult↗
PubMed1984

alpha 2-macroglobulin production by cultured human melanoma cells.

alpha 2-Macroglobulin (alpha 2M) was identified in chemically defined spent medium of cultured human melanoma cells. This wide-spectrum protease inhibitor was subsequently shown to be synthesized and was secreted by 10 of 13 cultured melanoma cells but not by neoplastic cells of other histologic origins (0/5 breast, 0/2 colon, 0/2 lung, 0/2 glioblastomas, 0/1 neuroblastoma, 0/4 lymphoid). alpha 2M was also produced by one strain of fetal lung fibroblasts, as was previously shown, but not by two strains of normal fetal uveal melanocytes or two strains of fetal skin fibroblasts. Biochemical characterization of melanoma alpha 2M indicated that it has a similar tetrameric structure but is smaller in size than authentic serum alpha 2M. Preliminary studies indicated that melanoma alpha 2M can bind to protease and has possible functional capability.

Cell Line↗
PubMed1984

Measurement of a monoclonal antibody-defined, melanoma-associated antigen in human sera: correlation of circulating antigen levels with tumor burden.

Quantities of a 100,000-mol wt human melanoma-associated antigen (MAA), defined by both monoclonal and polyclonal xenoantibodies, were measured in sera of 32 patients with malignant melanoma and 15 carefully documented healthy volunteers by use of an amplified sandwich enzyme-linked immunoabsorbent assay. Detectable levels of MAA were found in all normal adult sera. Five of 10 patients with stage III and 9 of 16 patients with stage IV disease had antigen levels that exceeded. the 95th percentile of serum levels in the normal donors (P less than .001). Elevated levels of the 100K MAA were associated with evidence of residual tumor (P less than .008): Only 3 of 13 patients with no evidence of tumor had abnormal values, whereas 9 of 16 patients with evident tumor had increased serum levels. Levels of the 100K MAA were unrelated to the levels of soluble immune complexes as detected by the fluid-phase C1q binding test. Molecular evaluation of the 100K MAA in serum indicated that the molecule associated with albumin in a strong, noncovalent manner. When the complex was dissociated by treatment with sodium dodecyl sulfate, the 100K MAA in serum comigrated with the molecule from spent culture medium of human melanoma cells. Antigen levels in sera were measured under these dissociating conditions. These studies suggest that measurement of the 100K MAA may be useful in monitoring tumor burden in patients with malignant melanoma.

Antibodies, Monoclonal↗