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Biomedical subjects

R M Sharkey

Publications and source records attributed to R M Sharkey.

At least 127 records · Page 7Linked to original sources
PubMed1988

Reduction of radioantibody-induced myelotoxicity in hamsters by recombinant interleukin-1.

Recombinant human interleukin 1 (IL-1) administered i.p. to tumor-bearing hamsters results in a dose-dependent 2- to 5-fold increase in total peripheral white blood cells. These levels remain elevated for 2 to 3 wk and then decline to base-line levels. Pretreatment of animals with similar doses of IL-1 prevents radioimmunotherapy-induced destruction of the radiosensitive hematopoietic system. Furthermore, recovery from radio-immunotherapy-induced myelosuppression is possible if animals are given IL-1 1 wk after radioimmunotherapy treatment. Thus, both protection and rescue from the hematopoietic damage associated with radioantibody treatment are feasible by pre- or posttreatment with IL-1.

Animals↗
PubMed1988

Site-specific linkage of methotrexate to monoclonal antibodies using an intermediate carrier.

The site-specific conjugation of methotrexate, 4-amino-N10-methylpteroylglutamic acid, to a monoclonal anti-carcinoembryonic antigen (CEA) antibody, using an intermediate amino-dextran carrier system, resulted in a ratio of 30-50 molecules of MTX per molecule of immunoglobulin. The immunoreactivity of the conjugate was analyzed using flow cytometry or a competitive binding assay, which showed that the conjugate has significant retention of the antigen-binding activity. The pharmacokinetic behavior of the immunoconjugate in BALB/c mice and tumor localization in hamsters indicated that the conjugate remained in the circulation with higher concentration than free antibody, and could recognize the tumor as efficiently as the unconjugated antibody. The high degree of drug incorporation with retained immunoreactivity makes this method preferable to direct antibody conjugation.

Animals↗
PubMed1988

Radioimmunotherapy of human colonic cancer xenografts with 90Y labeled monoclonal antibodies to carcinoembryonic antigen.

Monoclonal antibodies (MAbs) to carcinoembryonic antigen (CEA) or alpha-fetoprotein (AFP) were conjugated with diethylenetriaminepentaacetic acid and radiolabeled with 90Y at a specific activity of 4.0-6.0 mCi/mg. Approximately 50% of the radiolabeled anti-CEA antibody (90Y-labeled NP-2) bound to an immunoadsorbent containing CEA while analysis by high performance liquid chromatography revealed that 95-98% of the 90Y was associated with immunoglobulin. Less than 5% of the 90Y dissociated from either MAb after incubation in plasma for 48 h at 37 degrees C. After injection into nude mice, 98% of the circulating radioactivity remained associated with antibody and no loss of immunoreactivity was observed at 3 days. To evaluate 90Y-labeled NP-2 as a therapeutic agent, varied doses (10-100 microCi) were administered as a single i.v. injection into groups of nude mice bearing s.c. implants (0.3-0.4 g) of a CEA-producing human colonic cancer xenograft, GW-39. At the 10-microCi dose, no inhibition of tumor growth was observed. After 28 days, tumor growth was inhibited by as much as 77% in mice treated with 50 microCi of 90Y-labeled NP-2 as compared to tumor growth in control animals given 90Y-labeled anti-AFP. Doses higher than 50 microCi (75 and 100 microCi) were toxic to most of the animals, killing them within 2-3 weeks after administration. Marked suppression of circulating leukocytes was observed with 20 and 50 microCi by 1-2 weeks postinjection, but they returned to normal levels 3-4 weeks later. These studies show that treatment with 90Y-labeled MAbs against CEA can produce significant antitumor effects. However, toxicity to the bone marrow may limit the therapeutic efficacy of systemically administered 90Y-labeled MAbs.

Animals↗
PubMed1988

Factors influencing anti-antibody enhancement of tumor targeting with antibodies in hamsters with human colonic tumor xenografts.

The injection of an antiantibody (second antibody, SA) can enhance the clearance rate of a radiolabeled antitumor antibody (primary antibody, PA) from the blood. We have studied how the dose of the SA and the timing of the SA administration influence the rate of PA clearance and thereby improve tumor/nontumor ratios. Adult hamsters bearing the carcinoembryonic antigen-producing, GW-39 human colonic tumor xenograft were given injections of 131I-labeled, goat anti-carcinoembryonic antigen antibody, and after 6, 24, or 48 h, an injection of donkey anti-goat immunoglobulin was given at SA:PA ratios of 25, 50, 100, or 200:1. In comparison to a control group of animals that were only given 131I-PA, the administration of the SA improved tumor/blood ratios regardless of the SA:PA ratio or time the SA was given. The most important factor in optimizing this procedure was the timing of the SA injection. Significantly improved tumor/nontumor ratios were found when the SA was given between 24 and 48 h after the PA in comparison to 6 h. This was because maximum accretion of radiolabeled PA in the tumor was not achieved until 24 h. At SA:PA ratios of 25:1, only tumor/blood ratios were significantly improved in comparison to the control group. In addition, at SA:PA ratios of 25:1 and 50:1, tumor/spleen and tumor/kidney ratios were lower than the control group, whereas at higher SA:PA ratios, all tumor/nontumor ratios were significantly improved. These studies suggest that for this model, a ratio of SA:PA of 100:1 or higher given at 24 to 48 h after the PA is the best combination for maximizing tumor/nontumor ratios.

Animals↗
PubMed1988

Comparison of tumor targeting of mouse monoclonal and goat polyclonal antibodies to carcinoembryonic antigen in the GW-39 human tumor-hamster host model.

We have evaluated 4 radioiodinated mouse monoclonal anticarcinoembryonic antigen antibodies (MAbs) by using the GW-39 human colorectal tumor xenograft transplanted i.m. in immunocompetent hamsters to determine whether there were any differences in their tumor localization properties. Additional comparisons were made to affinity-purified goat anticarcinoembryonic antigen antibody. Statistically significant differences were found in the percentage/g of tumor uptake and tumor/nontumor ratios among the antibodies, so that the antibodies could be ranked according to their tumor localization properties (NP-2 greater than NP-4 = goat antibody greater than NP-1 greater than NP-3). Although statistical differences were found, tumor/nontumor values generally were not distinguished by a factor of more than 1.5, suggesting that these differences may not be biologically significant. F(ab')2 fragments of NP-2 were found to be superior to NP-4 F(ab')2 fragments, giving tumor/liver and tumor/blood ratios of 16 and 11.5, respectively, within 3 days, in comparison to 5.4 and 3.8 for NP-4 F(ab')2 fragments. Mixtures of all of the MAbs or a mixture of NP-2 and NP-4 did not improve tumor localization, in comparison to NP-2 alone. These studies suggest that mixtures of these anticarcinoembryonic antigen MAbs may not afford better tumor imaging than the use of a certain single antitumor MAb.

Animals↗
PubMed1987

Radioimmunotherapy of the GW-39 human colonic tumor xenograft with 131I-labeled murine monoclonal antibody to carcinoembryonic antigen.

We have investigated the therapeutic efficacy of a single injection of 131I-labeled murine mouse monoclonal antibody (NP-4) against carcinoembryonic antigen using the human colonic tumor xenograft, GW-39, grown in the cheek pouches of adult hamsters. Therapeutic efficacy was dependent on the dose of radioactivity, the specificity of the antibody for the tumor, and the size of the tumor when the radioantibody was administered. A dose of 1 mCi of 131I-labeled NP-4 given 1 day after tumor transplantation completely inhibited the growth of 6 of 11 tumors over a 12-week period, and histological evidence indicated that viable tumor was absent in the tissue remaining at the injection site. Lower doses (0.5 mCi) of 131I-labeled NP-4 inhibited tumor growth over 90% in comparison to untreated animals, but the tumors eventually resumed growth. Delaying the administration of radioantibody for 4 or 7 days after tumor transplantation significantly reduced the therapeutic efficacy. Although the same dose of 131I-labeled irrelevant immunoglobulin G also inhibited tumor growth, 131I-labeled NP-4 was generally 2-3 times more effective in reducing tumor growth than was the control IgG. There was a 13% loss in body weight within 7 days after treatment with 1 mCi, but all the animals regained their weight by day 14, indicating that the level of radioactivity was tolerated well. Dosimetric calculations predicted that over 14 days a dose of nearly 2400 rads was delivered to the tumors with 131I-labeled NP-4. These results confirm our previous studies that 131I-labeled antibody can effectively inhibit tumor growth, but suggest that radioantibody therapy is most effectively administered when there is a low tumor burden.

Animals↗
PubMed1987

Antibody protein dose and radioimmunodetection of GW-39 human colon tumor xenografts.

This study investigates the influence of antibody protein dose on the radioimmunodetection of a CEA-producing, human colonic tumor xenograft (GW-39) using affinity-purified goat anti-carcinoembryonic antigen (CEA) antibody and a murine monoclonal anti-CEA antibody (NP-2). Hamsters bearing GW-39 tumors were given an equal mixture of 131I-labelled antibody and 125I-labelled irrelevant IgG at doses varying from 0.01 to 1.0 mg (0.1 to 10 mg/kg body weight) for each antibody preparation. No differences were found in the percentage of antibody in the tumor or the clearance rate from the blood as the antibody dose was increased. The concentration of antibody in the tumor increased proportionally with the antibody dose and maintained a linear relationship with increasing dose, indicating that antigenic sites in the tumor were not saturated with antibody. The concentration of irrelevant IgG in the tumor also increased proportionally as the dose was increased, but the concentration of irrelevant IgG in the tumor was less than the antibody and was removed more rapidly from the tumor than the antibody. By considering the amount of irrelevant IgG in the tumor as a measure of the amount of antibody non-specifically bound, we determined that there was no change in the amount of antibody in the tumor between days 3 and 7, and the amount of antibody increased uniformly for both the tumor and non-tumor tissues, resulting in no improvement in the tumor/non-tumor ratios with increasing antibody dose. External scintigraphy verified that the dose of the antibody did not influence tumor imaging. Thus, tumor accretion of antibody in this model is not dependent principally on the antibody protein dose, and other factors such as accessibility to antigen and antibody metabolism may play important roles in regulating the uptake of antibody in tumor.

Animals↗
PubMed1987

Relationship of radioantibody localization and cell viability in a xenografted human cancer model as measured by whole-body autoradiography.

The simultaneous distribution of monoclonal 131I-labeled anti-carcinoembryonic antigen (CEA) immunoglobulin (IgG) (NP-2) or 131I-labeled irrelevant myeloma IgG (Ag8) and [3H]thymidine was studied in hamsters bearing transplants of the GW-39 human colon carcinoma by qualitative double-tracer whole-body autoradiography. Autoradiography showed that large solid GW-39 tumors are characterized by heterogeneity of radioantibody retention and uneven [3H]thymidine accumulation, reflecting zonal variations in antibody reactivity and tumor cell proliferation, respectively. The autoradiographic images showed that both 131I-labeled-monoclonal antibody and control 131I-labeled IgG targeted nonproliferating tumor zones, suggesting a mechanism of nonspecific tumor uptake of radioantibodies in these areas. Absence of tumor center labeling with [3H]thymidine, associated with cellular necrosis, was confirmed by histology and microautoradiography in separate animal studies. In confirmation of earlier reports, 131I-labeled anti-CEA monoclonal antibody gave higher tumor-to-non-tumor labeling patterns than did control 131I-labeled IgG, at both 3 and 7 days following treatment. Immunohistochemical localization of CEA in GW-39 tumors with necrotic centers showed the presence of CEA in nonviable cells, but CEA antigen concentrations were diminished as compared to cells located in the tumor's periphery. The results indicate that double-tracer whole-body autoradiography is well suited for studying the kinetics of radioantibody localization in relation to regional tumor cell viability.

Animals↗
PubMed1987

Anti-antibody enhancement of iodine-131 anti-CEA radioimmunodetection in experimental and clinical studies.

Imaging of tumors with radiolabeled antibodies, especially when located in the blood-rich visceral organs, may be improved through administration of a second antibody directed against the primary tumor-associated antibody. In hamsters bearing a human colonic carcinoma xenograft producing carcinoembryonic antigen (CEA), we injected donkey anti-goat IgG 24 hr after administration of 131I-labeled goat anti-CEA IgG and achieved enhanced tumor imaging 24-48 hr later, with a significant relative decrease of radioactivity in blood and all major organs except the spleen. In seven of nine patients, this method of anti-antibody clearance of nontargeted radioactive murine monoclonal antibodies revealed sites of cancer, including liver metastases. Characterization of radioactivity in the plasma before and after administration of the second antibody confirmed that complexes were quickly formed between primary and secondary antibodies, and imaging of the patients revealed a rapid uptake of radioactivity in the liver at 2 hr that dissipated within 24 hr. Radioactivity in the spleen gradually increased over time. The method of anti-antibody immunological enhancement of cancer imaging is feasible and may reveal tumor sites missed by conventional imaging.

Animals↗
PubMed1986

A human colon cancer metastasis model for radioimmunodetection.

One important issue in radioimmunodetection is how well the current methods can locate and disclose small metastatic foci in visceral sites. We have developed a human colonic tumor metastasis model by surgically implanting GW-39 tumor cells in the liver of unconditioned hamsters. Tumors were produced in 71 of 73 animals and were macroscopically apparent within 1 wk. In addition, multiple nodular lung metastases of GW-39 were found in about 80% of the animals given implants of tumor in the liver, but implantation of tumor in the spleen failed to show lung metastases even after 4 wk. Hamsters bearing GW-39 liver and cheek pouch grafts or normal hamsters were given injections of a mixture of 131I-labeled anti-carcinoembryonic antigen antibody and 125I-labeled irrelevant immunoglobulin G. After 7 days, tumor was localized by external scintigraphy without subtraction techniques in both the liver and cheek pouch, but even in animals with extensive lung metastases we failed to unequivocally detect tumor in the lungs by external imaging or by comparing tissue counting data from uninvolved and tumor-bearing lungs. However, whole-body autoradiography confirmed specific localization of anti-carcinoembryonic antigen antibody in the tumors at all sites indicating that tissue counting and external imaging were not sensitive enough to reveal micrometastatic tumors. Thus, the current methods used for this model appear to be useful for further investigation of the radioimaging of tumors growing in visceral organs.

Animals↗
PubMed1986

Quantitative whole-body autoradiography of radiolabeled antibody distribution in a xenografted human cancer model.

Quantitative whole-body autoradiography (WBAR) was used to study the biodistribution of goat anti-carcinoembryonic antigen and normal goat IgG, each labeled with 125I, in hamsters bearing the carcinoembryonic antigen-producing GW-39 human colonic carcinoma xenograft. Comparisons between computer-assisted videodensitometric profiles of WBARs and tissue radioactivity counts were made at 1, 3, and 7 days following administration of the radiolabeled IgGs. The results indicated that maximal tumor accretion of the radiolabeled antibody and normal IgG occurred within 1-3 days, with a marked selective accretion of antibody in the tumor being evidenced at 3-7 days because of clearance of normal IgG. Radioactivity derived from antibody IgG showed 6.5 to 118.7 times that found in other tissues, as measured by videodensitometry, whereas organ radioactivity counting revealed ratios of only 6.7 to 29.6. Specificity of tumor-cell accretion of the radiolabeled antibody was confirmed by microscopic autoradiography, showing intense labeling of the proliferating perimeters of GW-39 tumors. WBAR was found to have a resolution of 0.10 to 0.25 mm in 100-g hamsters, which appears to be greater than the resolving power of external body imaging by gamma camera scintigraphy. These studies suggest the use of WBAR and microautoradiography to complement external imaging methods for the analysis of antibody distribution and localization in cancer radioimmunodetection models.

Animals↗
PubMed1984

Neutron-capture therapy of human cancer: in vivo results on tumor localization of boron-10-labeled antibodies to carcinoembryonic antigen in the GW-39 tumor model system.

Antibody against carcinoembryonic antigen (CEA) was conjugated with p-[1,2-dicarba-closo-[1-3H]do-decaboran(12)-2-yl] benzenediazonium ion by an azo-coupling reaction, resulting in 30 boron atoms per IgG molecule with no loss of antibody protein. Antibody immunoreactivity was not appreciably affected by this conjugation and was stable after incubation in vitro in hamster plasma for 24 hr. The efficacy of the boron-conjugated anti-CEA IgG for localizing selectively in CEA-containing human colonic carcinomas propagated in the hind leg musculature of hamsters was evaluated by labeling the antibodies with 131I and determining distribution of the radioactivity in vivo. The results show that the boron-conjugated antibodies retain selective localization in the tumors, thus indicating their suitability for transporting boron-10 to tumors for use in neutron-capture therapy of cancer.

Antibodies, Neoplasm↗
PubMed1984

Second antibody clearance of radiolabeled antibody in cancer radioimmunodetection.

The imaging of tumors using radiolabeled antibodies previously has required the implementation of computer-assisted subtraction techniques to reduce background radioactivity. A decrease in radioactivity in the blood of hamsters bearing human colonic tumor xenografts has been achieved by administering a second antibody directed against a radiolabeled primary antibody to carcinoembryonic antigen (CEA). This method was found to reduce the level of blood radioactivity by a factor of 4 within 2 hr after injection of the second antibody and to enhance tumor/nontumor ratios within 24 hr. Unlike liposomally entrapped second antibody, the primary anti-CEA antibody did not show increased accretion of radioactivity in the liver, spleen, or other major organs. These results suggest that administration of a second antibody alone may improve tumor imaging with a radiolabeled antitumor antibody.

Animals↗
PubMed1980

Comparison of the sensitivity of the indirect, antibody-conjugated and the triple-bridge immunoperoxidase methods for immunohistochemical detection of carcinoembryonic antigen.

A comparison between two immunoperoxidase staining procedures, a triple-bridge and an indirect, antibody-conjugated method, was made to determine the relative sensitivity of each technique in the detection of carcinoembryonic antigen (CEA) in routine tissue sections. The enzyme-antibody conjugates for the indirect procedure were prepared according to the method of Nakane and Kawaoi (1974). The indirect, antibody-conjugated method, proved to be slightly more sensitive than the triple-bridge by two criteria. First, CEA could be localized using higher dilutions of the primary antiserum by the indirect technique, and secondly, tissues were shown to stain for CEA in specimens with lower tissue CEA levels by the indirect procedure than by the triple-bridge method. The preparation of enzyme-antibody conjugates is a relatively simple procedure and, in addition, the conjugates will remain stable when kept frozen or at 4 degrees C. Background staining due to non-specific interaction of the conjugate with the tissue can be eliminated easily by incubation with normal serum. These results indicate that the indirect, antibody-conjugated method can be used to enhance the staining of CEA in routine tissue sections.

Antibodies, Anti-Idiotypic↗
PubMed1979

Carcinoembryonic antigen in carcinoma of the uterine cervix. 2. Tissue localization and correlation with plasma antigen concentration.

Immunoperoxidase staining for carcinoembryonic antigen (CEA) was performed on the tumors of 241 patients with invasive carcinoma of the cervix. Positive tissue staining indicative of a CEA concentration of at least 3 microgram/gm was present in 154 tumors (63%) as opposed to 0 of 30 specimens of normal cervix (p less than .001). Plasma CEA values were obtained at the time of tissue staining on all patients. Plasma CEA concentration was related more directly to total tumor burden (tumor CEA content x extent of disease) than to tumor CEA concentration alone. Progressively rising plasma CEA levels predicted recurrent disease in over 80% of patients whose tumors stained positively for CEA. In contrast, serial plasma CEA values correlated positively with clinical disease status in only 28% of patients whose tumors were devoid of CEA. Immunoperoxidase staining of tissue specimens identifies those patients whose tumors contain high levels of CEA and who therefore should benefit most from subsequent plasma antigen determinations.

Adenocarcinoma↗
PubMed1978

Immunoperoxidase detection of carcinoembryonic antigen: an overview.

The advent of immunoperoxidase histochemistry techniques has allowed the more convenient visualization by light microscopy of antigenic cellular constituents. Application of the unlabeled and labeled antibody enzyme methods to the localization of carcinoembryonic antigen in conventionally prepared tissue specimens has revealed the feasibility of using immunoperoxidase techniques in routine diagnostic pathology. The methods involved are well defined and once antibody specificity and antigen stability are determined, they are adaptable to the identification of other immunological markers that may appear in malignant tissue specimens.

Antibody Specificity↗