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D J Buchsbaum

Publications and source records attributed to D J Buchsbaum.

At least 55 records · Page 3Linked to original sources
PubMed1997

Localization of iodine-125-mIP-Des-Met14-bombesin (7-13)NH2 in ovarian carcinoma induced to express the gastrin releasing peptide receptor by adenoviral vector-mediated gene transfer.

UNLABELLED: The gastrin releasing peptide receptor (GRPr) has a high affinity for the 14 amino acid bombesin peptide. For this analysis, [125I]-Tyr4-bombesin was compared with [125I]-mIP-bombesin (a seven amino acid bombesin analog) for in vitro binding and internalization into tumor cells and for tumor localization in vivo. Also, a recombinant adenoviral vector (AdCMVGRPr) was used for gene transfer to induce the expression of GRPr in human ovarian cancer cells for binding and tumor localization with these radiolabeled peptides. METHODS: [125I]-mIP-bombesin was synthesized and compared with [125I]-Tyr4-bombesin in internalization assays using BNR-11 cells (mouse fibroblast cells stably transfected with GRPr) over a 24-hr period. In vitro binding assays used BNR-11, and A427, HeLa and SKOV3.ip1 human cancer cells, which were either uninfected or infected with AdCMVGRPr. Biodistribution studies were performed in normal BALB/c mice and in athymic nude mice bearing orthotopic SKOV3.ip1 ovarian cancer tumors. The SKOV3.ip1 tumors were induced to express GRPr with the AdCMVGRPr adenoviral vector. RESULTS: Internalization assays showed that [125I]-Tyr4-bombesin was rapidly internalized and catabolized at 37 degrees C with approximately 10% of the radioactivity remaining intracellularly at 4 hr, compared with approximately 30% with [125I]-mIP-bombesin. HeLa, A427 and SKOV3.ip1 cells were all induced to express levels of GRPr that were higher than those seen with the positive control BNR-11 cells. Normal mice showed a lower level of radioactivity in both the blood and thyroid for [125I]-mIP-bombesin [0.26% +/- 0.10% injected dose per gram (ID/g) and 0.24% +/- 0.05% ID] than for [125I]-Tyr4-bombesin (3.5% +/- 1.6% ID/g and 5.2% +/- 4.4% ID) at 4 hr postinjection. Mice bearing intraperitoneal (i.p.) SKOV3.ip1 tumors and given AdCMVGRPr i.p. 5 days after tumor cell inoculation followed by [125I]-mIP-bombesin i.p. at day 7 showed 16.5% +/- 4.8% ID/g in tumor compared with 5.9% +/- 3.0% ID/g with [125I]-Tyr4-bombesin at 4 hr postinjection. Tumor bearing mice given saline or a control adenovirus expressing the beta-galactosidase (LacZ) gene showed significantly lower tumor uptake values of both bombesin peptides. CONCLUSION: Internalization assays showed that [125I]-mIP-bombesin has favorable characteristics compared with [125I]-Tyr4-bombesin with regards to cellular internalization and retention. The results demonstrate successful in vitro and in vivo transduction of human tumor cells with a recombinant adenoviral vector-expressing GRPr. Additionally, tumors transduced in vivo to express GRPr demonstrated significantly greater localization of [125I]-mIP-bombesin when compared with [125I]-Tyr4-bombesin.

Adenoviridae↗
PubMed1997

Adenoviral-mediated delivery of gastrin-releasing peptide receptor results in specific tumor localization of a bombesin analogue in vivo.

Radioimmunotherapy is hindered by a variety of factors linked to the utilization of monoclonal antibodies. These limitations include restricted tumor penetration as well as low levels of intratumoral antigen expression. To address the latter problem, we used a gene therapy approach to induce tumor cells to express enhanced levels of receptor with high binding affinity for a radiolabeled peptide. In this regard, a radiolabeled bombesin analogue was used in conjunction with a recombinant adenoviral vector encoding the murine gastrin-releasing peptide receptor (mGRPr). A panel of human carcinoma cell lines was infected in vitro with the recombinant adenoviral vector encoding the mGRPr vector to examine the induced binding of a 125I-labeled bombesin peptide. All cell lines examined displayed high levels of induced peptide binding, with approximately 60-80% of the radioactivity bound to the cells, in a live-cell binding assay. The human ovarian carcinoma cell line SKOV3.ip1 was chosen for in vivo analysis of radiolabeled bombesin analogue tumor localization in biodistribution and pharmacokinetic studies in athymic nude mice. Genetic induction of mGRPr in vivo resulted in selective tumor uptake of the radiolabeled peptide and high tumor:blood ratios. The biodistribution results compared favorably to those obtained with 131I-labeled e21 anti-erbB-2 monoclonal antibody in animals bearing i.p. SKOV3.ip1 tumors that endogenously express erbB-2. Thus, a novel method to combine gene transfer and radioimmunotherapy may result in augmented tumor cell targeting of radiopharmaceuticals.

Adenoviridae↗
PubMed1996

A quantitative study of radionuclide characteristics for radioimmunotherapy from 3D reconstructions using serial autoradiography.

PURPOSE: Using 131I-labeled monoclonal antibody (MoAb) data, assess the dosimetrical impact of labeling the same MoAb with 186Re or 90Y, under the assumption that the biodistribution of the radiolabeled MoAb in tumor relative to blood is independent of the radionuclide. METHODS AND MATERIALS: Radial radioactivity and dose-rate distributions at 1, 4, and 7 days postinjection were derived from three dimensional (3D) reconstructions of serial autoradiographs of LS174T human colon cancer xenografts in athymic nude mice treated with a single intraperitoneal administration of 300 microCi 131I-labeled MoAb 17-1A. Bone marrow dose was calculated taking into account energy deposited external to the bone marrow cavity due to the range of the beta particles. RESULTS: For 1 cm diameter tumors, uptake was mostly at the tumor surface for earlier postinjection times, but exhibited comparable activity levels from the surface to the core of the 7-day sample. The computed dose-rate distributions for 186Re and 90Y were more uniform than for 131I, but smaller fractions of the dose were deposited within the tumor volume due to the larger mean energies of 90Y and 186Re beta particles relative to those for 131I. However, when the tumor doses were normalized to the production of equivalent bone marrow doses, in the case of athymic nude mice, the tumor doses were calculated to be 15.3 Gy (131I), 14.1 Gy (186Re), and 12.0 Gy (90Y). For comparison, these calculations were extended to the case of human therapy, yielding tumor doses of 16.7 Gy (131I), 18.2 Gy (186Re), and 13.4 Gy (90Y). CONCLUSION: In the case of colon cancer xenografts where the MoAb uptake is initially concentrated at the tumor surface, we find a decreasing tumor dose per constant bone marrow dose for radionuclides of increasing mean beta energies and decreasing half-lives. However, a radionuclide with larger mean beta energy such as 90Y generates a significantly more uniform dose deposition within the tumor, especially concerning the core of the tumor, compared to 131I. For human therapy, a gamma component adds little to the tumor dose but increases dose to the marrow.

Animals↗
PubMed1996

Synthesis of a new class of isothiocyanatopeptide bifunctional chelating agents for coupling to monoclonal antibodies.

The preparation of a new class of isothiocyanatopeptide bifunctional chelating agents, Boc-glycyl-L-(p-NCS)phenylalanylglycylglycine ethyl ester 1, N-(S-acetylmercaptoacetyl)-L-(p-NCS)phenylalanylglycylglycine ethyl ester 2, and N-(S-acetylmercaptoacetyl)glycyl-L-(p-NCS)phenylalanylglycine ethyl ester 3, starting from Boc-L-(p-nitro)phenylalanine 5 is described. The key intermediates, nitropeptides 7, 8 and 12, were prepared by standard DCC coupling and a deprotection procedure. The nitropeptides 7 and 12 on condensation with N-succinimidyl-S-acetylthioacetate provided a good yield of the corresponding S-(acetylmercaptoacetyl)nitropeptides 10 and 13, respectively. Catalytic hydrogenolysis of compounds 8, 10 and 13, followed by thiophosgenyation gave 28-95% yield of target products 1, 2 and 3, respectively. Compounds 1-3 were conjugated to the monoclonal antibody D612 reactive with human colon carcinoma using 12/1 to 60/1 ligand to antibody molar ratios, and the conjugates were labeled with 99mTc. The in vitro cell binding results of these immunoconjugates demonstrate that they retained their antibody binding specificity.

Antibodies, Monoclonal↗
PubMed1996

Enhancement of radiolabeled antibody binding and tumor localization through adenoviral transduction of the human carcinoembryonic antigen gene.

Conventional radiolabeled antibody targeting utilized in radioimmunotherapy has resulted in limited success clinically due in part to inadequate tumor localization resulting from low expression of human tumor-associated antigens on target cells. We hypothesized that one could improve upon these limitations by genetically inducing tumor cells to express high levels of a new membrane-associated receptor with high affinity for a radioligand. As a preliminary strategy, we induced a human glioma cell line (D54 MG) to express human carcinoembryonic antigen (CEA) in vitro. To accomplish this, we constructed a recombinant adenoviral vector encoding the CEA cDNA inserted downstream of a cytomegalovirus (CMV) promoter (AdCMVCEA). D54 MG cells were transfected with AdCMVCEA or an adenoviral vector encoding lacZ reporter gene as a control (AdCMVlacZ). LS174T human colon cancer cells, known to express CEA constitutively, served as positive controls. Immunofluorescence and immunohistochemistry assays employing unlabeled anti-CEA COL-1 monoclonal antibody demonstrated expression of CEA antigen on the cell surface of transduced D54 MG cells in culture. In addition, assays utilizing 125I-labeled COL-1 indicated high binding to transduced D54 MG cells expressing CEA (4.7 +/- 0.5 x 10(5) COL-1 molecules bound per cell) as compared with minimal binding to nontransduced D54 MG cells. LS174T cells demonstrated only 2.7 +/- 0.5 x 10(6) COL-1 molecules bound per cell. Thus, AdCMVCEA was able to induce levels of cell surface CEA in target cells at a higher level than CEA-overexpressing tumor cells (P < 0.01). The efficacy of transduction of recombinant AdCMVCEA by direct intratumoral injection into D54 MG xenografts was investigated by immunohistochemical analysis, immunofluorescence and by measuring 131I-labeled COL-1 uptake through external scintigraphic imaging and biodistribution studies. Expression of CEA in the tumor xenografts by, and radiolabeled antibody tumor targeting to, AdCMVCEA transduced D54 MG xenografts was comparable to that seen with LS174T xenografts. Results of these studies indicate the potential of adenovirus-mediated delivery of targets to improve radiopharmaceutical tumor localization.

Adenoviruses, Human↗
PubMed1996

Approaches to enhance cancer radiotherapy employing gene transfer methods.

This review presents an overview and discussion of the potential synergistic strategies of radiation therapy and gene transfer for treating neoplastic disease. Topics discussed include radiation-inducible promoters coupled to genes which produce proteins that are cytotoxic or enhance radiosensitivity, employment of molecular chemotherapy approaches in conjunction with radiation therapy, and genetic induction of radiosensitization through modification of DNA repair, signal transduction, and cell cycle control genes. Additional topics discussed relate to gene transfer augmentation of radioimmunotherapy of cancer. Specifically, gene transfer methods to genetically induce tumor cells to express enhanced levels of cell surface antigens and receptors to increase radiolabeled antibody and peptide targeting and thus increase their therapeutic effect, selection of radionuclides for therapeutic ligand labeling, and computer simulation of genetic tumor-specific delivery of radiolabeled ligands are proposed.

Animals↗
PubMed1995

Experimental approaches to increase radiolabeled antibody localization in tumors.

Approaches have been developed to improve the localization of radiolabeled monoclonal antibodies (MAbs) in experimental tumors, to reduce their uptake in normal tissues, and, thus, to improve the time-dependent tumor: normal tissue (T:NT) ratios so that higher and more frequent doses of radionuclide could be used for radioimmunotherapy. These approaches involve three general strategies: (a) modifying antibodies or radiolabeling techniques; (b) increasing the clearance of radiolabeled MAbs; and (c) modifying tumor delivery, tumor antigen expression, or increasing tumor vascular permeability or blood flow. The use of animal models permits the assessment of a wide range of MAbs, radiolabeling conditions, and the efficacy of administration methods before their initial use in clinical trials. MAbs with specificity for binding to tumor-associated antigens or growth factor receptors expressed on tumor cells have been utilized in experimental studies of radiolabeled antibody targeting. Tumor-associated targets present on endothelial cells should be highly accessible to systemically administered radiolabeled MAbs. The use of indirect radio-iodination techniques and labile linker-chelates may provide an improvement in tumor retention and T:NT ratios. The addition or deletion of glycosylation to MAbs by alteration of recombinant immunoglobulin genes or by biochemical modification can alter the pharmacokinetics of blood and whole body clearance of radiolabeled MAbs. Genetically engineered chimeric or humanized MAbs have shown equivalent or greater tumor localization compared to murine MAbs. By using MAbs with greater affinity and avidity, an increase in the uptake and retention of radiolabeled MAbs in tumors and an increase in their therapeutic efficacy may be achieved. Several approaches in the administration methods of MAbs have been developed in an attempt to improve tumor localization and therapeutic results and to reduce toxicity. These approaches include: (a) predosing with unlabeled antibody before administering a radiolabeled MAb; (b) using a mixture or "cocktail" of MAbs rather than a single radiolabeled antibody; and (c) administering multiple doses of radiolabeled MAbs. Various approaches have been tested for increasing the blood clearance of radiolabeled MAbs and, thus, for increasing the T:NT ratio. It has been found that compared to intact antibody, the smaller antibody fragments (F(ab')2, Fab, or single-chain Fv) can bind to tumor cells with a more homogeneous distribution. The antibody fragments and domain deletions often have a more rapid catabolism in blood, in tumors, and in normal tissues than an intact antibody does. In general, the use of antibody fragments leads to higher T:NT ratios but a lower percentage of injected dose delivered to the tumor.

Animals↗
PubMed1995

Reconciliation of tumor dose response to external beam radiotherapy versus radioimmunotherapy with 131iodine-labeled antibody for a colon cancer model.

Reported doses of external beam radiotherapy and radioimmunotherapy (RIT) to produce equivalent therapeutic effects are inconsistent, with many proposed causes. Calculations of effective dose were performed for the case of LS174T human colon cancer xenografts, where a 60Co single fraction exposure (6 Gy) was matched with 131I-labeled 17-1A monoclonal antibody therapy (300 microCi injection, 19 +/- 2 Gy using the Medical Internal Radiation Dose uniform isotropic model). Measured three-dimensional dose-rate distributions were used to form a time-dependent description of the dose-rate nonuniformity. Included in the calculation of RIT effective dose was energy loss, dose nonuniformity, dose-rate dependence, hypoxic fraction, and cell proliferation. The calculations assumed the linear quadratic model for cell survival with alpha = 0.3 Gy-1, alpha/beta = 15 to 25 Gy, and mu = 0.46 h-1. The biologically effective dose for the single fraction 60Co exposure was 7.4 to 8.4 Gy. Estimates of dose efficiency factors consecutively applied to the RIT dose estimate were: (a) energy loss external to the tumor (x0.85); (b) effect of dose nonuniformity on cell survival (x0.65); and (c) effect of correlation of dose nonuniformity with cell proliferation rate (x1.08). The resulting effective dose for RIT was 11.4 Gy for tumor regrowth. This analysis substantially reconciles external beam radiotherapy/RIT dose-response results for this tumor model to within experimental uncertainties.

Animals↗
PubMed1994

A peptide-based bifunctional chelating agent for 99mTc- and 186Re-labeling of monoclonal antibodies.

BACKGROUND: The development of new bifunctional chelating agents for the labeling of monoclonal antibodies with radiometals is a desirable goal in the area of radioimmunodetection and radioimmunotherapy of cancer. The authors have developed a new N3S-ligand, N-(S-acetylmercaptoacetyl) (p-NCS)phenylalanylglycylglycine ethyl ester (MAIPGG) for technetium-99m (99mTc) or rhenium-186 (186Re) labeling of monoclonal antibody D612 reactive with human colon cancer. The biodistribution of 99mTc/186Re-MAIPGG-D612 conjugates was studied in nude mice bearing human colon cancer xenografts. METHODS: MAIPGG was synthesized from Boc-p-nitrophenylalanine and was coupled to antibody D612, and the conjugate was labeled with 99mTc using a Glucoscan kit (DuPont, North Billerico, MA) as the reducing system. 186Re-MAIPGG-D612 was prepared by radiolabeling MAIPGG with 186Re, with sodium citrate/SnCl2 used as a reducing system, after which the raiolabeled MAIPGG was coupled to monoclonal antibody D612. The biodistribution of these radioimmunoconjugates in athymic nude mice bearing LS174T human colon cancer xenografts was studied. RESULTS: The cold precursor MAIPGG was prepared easily from Boc-p-nitro phenylalanine with an overall yield of 12-15%, which, when coupled to monoclonal antibody D612, did not affect its binding activity to LS174T cells in vitro. The biodistribution and imaging results demonstrated that these radioimmunoconjugates localized preferentially in tumor. CONCLUSIONS: These preliminary results suggest that MAIPGG may be useful for the radiolabeling of a variety of monoclonal antibodies with 99mTc or 186Re, which then can be used for radioimmunodetection and radioimmunotherapy of cancer.

Animals↗
PubMed1994

Radioiodination of monoclonal antibodies D612 and 17-1A with 3-iodophenylisothiocyanate and their biodistribution in tumor-bearing nude mice.

BACKGROUND: The development of a metabolically stable radioiodination reagent for coupling to monoclonal antibodies is a desirable goal. The radioiodination of monoclonal antibodies D612 and 17-1A reactive with human colon cancer with 3-iodophenylisothiocyanate has been investigated. This new ligand, on coupling with monoclonal antibodies, should form a stable thiourea linkage via a reaction of the isothiocyanate moiety with the epsilon-amino group of lysine. METHODS: The starting material, 125I- or 131I-labeled 3-iodophenylisothiocyanate, was synthesized in good radiochemical yield with a purity of > 99% via a reaction of electrophilic radioiodine with 3-tri-n-butylstannylphenylisothiocyanate. The coupling of radiolabeled 3-iodophenylisothiocyanate with monoclonal antibodies D612 and 17-1A in different buffers was investigated. Biodistribution of these radioimmunoconjugates in athymic nude mice bearing colon cancer xenografts was studied. RESULTS: The results demonstrated that monoclonal antibodies labeled with 3-iodophenylisothiocyanate retained specific binding activity and showed significantly less thyroid uptake than did directly radioiodinated antibodies prepared by the iodogen method. Radioimaging and biodistribution studies demonstrated that uptake of these new radioimmunoconjugates in LS174T colon cancer xenografts was similar to that of directly radioiodinated antibodies, while their uptake in other normal tissues was similar to or lower than that of directly radioiodinated antibodies. CONCLUSIONS: These results demonstrate that high specific activity can be achieved and pure 3-iodophenylisothiocyanate can be derived easily from 3-tri-n-butyl-phenylisothiocyanate. Biodistribution and imaging studies revealed that monoclonal antibodies conjugated with 3-iodophenylisothiocyanate are metabolically more stable in vivo in an animal model than directly radioiodinated antibodies, and that these new radioimmunoconjugates are localized selectively in tumors.

Animals↗
PubMed1994

Three-dimensional reconstruction of monoclonal antibody uptake in tumor and calculation of beta dose-rate nonuniformity.

BACKGROUND: The measurement of the heterogeneity of radiolabeled monoclonal antibody uptake in tumor has an essential role in the calculation and interpretation of the absorbed dose of radiation. Large data arrays and long calculation times have been limiting factors in the calculation of three-dimensional dose-rate distributions used to study the relationship between uptake heterogeneity and dose. METHODS: Serial autoradiographs of tumor sections were digitized with approximately 100 microns resolution using a laser densitometer. The section images were aligned to form a registered tumor-image data set. The image data were corrected for film response versus activity density to create a three dimensional activity density distribution using features of a three-dimensional radiotherapy treatment planning system. Dose-rate distributions were formed by convolution with a beta dose kernel using fast Fourier transforms. RESULTS: Differential dose-rate-volume histograms (derived from the dose-rate distribution) were created to summarize the dose-rate nonuniformity throughout the tumor volume. Effects of section sampling interval, interpolation methods between section planes, and calculation resolution on the dose-rate-volume histograms were illustrated. CONCLUSIONS: The several orders of magnitude improvement in calculational speed provided by the fast Fourier transform technique allowed an investigation of the effects of the calculational parameters. This investigation enabled tuning of both data acquisition and dose computation. These studies can lead to further enhancements in the calculational efficiency of three-dimensional dose-rate distributions. These improvements will allow the study of summing techniques to yield average total dose distributions.

Animals↗
PubMed1994

Sensitization of radiolabeled monoclonal antibody therapy using bromodeoxyuridine.

BACKGROUND: Although treatment with radiolabeled monoclonal antibodies (MoAb) against tumor-associated antigens offers the potential for targeted therapy, the efficacy of this approach is limited by the low dose-rate delivered. This could be overcome by increasing tumor sensitivity through the use of radiation sensitizers. METHODS AND RESULTS: In vitro studies using LS174T human colon cancer cells showed that exposure to 1 microM bromodeoxyuridine (BrdUrd), a thymidine-analog radiation sensitizer, at a plasma concentration easily achievable through systemic administration in both animals and patients, increased the cytotoxicity of continuous low dose-rate irradiation delivered by a cesium-137 irradiator (at 12 cGy/h which resembles the dose-rate delivered by radiolabeled MoAb therapy). It was found that 1 microM BrdUrd produced marked radiosensitization (enhancement ratio of 1.42 +/- 0.03) but did not affect cell cycle distribution. Systemic administration of BrdUrd in athymic nude mice bearing LS174T xenografts was performed using osmotic pumps. Animals tolerated infusions of 200 mg/kg/day BrdUrd for 4 days, which resulted in 8.4 +/- 0.8% of thymidine replacement by BrdUrd in tumors. However, bone marrow incorporation was 15.8 +/- 1.1% under these conditions. To improve the ratio of incorporation in the tumor compared to that in the bone marrow, animals were given an infusion of BrdUrd and the pumps were removed. Incorporation of BrdUrd in the bone marrow and intestine decreased rapidly after the infusion was completed. In contrast, there was relatively little change in the incorporation into the tumor after an initial decrease. Based on these data, experiments were performed comparing the effects of 500 microCi iodine-131-labeled 17-1A MoAb alone to the same dose of iodine-131-labeled 17-1A administered 1 day after discontinuation of the infusion of BrdUrd (200 mg/kg/day for 4 days). BrdUrd tended to increase the delay in tumor growth produced by iodine-131-labeled 17-1A administration. CONCLUSIONS: Radiosensitization by BrdUrd in vitro appears to be caused not by cell cycle effects but by increased radiation sensitivity. The in vivo data suggests that BrdUrd improved the efficacy (tumor growth inhibition) of radiolabeled MoAb.

Animals↗
PubMed1993

Comparison of 131I- and 90Y-labeled monoclonal antibody 17-1A for treatment of human colon cancer xenografts.

The choice of radionuclide remains an important question in clinical radioimmunotherapy. Therefore, a study was initiated, using an in vivo model system, to assess the relative merits of 131I- and 90Y-labeled 17-1A monoclonal antibody as therapeutic agents in the treatment of colon cancer. 131Iodine- and 90Y-labeled 17-1A were assessed in animal therapy trials using athymic nude mice bearing LS174T human colon cancer xenografts. 131Iodine-labeled 17-1A decreased tumor growth in a dose-dependent fashion without lethality. In contrast, the doses of 90Y-labeled 17-1A which were required to produce a significant increase in tumor doubling time also caused marked toxicity. Although similar tumor growth inhibition was produced by 250 microCi 90Y- and 150 microCi 131I-labeled 17-1A, Medical Internal Radiation Dose calculations based on biodistribution data estimated that the dose delivered by 90Y was greater than that delivered by 131I. To investigate this discrepancy, 3-dimensional dose distributions within LS174T tumors were assessed using autoradiography and 3-dimensional calculational techniques. It was found that a greater fraction of the dose was deposited in the tumor after treatment with 131I- compared to 90Y-labeled 17-1A. When the Medical Internal Radiation Dose calculations were adjusted using the 3-dimensional dose distributions, 250 microCi of 90Y- and 150 microCi of 131I-labeled 17-1A were found to deliver similar tumor doses. These studies suggest that 131I-labeled 17-1A is superior to 90Y-labeled 17-1A, since 131I-labeled antibody produced less hematological and animal toxicity and was more effective at inhibiting LS174T tumor growth than 90Y-labeled antibody across the range of radionuclide doses tested. Furthermore, they suggest that it will be necessary to perform 3-dimensional dose calculations in addition to Medical Internal Radiation Dose calculations in order to interpret tumor dosimetry.

Adenocarcinoma↗
PubMed1992

Therapy with unlabeled and 131I-labeled pan-B-cell monoclonal antibodies in nude mice bearing Raji Burkitt's lymphoma xenografts.

Clinical trials of radioimmunotherapy (RIT) of lymphoma have produced frequent tumor regressions and remissions, but it has been difficult to determine to what extent these tumor responses have been due to antibody-specific targeted radiation, nontargeted radiation, and/or cytotoxicity mediated by the carrier monoclonal antibody (MoAb). In this report, RIT was studied in athymic nude mice bearing s.c. Raji human Burkitt's lymphoma xenografts using two different pan-B-cell MoAbs, MB-1 (anti-CD37) and anti-B1 (anti-CD20), which differ in isotype (and thus the potential for interaction with host effector mechanisms) and isotype-matched control antibodies either in the unlabeled state or labeled with 131I. When a single i.p. injection of 300 microCi 131I-labeled MB-1 (IgG1) was compared to treatment with unlabeled MB-1 or 300 microCi 131I-labeled MYS control IgG1 MoAb, an antibody-specific targeted radiation effect of RIT was seen. 131I-labeled MB-1 produced a 44 +/- 19% (SEM) reduction in tumor size at 3 weeks posttreatment, while unlabeled MB-1 or 300 microCi 131I-labeled MYS control IgG1 antibody treatment resulted in continued tumor growth over this period of time. In vitro studies demonstrated that MB-1 was incapable of mediating antibody-dependent cellular cytotoxicity using Raji tumor cell targets and human peripheral blood mononuclear cells. Similar to the MB-1 studies, treatment with 300 microCi 131I-labeled anti-B1 produced a 64% reduction in mean tumor size, while 300 microCi of control antibody resulted in a 58% increase in tumor size over the same 3-week period. In contrast to MB-1, however, unlabeled anti-B1 (an IgG2a MoAb which in vitro studies showed to be capable of antibody-dependent cellular cytotoxicity) also had a substantial antitumor effect. Indeed, 300 microCi 131I-labeled anti-B1 and unlabeled anti-B1 treatment (using an equivalent amount of total protein in the treatment dose) produced a similar specific reduction in tumor size. Increasing the radionuclide dose of anti-B1 to 450 microCi in another experiment did not produce a significant difference in tumor regression compared to a 300-microCi dose. These results suggest that the antitumor effects of 131I-labeled anti-B1 treatment were dominated by antibody-mediated cytotoxicity mechanisms, such that an antibody-specific targeted radiation effect could not be distinguished. In contrast, antibody-specific targeting of radiation was the dominant mechanism of tumor killing with 131I-labeled MB-1.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Improved delivery of radiolabeled anti-B1 monoclonal antibody to Raji lymphoma xenografts by predosing with unlabeled anti-B1 monoclonal antibody.

A human B-cell lymphoma xenograft model was used to test whether the administration of unlabeled MoAb prior to injection of radiolabeled monoclonal antibody (MoAb) improves delivery of the radiolabeled MoAb to tumor prior to testing in clinical radioimmunotherapy trials. The anti-B1/CD20 pan-B-cell MoAb reactive with human B-cell lymphomas and leukemias but not reactive with mouse B-cells was used in this study. Athymic nude mice bearing human Raji Burkitt lymphoma xenografts were given injections of 2.5 muCi (0.3 microgram) 131I-labeled anti-B1 with or without a 2-h prior single injection of 100 micrograms of unlabeled anti-B1 antibody. Four days later the animals given injections of 131I-labeled anti-B1 and the unlabeled anti-B1 predose had a tumor uptake of 12.72 +/- 1.17% (SEM) of injected dose/g which was 44% greater than the animals receiving the 131I-labeled anti-B1 alone (P = 0.014). The uptake in most normal tissues was unchanged, although the blood level of 131I-labeled anti-B1 appeared to be greater following unlabeled anti-B1 predosing (P = 0.067). Predosing with isotype matched irrelevant MoAb did not result in a greater tumor uptake or blood concentration of 131I-labeled anti-B1 compared to the administration of 131I-labeled anti-B1 alone. In studies using 111In-labeled anti-B1, the effect of unlabeled antibody predosing was more pronounced. For animals given injections of 4.5 muCi (0.4 microgram) 111In-labeled anti-B1 and the unlabeled anti-B1 predose, the uptake in tumor was 12.37 +/- 2.07% of injected dose/g which was 162% greater than the animals receiving the 111In-labeled anti-B1 alone (P = 0.009). Predosing decreased 111In-labeled anti-B1 uptake in spleen, while the blood level was significantly greater. Predosing was more effective than simultaneous injection in improving tumor delivery. When tumor-bearing mice were either simultaneously given injections of 36 micrograms of unlabeled anti-B1 and 4 micrograms 111In-labeled anti-B1 or were given preinjections of 36 micrograms unlabeled anti-B1 3 h prior to injection of 4 micrograms 111In-labeled anti-B1, tumor uptake 3 days later was 1.3-fold higher in the animals which received the preinjection of unlabeled antibody (P = 0.011). As the quantity of unlabeled anti-B1 was increased (36, 96, 996 micrograms) in the predose, significantly greater uptake in tumor was observed, although this uptake appeared to plateau at the highest predoses.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Three-dimensional tumor dosimetry for radioimmunotherapy using serial autoradiography.

Three-dimensional dose distributions have been calculated for LS174T human colon cancer xenografts in athymic nude mice treated with 131I-labeled 17-1A monoclonal antibody. Autoradiographs were made for fifteen to twenty 32-micron-thick representative serial sections of tumors removed 1 and 4 days postinjection. Film density readings were converted to activity density and entered into a radiotherapy treatment planning system. Three-dimensional dose distributions were obtained by summing the dose contributions due to each voxel of uniform activity. Isodoserate distributions and dose-rate-volume histograms for representative tumors at 1 and 4 days following 131I-labeled 17-1A injection showed a progressive change from a predominantly surface deposition (day 1) to a more volumetric deposition (day 4). Average tumor doses calculated using the assumptions of uniform source distribution and local dose deposition resulted in a poor estimation of the cumulative dose because of the significant time-dependent dose-rate nonuniformities.

Animals↗
PubMed1992

Development of 3-iodophenylisothiocyanate for radioiodination of monoclonal antibodies.

A new radioiodination reagent, 3-iodophenylisothiocyanate (3-IPI) has been developed for coupling to monoclonal antibodies. The starting material, 3-tri-n-butylstannylphenylisothiocyanate was prepared via a reaction of hexabutylditin with 3-bromoaniline, followed by treatment with thiophosgene with an overall yield of 72%. The radioiodination of this tin precursor with Na[125I]I/iodogen in chloroform gave 3-[125I]IPI in 23-55% radiochemical yield and 81-99.6% radiochemical purity. Purification of the impure product by high pressure liquid chromatography increased the radiochemical purity of the product up to 99%. These results suggest that 3-IPI may be a useful ligand for radioiodination and coupling to a variety of monoclonal antibodies.

Antibodies, Monoclonal↗