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1.
Accurate dosimetry is essential for the assessment of radioimmunotherapy. Most often studied to date has been the macroscopic dosimetry related to organ and tumor distribution of the radiolabeled antibody, but the question of microscopic dose heterogeneity is also important. To address the latter issue, we have taken an integrated approach to the pharmacology, taking into account whole-body distribution, transcapillary transport, percolation through the tumor interstitial space, antigen-antibody interaction, and antibody metabolism. The first step is to simulate the spatial antibody concentration profile in a tumor as a function of time after i.v. (e.g., bolus) injection, using reasonable values for the parameters involved. The second step is to calculate, also as a function of time, the absorbed radiation dose distribution resulting from each concentration profile. Parameter values for IgG pharmacology and a radiation point source function for 131I are used to explore the effect of antibody distribution profiles on absorbed dose in the tumor. The geometry simulated corresponds to a spherical nodule of densely packed tumor cells. Absorbed doses are calculated for radiation from a single nodule (e.g., a micrometastasis or prevascular primary tumor) and for a cubic lattice of such nodules (e.g., corresponding to nodular lymphoma). As noted in our previous studies, there is a "binding site barrier." Binding to antigen retards antibody percolation into the nodules; high antibody affinity tends to decrease percolation and give a higher absorbed dose near the surface of each nodule. Heterogeneous antibody distribution results in a heterogeneous absorbed dose. This is more apparent in the case of radiation from a single nodule than it is for radiation from within an array of nodules. Dehalogenation results in a lower absorbed dose over time, and the effect is more apparent at later times after injection. PERC-RAD, the computer program package developed for these analyses, provides a convenient and flexible way to assess the impact of macroscopic and microscopic parameters on the distribution of radioimmunoconjugates and on the consequent profile of absorbed radiation dose in tumors. This mathematical model and the general principles developed here can be applied as well to other radiolabeled biological ligands.  相似文献   

2.
In order to understand the pharmacology of monoclonal antibodies and their conjugates, one must consider both global and microscopic aspects of antibody distribution. Here we present an analysis of antibody distribution in tumors based on the following factors: (a) molecular weight and valence of the antibody; (b) global pharmacokinetic profile following i.v. bolus injection; (c) penetration through the vascular wall; (d) diffusive and convective transport through interstitial space in the tumor; (e) antigen-antibody interaction; (f) antibody metabolism. Partial differential equations were developed to incorporate these factors and then solved numerically using parameter values from animal experiments, from clinical protocols at our institution, from studies of antibody binding characteristics in vitro, and from the literature. Salient findings from this model are that (a) antigen-antibody interaction in the tumor can retard antibody percolation away from blood capillaries, thus constituting a "binding site barrier"; (b) high antibody affinity tends to decrease antibody penetration and result in a more heterogeneous distribution; (c) high molecular weight [IgG greater than F(ab')2 greater than Fab] slows percolation and results in less uniform spatial distribution; (d) the average antibody concentration in the tumor does not increase linearly with antibody dose; (e) raising the rate of antibody metabolism results in low concentration and poor percolation; (f) perhaps most interesting, there is predicted to be a range of antibody dose and affinity within which the specificity ratio and average concentration could be kept high while limiting the heterogeneity of distribution. PERC, the computer program package developed for these analyses, provides a convenient and flexible way to assess the impact of global and microscopic parameters on the distribution of immunoglobulin in tumors. For calculations presented here, the input data were obtained from experimental sources, and qualitative features of the output proved consistent with the few interpretable observations available. However, detailed validation would require much more data than are currently at hand. The mathematical findings should therefore be considered as aids to concept development and as a set of null hypotheses with which to guide experimentation. Experiments and simulations will continue in tandem. It should be noted that the PERC package (and also the general principles delineated here) can be applied as well to biological ligands other than antibodies.  相似文献   

3.
Graff CP  Wittrup KD 《Cancer research》2003,63(6):1288-1296
The interplay among antibody/antigen binding kinetics, antibody diffusion, and antigen metabolic turnover together determines the depth of penetration of antitumor antibodies into prevascular tumor spheroid cell clumps. A sharp boundary between an outer shell of bound high-affinity antibody and an inner antibody-free core has been previously observed and mathematically modeled and was termed the "binding site barrier." We show here that this process is well described by a simplified shrinking core model wherein binding equilibration is much more rapid than diffusion. This analysis provides the following experimentally testable predictions: (a) the binding site barrier is a moving boundary whose velocity is proportional to the time integral of antibody concentration at the spheroid surface (i.e. plasma antibody AUC); (b) the velocity of this moving boundary is independent of binding affinity, if the affinity is sufficiently high to strongly favor antibody/antigen complex formation at prevailing antibody concentrations; and (c) maximum tumor retention is achieved when the antibody/antigen dissociation rate approaches the rate of antigen metabolic turnover. The consistency of these predictions with published experimental results is demonstrated. The shrinking core model provides a simple analytic relationship predicting the effects of altered antibody pharmacokinetics, antibody molecular weight, antigen turnover rate, antigen expression level, and micrometastasis size on antibody penetration and retention. For example, a formula is provided for predicting the bolus dose necessary to accomplish tumor saturation as a function of antibody and tumor properties. Furthermore, this analysis indicates certain attributes necessary for an optimal tumor targeting agent.  相似文献   

4.
Using rat monoclonal antibody (MAb) 12-15A against the spontaneously metastasizing mouse lymphoma variant ESb-MP, we elaborated conditions for targeting. In vitro, high binding of labelled antibody to ESb-MP cells and low binding to lymphoid cells (e.g., spleen cells) was noted. In vivo, we observed pronounced accumulation in spleen, lymph nodes and bone marrow, the uptake kinetics indicating high accessibility of the target antigen in these tissues, and rapid clearance of radioactivity from blood and most normal tissues, indicating degradation of the antibody and excretion of the label. Binding to lymphoma tissue was slow but persistent, resulting in high tumor:tissue ratios only after 2-3 days. Biodistribution could be dramatically changed by pre-treatment of animals with excess cold antibody, which reduced trapping of labelled antibody in normal lymphatic tissue, leading to prolonged persistence in the blood and preferential uptake into tumor tissue. Monovalent 12-15A fragments showed less pronounced binding to lymphatic tissue, while being rapidly cleared from the circulation by virtue of their inherent tendency to bind to kidney tissue. Tumor:tissue ratios up to 56:1 were obtained by a combination of pre-treatment with unlabelled 12-15A IgG or Fab fragment, followed by injection of labelled fragment or IgG, respectively. This is interpreted on the basis of differences in the internalization and retention of antigen-antibody complexes. Pre-treatment obviously leads to a temporary blockade or removal of the target antigen, which is much more efficient with normal lymphoid cells than with tumor cells. Thus, it may become possible to target antibodies into the tumor despite concurrent antigen expression on normal tissue.  相似文献   

5.
Metastatic melanoma is almost always deadly and new methods of treatment are urgently needed. Recently, we established the feasibility of radioimmunotherapy (RIT) for experimental melanoma in mice using a 188-rhenium (188Re)-labeled monoclonal antibody (mAb) 6D2 (IgM) to melanin. Our objective was to determine the effects of varying tumor melanin concentration and of different diffusivities and lymphatic clearance rates of the normal tissue, on the absorbed dose to the tumor in simulated therapy, in preparation for a clinical trial of RIT for melanoma. Using finite element analysis (FEA), we created a pharmacokinetic model that describes melanin-targeting RIT of a melanoma micrometastasis (1.3-mm radius) imbedded in normal tissue (14.3-mm radius). Our method incorporates antibody plasma kinetics, transcapillary transport, interstitial diffusion, and lymphatic clearance. Michaelis-Menten kinetics was used to model mAb binding to tumor melanin for melanin concentrations of 76, 7.6, 0.76, 0.076, and 0.0076 micromol/l. An absorbed dose was calculated, after accounting for direct and crossfire irradiation, on the basis of a 7.4-GBq intravenous dose of 188Re-6D2. The results showed that penetration of mAb into the tumor was inversely proportional to tumor melanin concentration. Decreased diffusivity and increased lymphatic clearance of the surrounding normal tissue decreased the dose to the tumor. The formation of mAb-melanin complex was remarkably similar within a 1000-fold range of melanin concentration, resulting in total doses of 2840, 2820, 2710, and 1990 cGy being delivered to tumors with melanin concentrations of 76, 7.6, 0.76, and 0.076 micromol/l, respectively. In conclusion, RIT of metastatic melanoma can be effective over a wide range of tumor melanin concentrations. The results can be useful in the design of a clinical trial of melanin-targeting RIT in patients with metastatic melanoma.  相似文献   

6.
L T Baxter  F Yuan  R K Jain 《Cancer research》1992,52(20):5838-5844
A mathematical model is developed to describe the concentration profiles around individual tumor blood vessels for two-step approaches to cancer treatment. The model incorporates plasma pharmacokinetics, interstitial diffusion, reversible binding between antibody and hapten and between antibody and tumor-associated antigens, and physiological parameters to evaluate present experimental approaches and to suggest new guidelines for the effective use of two-step approaches. Results show considerable interaction between the binding kinetics, initial drug doses, and antigen density, with optimal parameter ranges depending on the desired goal: treatment or detection. The hapten concentration in tumors was found to be nonuniform because of specific binding to antibodies. While binding of the hapten to the bifunctional antibody is necessary for improved retention, too large a binding affinity may lead to very poor penetration of the hapten into regions far away from blood vessels. The time delay between antibody and hapten injection was found to be an important parameter. Longer time delays were found to be advantageous, subject to constraints such as internalization of the antibody and tumor growth during treatment. A proper combination of initial doses for the two species was also seen to be crucial for maximum effectiveness. Comparison of the model with the experimental data of Le Doussal et al. (Cancer Res., 51: 6650-6655, 1991) and Stickney et al. (Cancer Res., 50: 3445-3452, 1990) suggests two novel, yet testable, hypotheses: (a) the early pharmacokinetics of low molecular weight agents can have an important effect on later concentrations using two-step approaches; and (b) metabolism may play an important role in reducing concentrations in the tumor and tumor:plasma concentration ratios. These results should help in the effective design of two-step strategies.  相似文献   

7.
A mathematical model has been developed to determine the best approach to improving tumor targeting with antibody. The amount of antibody in the tumor (tumor content) and the tumor:normal tissue antibody concentration ratio (uptake ratio) were calculated over 12 days from injection, using the computer program FACSIMILE to solve the stiff nonlinear differential equations describing the system. Results indicate that success requires an optimal combination of dose, size, and binding affinity of antibody. Increasing the dose to 100 times that presently used for scanning increased both the percentage of injected antibody in the tumor and the uptake ratio by up to 2 orders of magnitude to maximal values determined by affinity. This result could be achieved by coinjecting unlabeled antibody. Increasing affinity from Keq = 10(9) to 10(13)M-1 increased the uptake ratio from 5 to 100 for whole antibody and to 550 for a small ligand, at the calculated optimal dose, but had no effect at the current scanning dose. With decreasing molecular size at average affinity, the same maximum tumor content and uptake ratio were achieved but progressively earlier. At high affinity there was a substantial advantage for a small ligand compared with whole antibody in terms of uptake ratio (550 versus 100) and tumor:normal tissue integral dose ratio (330 versus 60). The uptake of a small ligand was not increased by binding to plasma protein but with increasing time the tumor content was higher than without protein binding.  相似文献   

8.
G L Ong  M J Mattes 《Cancer research》1989,49(15):4264-4273
Monoclonal antibody localization to human carcinoma xenografts in nude mice was investigated by injecting biotinylated antibody. The antibody used in most experiments, MA103, reacts with a widely distributed human antigen present at a high density on the cell surface and has a relatively high effective affinity, 5.8 x 10(9) M-1. Various doses of antibody were injected, and tumors were collected at various times after injection. Frozen sections were stained by the immunoperoxidase method to detect bound antibody, and adjacent sections were stained with the same antibody in vitro to demonstrate total antigen distribution. In complementary experiments, unconjugated MA103 was injected in high doses to determine whether subsequent in vitro staining of frozen sections by biotinylated MA103 would be inhibited. The results demonstrate that: (a) approximately 0.5 mg antibody was sufficient to saturate antigenic sites on viable tumors cells; (b) saturation was achieved on viable tumor cells throughout the tumor 3 days after injection; (c) in necrotic areas, some antigen was accessible to antibody in vivo, but a considerable fraction of the antigen was inaccessible; (d) at 1 day after injection, stained cells were confined to areas near the blood vessels in the stroma; (e) for i.p. tumors, there was no difference between i.p. and i.v. injection of antibody and no indication of solid tumor penetration directly from the peritoneal cavity; and (f) nonspecific localization of a nonreactive biotinylated monoclonal antibody was weakly detectable and when present was seen as diffuse staining in the connective tissue only. A more limited range of experiments was performed with a second biotinylated antibody, MH99, which reacts with an epithelial cell surface antigen also recognized by many other antibodies, including 17-1A, AUA1, and KS1/4. Results were generally similar, except that a higher dose, 1.5 mg, was required to obtain homogeneous dark staining of tumor cells, and there appeared to be a considerable amount of antigen in viable areas of the tumor that was not accessible in vivo, possibly because it was intracellular. This approach appears to demonstrate tumor localization of antibody more impressively than other methods that have been used. This is partly because of the excellent resolution attained, since the reactive antibody produces a sharp membrane-staining pattern that is totally absent using a nonreactive control antibody. In addition, use of a target antigen that is predominantly on the cell surface, as opposed to cytoplasmic or secreted, is probably important. These data will be of value in attempting to use antibodies for immunotherapy.  相似文献   

9.
Monoclonal antibodies (MAbs) often distribute nonuniformly in tumors. In part, that observation reflects intrinsic heterogeneity within the tumor; in part, it reflects poor penetration through tumor substance. Several years ago, we proposed the "binding site barrier" hypothesis (J.N. Weinstein, R.R. Eger, D.G. Covell, C.D.V. Black, J. Mulshine, J.A. Carrasquillo, S.M. Larson, and A.M. Keenan, Ann. NY Acad. Sci., 507: 199-210, 1987; K. Fujimori, D.C. Covell, J.E. Fletcher, and J.N. Weinstein, Cancer Res., 49: 5656-5663, 1989), the idea that antibodies (and other ligands) could be prevented from penetrating tumors by the very fact of their successful binding to target antigen. Calculations suggested that this might be a significant factor in the therapy of even microscopic nodules. The higher the affinity and the higher the antigen density, the greater the barrier. Here, we provide direct experimental evidence of such a barrier to the percolation of D3 MAb through intradermally implanted line 10 carcinoma of guinea pigs. After affinity purification using glutaraldehyde-fixed line 10 cells, the D3 had an average immunoreactivity of 88%, a binding constant of 1.6 +/- 0.3 (SEM) x 10(10) M-1, and saturation binding of 355,000 +/- 15,000 molecules/cell. Using a combination of double-label autoradiography and double-chromagen immunohistochemistry, we determined simultaneously the distribution of (a) i.v. injected D3 MAb; (b) coinjected isotype-matched control IgG (BL3); (c) D3 antigen; (d) blood vessels. The previously developed mathematical models aided in the design of these experiments. Double immunochemical staining of the tumors showed antigen-rich patches 100-800 microns across, surrounded by blood vessels. At a low MAb dose (30 micrograms), binding to antigen severely hindered penetration into antigenic patches as small as 200 microns, even at 72 h. Explanation of this finding by a physical barrier was ruled out by the observation that BL3 distributed uniformly in the same patches. At a higher dose (1000 micrograms), the binding site barrier could be partially overcome. The same general principles of micropharmacology may apply to biological ligands other than antibodies, including those secreted by genetically modified cells.  相似文献   

10.
The therapeutic potential of radiolabeled antibodies is usually evaluated in experimental animal models bearing s.c. xenografts. We have established a micrometastatic model of the GW-39 human colonic carcinoma in the nude mouse lung (J. Natl. Cancer Inst., 83: 627-632, 1991) and presented preliminary findings on the efficacy of a 131I-anticarcinoembryonic antigen (CEA) antibody in this model. We now extend our observations on the use of radioiodinated labeled monoclonal antibodies (MAbs) to treat multiple small tumor nodules. Biodistribution and dosimetry analysis was performed for intact and F(ab')2 of NP-4 anti-CEA IgG, Mu-9 anti-colon-specific antigen IgG, isotype-matched irrelevant anti-AFP IgG, and intact MAb 34A anti-lung endothelial IgG antibody. Comparisons were made for rad dose delivered to small s.c. tumors, normal lung, lung with tumor nodules, and isolated tumor nodules. Survival curves were generated for tumor-bearing animals treated 1, 7, or 14 days after tumor cell implantation with these antibodies using the maximal tolerated dose for intact antibodies (275 microCi) and for F(ab')2 fragments (1.2 mCi). The studies established the following observations: (a) in contrast to previous results in a bulky tumor model in hamsters, intact antibodies are more therapeutic than MAb fragments for both NP-4 and Mu-9; (b) tumor nodule size, even on the microscopic level, affects therapeutic outcome; antibodies were more effective when administered 7 days postimplantation (mean nodule diameter, 150 microns) compared with treatment 14 days postimplantation (mean nodule diameter, 750 microns); (c) administration of radioiodinated Mu-9 was exquisitely effective on single avascular tumor cells that had seeded in lung; irrelevant antibody was minimally radiotoxic; (d) as in the bulky disease model, the anti-colon-specific antigen p antibody delivers a higher rad dose than the anti-CEA antibody and is significantly more therapeutic in the micrometastasis model; (e) a higher affinity anti-CEA antibody (MN-14) recognizing the same epitope on CEA as NP-4 was equally therapeutic; (f) the use of MAb directed against the lung endothelium was not as therapeutic as a tumor-associated antibody; and (g) all tumor-associated antibodies were more efficacious than administration of the maximal tolerated dose of 5-fluorouracil and leucovorin in this human tumor-xenograft model. These results provide further support for the use of radioimmunotherapy in the handling of minimal disease, probably as part of an adjuvant treatment regimen.  相似文献   

11.
Although many antibodies are being used for imaging studies, it is not clear which in vitro properties of antibodies will best reflect their in vivo characteristics. The ability to correlate in vitro binding characteristics of monoclonal antibodies to tumor antigens with their in vivo localization characteristics, particularly with respect to tumor localization properties, is desirable for rapid selection of monoclonal antibodies with potential for clinical use. The in vitro binding characteristics of three monoclonal antibodies to the murine Ly-2.1 antigen and one to the Ly-3.1 antigen have been studied on cultured tumor cells bearing these antigens. The association and dissociation rate constants, apparent affinity, and immunoreactivity of each antibody in vitro were compared with their ability to localize the s.c. tumors from the same cell line growing in Ly-2.1-/Ly-3.1-mice. The antibody with the highest affinity and fastest association rate localized to tumor at the earliest time (16-20 h after injection) and had the highest percentage of the injected dose/g in the tumor (greater than 25%). The antibody with the lowest affinity showed significantly less localization to tumor cells, compared with the other three antibodies. The ranking of the antibodies by affinity agreed with the ranking in terms of their ability to localize to tumors, but the in vitro immunoreactivity of the antibodies, as measured by a cell binding assay, did not correlate with their tumor localization properties. Immunoscintigraphic studies did not precisely correlate with biodistribution data or in vitro binding characteristics, because tumors could be satisfactorily imaged with each antibody, although it was noted that the antibody with the highest affinity gave the best image. The results indicate that kinetic binding parameters and affinity of monoclonal antibodies may be useful in predicting their potential for tumor localization and that kinetics of association of antibodies in vitro may predict localization kinetics in vivo.  相似文献   

12.
One of the problems of in vivo diagnosis and therapy of tumors with monoclonal antibodies is their heterogeneity with respect to antigen expression, with some cells expressing no antigen and others being weakly or strongly positive. Selected mixtures of antibodies to different antigens are therefore likely to react with more cells than single antibodies and be more effective for imaging and therapy. With this in mind, we have examined a new human colon cancer cell line (LIM1899) which has a heterogeneous expression of several cell surface molecules: by flow cytometry 38% were carcinoembryonic antigen positive; 64%, human milk fat globule positive, and 73%, CD46 positive; 87% of tumor cells bound a mixture of all three antibodies in vitro. Some blocking of the binding of anti-human milk fat globule antibody by the anti-CD46 antibody was noted. LIM1899 was established as a xenograft in nude mice and in vivo biodistribution studies performed using antibodies alone or in combination. Mixtures of antibodies clearly showed a higher percentage of injected dose of antibody in the tumor than did single antibodies: one antibody gave 10%; two together, 17 to 21%; and all three together gave 29% of the injected dose in the tumor. Tumor:blood ratios were also superior for combinations of antibodies, provided that low doses of the antibodies were used; at higher doses the effect was lost. The study demonstrates that combinations of antibodies are better than single antibodies for localization, provided that the dose used is carefully selected.  相似文献   

13.
Tumors H-59 and M-27, two stable metastatic variants of the Lewis lung carcinoma, differ in their ability to disseminate lymphatically. Tumor H-59 metastasizes to the regional lymph nodes regardless of the local site of growth and gives rise to widespread lymphatic dissemination, whereas tumor M-27 disseminates hematogenously without involvement of the regional nodes (P. Brodt, Cancer Res., 46: 2442-2448, 1986). In a previous paper we reported that this divergent potential to disseminate lymphatically correlated well with adhesion to frozen sections of syngeneic lymph nodes and spleens (P. Brodt, Clin. Exp. Metastasis, 7: 343-352, 1989). A monoclonal antibody (12/50) specific for tumor H-59 was subsequently generated. This antibody (an IgG1) but not three control antibodies, which reacted with tumor H-59, significantly reduced tumor cell binding to the frozen sections. Western blot analysis revealed that it recognized a plasma membrane protein of Mr 37,000 on tumor H-59 cells. No antibody binding was detected when solubilized plasma membrane preparations of tumor M-27 were used. Subsequent enzymatic assays indicated that the binding of monoclonal antibody 12/50 was insensitive to cell treatment with exoglycosidases but could be significantly reduced by pretreatment of the tumor cells with Pronase. Together these results suggest that monoclonal antibody 12/50 recognizes a cell surface adhesion protein relevant to lymphatic dissemination of this tumor.  相似文献   

14.
Humoral immune responses against the "Cancer-Testis" (CT) antigen NY-ESO-1 are frequently observed in patients with NY-ESO-1 expressing tumors. This is in contrast to other known tumor antigens (TA) defined by antibody or cytotoxic T cell (CTL) reactivity, i.e., MAGE-1, MAGE-3, SSX2, Melan A, and tyrosinase. No NY-ESO-1 antibody has been detected in healthy controls and patients with NY-ESO-1 negative tumors. In this study, we have assessed the NY-ESO-1 serum antibody response in patients with NY-ESO-1 positive tumors of different histological types and stages using Western blotting and an ELISA. Of the 12 patients analyzed, 10 had demonstrable NY-ESO-1 antibodies at the start of the study. All patients were followed for changes in NY-ESO-1 antibody titers during the course of tumor treatment and clinical evolution. In 4 patients, an increase of NY-ESO-1 antibody titer was observed with progression of disease or extensive tumor necrosis under treatment. One patient showed a stable NY-ESO-1 antibody titer over 3 years along with gradual regression of a large tumor mass. In 5 patients, a decrease of NY-ESO-1 antibody was detected: in 1 patient after curative tumor resection, in 3 patients with partial regression of metastatic disease under chemo- and immunotherapy, and in another patient with a NY-ESO-1 negative tumor relapse. Our results indicate that the induction and maintenance of NY-ESO-1 antibody is dependent on the presence of NY-ESO-1 expressing tumors. Furthermore, changes in NY-ESO-1 antibody titers correlate with the evolution of NY-ESO-1 positive disease.  相似文献   

15.
The murine monoclonal antibody LS2D617, which reacts with an antigen associated with human small cell lung carcinoma (SCLC), was tested in preclinical models to assess its potential for specific targeting of tumors in human SCLC cancer patients. LS2D617 detects a cell antigen on the surface of cultured SCLC and neuroblastoma cell lines. Scatchard analysis of the binding of LS2D617 to NCIH69 SCLC cells indicates an affinity constant of about 1 x 10(8) M-1 and an epitope expression level of approximately 2 x 10(6) antigenic sites/cell. Molecular weight analysis of the target antigen and antibody competition experiments showed that LS2D617 should be classified as a SCLC Cluster 1 antibody (i.e., reacts with the neural cell adhesion molecule). LS2D617 was labeled with 111In and tested for biodistribution (4, 24, 48, 72, and 96 h postinjection) in nude mice bearing the human SCLC NCIH69 tumor. Tumor values peaked at about 35% injected dose/g (Day 3) compared with about 8% injected dose/g for an irrelevant IgG1 antibody while normal tissue accumulation for both antibodies was about 2-8% injected dose/g. Immunohistochemical studies demonstrated that LS2D617 reacts with the central nervous system, peripheral nerves, endocrine tissues, and heart tissue of rabbits as it does in human tissues. The ability of LS2D617 to accumulate in vivo in normal tissues that express the specific target antigen was tested in rabbits. Rabbits given i.v. injections of 111In-LS2D617 or control labeled antibody were sacrificed at 48 h and tissues were examined by gamma well counting, autoradiography, and immunohistochemical staining for murine immunoglobulin. Specific uptake was seen in all sites defined as antigen positive by immunohistology (i.e., heart, liver bile duct, peripheral nerves, pituitary, adrenal), excepting the central nervous system (brain and spinal cord) which was inaccessible to antibody because of the blood brain barrier. The use of preclinical in vivo targeting models to assess tumor as well as antigen-positive normal tissue targeting should aid in the strategy of antibody-based therapeutic intervention of human cancer by providing insight into the potential for tumor targeting and normal tissue toxicity that may be encountered in the clinic.  相似文献   

16.
Marked differences in the tumor uptake of a 125I-labeled monoclonal antibody (MAb) directed against carcinoembryonic antigen (CEA) were observed in 4 serially transplanted human colorectal carcinomas in nude mice. A comparative study showed that elevated values of measurable tumor vascular parameters, such as permeability, blood flow and blood volume, correlated better with high MAb tumor uptake than the concentration of target antigen in the tumor. In an attempt to modify the vascular parameters and to determine if this could increase antibody uptake by the tumor, rhTNFα (TNF) was injected i.t. or i.v. and antibody localization experiments were performed immediately thereafter. Results showed that the permeability of the tumor vessels increased 8 to 10 fold 1 hr after i.t. injection of TNF as compared to control tumors injected with saline. Tumor uptake of 125I-labeled anti-CEA MAb, was 3 times higher 2 hr after i.v. injection and still 27% higher 22 hr later, as compared to results from controls. Intravenous injection of TNF simultaneously with the l25I- labeled anti-CEA MAb also resulted in a 2-fold increase in tumor uptake 4 hr after injection, but the increase was no longer significant 24 hr after injection. Interestingly after i.v. injection of TNF, the MAb concentration in the blood and other normal tissues, such as liver, kidneys, lungs and heart was decreased, resulting in significantly higher ratios of tumor to normal tissue. Taken together the results demonstrate that injection of TNF can increase tumor vascular permeability and improve radioantibody uptake. This raises the possibility of increasing the radiation dose delivered by antibody to the tumor in the course of radioimmunotherapy.  相似文献   

17.
An assay method that uses 125I-labeled monoclonal antibody (MoAb) and in vitro quantitative autoradiography was developed to determine the local concentration of tumor-associated antigens in tissue sections. Human melanoma biopsy specimens were evaluated for the expression of the Mr 97,000 and 250,000 protein antigens using MoAb-96.5 and MoAb-9.2.27, respectively. Tissue sections were incubated in solutions of increasing concentration of 125I-labeled MoAb with or without an excess of unlabeled antibody. Quantitative autoradiography was performed on the sections and compared with 125I standards to determine tumor-bound radioactivity and calculate bound pmol of MoAb per g of tumor. The total binding, nonsaturable binding, and specific binding of 125I-labeled MoAb to tumor were then computed. Specific binding of MoAbs to tumor tissue was saturable in all antigen-positive tumors. The maximal concentration of specific binding of antibody to tissue (Bmax) represented the tissue antigen concentration. Estimates of the Ka of antigen/antibody binding were also made. The reliability of the measurements was confirmed by testing sections from mixtures of antigen-positive and antigen-negative cells.  相似文献   

18.
Monoclonal antibodies against the Thy 1.1 differentiation antigen are ineffective in the treatment of transplanted AKR T-cell lymphoma once a palpable tumor nodule is present, due to the inability of the host to eliminate antibody-coated tumor cells. To overcome this limitation, we have evaluated the use of 131I-labeled anti-Thy 1.1 antibodies for the therapy of established AKR/J SL2 lymphoma (Thy 1.1+) nodules growing in congeneic AKR/Cu mice (Thy 1.2+). In these experiments, 131I-anti-Thy 1.1 antibody specifically localized to a s.c. tumor with a mean of 6.5% of the infused dose per g of tumor at 24 h after infusion. The proportion of infused anti-Thy 1.1 antibody localizing to tumor was constant following antibody doses of up to 400 micrograms/animal. Antibody iodinated with up to 2 atoms of iodine per antibody of molecule maintained binding activity and localization to tumor equivalent to antibody labeled with less iodine. The concentrations of 131I-anti-Thy 1.1 in tumor would result in delivery of a mean of 1600 cGy to tumor following infusion of 500 muCi of 131I-labeled anti-Thy 1.1 antibody. In comparison, 500 muCi 131I-labeled irrelevant antibody would deliver a mean of 380 cGy to tumor. Treatment of animals with palpable tumor nodules with 500 muCi 131I-anti-Thy 1.1 led to regression of the tumor nodule in 44% of animals, significantly prolonged survival, and cured two of five of the animals treated prior to the development of metastatic disease. In contrast, unlabeled anti-Thy 1.1 led to tumor response in 6% of animals, and up to 1000 muCi 131I-labeled irrelevant antibody had no effect on tumor growth. Therapy was limited by the emergence of variant tumor cells lacking the target antigen and by bone marrow toxicity following 131I-labeled antibody doses of greater than or equal to 1000 muCi/animal. These studies demonstrate that 131I-labeled monoclonal antibodies can have a significant antitumor effect in a situation where unmodified antibody is ineffective.  相似文献   

19.
The monoclonal antibody (MAb) SEN3I, a mouse IgG1 which recognizes the cluster-5a antigen on small-cell lung cancer (SCLC) cells, was used to prepare a selective and potent blocked ricin immunotoxin. In a series of experiments in vitro and in a SCLC xenograft model in nude mice, the tumor localization potential of the radiolabeled antibody SEN31 and the anti-tumor activity of the immunotoxin SEN31-bR, the non-specific binding activity of which had been greatly reduced by blocking of the galactose binding domains of the B-chain, was determined. Radiolabeling of SEN31 was performed by linking a 67Ga-labeled desferrioxamine moiety to the oligosaccharide side chains of the antibody in order to preserve the specific cell-binding activity. 67Ga-SEN31 bound to the antigenic sites on cells of the SW2 SCLC cell line, with a dissociation constant of 3.5 nM and, when injected i.v., selectively localized at the site of s.c.-growing SW2 tumor xenografts in nude mice, with a tumor-to-blood ratio of 3.5. The immunotoxin SEN31 -bR was potently and selectively active against SCLC cell lines both of classic and of variant morphologies. At a concentration of 300 pM the immunotoxin selectively eliminated 4.5 logs of clono-genic tumor cells. In nude mice, SEN31 -bR was cleared from the blood with biphasic kinetics following i.v. injection and maintained a stable serum level during continuous i.p. infusion. The growth of s.c. SW2 solid-tumor xenografts was delayed following a single i.v. injection or a continuous i.p. infusion, each at a non-toxic dose.  相似文献   

20.
Tumor-associated antigens are typically nonimmunogenic in cancer patients, "immune surveillance" having manifestly failed. The fact that most tumor antigens are normal human proteins presents significant obstacles to current cancer immunization approaches that researchers are presently striving to overcome. An alternative strategy bypasses immunization altogether by direct genetic alteration of autologous patient T cells, to create "designer T cells" specific to a particular antigen. Chimeric immunoglobulin-T cell receptors (IgTCR) with a specificity for carcinoembryonic antigen (CEA) were created to evaluate the optimal IgTCR structure for cancer therapy. Antigen-binding domains of a humanized antibody were combined with TCR signaling chains to yield four different chimeric IgTCR: single chain Fv fragment (sFv)-zeta, fragment antigen-binding (Fab)-zeta, sFv-epsilon, and Fab-epsilon. All of the IgTCR were well expressed on T cells, and all showed specific binding and activation, as demonstrated by IL-2 production on contact with immobilized or cellular CEA, excepting sFv-epsilon alone which was inert solely against cellular targets for steric reasons unique to this construct. In contrast to prior studies of isolated TCR chains that related increased tyrosine-based activation motifs in zeta as a reason for superior signaling potency, these tests are the first to show that epsilon and zeta are indistinguishable for T cell signaling when assayed in the context of the intact TCR complex. Further, Fab was equivalent to sFv as an IgTCR component for expression and antigen binding, establishing an important alternative for IgTCR antigen recognition because sFvs may often lose antigen affinity. When IgTCR was expressed on normal human T cells, cytotoxic potency was demonstrated at low E:T ratios, with T cell recycling and progressive tumor cell destruction. Contrary to recent speculations, these observations prove that high affinity TCR interactions are not an impediment to serial target engagement and disengagement by cytotoxic T cells. The multivalent intercellular interactions of target cell binding, activation, and cytotoxicity were resistant to inhibition by soluble CEA. These studies establish a potentially important new immunotherapeutic modality for the treatment of CEA-expressing tumors.  相似文献   

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