Imaging and therapy with monoclonal antibodies in non-hematopoietic tumors.

Although radiolabelled monoclonal antibodies are useful in tumor imaging, in our opinion their most important role is in the evaluation of the capacity of newly developed monoclonal antibodies to localize in tumors specifically. Intravenous injections of monoclonal antibody fragments, labelled with beta-emitting radionuclides, can completely eradicate large human colon carcinoma xenografts in nude mice whereas this is not achieved by unconjugated monoclonal antibodies. New strategies are being developed to make radioimmunotherapy applicable to carcinoma patients.

Immunochemical characterization of two antigens recognized by new monoclonal antibodies against human colon carcinoma.

Two different monoclonal antibodies (MAb), called L-D1 and L-C5, were produced after immunization with either intact cells or the methanol phase of glycolipid extracts, respectively, from the same human colon carcinoma line, LoVo. As determined by an antibody-binding radioimmunoassay (RIA) on intact cells, MAb L-D1 and MAb L-C5 were highly reactive with all five colon carcinoma lines tested and with only one out of the 21 cell lines of various tissue origin tested. No reactivity of either MAb was observed with peripheral blood lymphocytes, granulocytes, or erythrocytes from healthy donors of various blood groups. Both MAb were tested in competitive binding experiments with an anti-CEA MAb from our laboratory (CEA 35) and with two previously described anti-colon carcinoma MAb from the Wistar Institute called 1083-17-1A (17-1A) and NS-19.9. In competitive binding experiments, MAb L-D1 was inhibited by MAb 17-1A and reciprocally, whereas MAb L-C5 was not inhibited by any of the other MAb tested. MAb L-D1 precipitated a major protein band with an apparent molecular weight (MW) of 41 kilodaltons (kD); interestingly, MAb 17-1A, which was reported to react with an uncharacterized antigen, precipitated the same protein band of 41 kD. This was confirmed with immunodepletion experiments. Furthermore, after treatment of the colon carcinoma cell line with tunicamycin, both MAb L-D1 and 17-1A precipitated a protein band of 35 kD. This shift of 6 kD suggests that the glycoprotein recognized by these 2 MAb contains two to three N-linked carbohydrate side chains. MAb L-C5 precipitated a group of three to four protein bands ranging from 43 to 53 kD that were not modified by tunicamycin treatment. A preliminary study conducted by using immunoperoxidase labeling on frozen sections of primary colon carcinoma showed that the two new MAb react strongly with these tumors, but also weakly with the normal adjacent mucosa, as did the other anti-colon carcinoma MAb tested.

Molecular and therapeutic characterization of anti-ectodysplasin A receptor (EDAR) agonist monoclonal antibodies.

The TNF family ligand ectodysplasin A (EDA) and its receptor EDAR are required for proper development of skin appendages such as hair, teeth, and eccrine sweat glands. Loss of function mutations in the Eda gene cause X-linked hypohidrotic ectodermal dysplasia (XLHED), a condition that can be ameliorated in mice and dogs by timely administration of recombinant EDA. In this study, several agonist anti-EDAR monoclonal antibodies were generated that cross-react with the extracellular domains of human, dog, rat, mouse, and chicken EDAR. Their half-life in adult mice was about 11 days. They induced tail hair and sweat gland formation when administered to newborn EDA-deficient Tabby mice, with an EC(50) of 0.1 to 0.7 mg/kg. Divalency was necessary and sufficient for this therapeutic activity. Only some antibodies were also agonists in an in vitro surrogate activity assay based on the activation of the apoptotic Fas pathway. Activity in this assay correlated with small dissociation constants. When administered in utero in mice or at birth in dogs, agonist antibodies reverted several ectodermal dysplasia features, including tooth morphology. These antibodies are therefore predicted to efficiently trigger EDAR signaling in many vertebrate species and will be particularly suited for long term treatments.

Covalent binding of C3b to monoclonal antibodies selectively up-regulates heavy chain epitope recognition by T cells.

Protein C3 of the complement system is known for its role in the nonspecific immune response. Covalent binding of C3b to antigen upon complement activation also plays a significant role in specific T cell immune response. C3b-antigen complexes can bind to complement receptors on the antigen-presenting cell, and the C3b antigen link (most often an ester link) remains fairly stable inside the cells. In this study, IgG1,kappa and IgG2a,kappa murine monoclonal antibodies (mAb) were used as antigens; covalent complexes between mAb and C3b were produced and purified in vitro from purified proteins; human B cell lines and T cell clones were raised from tumor patients who received mAb injections for cancer therapy or diagnosis. Recognition of epitopes of these mAb by T cell clones when the mAb were processed alone or bound to C3b was compared. IgG or IgG-C3b complexes presented by B cell lines were able to stimulate proliferation of kappa light chain-specific T cell clones at similar concentrations. In contrast, IgG-C3b complex recognition by heavy chain-specific T cell clones required 100-fold less IgG-C3b than uncomplexed IgG. As C3b was shown to be covalently bound only to the IgG heavy chains in the complexes, C3b chaperoning is restricted to only the IgG heavy chain and selectively influences intracellular steps of IgG heavy chain processing. This differential modulation of C3b suggests an early dissociation of IgG heavy and light chains in antigen-presenting cells.

Tomoscintigraphy for detecting gastrointestinal and medullary thyroid cancers: first clinical results using radiolabelled monoclonal antibodies against carcinoembryonic antigen.

Transaxial tomoscintigraphy (or single-photon emission computerised tomography) was used to detect secondary deposits of carcinoma in 17 patients who had been injected with iodine-131-labelled monoclonal antibodies against carcinoembryonic antigen. Of 17 tumor sites studied by tomoscintigraphy 16 were detected (sensitivity 94%); five sites had a volume smaller than 10 cm3. Tomoscintigraphy also detected three unknown tumour deposits later confirmed by surgery or radiology. In contrast, when 21 tumour sites in the same patients were studied by rectilinear scintigraphy, only nine tumour sites were detected (sensitivity 43%), of which eight had a volume larger than 50 cm3.

Comparative localization of glioma-reactive monoclonal antibodies in vivo in an athymic mouse human glioma xenograft model.

Radioiodinated murine monoclonal antibodies (Mabs) 81C6, Me 1-14, C12, D12, and E9, made against or reactive with human gliomas but not normal brain, and Mab UJ13A, a pan-neuroectodermal Mab reactive with normal human glial and neural cells, were evaluated in paired label studies in the D-54 MG subcutaneous human glioma xenograft model system in nude mice. Following intravenous injection in the tail vein of mice bearing 200-400 mm3 tumors, specific localization of Mabs to tumor over time (6 h-9 days) was evaluated by tissue counting; each Mab demonstrated a unique localization profile. The comparison of localization indices (LI), determined as a ratio of tissue level of Mab to control immunoglobulin with simultaneous correction for blood levels of each, showed Mabs 81C6 and Me 1-14 to steadily accumulate in glioma xenografts, maintaining LI from 5-20 at 7-9 days after Mab injection. Mab UJ13A peaked at day 1, maintaining this level through day 2, and declining thereafter. Mabs D12 and C12 peaked at days 3 and 4, respectively, and E9 maintained an LI of greater than 3 from days 3-9. Percent injected dose localized/g of tumor varied from a peak high of 16% (81C6) to a low of 5% (Me 1-14 and UJ13A). Immunoperoxidase histochemistry, performed with each Mab on a battery of primary human brain neoplasms, revealed that Mabs 81C6 and E9, which demonstrated the highest levels of percent injected dose localized/g of tumor over time, reacted with antigens expressed in the extracellular matrix. This finding suggests that extracellular matrix localization of antigen represents a biologically significant factor affecting localization and/or binding in the xenograft model used. The demonstration of significant localization, varied kinetics and patterns of localization of this localizing Mab panel warrants their continued investigation as potential imaging and therapeutic agents for human trials.

Sandwich enzyme immunoassay using three monoclonal antibodies against different epitopes of carcinoembryonic antigen (CEA).

Purified monoclonal antibodies (Mab) produced by 3 hybridomas and reacting with 3 different epitopes of carcinoembryonic antigen (CEA) were used in a solid phase enzyme immunoassay. Two Mabs were physically adsorbed to polystyrene balls and the third Mab was coupled to alkaline phosphatase using the bifunctional reagent N-succinimidyl-3-(2-pyridyldithio)-propionate. During a first incubation, CEA from heat-extracted serum samples was immunoadsorbed to the antibody coated balls. After washing of the balls, bound CEA was detected by a second incubation with the enzyme coupled Mab. The sensitivity of the assay was 0.6 ng per ml of serum. A total of 196 serum samples from patients with various types of carcinoma, with liver cirrhosis, or from healthy blood donors with or without smoking habits, were tested. The results obtained with the monoclonal enzyme immunoassay (M-EIA) were compared with those obtained with perchloric acid extracts of the same serum samples tested by an inhibition radioimmunoassay using conventional goat anti-CEA antiserum. There was an excellent correlation between the two assays. In particular, the new M-EIA gave good results for the detection of tumor recurrences in the follow-up of colon carcinoma patients. However, despite the use of exclusively monoclonal antibodies the new assay detected a similar percentage of slightly elevated CEA values as the conventional assay in patients with non-malignant disease, suggesting that the CEA associated with non-malignant diseases is immunologically identical to the CEA released by colon carcinoma.

Specificity and affinity of monoclonal antibodies against carcinoembryonic antigen.

The binding specificities of 52 well-characterized monoclonal antibodies (Mabs) against carcinoembryonic antigen (CEA) from 12 different research groups were studied by immunohistochemistry and immuno flow cytometry. In addition, the binding constant for the interaction between Mab and CEA was determined by a solution-phase assay. Cryostat sections of colon carcinoma and normal colon, stomach, liver, pancreas, and spleen were studied by immunohistochemistry. Peripheral blood granulocytes, monocytes, and lymphocytes were assayed by immuno flow cytometry. The Mabs used here have previously been classified into five essentially nonoverlapping epitope groups (GOLD 1-5) (Cancer Res., 49: 4852-4858, 1989). Most Mabs cross-reacted with different normal tissues, ranging from highly cross-reactive Mabs (positive reaction with 8 of 9 discriminating tissues) to relatively specific Mabs (positive reaction with 1 of 9 discriminating tissues). Five Mabs (10%) were specific, reacting only with colon carcinoma, normal colon mucosa, and normal gastric foveola. There was a correlation between epitope group and binding specificity. Mabs with a high degree of CEA specificity almost exclusively belonged to epitope groups 1, 2, and 3, while highly cross-reactive Mabs belonged to epitope groups 4 and 5. There was no correlation between antibody specificity and affinity for CEA. Specific Mabs with high as well as low affinity were found.

Swine monoclonal antibodies of high affinity and specificity to carcinoembryonic antigen.

To avoid the exclusive use of rodent monoclonal antibodies (MAbs) in patients for the detection of tumors by immunoscintigraphy and for radioimmunotherapy, swine MAbs were produced that are directed against carcinoembryonic antigen (CEA). Spleen cells from 2 pigs immunized with purified colon carcinoma CEA were fused with a nonsecreting mouse myeloma cell line by conventional methods, except that a particularly long immunization protocol and large amounts of spleen and myeloma cells were used. Of 1,200 growing hybrids tested, 20 were found initially to produce antibodies binding to radiolabeled CEA. Seven stable clones producing anti-CEA MAbs for more than 6 months were derived from these hybrids by repeated subcloning. The pig origin of the seven MAbs was demonstrated in a solid-phase CEA enzyme immunoassay where anti-pig immunoglobin (Ig) antibodies coupled to peroxidase gave a positive reaction while anti-mouse Ig antibodies were entirely negative. All swine MAbs were of the IgG isotype. Three anti-CEA MAbs showed no cross-reactivity with granulocytes, while four others gave various degrees of reactivity with different granulocyte glycoproteins. Competitive binding to CEA performed for two purified swine MAbs showed that they recognized two different epitopes. The affinity constants measured for these two MAbs by Scatchard plot on purified CEA were high (1.2 X 10(9) and 1.2 X 10(10) liter/mol). One of the MAbs was tested in vivo for tumor localization by injection, after radiolabeling, in nude mice bearing human colon carcinoma xenograft. High ratios of tumor to normal tissue were obtained with mean values of 10.5 for intact MAbs and of 26.8 for F(ab')2 fragments of the porcine MAb. The results showed that heterofusion with this particular protocol can be used to produce swine MAbs of high affinity and specificity for a well-defined tumor marker. These reagents may have an important clinical utility, particularly in patients who became sensitized to mouse immunoglobulins.

Reactivity of antiglioma monoclonal antibodies for a large panel of cultured gliomas and other neuroectoderm derived tumors.

We produced three monoclonal antibodies, BF7, GE2 and CG12, against cultured human glioma cells. Their specificity was tested by an indirect antibody-binding radioimmunoassay on a panel of glial and non-glial tumor cell lines. BF7 and GE2 react preferentially with glioma cells and, except for one colon carcinoma line, they do not bind to the control non-neuroectodermal cells; they appear to be directed against common malignant glioma associated antigens. CG12, the third monoclonal antibody, binds to the great majority of tumor cell lines of neuroectodermal origin and does not bind to any other cell lines tested.

Common human melanoma-associated antigen(s) detected by monoclonal antibodies.

Hybridoma cells have been derived from a fusion between mouse myeloma cells (P3-NSI/1Ag4) and spleen cells from a mouse immunized with membrane-enriched fractions from the human melanoma cell line Me-43. Of the 26 hybrids obtained, seven secreted antibodies which reacted with the melanoma cell line used for immunoassay. The specificity of the antibodies produced by the seven positive hybrids was further investigated on 16 melanoma cell lines, 15 other tumors, and 14 lymphoblastoid cell lines. The antibodies from four positive hybrids showed a broad reactivity, whereas those from three hybrids reacted exclusively with melanoma cells. The antibodies from two of these three hybrids, alpha-Mel/5 and alpha-Mel/14, seem to be directed against common melanoma antigen(s) since they reacted with all (with one exception) of the 16 melanoma cell lines tested only with five of the 16 melanoma lines. Reciprocal binding inhibition tests using [3H]leeucine-labeled antibodies showed that alpha-Mel/5 and alpha-Mel/14 antibodies were directed against different antigenic determinants.

Phenotyping of 60 cultured human gliomas and 34 other neuroectodermal tumors by means of monoclonal antibodies against glioma, melanoma and HLA-DR antigens.

The reactivity spectrum of three monoclonal antibodies (Mabs) to human malignant glioma, five Mabs to melanomas and one Mab anti-HLA-DR was investigated by an indirect antibody binding radioimmunoassay on a panel of cells derived from 60 glioma lines, including 47 malignant astrocytomas, 11 low-grade astrocytomas and two malignant ependymomas as well on cells from 12 melanoma, three neuroblastoma, three medulloblastoma, two schwannoma, two retinoblastoma, two choroïd plexus papilloma, ten meningioma and 12 unrelated tumor lines. The anti-glioma Mabs BF7 and GE2 reacted preferentially with gliomas, while the anti-glioma Mab CG12 reacted with gliomas, melanomas, neuroblastomas and medulloblastomas. The five anti-melanoma Mabs reacted with gliomas, neuroblastomas and medulloblastomas. The anti-HLA-DR Mab D1-12 reacted with gliomas, melanomas and some meningiomas. On the basis of the data presented, we describe three different antigenic systems; the first one is glioma-associated, the second one is related to differentiation antigens expressed on cells derived from the neuroectoderm and the third is represented by HLA-DR antigens which are expressed not only on B-lymphoblastoid cells but also on melanomas and gliomas.

Monoclonal antibodies identify a CEA crossreacting antigen of 95 kD (NCA-95) distinct in antigenicity and tissue distribution from the previously described NCA of 55 kD.

During the selection of monoclonal antibodies (MAb) raised against purified carcinoembryonic antigen (CEA), two MAbs were identified which immunoprecipitated a glycoprotein of 95 kD present both in perchloric acid extracts of normal lung and on the surface of normal granulocytes. This antigen was distinct from the previously reported normal glycoprotein crossreacting with CEA (NCA) which had a molecular weight of 55 kD. The difference between the smaller and the larger crossreacting antigens termed NCA-55 and NCA-95, respectively, was demonstrated by SDS-polyacrylamide gel electrophoresis, by elution from Sephadex-G200 and by selective binding to a series of anti-CEA MAb. Out of six MAb which all bound CEA purified from colon carcinoma, three did not react with these two crossreacting antigens, one bound only NCA-95, one reacted only with NCA-55 and one reacted with both NCA-55 and NCA-95. Immunoadsorbent purified preparations of 125I labelled NCA-95 and NCA-55 were found useful for the screening of new anti-CEA MAb. In addition, when tested on frozen sections of colon carcinoma, normal spleen, normal lung and pancreas, each type of MAb gave a clearly different pattern of reactivity. The three anti-CEA MAb which did not bind any of the crossreacting antigens stained only the colon carcinoma cells; the MAb binding to either one of the two types of NCA gave a similar pattern of reactivity both on colon carcinoma cells and on granulocytes. However, on normal lung and pancreas, the MAb binding NCA-55 stained granulocytes as well as bronchiolar and alveolar epithelial cells in lung and inter- and intra-lobular duct epithelial cells in pancreas, whereas the MAb binding only NCA-95 stained only the granulocytes. Thus, the newly identified NCA-95 appears to differ from NCA-55 not only in terms of molecular size and antigenicity but also by the fact that in normal lung and pancreas it is found in granulocytes but not in epithelial cells.

Inhibition and enhancement of in vitro helper activity of apocytochrome c-specific murine T cell populations and clones by anti-apocytochrome c-specific monoclonal antibodies.

A murine monoclonal antibody (mAb) specific for apocytochrome c was found to be able to either inhibit or enhance the helper activity of mouse apocytochrome c-specific T cell clones and populations in a hapten (trinitrophenyl)-carrier (apocytochrome c) system of T-B cell cooperation. This effect of the mAb was carrier specific, could not be ascribed simply to a shift in the kinetics of the antibody response and was observed using apocytochrome c T helper cells of different mouse haplotypes. In addition, the anti-apocytochrome c mAb was able to inhibit specific T helper cell activity even when the T cells were triggered with antigen-presenting cells pulsed with antigen. Taken together, these results suggested that the mAb was inhibiting helper activity due to its ability to modify the interaction between T cells and antigen-presenting cells.