Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0026764 (multiple myeloma)
 36,148 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In order to develop a reagent capable of killing cells with high-affinity IgE Fc receptors, such as mast cells and basophils, ricin A-chain (the toxic portion of ricin) was conjugated to rat IgE myeloma protein, IR 162, via derivatization of the IgE by n-succinimidyl-3-(2-pyridyldithio)propionate (SPDP) thus creating an IgE-immunotoxin. Monensin (10(-7)-10(-8)M), a carboxylic ionophore, facilitated IgE-ricin A-chain (3 X 10(-7)M) toxicity in a dose-related fashion ith significant reductions in [3H]leucine incorporation compared to cells exposed only to monensin. This enhanced toxicity could be inhibited by the addition of both anti-ricin A-chain or anti-IgE, suggesting that different routes of intracellular processing may play a role in determining the toxicity of the IgE-ricin A-chain conjugate. Ricin B-chain (5 X 10(-7) and 5 X 10(-8)M) added to free ricin A-chain (10(-6)-10(-8)M) reproducibly facilitated toxicity, and this toxicity could be inhibited (30-90%) by lactose (50 mM). Ricin B-chain also facilitated IgE-ricin A-chain (2.75 X 10(-8)M) toxicity; however, this toxicity was not affected by lactose. The data suggest that ricin B-chain potentiates the cytosolic access of internalized IgE-immunotoxin and that the binding and internalization of the toxin was mediated via the IgE Fc receptor. A second type of IgE-ricin A-chain conjugate was synthesized whereby both IgE and ricin A-chain were derivatized with SPDP. RBL cells were killed in a dose-dependent manner by this IgE-ricin A-chain conjugate (2.5 X 10(-6)-2.5 X 10(-9)M) without requiring the addition of monensin or ricin B-chain. These data indicate that the intracellular route and processing of internalized immunotoxin is critical to eliciting toxicity.
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PMID:IgE-immunotoxins. II. IgE-ricin A-chain. 350 Jan 50

Ricin A-chain was purified from native ricin using lactosyl-Sepharose. It was non-toxic to whole cells at a concentration of 1 microM yet nearly as effective as an equimolar concentration of ricin in blocking in vitro protein synthesis. Hybridomas secreting monoclonal antibodies to ricin A-chain were produced using the murine myeloma cell line NS-1. These anti-ricin A-chain antibodies cross-reacted with whole ricin but exhibited little cross-reactivity with purified ricin B-chain. Antibodies 2F2 and 2F5 both immunoprecipitated ricin A-chain. Both antibodies also precipitated ricin B-chain, as did the irrelevant control antibodies MOPC-21 and MPC-11. Pre-incubation of B-chain with 0.1 M galactose eliminated greater than 90% of precipitation by 2F2, MOPC-21 and MPC-11 but effected minimally precipitation by 2F5. Enzyme-linked immunosorbent assays using antibodies 2F2 and 2F5 to detect ricin A-chain in murine or human serum were linear between 40 and 800 ng ricin A-chain per ml. Anti-ricin A-chain antibodies 2F2 and 2F5 produced some inhibition of in vitro A-chain catalytic activity. Specific monoclonal antibodies to A-chain hemitoxin will be useful for characterization of functional hemitoxin domains, in in vitro assays for the stability of A-chain immunotoxins, and in characterizing the cellular internalization and processing of conjugates containing ricin or ricin A-chain.
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PMID:Monoclonal antibodies to purified ricin A-chain: production and properties. 357 Mar 4

Three monoclonal antiidiotypic antibodies (AIA) to MOPC 315 IgA, G3 (IgG2b), A2 (IgG1) and D10 (a hybrid molecule consisting of gamma 1 and gamma 2a heavy chains), were characterized with respect to their binding constants (Ka) to MOPC 315 mouse myeloma cells. The Ka of G3 and A2 was 10(8)/mole; and that of D10 was 3 X 10(7)/mole. The AIA did not bind to a non-immunoglobulin (Ig) producing subclone of MOPC 315 cells (MOPC 315.36). Immunotoxins derived by conjugating ricin A chain (RTA) to G3 and A2 but not to D10 preferentially inhibited protein synthesis in MOPC 315 over MOPC 315.36 cells. These results suggest that the effectiveness of these immunotoxins assessed on the basis of their targeted cytotoxicity against MOPC 315 cells was dependent on the Ka but not on the Ig subclass of the AIA component of the immunotoxin.
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PMID:Inhibition of protein synthesis by monoclonal anti-idiotypic antibody-ricin A chain conjugates in MOPC 315 myeloma cells. 403 40

Ferritin conjugates of two plant agglutinins, concanavalin A and ricin, have been used as specific electron microscopic stains for covalently-bound saccharide residues on membrane fragments from a myeloma-cell homogenate. The results indicate that different saccharide residues are uniformly localized to a single surface of each membrane fragment. In particular, the ferritin-concanavalin A conjugate binds exclusively to the cisternal side of membrane fragments of the rough endoplasmic reticulum. If it is postulated that the biogenesis of eukaryotic plasma membranes involves an assembly-line process from precursor intracellular membranes, these observed asymmetric distributions of saccharides on cell membranes can be explained.
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PMID:Distribution of saccharide residues on membrane fragments from a myeloma-cell homogenate: its implications for membrane biogenesis. 411 11

A mouse myeloma cell line, 45.6.3, produces an IgG2b immunoglobulin (Ig) with 2 carbohydrate attachment sites on the heavy chains. One site is in the CH2 domain and the other in the VH region. The oligosaccharides at each site have different structures. The ratio of radioactive glucosamine incorporated in the VH compared with the CH2 oligosaccharide is approximately 1 to 3. In an attempt to understand this observation further, variant cell lines derived from 45.6.3 were isolated and their Ig were characterized. A ricin-resistant line, R4R1.5, has the same 2 attachment sites as the wild type, but the ratio of radioactive glucosamine in VH compared with CH2 was 1:1 and not 1:3 as in the wild type. This alteration is most probably due to cellular factors, since the Ig protein is unchanged. The M3.11 cell line produces an Ig with a polypeptide deletion involving the CH3 domain. In this Ig, a 3rd carbohydrate attachment site can be demonstrated. The percentage of radioactivity glucosamine in the CH2 domain compared with the total Ig is about 25% instead of 75% as in the wild type. These results suggest that the extent of glycosylation of different sites on Ig can be affected by both cellular factors and structural changes in the Ig protein.
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PMID:Immunoglobulin glycopeptides from an IgG2b-producing mouse myeloma cell line and from variant cell lines. 729 24

The lectin peanut agglutinin (PNA) and CD19 monoclonal antibody have been covalently linked to magnetic beads and utilized in an in vitro purging system for autologous bone marrow in multiple myeloma (MM). An alternative to mechanical purging involves the use of immunotoxins to provide specifically targeted cellular toxicity; however, no studies to date have examined the utility of a lectin-ricin A chain (RCA) combination as a purging agent in MM. Initially, we studied the internalization of PNA by target cells (Raji) using flow cytometry. The surface fluorescence intensity of PNA-treated Raji cells was reduced upon incubation at 37 degrees C, and subsequent studies with fixed cells detected the endocytosed PNA. Complete internalization occurred within 120 minutes, indicating the potential of PNA as a purging agent. We manufactured a novel PNA-RCA conjugate and demonstrated its strong and specific binding to PNA reactive cell targets. Subsequent experiments assessed the toxicity of the conjugate to Raji cells and normal bone marrow progenitor cells. 3H-leucine uptake assays showed that PNA-RCA was capable of reducing protein synthesis in Raji cells and that the toxic effects were specific. In addition, at concentrations of conjugate achieving greater than 99% selective cytotoxicity for Raji cells, adequate CFU-GM were preserved in normal marrow. These studies suggest that PNA-RCA may be of value as an in vitro purging agent for MM.
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PMID:The synthesis of a peanut agglutinin-ricin A chain conjugate: potential as an in vitro purging agent for autologous bone marrow in multiple myeloma. 749 62

We report the development of a potent anti-CD38 immunotoxin capable of killing human myeloma and lymphoma cell lines. The immunotoxin is composed of an anti-CD38 antibody HB7 conjugated to a chemically modified ricin molecule wherein the binding sites of the B chain have been blocked by covalent attachment of affinity ligands (blocked ricin). Conjugation of blocked ricin to the HB7 antibody has minimal effect on the apparent affinity of the antibody and no effect on the ribosome-inactivating activity of the ricin A-chain moiety. Four to six logs of CD38+ tumor cell line kill was achieved at concentrations of HB7-blocked ricin in the range of 0.1 to 3 nmol/L. Low level of toxicity for normal bone marrow (BM) granulocyte-macrophage colony-forming units (CFU-GM), burst-forming units-erythroid (BFU-E), colony-forming units-granulocyte/erythroid/monocyte/macrophage (CFU-GEMM) cells was observed. Greater than two logs of CD38+ multiple myeloma cells were depleted from a 10-fold excess of normal BM mononuclear cells (BMMCs) after an exposure to HB7-blocked ricin under conditions (0.3 nmol/L) that were not very toxic for the normal BM precursors. HB7-blocked ricin was tested for its ability to inhibit protein synthesis in fresh patients' multiple myeloma cells and in normal BMMCs isolated from two healthy volunteers; tumor cells from four of five patients were 100-fold to 500-fold more sensitive to the inhibitory effect of HB7-blocked ricin than the normal BM cells. HB7 antibody does not activate normal resting peripheral blood lymphocytes, and HB7-blocked ricin is not cytotoxic toward these cells at concentrations of up to 1 nmol/L. The potent killing of antigen-bearing tumor cells coupled with a lack of effects on peripheral blood T cells or on hematopoietic progenitor cells suggests that HB7-blocked ricin may have clinical utility for the in vivo or in vitro purging of human multiple myeloma cells.
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PMID:Anti-CD38-blocked ricin: an immunotoxin for the treatment of multiple myeloma. 771 3

We have generated a murine monoclonal antibody (UV3) which recognizes an epitope on ICAM-1 expressed on myeloma cells. By flow cytometric analysis, the epitope on ICAM-1 recognized by this antibody is strongly expressed on human myeloma cells, pre-B leukemia cells and Burkitt's lymphoma cell lines. Most human T cell lines are weakly positive. The antibody does not react with red blood cells, polymorphonuclear leukocytes (PMNs) or resting B lymphocytes from normal donors, and reacts very weakly with resting T cells. Immunohistochemical assays indicate that the antibody does not react with normal liver, kidney, heart, brain, thymus or lung. An immunotoxin (IT) was prepared by coupling UV3 to deglycosylated ricin A-chain (dgA). In protein synthesis inhibition assays it was highly cytotoxic to the human myeloma cell lines HS-SULTAN (IC50 = 1 x 10(-11)M) and ARH-77 (IC50 = 9 x 10(-11)M), but not to cell lines of T cell lineage or most cell lines of the B lineage. Our results suggest that the UV3-dgA may have therapeutic potential for the treatment of human multiple myeloma.
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PMID:Cytotoxicity of a novel anti-ICAM-1 immunotoxin on human myeloma cell lines. 790 88

Expression plasmids carrying a humanized N901 immunoglobulin heavy chain gene (hN901HC) fused to a gene encoding the native B chain of ricin toxin (RTB), hN901HC-RTB, or a sugar binding mutant of RTB, hN901HC-RTB delta gly, were constructed. In each case, the fused gene constructions were co-expressed in murine myeloma cells (Sp2/0) with the gene for humanized N901 immunoglobulin light chain to produce the secreted recombinant products hN901-RTB and hN901-RTB delta gly, respectively. When purified by affinity chromatography, both the hN901-RTB and hN901-RTB delta gly products were found to have an apparent molecular mass of M(r) = 210,000 and to be composed of two hN901 antibody heavy chains each fused to a full-length copy of RTB and two hN901 antibody light chains. In each of the recombinant fusions the hN901 antibody moiety retained the full binding affinity and specificity for its cognate antigen, CD56. Moreover, when mixtures of hN901-RTB and native ricin A chain were incubated in the presence of the antigen-positive target cell line SW-2, antigen-specific potentiation of ricin A chain cytotoxicity was observed. It has been demonstrated previously that lectin activity of the B chain is essential for A chain cytotoxicity, and we conclude that the fused wild-type B chain was properly folded and maintained lectin activity. These data demonstrate that feasibility of using recombinant ricin B chain in an immunotoxin and of using mammalian cell culture for its expression. The use of recombinant hN901-RTB fusion protein to evaluate the contribution of the lectin activity of ricin B chain in the penetration of cell membranes by ricin A chain is proposed.
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PMID:Expression and secretion of a recombinant ricin immunotoxin from murine myeloma cells. 853 70

The cytotoxicity of ricin and diphtheria toxin was studied in culture-adapted bloodstream forms of Trypanosoma brucei. Although ricin is endocytosed at a rate comparable to that of other internalized macromolecules, it is nontoxic to bloodstream-form trypanosomes. The resistance lies partly in low susceptibility of the targeted ribosomes: T. brucei cell-free protein biosynthesis is only partially inhibited by ricin A chain. In addition, ricin is degraded before it reaches the ribosomes, as the toxin is delivered to lysosomes. In contrast, diphtheria toxin shows similar cytotoxicities for bloodstream-form trypanosomes and mouse myeloma cells. Both trypanosome and myeloma cells are more than 1000-fold less sensitive to the action of the toxin than most other mammalian cell lines, although nicked reduced diphtheria toxin inhibits cell-free protein synthesis of T. brucei and myeloma cells to the same extent as that of a rabbit reticulocyte lysate. The effect of diphtheria toxin on T. brucei in vitro translation is NAD+ dependent, suggesting that ADP-ribosylation of elongation factor 2 could be the cause of the inhibition as it is in mammalian cells. Thus, the toxic moiety of diphtheria toxin is suitable for preparation of cell-type-specific cytotoxic reagents directed towards trypanosomes.
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PMID:Differential toxicity of ricin and diphtheria toxin for bloodstream forms of Trypanosoma brucei. 949 50


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