EWS and ATF-1 gene fusion induced by t(12;22) translocation in malignant melanoma of soft parts.

The genes involved in the t(12;22)(q13;q12) translocation found recurrently in malignant melanoma of soft parts have been characterized and shown to form, in four cases studied, hybrid transcripts. The deduced chimaeric protein encoded by the der(22) chromosome consists of the N-terminal domain of EWS linked to the bZIP domain of ATF-1, a transcription factor which may normally be regulated by cAMP. ATF-1 has not previously been implicated in oncogenesis. EWS was first identified as forming a hybrid transcript in Ewing's sarcoma, which links its N-terminal domain to the DNA binding domain of the FLI-1 gene. Thus the oncogenic conversion of EWS follows a common scheme of activation, exchanging its putative RNA binding domain with different DNA binding domains that appear to be tumour-specific.

Progress and prospects: biological properties and technological advances of herpes simplex virus type 1-based amplicon vectors.

The last two years have seen significant advances in our understanding of the cellular innate responses elicited or activated by the entry of amplicon particles, which may, in part, explain the transient nature of transgene expression often observed in cells infected with helper-free amplicon stocks. At the technological level, the most consistent progress has been in strategies to enhance the stability of transgene cassettes, either through integration into host chromosomes or through the conversion of the amplicon genome into a replication-competent extrachromosomal element.

Cytokine, chemokine, and co-stimulatory fusion proteins for the immunotherapy of solid tumors.

This chapter describes the generation of novel reagents for the treatment of cancer using fusion proteins constructed with natural ligands of the immune system. Immunotherapy is a powerful therapeutic modality that has not been fully harnessed for the treatment of cancer. We and others have hypothesized that if the proper immunoregulatory ligands can be targeted to the tumor, an effective immune response can be mounted to treat both established primary tumors and distant metastatic lesions. Though it is generally believed that immunotherapy has the potential to treat only residual disease, we offer evidence that this approach can, by itself, destroy large tumor masses and produce lasting remissions of experimental solid tumors. From these studies, three major classes of immune activators, namely, cytokines, chemokines, and costimulatory molecules, have been shown to generate antitumor responses in animal models. In addition, the reversal of immune tolerance by the deletion of T regulatory (Treg) cells has been shown to be equally important for effective immunotherapy. In an attempt to identify reagents that can provide an enhanced immune stimulation and treatment of cancer, our laboratory has developed a novel monoclonal antibody targeting approach, designated Tumor Necrosis Therapy (TNT), which utilizes stable intracellular antigens present in all cell types but which are only accessible in dead and/or dying cells. Since tumors contain necrotic and degenerating regions that account for 30-80% of the tumor mass, this targeting approach can be used to deliver therapeutic reagents to the core of tumors, a site abundant in tumor antigens. In our first set of reagents, a panel of cytokine fusion proteins was genetically engineered using monoclonal antibody chimeric TNT-3 (chTNT-3) directed against necrotic regions of tumors (single-stranded DNA) fused with IL-2, or GM-CSF, or TNFalphaa, or IFNgamma. Tested against different solid tumors, these reagents were found to mount an effective although transient immune response to tumor especially when used in combination. To improve upon these results, additional chTNT-3 fusion proteins using the liver-expression chemokine (LEC) and the costimulatory molecule B7.1 were constructed. Both of these reagents were found to work significantly better than the above cytokine fusion proteins due to their ability to stimulate multiple arms of the immune system deemed useful for cancer immunotherapy. Finally, the Tumor Necrosis Factor Superfamily (TNFSF) gene DC137L was used to generate chTNT-3 antibody (targeted) and soluble Fc (untargeted) fusion proteins. When used alone, both forms of costimulatory fusion proteins were found to produce in a s dose-dependent manner, complete regression of murine solid tumors. Evidence is presented to show that Treg cells play an important role in suppressing antitumor immunity since the deletion of these cells, when used in combination with LEC or costimulatory fusion proteins, produced profound and effective treatment with sustained memory. It is hoped that these data will further the preclinical development of soluble Fc and antibody based fusion proteins fro the immunotherapy of cancer.

[HSV1-derived vectors: a powerful and flexible system for genes transfers]. / Les vecteurs amplicons dérivés du virus HSV1 : un système souple et puissant pour le transfert de gènes.

Amplicons are non-integrative defective herpes simplex type 1 (HSV1) derived vectors. Their genomes are entirely free of viral genes, making these vectors non toxic for infected cells and non pathogenic for inoculated animals. In addition, amplicon vectors possess the unique property of delivering up to 150 kbp of foreign DNA. These characteristics make amplicon vectors one of the most powerful and promising viral vectors for gene transfer. This review illustrates several interesting applications using amplicon vectors, as well as problems that need to be resolved in order to obtain stable and physiological transgene expression.

Diffusion and binding of monoclonal antibody TNT-1 in multicellular tumor spheroids.

Tumor spheroids of HT-29 human colon adenocarcinoma and A375 melanoma were established to investigate the uptake and clearance kinetics of TNT-1, a monoclonal antibody that targets necrotic cells of tumors. Our data reveal that there was rapid uptake of TNT-1 and its F(ab')2 fragment in both spheroid models, whereas an antibody of irrelevant specificity, Lym-1, and its F(ab')2 fragment bound poorly to the spheroids. Unlike previously reported monoclonal antibodies to tumor cell-surface antigens, TNT-1 showed 1) a linear uptake that increased over time without saturation in tumor spheroids and 2) an unexpected uptake by a subpopulation of cells in the viable outer rim of the spheroids. These preclinical studies provide important information concerning the therapeutic potential of TNT monoclonal antibodies for the treatment of cancer and micrometastases.

Feeder layer and nutritional requirements for the establishment and cloning of human malignant lymphoma cell lines.

Cell lines were successfully established in continuous suspension culture from 10 patients with a histopathological diagnosis of diffuse histiocytic lymphoma (SU-DHL-1 to SU-DHL-10), two with North American Burkitt's lymphoma (SU-AmB-1 and SU-AmB-2), and one with acute lymphoblastic leukemia (SU-ALL-1). By screening a variety of parameters, including media, sera, effusion fluids, feeder layers, and chemical supplements, the nutritive growth requirements of lymphoma cells obtained from malignant effusions and lymph node biopsies were determined for each tumor. Most of these cell lines initially required human skin fibroblast or epithelial cell feeder layers from which they could be weaned after one to six weeks in culture and maintained in Roswell Park Memorial Institute Tissue Culture Medium 1640 containing 20% fetal calf serum and 10% pooled human serum. Several of these cell lines were successfully cloned on 0.5% Noble agar substrates. In the presence of human serum and selected feeder monolayers, cloning efficiencies increased significantly from less than 1% to 15 to 25%. In addition, the cloning efficiencies of certain cell lines showed a concentration-dependent increase with specific chemical supplements including L-cysteine and dithiothreitol. Placental colony-stimulating factor, nerve growth factor, epithelial growth factor, and fibroblastic growth factor were ineffective in augmenting the cloning efficiencies of the human lymphoma cell lines. After a single passage on agar, cells subpassaged from visible colonies showed markedly increased cloning efficiencies to levels as high as 50%. Such cloning efficiencies, coupled with the use of replica plating, make this technique applicable to genetic and quantitative radiobiological, immunological, and chemotherapeutic studies. Although these methods have thus far been used only with lymphoreticular tumors, they may also be applicable to the cell culture of other human neoplasms and normal tissues.

A novel method for the detection of necrotic lesions in human cancers.

Data are presented in support of the hypothesis that malignant tumors, containing abnormally permeable, degenerating cells, can be selectively detected using monoclonal antibodies to intracellular antigens. Biodistribution, imaging, and autoradiographic studies were performed in nude mice transplanted with four different human tumor cell lines to demonstrate the binding of radiolabeled antinuclear monoclonal antibodies within bulky tumors containing necrotic lesions. For these studies, two monoclonal antibodies, designated TNT-1 (IgG2a) and TNT-2 (IgM) were chosen since they were found to bind to abundant nuclear antigens which are retained in permeable, dying cells. F(ab')2 fragments prepared by pepsin digestion were radiolabeled with iodine-125 or iodine-131 by the iodogen method for i.v. administration. Biodistribution studies in nontumor-bearing BALB/c mice at various time intervals revealed normal patterns of antibody excretion with no accumulation of antibody in healthy organs. In contrast, biodistribution studies performed on Day 3 in tumor-bearing nude mice showed high tumor to organ ratios in those animals bearing necrotic tumors. Necrotic regions dissected at necropsy gave tumor to blood ratios as high as 131:1. Transplants having little demonstrable necrosis were found to have low tumor to blood ratios (0.4:1). Sequential imaging studies confirmed the high tumor-to-organ ratios and showed positive tumor imaging as early as 4 h. Autoradiographic studies of excised tumors showed the presence of label selectively in necrotic areas with preferential labeling over the nuclei of degenerating cells. Because of the universal presence of these nuclear antigens and the known prevalence of necrosis in tumors, this approach may be of value for the imaging and treatment of a wide variety of cancers in humans.

Tumor necrosis treatment of ME-180 human cervical carcinoma model with 131I-labeled TNT-1 monoclonal antibody.

In contrast to normal tissues, many malignant tumors contain a high proportion of dead and dying cells. The loss of membrane integrity that accompanies cellular degeneration permits macromolecules, including antibodies, to freely enter the cell cytoplasm. Based upon these observations, it was hypothesized that monoclonal antibodies to intracellular antigens, which are integral structural components and are retained by degenerating cells, may be used to target a wide range of human malignancies. Previous studies by our laboratory utilizing these principles have demonstrated the feasibility of imaging four different histological types of human cancer in a nude mouse model, using monoclonal antibodies directed against insoluble intranuclear antigens. The present study describes the application of this approach, designated tumor necrosis treatment, for the radioimmunotherapy of transplantable ME-180 human cervical carcinomas in the nude mouse. Groups of tumor-bearing nude mice received three weekly treatments of 150 or 300 microCi of 131I-labeled experimental (TNT-1) or control (Lym-1) monoclonal antibodies. Detailed biodistribution data, dosimetric evaluations, and therapeutic results are presented to demonstrate the effective and preferential targeting of 131I-labeled TNT-1 monoclonal antibody within the tumor. In the experimental groups, the dose delivered to the tumor was sufficient to induce clinical regressions in 88% of treated animals, without evidence of toxicity to normal tissues. Complete regressions were obtained in 25% of the mice treated with high dose TNT-1. Microscopic examination of the implantation sites of these mice demonstrated the presence of acute radiation damage and residual keratin-positive tumor cells showing marked evidence of degeneration. Dosimetric data obtained over the 3-week treatment period showed that, unlike control treated mice, which received approximately 500 cGy each week, the experimental animals received increasing doses of radiolabeled antibody with each treatment (averages for weeks 1, 2, and 3: 1066, 2046, and 2476 cGy, respectively). In accordance with these data, enhanced imaging and therapeutic responses were observed with each therapeutic dose in the TNT-1-treated groups, compared with controls. These results indicate that TNT-1 therapy produces an ever expanding population of TNT-1-positive targets in the tumor as a result of the centrifugal killing of adjacent viable tumor cells. To help illustrate these results, a four-compartment model of the dose distribution kinetics of TNT-1 is presented for discussion with respect to the possible application of this method for the imaging and treatment of cancer in

Use of a newly established human cell line (SU-CCS-1) to demonstrate the relationship of clear cell sarcoma to malignant melanoma.

A new tumor cell line, designated SU-CCS-1, was established from the malignant pleural effusion of a 16-year-old Caucasian girl with clear cell sarcoma. Morphological studies at the light- and electron-microscopic levels revealed similar features between the SU-CCS-1 cells and the primary tumor. Ultrastructural and cytochemical techniques showed that both the SU-CCS-1 cell line and the original tumor were amelanotic in nature. The malignant derivation of the SU-CCS-1 cell line was demonstrated by intracranial and s.c. heterotransplantation in the nude, athymic mouse and by cytogenetic analysis which showed that the cell line had a hypodiploid chromosome number and several karyotypic abnormalities. Live-cell radioimmunoassay procedures using a large panel of monoclonal antibodies directed against tumor-associated antigens revealed that, phenotypically, SU-CCS-1 closely resembled melanoma tumor cell lines. Immunological assays for the detection of neuroendocrine-associated peptides, hormones, and enzymes revealed that, like melanoma, the SU-CCS-1 cell line was actively producing alpha-melanotropin, S-100 antigen, and nerve growth factor. A notable difference between these tumor types was the capacity of SU-CCS-1 to produce bombesin, an active neuropeptide whose synthesis has been found in cell lines from patients with small cell carcinoma of the lung. From these studies, we concluded that the SU-CCS-1 cell line is phenotypically similar to melanoma, yet displays unique characteristics which distinguishes it from other sarcomas. The availability of an established clear cell sarcoma cell line will greatly facilitate further studies aimed at uncovering the histogenesis of this rare cancer.

Identification of a monoclonal antibody, TV-1, directed against the basement membrane of tumor vessels, and its use to enhance the delivery of macromolecules to tumors after conjugation with interleukin 2.

mAbs reactive with epitopes expressed on tumor vessels were evaluated as universal delivery agents of peptides with vasoactive properties to enhance the uptake of macromolecules in tumors. Unlike other reported approaches to target tumor vessels, a mAb designated TV-1 targets a basement membrane antigen that is found in all tissues but that is accessible only in tumor vessels, making it an alternative vehicle for the delivery of biologically active peptides to tumors. A panel of 30 monoclonal and polyclonal antibodies was screened by immunohistochemistry on sections of human tumors, normal vascular endothelium, and connective tissues. Five antibodies were chosen for in vivo evaluation, including two antifibronectin antibodies (TV-1, HFN 7.1), one anti-basic fibroblast growth factor antibody (anti-BFGF), and two antibodies reactive with a mesenchymal cell antigen (TP-1, TP-3). Three nude mouse tumor models characterized by varying degrees of vascularization (low to high) were used. After chemical conjugation to interleukin 2 (IL-2), these antibodies were used to pretreat tumor-bearing nude mice 3 h before injection with a radiolabeled mAb directed to the transplanted tumors. Pretreatment with TV-1/IL-2 or HFN 7.1/IL-2 produced a 3-fold higher tumor uptake of radiolabel compared to control mice pretreated with mAb alone. The other three vasoactive immunoconjugates failed to show significant increases in these tumor models. When TV-1/IL-2 was compared with the specific vasoconjugate (Lym-1/IL-2) as a pretreatment in the Raji lymphoma model, which has low vascularization, TV-1/IL-2 yielded approximately 60% of the tumor uptake seen with Lym-1/IL-2. In comparison, pretreatment with TV-1/IL-2 in the LS174T colon carcinoma model, which has high vascularization, yielded approximately the same tumor uptake seen with the B72.3/IL-2 vasoconjugate, which directly targets the tumor cells. These studies demonstrate that a mAb directed against fibronectin in the endothelial subcellular matrix can be used to deliver vasoactive agents to tumors.

Expression of maturation-specific nuclear antigens in differentiating human myeloid leukemia cells.

The expression of three myeloid-specific nuclear antigens was studied by indirect immunofluorescence with murine monoclonal antibodies in human myeloid (HL-60, ML-2, KG-1, and B-II) leukemia cells treated with chemical inducers of cell differentiation. Treatment of the promyelocytic HL-60 cells with dimethyl sulfoxide or 1,25-dihydroxyvitamin D3 induced the cells to acquire a phenotype that resembled that of granulocytes and monocytes-macrophages, respectively. These phenotypes were characterized by changes in cell growth, cell morphology, expression of specific cell surface antigens, and activities of lysozyme and nonspecific esterase enzymes. Induction of these differentiation markers in the HL-60 cells was associated with induction of the myeloid-specific nuclear antigens. The ML-2 cells, which are arrested at the myeloblast-promyelocyte stage, were also susceptible to the induction of cell differentiation and to changes in the expression of the nuclear antigens, but the degree of susceptibility was less than in the HL-60 cells. The less-differentiated KG-1 and B-II myeloid cells were either not responsive or responded only in a limited degree to the induction of cell differentiation or to changes in the expression of the nuclear antigens. We suggest that the reactivity of cells with monoclonal antibodies to specific nuclear antigens can be used as a maturational marker in cell differentiation studies. Furthermore, nuclear antigens expressed early in cellular differentiation may provide information about changes in regulatory elements in normal and malignant cells.

Simultaneous nuclear antigen and DNA content quantitation using paraffin-embedded colonic tissue and multiparameter flow cytometry.

The simultaneous quantitation of nuclear antigens and DNA content is presented using monoclonal antibodies and flow cytometric analysis, with paraffin-embedded human colonic pathology specimens utilized as source material. The monoclonal antibodies evaluated were shown by immunogold electron microscopy to recognize nuclear proteins preferentially associated with interchromatin (p105) and heterochromatin (p34) regions. Indirect immunofluorescence analysis of p105 revealed two distinct G1-G0 cell subpopulations in cells from normal colonic epithelium and colonic adenocarcinomas. In addition, enhanced levels of both p105 and p34 were observed in aneuploid DNA content stemlines, relative to diploid cells. Cell-sorting experiments performed on cells sorted on the basis of p105 and DNA contents reveal the capability of this method for identifying morphologically heterogeneous cell subpopulations. Other data suggest that p105 is differentially expressed in well-differentiated versus poorly differentiated tumor regions. The potential utility of this approach for the retrospective study of proliferation-associated antigens and protooncogene protein products is discussed.

Characterization of a cell surface molecule expressed on B-lymphocytes and Hodgkin's cells.

An antigen specifically expressed on the surface of plasma membrane of B-lymphocytes and Reed-Sternberg cells was identified using a newly developed monoclonal antibody produced by immunization by BALB/c mouse with a Hodgkin's cell line (HDLM-3). The antibody was termed anti-BLA.36 (B lymphocyte antigen.36) to indicate its predominant reactivity and the molecular weight of the corresponding antigen. By using immunoperoxidase techniques, expression of BLA.36 was detected on Hodgkin's, B-, and pre-B-cell lines, but not on other hematopoietic, melanoma, or carcinoma cell lines. In normal tissues, BLA.36 was detectable predominantly on cells in the germinal center and mantle zone of reactive follicles in lymph nodes and spleen. In hematopoietic malignancy, BLA.36 was detectable on the surface of Reed-Sternberg cells, mononuclear Hodgkin's cells, and also on malignant cells of B-cell lineage. Under these conditions, T-lymphocytes, histiocytes, granulocytes, macrophages, stromal cells in lymphoid tissue, and both normal and neoplastic epithelial cells were consistently negative for the expression of the antigen, with the single exception of a variable proportion of Kupffer cells in normal liver. Biochemical and immunological analyses indicate that BLA.36 is distinct from previously identified antigens of hematopoietic cell lineage, including CD20 and CD75 (LN2) which have similar molecular weights. When BLA.36-positive cell lines were cultured in the presence of the antibody, cell growth was adversely affected. Such an effect was eliminated by removal of the antibody from the culture, suggesting a possible growth-related function of the antigen. Anti-BLA.36 may serve as a probe to study growth-related functions of the corresponding antigen during normal growth of the B-lymphocyte, as well as in the neoplastic proliferations occurring in Hodgkin's disease and antigen-positive B-cell lymphomas. Finally, the antibody has already demonstrated its usefulness for the identification of Reed-Sternberg and Hodgkin's cells, and also normal and malignant B-lymphocytes in frozen as well as formalin- or B5-fixed/paraffin-embedded tissue sections.

Enhanced tumor uptake of macromolecules induced by a novel vasoactive interleukin 2 immunoconjugate.

Low uptake of monoclonal antibodies (MAbs) in cancer lesions is a significant problem in cancer therapy. Recent studies have shown that antibody uptake in tumor is controlled in large part by the tumor blood flow and the vascular permeability of the tumor endothelium. We have hypothesized that these physiological properties of tumor vessels may be altered by pretreatment with vasoactive drugs or peptides linked to tumor-specific MAbs. To test this hypothesis, two MAbs, Lym-1 directed against human malignant lymphomas and B72.3 reactive with the TAG-72 antigen expressed in solid tumors, were chemically conjugated with human recombinant interleukin 2 (IL-2). IL-2 has been used in humans to activate lymphokine-activated killer cells for the treatment of cancer but is also known to produce a generalized vascular permeability by an unknown mechanism when used systemically. Chemical conjugation of IL-2 to MAbs appears to destroy its cytokine function as shown by T-cell proliferation studies in vitro. Despite this finding, MAb/IL-2 immunoconjugates retain their ability to produce an enhanced vascular permeability when injected i.v. into nude mice bearing relevant tumor models only. Biodistribution studies using 125I-labeled tracer Lym-1 have demonstrated that the Lym-1/IL-2 immunoconjugate can increase antibody uptake in tumor by a factor of 4 in a time (2.5-h pretreatment)- and dose (30 micrograms/mouse)-dependent manner. In contrast, treatment of mice with free IL-2 and antibody showed this effect in all organs of the mouse including the tumor. Bidirectional crossover imaging studies in individual tumor-bearing nude mice showed improved uptake and decreased blood pool when the MAb/IL-2 immunoconjugates were used compared to controls. Finally, tumor blood flow and vascular permeability studies demonstrate that the physiological effect of the MAb/IL-2 is due to a reversible and specific vascular leakage at the tumor site. These studies indicate that pretreatment with this novel immunoconjugate may enhance the diagnostic and therapeutic potential of MAbs, drugs, and other macromolecules for the treatment of cancer.

Two new monoclonal antibodies, Lym-1 and Lym-2, reactive with human B-lymphocytes and derived tumors, with immunodiagnostic and immunotherapeutic potential.

Two new monoclonal antibodies (Lym-1 and Lym-2), reactive with the cell surface of B-lymphocytes and derived tumors, have been produced using tumor cell nuclei preparations as immunogens. Specificity screens using live cell radioimmunoassay techniques with 52 well-characterized human lymphoma and leukemia cell lines showed that both Lym-1 and Lym-2 bound to cell lines of B-cell lineage but were unreactive with those of T-cell, myeloid, or erythroid derivation. The B-cell specificity of these reagents was confirmed on 36 lymphoma and 15 leukemia biopsy specimens by using immunoperoxidase or immunofluorescence techniques. Additionally, flow cytometric analysis of 22 lymphoma biopsies showed that the majority of B-cell tumors were Lym-1 and/or Lym-2 positive and that within a given biopsy, a high percentage of the malignant cell population was stained. In both the immunoperoxidase and flow cytometric studies, reactive T-cells or T-cell lymphomas were consistently negative with the exception of Hodgkin's disease tissues which, in some instances, showed a higher than expected positivity with Lym-1 and Lym-2. Approximately 40% of B-cell chronic lymphocytic leukemias were found to be positive with Lym-1 while 80% were positive with Lym-2. Immunoperoxidase staining of frozen sections of human lymphoid tissues showed that both Lym-1 and Lym-2 stained germinal center and mantle zone B-lymphocytes as well as interfollicular histiocytes. Flow cytometric analysis of normal peripheral blood demonstrated specific staining of B-cells which comprised approximately 8% of circulating lymphocytes. Immunoperoxidase staining of nonlymphoid human organs and tissues revealed weak reactivity of Lym-1 with surface colonic epithelium only. Consistent with these findings, 35 solid tumor cell lines of diverse nature were found unreactive with both Lym-1 and Lym-2. Although standard techniques have thus far failed to identify the antigen recognized by Lym-2, the membrane antigen which binds Lym-1 has been shown by immunoprecipitation and competitive radioimmunoassay studies to be a polymorphic variant of the HLA-Dr antigen. Solid-phase radioimmunoassay techniques have shown that the antigens recognized by Lym-1 and Lym-2 are not significantly modulated after antibody exposure nor shed into the circulation of lymphoma patients. Finally, using iodine-125 labeled preparations of purified Lym-1 and Lym-2, we have determined that both reagents have a relatively large number of antibody binding sites per tumor cell and increased avidity for lymphoma cells when compared to normal and reactive lymph node B-cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of mass of 111In-benzyl-EDTA monoclonal antibody on hepatic uptake and processing in mice.

In patients, the pharmacokinetic behavior of murine monoclonal antibodies has been observed to vary with the amount of antibody administered. It has been suggested that this reflects human recognition of the foreign mouse protein. We have found that the amount of antibody administered also influenced pharmacokinetic behavior when murine monoclonal antibody was administered to mice. p-Isothiocyanatobenzyl-EDTA, a new chelator which forms complexes with 111In that are stable in vivo, was conjugated to Lym-1, a murine anti-Burkitt's lymphoma monoclonal antibody. The pharmacokinetics of two doses (20 and 0.2 micrograms) of the 111In labeled radiopharmaceutical were studied in non-tumor bearing BALB/c mice. About 20% (0.04 microgram) of the 0.2-microgram dose, compared with 8% (1.6 micrograms) of the 20-micrograms dose, was found in the liver at 48 h after injection. Both doses demonstrated a biological half-life of approximately 120 h. At least 75% of the 111In was excreted by the kidneys, and essentially all 111In in the urine remained chelated by the EDTA portion of p-isothiocyanatobenzyl-EDTA. From these observations of a dose dependent uptake of this radiopharmaceutical by the liver we conclude that there is a recognition phenomenon in mice for this murine monoclonal antibody.

A chimeric Lym-1/interleukin 2 fusion protein for increasing tumor vascular permeability and enhancing antibody uptake.

A murine antihuman B-cell monoclonal antibody, Lym-1, has shown considerable promise for the treatment of human malignant lymphomas. To enhance its clinical potential, a genetically engineered fusion protein consisting of a chimeric Lym-1 (chLym-1) and interleukin 2 (IL-2) was tested for mediating cytotoxicity, increasing vasopermeability, and enhancing antibody uptake in human malignant lymphomas. The chLym-1/IL-2 fusion protein, which was expressed initially in a baculovirus system and more recently in the glutamine synthetase gene amplification system, was shown to be processed and assembled into a normal immunoglobulin monomer with two IL-2 molecules per antibody. It was found to be equivalent to the chLym-1 antibody in antigen-binding specificity and relative affinity. In addition, it maintains IL-2 cytokine activity as demonstrated by support of T-cell proliferation. Moreover, in antibody-dependent cellular cytotoxicity assays against Raji target cells, chLym-1/IL-2 had approximately 2-fold and 4-fold higher cytotoxicity than chLym-1 and murine Lym-1, respectively. Used as a pretreatment, chLym-1/IL-2 enhances the uptake of chLym-1 at the tumor site by altering the permeability of tumor vessels producing tumor:normal organ ratios of 420:1 for blood and 1708:1 for muscle at 3 days. The in vitro and in vivo activities of chLym-1/IL-2, therefore, suggest that this genetically engineered antibody fusion protein may represent a new immunotherapeutic reagent for the treatment of human malignant lymphomas.

Evaluating antibodies for their capacity to induce cell-mediated lysis of malignant B cells.

Promising results from clinical trials have led to renewed interest in effector mechanisms operating in antibody-based therapy of leukemia and lymphoma. We tested a panel of B-cell antibodies from the Sixth Human Leukocyte Differentiation Antigen workshop for their capacity to mediate antibody-dependent cellular cytotoxicity, often considered to be one of the most potent effector mechanisms in vivo. As effector cells, mononuclear cells and polymorphonuclear (PMN) cells from healthy donors were compared with Fc gammaRI (CD64)-expressing PMN cells from patients receiving granulocyte colony-stimulating factor (G-CSF) treatment. Of the 29 IgG workshop antibodies binding most strongly to the tested malignant human B-cell lines, only 3 consistently induced target cell lysis. These three antibodies were determined to be HLA DR reactive. Experiments with a panel of HLA class II antibodies showed the involvement of individual Fc gamma receptors on effector cells to be strongly dependent on the antibody isotype. We then compared killing mediated by chimeric IgG1 antibodies with that from Fc gammaRI-directed bispecific antibodies, targeting classical HLA class II, or the Lym-1 and Lym-2 antigens. The latter two are variant forms of HLA class II, which are highly expressed on the surface of malignant B cells but which are found only at low levels in normal cells. With blood from G-CSF-treated donors, bispecific antibodies showed enhanced killing compared to their chimeric IgG1 derivatives, because they were more effective in recruiting Fc gammaRI-expressing PMN cells. G-CSF- and Fc gammaRI-directed bispecific antibodies to HLA class II, therefore, seem to be an attractive combination for lymphoma therapy.

Therapeutic efficacy in experimental polyarthritis of viral-driven enkephalin overproduction in sensory neurons.

Rheumatoid arthritis is characterized by erosive inflammation of the joints, new bone proliferation, and ankylosis, leading to severely reduced locomotion and intense chronic pain. In a model of this disease, adjuvant-induced polyarthritis in the rat, neurons involved in pain transmission and control undergo plastic changes, especially at the spinal level. These changes affect notably neurons that contain opioids, such as enkephalins deriving from preproenkephalin A (PA) precursor protein. Using recombinant herpes simplex virus containing rat PA cDNA, we enhanced enkephalin synthesis in sensory neurons of polyarthritic rats. This treatment markedly improved locomotion and reduced hyperalgesia. Furthermore, the progression of bone destruction slowed down, which is the most difficult target to reach in the treatment of patients suffering from arthritis. These data demonstrate the therapeutic efficacy of enkephalin overproduction in a model of systemic inflammatory and painful chronic disorder.

Pretreatment with a monoclonal antibody/interleukin-2 fusion protein directed against DNA enhances the delivery of therapeutic molecules to solid tumors.

The efficacy of molecular therapies for human malignancies is limited by inadequate accumulation within solid tumors. Our laboratory has developed a novel approach that uses monoclonal antibodies (MAbs) to direct vasoactive proteins to tumor sites to increase local vascular permeability and, in turn, improve the delivery of therapeutic reagents. Previously, we demonstrated that pretreatment with immunoconjugates containing interleukin-2 (IL-2) enhances specific tumor uptake of radiolabeled MAbs without affecting normal tissues. In the present study, we describe a fusion protein consisting of a chimeric antinuclear antibody and IL-2 (chTNT-3/IL-2) and illustrate its potential for improving the delivery of both MAbs and drugs. The ability of pretreatment with chTNT-3/IL-2 to increase specific tumor uptake of the MAb B72.3 was demonstrated in LS174T colon tumor-bearing mice. Tumor accretion of B72.3 increased nearly 3-fold, with no changes in normal tissues. Abrogation of this effect with N(G)-methyl-1-arginine, a chemical inhibitor of nitric oxide synthase, suggests that rapid generation of nitric oxide in the tumor is responsible for the enhanced uptake. To demonstrate that pretreatment with chTNT-3/IL-2 can improve the uptake of other clinically relevant MAbs in different tumor models, additional studies were performed in both lung and prostate xenograft models. Pretreatment with the fusion protein increased specific tumor uptake of the MAb NR-LU-10 in A427 lung tumor-bearing mice and enhanced tumor uptake of the MAb CYT-351 in LNCaP prostate tumor-bearing mice, 2.1-fold and 1.7-fold, respectively. Finally, tumor uptake of the radiolabeled thymidine analogue 125IUdR also increased approximately 3-fold after pretreatment, indicating that this approach can be extended to small molecules such as chemotherapeutic drugs. Because TNT-3 recognizes a universal nuclear antigen accessible in degenerating and necrotic cells within all solid tumors, this strategy may be applicable to the majority of human cancers.