Elimination of malignant clonogenic cells from human bone marrow using multiple monoclonal antibodies and complement

A clonogenic assay has been developed that utilizes Burkitt's lymphoma tumor cell lines to detect elimination of up to 5 logs of tumor cell contamination within human bone marrow. Different Burkitt's lymphoma lines bear one or more of a group of markers, including common acute lymphoblastic leukemia antigen gp26 (glycoprotein with a molecular weight of 26,000), B1, surface membrane immunoglobulin, HLA, beta 2-microglobulin, and Ia. Burkitt's tumor cells of the Namalwa line have been mixed with a 20-fold excess of irradiated human bone marrow cells. After treatment with one or more monoclonal antibodies and rabbit complement (RC), mixtures have been grown on a monolayer of irradiated human bone marrow cells and tumor cells enumerated by limiting dilution. Multiple treatments with antibody and RC were more effective than a single treatment in destroying clonogenic tumor cells which bore relevant determinants. Human serum components inhibited the lytic activity of RC in the presence of murine monoclonal antibodies. The total concentration of bone marrow cells proved critical in determining the complete elimination of tumor. Incubation of the Namalwa tumor cell line with RC and the J2 anti-gp26 eliminated more than 3 logs of malignant cells from a 20-fold excess of human bone marrow. Combinations of two monoclonal antibodies were more effective than any single antibody in eliminating Namalwa cells. A combination of three monoclonal reagents was no more effective than a combination of J2 and B1 or J2 and J5 in eliminating Namalwa cells. Treatment of human bone marrow with three antibodies and RC did not, however, produce a selective loss of nonmalignant GM-CFU-C, CFU-E, or BFU-E.     

Elimination of malignant clonogenic breast cancer cells from human bone marrow

Autologous bone marrow transplantation is a promising approach to the treatment of breast cancer but is at present limited to patients without bone marrow metastases. To eliminate malignant clonogenic breast cancer cells from normal human bone marrow, immunomagnetic separation has been combined with chemoseparation using 4-hydroperoxycyclophosphamide. Breast cancer cell lines have been mixed with a 10-fold excess of irradiated human bone marrow from normal donors. Mixtures have been incubated with a combination of five different monoclonal antibodies which bind to epithelial cell surface antigens of Mr 42,000, 55,000, 72,000, 200,000, and greater than 200,000. Antiglobulin coated microspheres which contained magnetite were added, and tumor cells were trapped in a magnetic field. Elimination of tumor cells from the decanted marrow was measured in a limiting dilution assay. Two treatments with antibody and microspheres permitted elimination of 2-4 logs of clonogenic breast cancer cells, depending upon the cell line studied. Similar treatment of nonirradiated normal marrow failed to affect levels of colony forming units-granulocyte-macrophage significantly. Use of immunomagnetic purging in combination with 4-hydroperoxycyclophosphamide eliminated up to 5 logs of tumor cells but reduced the recovery of colony forming units-granulocyte-macrophage. If prompt engraftment is observed following reinfusion of similarly treated marrow in phase I trials, these techniques should permit extension of autologous bone marrow transplantation to a larger population of breast cancer patients.     

Elimination of B-lymphoma cells from human bone marrow: model experiments using monodisperse magnetic particles coated with primary monoclonal antibodies

Conditions for removing B-lymphoma cells from human bone marrow using "immunobeads" (IBs) were investigated. The IBs were prepared by coupling monoclonal antibodies directly to a new type of monodisperse magnetic polymer particles (M 450). Two monoclonal immunoglobulin M antibodies, AB-1 (CD 19), a B-cell-specific antibody, and AB-4, an HLA-DR-specific antibody, were used. The IBs were incubated with Rael Burkitt lymphoma cells admixed to fresh, mononuclear human bone marrow cells. After incubation for 30 min at 4 degrees C, the IBs were removed using cobalt samarium magnets. The number of remaining clonogenic tumor cells was assayed by the Courtenay and Mills soft agar procedure, and the clonogenic capacity of the bone marrow progenitor cells was measured by granulocyte-monocyte and granulocyte-erythroid-monocyte-megakaryocyte assays. With a ratio of tumor cells to normal bone marrow cells of 0.1 or 0.01 and a ratio of immunobeads to tumor cells in excess of 75, a tumor cell depletion of more than 3 logs was achieved with the AB-4 IBs and slightly less with the AB-1 beads. After two consecutive cycles of purification with the AB-4 beads, no colonies were found, corresponding to more than 6 logs of purification. In the case of the AB-1 beads, 4 to 5 logs of purification were achieved. The concomitant reduction in clonogenic bone marrow progenitor cells was only 30 to 40%. Flow cytometric studies showed that the tumor cell population contained appreciable proportions of cells binding only small amounts of the antibodies used. The results indicate that the IB procedure is highly efficient and capable of removing tumor cells expressing low levels of antigen. Compared to other purging methods in use the procedure described seems to offer several advantages with respect to efficacy, speed, and simplicity. By the use of a panel of suitable antibodies the new immunobead procedure may be potentially useful in autologous bone marrow transplantation of B-lymphomas and non-T-leukemias with poor prognosis.     

Elimination of clonogenic tumor cells from human bone marrow using a combination of monoclonal antibody:ricin A chain conjugates

Effective autologous bone marrow transplantation for leukemia and lymphoma is likely to depend upon the selective removal in vitro of malignant cells from normal human bone marrow precursors. Highly specific cytotoxic conjugates formed by coupling ricin A chain to monoclonal antibodies might prove useful for the selective elimination of malignant cells. Consequently, ricin A chain conjugates have been prepared with several different murine monoclonal antibodies and tested for their ability to eliminate clonogenic Burkitt's lymphoma cells from an excess of human bone marrow. The most active reagents included an antibody:A chain conjugate which bound to the nonpolymorphic chain of the la molecule and another which reacted with the mu heavy chain of cell surface immunoglobulin. Conjugates formed with anti-common acute lymphoblastic leukemia antigen, anti-Mr 26,000 glycoprotein, and anti-B1 were much less active on these Burkitt's cells, contrasting with results of complement-dependent tumor cell lysis. Tumor cell kill was partially inhibited by the addition of greater than 2 X 10(6) human bone marrow cells/ml but could be potentiated by increasing the concentration of conjugate or by the addition of 10 mM ammonium chloride. In the presence of ammonium chloride, at least 4 logs of clonogenic tumor cells could be eliminated within 24 h from a 20-fold excess of bone marrow using 10(-7) M ricin A chain linked to one or two different antibodies. Similar treatment of normal human bone marrow temporarily inhibited granulocyte-macrophage colony-forming units (cell) formation but did not compromise establishment of continuous bone marrow cultures. The degree of selective elimination of tumor cells with A chain antibody conjugates was comparable to that achieved with 4-hydroperoxycyclophosphamide or with multiple monoclonal antibodies and complement.     

Elimination of clonogenic malignant human T cells using monoclonal antibodies in combination with 2'-deoxycoformycin

2'Deoxycoformycin (dCF) specifically inhibits adenosine deaminase (ADA) and causes selective cytotoxicity of normal and malignant T cells. In clinical trials, dCF caused rapid lysis of malignant T lymphoblasts. Although dCF has been associated with dose-limiting nonhematopoietic toxicities, myelosuppression has not been observed. Since dCF is relatively nontoxic to hematopoietic stem cells, we tested dCF for utility in the ex vivo purging of malignant T lymphoblasts from remission leukemic bone marrow for autologous bone marrow transplantation. We found that T lymphoblast cell lines were sensitive to dCF (plus deoxyadenosine [dAdo]) under conditions that did not ablate human hematopoietic colony-forming cells. Moreover, combined pharmacologic (dCF plus dAdo) and immunologic (anti-T cell monoclonal antibodies [McAb] plus complement) purging resulted in additive reduction in clonogenic T lymphoblasts. These results provide the basis for a clinical trial of bone marrow transplantation using combined pharmacologic/immunologic purging of T lymphoblasts from patients' harvested autologous marrow.     

Model system for removing neuroblastoma cells from bone marrow using monoclonal antibodies and magnetic immunobeads

Variables effecting removal of neuroblastoma cells from bone marrow using monoclonal antibodies and magnetic immunobeads were studied. Human neuroblastoma cell lines were labeled with the supravital DNA stain Hoechst 33342, seeded into normal bone marrow, incubated with monoclonal antibodies recognizing neuroblastoma cell surface antigens (HSAN 1.2, antibody 459, antibody 390, BA-1, and Leu-7), and then mixed with magnetic microspheres coated with goat anti-mouse immunoglobulin. Tumor cells that attached to the magnetic immunobeads were then removed from the marrow with magnets. The efficacy of tumor cell removal depended on the amount of monoclonal antibody bound to tumor cells and the immunobead/tumor cell ratio. In addition, two cycles of purging with both monoclonal antibodies and immunobeads was superior to one cycle. Using a cocktail of the five antibodies, 3 to 4 logs of tumor cells could be depleted from marrow with good recovery of viable hematopoietic cells.     

Specific monoclonal antibodies reacting with human breast cancer cells

Spleen cells from Balb/c mice immunized with human breast cancer cells (MCF-7) were fused with murine myeloma SP2/0 cells. Screening of the monoclonal antibodies produced was carried out on glutaraldehyde fixed cells coated on microtiterplates. An initial evaluation of the specificity was obtained by comparing the binding of the monoclonal antibodies to MCF-7 cells with the binding to human peripheral blood lymphocytes. Eight monoclonal antibodies reacting with different epitopes on the MCF-7 cells were obtained. On the basis of their clonal origin, isotype and reaction pattern towards the MCF-7 cells these monoclonal antibodies were subdivided into two classes. Both groups of antibodies reacted with fixed and unfixed MCF-7 cells. The cellular distribution of the antigens recognized by the monoclonal antibodies was determined. To check for specificity a panel of different cells (of human and animal origin) was evaluated by immunocytochemical techniques.     

Elimination of small cell lung cancer cells in vitro from human bone marrow by a monoclonal antibody

We report here a useful method for elimination of small cell lung cancer cells in vitro from bone marrow. A monoclonal antibody, TFS-2, which mediates complement lysis and recognizes an antigen present on small cell lung cancer cells but not lymphoid cells or bone marrow cells, was used to clear infiltrated bone marrow. The antibody in the presence of complement effectively killed tumor cells, but it was not cytotoxic to bone marrow cells. When mixed populations consisting of tumor cells and bone marrow cells were treated with antibody and complement, the tumor cells were also effectively killed, except when large numbers of bone marrow cells were present, whereas TFS-2 had no significant effect on bone marrow stem cells, as judged by colony-forming unit assays.     

Survival of highly proliferative colony forming cells after treatment of bone marrow cells with 4-hydroperoxycyclophosphamide

We investigated the in vitro effects of 4-hydroperoxycyclophosphamide (4-HC) on human hemopoietic stem cells. Marrow cells were exposed to 4-HC and then assayed for mixed (CFU-GEMM), erythroid (BFU-E), megakaryocyte (CFU-M), and granulocyte-macrophage (CFU-GM) colony forming cells. We found that highly proliferative colony forming cells, especially CFU-GEMM and BFU-E, were relatively spared by 4-HC treatment. One third of the surviving progenitors formed large colonies, some of which contained more than 50,000 cells. By sequential examination of the formation of these large colonies, we found immature colonies consisting of blasts at the early stage of culture. The morphology of these "blast cell colonies" in situ was arbitrarily classified into four types. Among them were the blast cell colonies consisting of the individual cells that were dispersed and had a few granules within the cytoplasm (type A); these cells finally formed very large colonies on day 22 of culture. Approximately 70% of the single cells derived from type A blast cell colonies produced secondary colonies consisting of erythroblasts, macrophages, eosinophils, and/or basophils. These results show that the blast cells in type A colonies have a highly proliferative capacity. The availability of a highly enriched population of primitive hemopoietic progenitors will provide us with a unique opportunity to study the interaction between a single stem cell and purified hemopoietic factors.     

Combined chemoseparation and immunoseparation of clonogenic T lymphoma cells from human bone marrow using 2'-deoxycoformycin, deoxyadenosine, 3A1 monoclonal antibody, and complement

Chemoseparation and immunoseparation techniques have been combined to eliminate malignant clonogenic T lymphoma cells from human bone marrow. Incubation with 5 microM 2'-deoxycoformycin and 500 microM deoxyadenosine has eliminated 2 logs of HSB-2 T lymphoma cells from a 20-fold excess of irradiated human bone marrow. Multiple incubations with 3A1 antibody and rabbit complement eliminated approximately 2 logs of HSB-2 cells from similar mixtures. Used in combination, the 2 techniques eliminated up to 4 logs of T lymphoma cells. Incubation of normal human bone marrow under similar conditions failed to affect growth of granulocyte-macrophage colony-forming cell units, burst-forming erythroid units, or multipotential erythroid-granulocyte-megakaryocyte-macrophage colony-forming hematopoietic progenitor cells units.     

Selective elimination of breast cancer cells from human bone marrow using an antibody-Pseudomonas exotoxin A conjugate

A pancarcinoma monoclonal antibody (NR-LU-10), homogeneously reactive with human breast cancer cells, was conjugated to Pseudomonas exotoxin A. The immunotoxin was evaluated for its potential for purging breast cancer cells from human bone marrow. The immunotoxin NR-LU-10 antibody did not react with normal bone marrow preparations yet readily detected 1% contamination of bone marrow by MCF-7 breast cancer cells added to normal bone marrow without significantly inhibiting the colony-forming ability of bone marrow progenitor cells. NR-LU-10-Pseudomonas exotoxin A has potential for purging bone marrow of breast cancer cells without impairing the growth of bone marrow progenitor cells.     

Magnetic microspheres and monoclonal antibodies for the depletion of neuroblastoma cells from bone marrow: experiences, improvements and observations

Improvements to the original procedure of using a panel of monoclonal antibodies and magnetic microspheres for the depletion of tumour cells from bone marrow are described. These include a completely disposable system for the magnetic depletion of tumour cells coated with magnetic microspheres. Properties of a new series of microspheres are compared with the old M330 beads in their ability to deplete neuroblasts from both model systems and 50 bone marrows harvested from Stage IV neuroblastoma patients. Using human neuroblastoma cell lines labelled with the DNA intercalating, Hoechst dye 33342 a 5% tumour contamination can routinely be removed from 5 X 10(6) - 5 X 10(7) nucleated cells. Analysis of the 50 purged marrows revealed that 10 were visibly contaminated with tumour (by conventional cytology and immunological procedures). In all but one case, tumour cells were removed. In this instance the tumour:bead ratio fell to 1:4 indicating the importance of maintaining a sufficient number of beads in the system. Red cell contamination of marrow was also kept extremely low so preventing possible physical blockade of bead:tumour cell interaction. Marrow engraftment was rapid in this group, apart from patients who had been exposed to high doses of alkylating agents prior to autografting.     

Elimination of small cell carcinoma of the lung from human bone marrow by monoclonal antibodies and immunomagnetic beads

The majority of patients with small cell carcinoma of the lung (SCCL) have bone marrow involvement detected by monoclonal antibodies (mAb). High dose chemotherapy followed by autologous bone marrow transplantation may improve treatment results for patients with SCCL, but the bone marrow may need to be purged of contaminating tumor cells. This study investigates the reactivity of a panel of mAb with two SCCL cell lines and normal bone marrow and the ability of the mAb and immunomagnetic beads to eliminate the SCCL cells from a mixture of 90% normal bone marrow cells and 10% SCCL cells. The mAb and immunomagnetic beads removed 4 to 5 log of SCCL cells in the model system. The immunomagnetic separation did not significantly adversely affect normal hematopoietic progenitor cells, as determined by bone marrow colony-forming units. The results suggest that the mAb and immunomagnetic beads could safely and effectively separate SCCL cells from the bone marrow for autologous bone marrow transplantation following high dose chemotherapy.     

Production and characterization of monoclonal antibodies to mesenchymal stem cells derived from human bone marrow

The bone marrow (BM) serves as a reservoir for different classes of stem cells. In addition to haematopoietic stem cells, bone marrow contains a population of mesenchymal stem cells (MSCs). These cells have a multilineage differentiation capacity and are able to generate progenitors with restricted developmental potential, which include fibroblasts, osteoblasts, adipocytes, and chondrocytes. Characteristic markers have been reported for expanded MSCs, but none of these markers are specific for MSCs. Thus, the objective of this study was to produce monoclonal antibodies against MSCs. MSCs derived from human bone marrow were cultured, expanded, and immunized into mice, and spleen cells subsequently harvested were used to generate hybridoma cell lines secreting antibodies against MSCs. Hybridoma culture supernatants were screened for antibodies against MSCs by enzyme-linked immunosorbent assay (ELISA), and 33 positive clones were then screened against cell suspensions of MSCs by immunofluorescence staining and flow cytometry. Ten clones were positive in immunofluorescence staining. Among these, three hybridoma cell lines, namely, YS08, YS14, and YS18 were found to be reactive with MSC by flow cytometry, but non-reactive with human tumor cell lines and hematopoietic stem cells. YS08 and YS14 showed specific bands in Western blotting. In conclusion, we developed three monoclonal antibodies, YS08, YS14, and YS18, that recognize human MSC cell surface antigen.     

Effective removal of SCLC cells from human bone marrow. Use of four monoclonal antibodies and immunomagnetic beads.

High dose chemotherapy with autologous bone marrow transplantation (ABMT) has shown promise in several types of cancer. There is, however, a risk of transfusing contaminating tumour cells with the bone marrow cells, e.g. in patients with small cell lung carcinoma (SCLC). To eliminate SCLC cells from normal human bone marrow, four monoclonal antibodies reactive with SCLC cells were used with immunomagnetic beads in model experiments. With two cycles of immunomagnetic elimination the individual antibodies removed 2.5-4.4 log of H-146 tumour cells from a single cell suspension, as assessed in a highly reproducible soft agar assay. Different combinations of two antibodies were only marginally more effective than the individual MAbs, whereas 5-6 log removal was obtained with a combination of all four antibodies. The method was equally effective when the tumour cells were mixed with bone marrow cells at a ratio of 1:10. The immunomagnetic procedure did not significantly affect the survival of normal progenitor cells, assessed in CFU-GM and CFU-GEMM assays. The results indicate that the procedure safely and effectively can be used to eliminate tumour cells from the bone marrow in conjunction with ABMT in patients with SCLC.     

Reactivity of anti-CD15 monoclonal antibody PM-81 with breast cancer and elimination of breast cancer cells from human bone marrow by PM-81 and immunomagnetic beads.

The CD15 carbohydrate antigen, lacto-N-fucopentaose III is expressed on a variety of human cancer cells including acute myeloid leukemia, small cell carcinoma of the lung, and colorectal carcinomas. We have found that cells from breast cancer cell lines and patient-derived tissue are strongly CD15 positive, as seen by binding to the PM-81 monoclonal antibody. In this report we show that monoclonal antibody PM-81 and immunomagnetic beads can remove breast cancer cells from bone marrow and thus be used as "purging" agents for autologous bone marrow transplantation. PM-81 and immunomagnetic beads removed up to 3 log of SK-BR-3 and MCF7 breast carcinoma cell line cells while minimally affecting normal hematopoietic progenitor cells. This technique may be useful for purging marrow for autologous bone marrow transplantation in breast cancer.     

Detection of neuroblastoma cells in bone marrow using GD2 specific monoclonal antibodies

Three murine monoclonal antibodies (Mab) against a cell surface antigen, the disialoganglioside GD2, were investigated for detecting bone marrow metastasis in patients with neuroblastoma (NB) by indirect immunofluorescence (IF). As few as 0.01% NB cells could be detected. No Mab reactivity was found in 60 non-NB marrows. Thirty-five marrows from patients with stage III and stage IV NB at diagnosis were examined during the course of their disease. Tumor involvement was found in 74% by Mab, 55% by the two-layer soft agar clonogenic assay (CA), and 27% by conventional histochemical stains. All marrows containing NB histologically were positive for tumor by Mab; 71% were also positive by CA. Of histologically negative marrows, 63% were Mab positive, the majority (78%) of which were also positive by CA. All Mab nonreactive samples were negative histologically and by CA. We conclude that these antibodies are highly sensitive and specific in detecting NB metastasis in bone marrow.     

In vitro purging of clonogenic leukemic cells from human bone marrow by heat: simulation experiments for autologous bone marrow transplantation.

In order to apply a simple purging method by heat to autologous bone marrow transplantation (ABMT), we have revaluated the ability to purge clonogenic leukemic cells from the simulated marrow mixture of normal marrow cells and leukemic cell lines (HL-60, Molt-3 and HEL) in vitro by heat, using two different clonogenic assays for normal granulocyte-macrophage progenitors (CFU-GM) and leukemic cell lines. It appeared that in vitro hyperthermia (42 degrees C for 120 min) is able to selectively remove clonogenic leukemic cells from simulated tumor cell-normal marrow mixtures even when leukemic cell concentrations are increased up to 3 x 10(6) cells/ml in vitro, and results in a 4-6 log destruction of clonogenic leukemic cells/ml according to a limiting dilution assay, while leaving half of normal CFU-GM surviving. The hyperthermic purging of clonogenic leukemic cells was not affected in the presence of normal marrow cells in vitro. This high level of clonogenic leukemic cell depletion by heat correlated with that of immunologic and pharmacologic studies. These results suggest that in vitro hyperthermia could be applied effectively and safely for the elimination of residual clonogenic leukemic cells in autologous marrow grafts before ABMT.     

Characterisation of breast cancer infiltrates using monoclonal antibodies to human leucocyte antigens

Serial frozen sections from eleven patients with malignant breast tumours and five patients with benign disease were studied by indirect immunoperoxidase using a panel of mouse monoclonal antibodies to human leucocyte antigens. More infiltrating leucocytes were seen in tumour sections than those of benign conditions. A considerable proportion of the infiltrating cells were T cells, and more of these were of the suppressor/cytotoxic subset than the helper/inducer subset. The T cells were apparently not all activated as indicated by lower levels of staining with anti HLA-DR than anti-leucocyte antibody. Diffuse staining was sometimes seen with HLA-DR and T cell subset antibodies. Tumour cells did not stain or were only very weakly positive with anti HLA-A, B, C.