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PubMed2003

Bone marrow purging studies in acute myelogenous leukemia using the recombinant anti-CD33 immunotoxin HuM195/rGel.

This study was designed to determine the effect of immunotoxin HuM195/rGel on normal human bone marrow before clinical purging. HuM195/rGel is composed of the recombinant plant toxin gelonin (rGel) chemically coupled to the anti-CD33 human chimeric antibody HuM195. The CD33 antigen is of significant interest as a target for therapy of acute myelogenous leukemia because it is present in leukemic blasts of most patients but absent in the earliest progenitor bone marrow cells. HuM195/rGel was optimally cytotoxic to acute myelogenous leukemia HL60 cells with 24 hours of exposure. We developed an in vivo purging model by mixing mobilized peripheral blood progenitor cells with HL60 cells to simulate a remission in bone marrow. Cells were treated with 10 nmol/L of HuM195/rGel either with or without exposure to freeze/thaw procedure, which has been reported to act synergistically with HuM195/rGel to produce cytotoxic effect. When clonogenic cell recovery rates were determined, HuM195/rGel alone did not affect normal peripheral blood progenitor cells, whereas HuM195/rGel plus freeze/thaw provided 2 logs of tumor cell elimination in our purging model. We also observed similar results under conditions used in the transplantation setting. We concluded that for acute myelogenous leukemia blasts expressing CD33, HuM195/rGel could be useful as a purging reagent for autologous transplantation.

Acute Disease↗
PubMed1989

An immunotoxin containing momordin suitable for bone marrow purging in multiple myeloma patients.

Attempts have been made by a number of methods to eliminate minimal residual disease from bone marrow to be reinfused in autologous transplantation. In this paper we describe a conjugate containing a monoclonal antibody, named 8A, recognising a plasma cell-associated antigen, and momordin, a ribosome-inactivating protein similar to the ricin A-chain. This immunotoxin is active on target cell lines and on neoplastic plasma cells, while myeloid progenitors are fairly resistant. The conjugate is shown to be acceptable for ex vivo purging in autologous bone marrow transplantation in multiple myeloma patients.

Antibodies, Monoclonal↗
PubMed1997

Merocyanine 540 mediated photolysis of normal bone marrow, committed hemopoietic progenitors and neoplastic cells. implications for bone marrow purging.

The effect of merocyanine 540 (Mc 540) mediated photoirradiation on both neoplastic and normal hemopoietic progenitor cells was studied. Bone marrow (BM) cells from children with acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML) at initial diagnosis, ALL in remission, neuroblastoma and normal children as well as cells of Reh-6 and HL-60 cell lines were incubated with Mc 540 in the presence of human albumin (HA) and exposed to different argon laser 514 nm doses. Cell survival was estimated using Trypan Blue supravital stain following a 24-h incubation and leukemic cell lines were studied in continuous cell cultures of 4 weeks duration. Our results showed that HA protects normal BM cells from Mc 540 mediated phototoxicity. A 99.9999% inhibition of Reh-6 and HL-60 was noted at irradiation doses where the corresponding mean survival of normal BM cells was 77.4 +/- 12 and 70.3 +/- 10%, respectively. BM leukemic cells from children with ALL and AML were also very sensitive to Mc 540 photoirradiation in contrast to neuroblastoma cells where only a three-fold reduction was observed. Finally, the survival of normal BM progenitors was 38% for colony forming unit erythroid CFU-E, 37% for burst forming unit erythroid BFU-E, 55% for CFU-GM and 29% for CFU-GEMM. In conclusion it seems that Mc 540 mediated photoirradiation in neoplastic cells exerts selective cytotoxicity and can be used in ex vivo purging of malignant cells in BM.

Bone Marrow↗
PubMed2003

[Effect of zinc phthalocyanine-mediated photodynamic therapy on bone marrow purging, an experimental study].

OBJECTIVE: To probe into the purging effects of zinc phthalocyanine-mediated photodynamic therapy (PDT) on simulated remission bone marrow grafts of chronic granulocytic leukemia. METHODS: (1) K562 cells, aline chronic granulocytic leukemia cells, and normal mononuclear cells (MNC) were cultured. Zinc phthalocyanine (ZnPcS(2)P(2)), a photosensitizer, with the terminal concentration of 1.0 micro g/ml was added into the cultures. The K562 cells and normal MNCs in the suspensions were broken. Fluorescence spectrophotometry was used to determine the concentration of zinc phthalocyanine in cells at different time points so as to find the optimal time for photodynamic purging process. (2) Suspensions of K562 cells and MNCs were made and incubated with zinc phthalocyanine of different concentrations (0.062 5, 0.125, 0.25, 0.5, and 1.0 micro g/ml) for 5 hours. A blank control group (sodium chloride of the same volume was added), a PDT control group (without photosensitizer), and a photosensitizer control group (zinc phthalocyanine was added without PDT) were established. Then the suspensions were irradiated with 670 nm laser. Trypan blue dye exclusion technique was used to calculate the number of live cells for a period of 5 days. The proliferative potency of K562 cells was detected by MTT colorimetric assay. The OD value was detected with ELISA apparatus to calculate the inhibition rate. Colony formation of K562 cells and MNCs was determined. (3) K562 cells were mixed into normal MNCs at the ratios of 1:100 and 1:1,000 so as to create the model of simulated remission bone marrow. After PDT treatment, colony formation test was done and nested-PCR was used to detect the bcr-abl mRNA expression in K562 cells. Colony formation test was made on the MNCs treated with PDT. The antiproliferative effects of PDT on normal hematopoietic progenitors were evaluated by CFU-Mix, CFU-GM and CFU-E assays. RESULTS: (1) The zinc phthalocyanine content in the MNCs reached its peak within the first hour of incubation and then rapidly decreased to the lowest value in 4 hours. However, the zinc phthalocyanine content in the K562 cells gradually increased within the first 4 hours of incubation and reached its peak by the fifth hour with a ratio of zinc phthalocyanine content in K562 cells to that in MNCs of 4.59. Therefore, the fifth hour after incubation was selected as the optimal time to irradiate the suspensions using the laser with a wavelength of 670 nm. (2) The inhibitory rate of laser on the colony information rate was 91.1% for the K562 cells, 18.0% for the MNCs in CFU-Mix methyl cellulose culture system, 18.6% for the MNCs in CFU-GM methyl cellulose culture system, and 17.8% for the MNCs in CFU-E methyl cellulose culture system At the concentration of 0.25 micro g/ml, K562 cells were inhibited by 91.1%, however, CFU-Mix, CFU-GM and CFU-E were relatively spared, inhibitory rate being 18.0%, 18.6% and 17.8% respectively. (3) At the concentration of 0.25 micro g/ml, residual K562 cells in the simulated remission bone marrow were completely photoinactivated. CONCLUSION: Zinc phthalocyanine -based PDT selectively kills K562 cells. It would be a promising purging technique for chronic granulocytic leukemia.

Bone Marrow Purging↗
PubMed1990

Survival and characteristics of murine leukaemic and normal stem cells after hyperthermia: a murine model for human bone marrow purging.

The effect of hyperthermia in vitro on the survival and leukaemogenic effectiveness of WEHI 3-B cells and on the survival and transplantation efficiency of bone marrow cells was compared in a murine model system. Normal murine clonogenic haemopoietic cells (day 9 CFU-S and CFU-GM) proved to be significantly less sensitive to 42.5 degrees C hyperthermia (Do values: 54.3 and 41.1 min, respectively) than leukaemic clonogenic cells (CFU-L) derived from suspension culture or from bone marrow of leukaemic mice (Do: 17.8 min). Exposure for 120 min to 42.5 degrees C reduced the surviving fraction of CFU-L to 0.002 and that of CFU-S to 0.2. If comparable graft sizes were transplanted from normal or heat exposed bone marrow, 60-day survival of supralethally irradiated mice was similar. Surviving WEHI 3-B cells were capable of inducing leukaemia in vivo. The two log difference in the surviving fraction of CFU-L and CFU-S after 120 min exposure to 42.5 degrees C suggests that hyperthermia ex vivo may be a suitable purging method for autologous bone marrow transplantation.

Animals↗
PubMed1990

Preclinical evaluation of immunoconjugates consisting of doxorubicin linked to complement-fixing monoclonal antibody DLC-48 for bone marrow purging of B-cell lymphomas.

Complement-fixing monoclonal antibody DLC-48 was linked covalently to doxorubicin using two methodologies, and the resulting conjugates were evaluated for their usefulness in purging B-cell lymphomas from human bone marrow autografts using a clonogenic assay for the large cell lymphoma cell line SU-DHL-4. Conjugation did not impair the reactivity of the antibodies. The resultant molar ratios provided for maximal immunoreactivity at doxorubicin concentrations that would permit the growth of CFU-GM. Conjugate DLC-48D-G retained its complement-fixing capacity, and was more cytotoxic to SU-DHL-4 cells, even in the absence of complement, than equivalent doses of doxorubicin. This effect appeared to be non-specific, in that CFU-GM were eliminated, even at low concentrations. DLC-48D-G was no more effective than equivalent doses of doxorubicin, and equally cytotoxic to CFU-GM. Mixtures of unconjugated DLC-48 and doxorubicin, however, were more effective than doxorubicin alone. The mechanism of action of these conjugates is under study. Alternative methods of conjugation will be investigated.

Animals↗
PubMed2000

Bone marrow purging by photodynamic treatment in children with acute leukemia: cytoprotective action of amifostine.

In order to evaluate the combined effect of Amifostine and Merocyanine 540 during photoirradiation in neoplastic cells, bone marrow cells from children with acute leukemia (AL), age-matched controls as well as HL-60 cell line were studied. Cell suspensions were incubated with Amifostine, then with MC 540 and they were subsequently exposed to different irradiation doses by Argon Laser 514 nm. Cell survival was estimated by trypan blue supravital stain following a 24-h incubation. The leukemic cell line was studied in continuous liquid cell cultures for 4 weeks. The survival of normal bone marrow progenitors has been estimated by colony formation assay in methylcellulose cultures. Our results showed that Amifostine enhances the photokilling effect of MC 540 on leukemic cells and significantly protects bone marrow nucleated and committed progenitors (BFU-E and CFU-GM) from children with AL under chemotherapy. In conclusion, Amifostine seems to be a promising cytoprotective agent in the clinical use of purging with MC 540 mediated phototherapy.

Amifostine↗
PubMed2005

Development of a gene therapy based bone marrow purging system for leukemias.

Although viable gene therapy based methods have been reported for the selective removal or purging of contaminating epithelial derived cancer cells from stem cell grafts, similar strategies for the purging of leukemia cells have been significantly less efficient. Hematopoietic cells are difficult targets for transduction with currently available vectors. Polylysine based molecular conjugate vectors (MCV) were previously found to effectively transduce both normal and malignant hematopoietic cells. A panel of human leukemia cell lines as well as CD34+ selected primary human hematopoietic progenitor cells (HPC) were tested for differential gene expression utilizing different promoters. Reporter gene expression under the control of RSV and SV40 promoters showed a 6-log fold increase in leukemia cells when compared to primary HPC. Using a polylysine based recombinant molecular conglomerate vector (recMCV) encoding the HSV-tk suicide gene under control of RSV, we demonstrated effective and specific cell killing in all leukemia cell lines as well as in primary human leukemia cells derived from chemotherapy refractory patients, while HPC survived under the same conditions at approximately 20% viability. These proof of principle experiments demonstrate that gene therapy technology could be utilized to successfully purge leukemia cells from HPC.

Antigens, CD34↗
PubMed2002

Sensitivity of myeloid leukemia cells to calcium influx blockade: application to bone marrow purging.

OBJECTIVE: The aim of this study was to assess the potential of store-operated Ca(2+) channel (SOC) antagonists as purging agents for leukemia cells. MATERIALS AND METHODS: Clonogenic, limiting dilution, and nuclear condensation assays were used to evaluate SOC antagonist efficacy. SOC activity and endoplasmic reticulum Ca(2+) content were measured by flow cytometry. Murine bone marrow transplantation was used to determine purging efficacy and effects on hemopoietic reconstitution. RESULTS: Econazole (Ec) and ketotifen (Ke) were variably effective against human and murine leukemia cell lines after 24 hours of incubation. However, a 2-hour serum and bovine serum albumin-free treatment protocol with Ec was found to maximize differential sensitivity between leukemic cells and normal hemopoietic progenitors. Primary acute myelogenous leukemia blast cell viability was reduced 4.2 to 5.1 logs by 2-hour Ec treatment as measured by limiting dilution. An inverse relationship between endoplasmic reticulum Ca(2+) content and Ke sensitivity in leukemia and untransformed cells was observed. Nuclear condensation, an index of apoptosis, which occurred after 24-hour treatments with either Ec or Ke, was not observed after 2-hour serum- and bovine serum albumin-free Ec exposures; however, condensed nuclei were observed after an additional 10-hour incubation in growth medium without drug. Using bone marrow deliberately contaminated with 1% P815 cells, we showed that highly effective in vitro purging can be accomplished using Ec with no adverse effects on bone marrow reconstitution in mice. CONCLUSIONS: These studies suggest that SOC antagonists have potential as purging agents for residual leukemia cells present in bone marrow in the context of high-dose chemotherapy and autologous transplantation for leukemia.

Animals↗
PubMed1989

Elimination of clonogenic tumor cells from HL-60, Daudi, and U-937 cell lines by laser photoradiation therapy: implications for autologous bone marrow purging.

Laser photoradiation therapy was tested in an in vitro model for its efficacy in the elimination of non-Hodgkin's lymphoma cells. Results show that at 31.2 J/cm2 of laser light in the presence of 20 micrograms/mL of merocyanine 540 (MC540) there was greater than 5 log reduction in Burkitt's lymphoma (Daudi) cells. Similar tumor cell kill was obtained for leukemia (HL-60) cells at a laser light dose of 93.6 J/cm2. However, to obtain the same efficiency of killing for histiocytic lymphoma (U-937) cells, a higher dose of MC540 (25 micrograms/mL) was required. Clonogenic tumor stem cell colony formation was reduced by greater than 5 logs after laser photoradiation therapy. Under identical conditions for each cell line the percent survival for granulocyte-macrophage colony-forming units (CFU-GM, 45.9%, 40%, 17.5%), granulocyte/erythroid/macrophage/megakaryocyte (GEMM, 40.1%, 20.1%, 11.5%), colony-forming units (CFU-C, 16.2%, 9.1%, 1.8%), and erythroid burst-forming units (BFU-E, 33.4%, 17.8%, 3.9%) was significantly higher than the tumor cells. Mixing of gamma ray-irradiated normal marrow cells with tumor cells (1:1 and 10:1 ratio) did not interfere with the elimination of tumor cells. The effect of highly purified recombinant interferon alpha (rIFN) on laser photoradiation therapy of tumor cells was also investigated. In the presence of rIFN (30 to 3,000 U/mL), the viability of leukemic cells was observed to increase from 0% to 1.5% with a concurrent decrease in membrane polarization, suggesting an increase in fluidity of cell membrane in response to rIFN. However, at higher doses of rIFN (6,000 to 12,000 U/mL) this phenomenon was not observed. The viability of lymphoma cells remained unaffected at all doses of rIFN tested. These results may have therapeutic relevance in patients undergoing interferon treatment who require bone marrow transplantation, as the complete elimination of tumor cells by marrow-purging procedures may be hampered by this increased survival in the presence of interferon.

Bone Marrow↗
PubMed1988

S-L 11.14: a monoclonal antibody recognizing neuroectodermal tumors with possible value for bone marrow purging before autograft.

A new monoclonal antibody (S-L 11.14) raised against small cell lung cancer reacted with all but one neuroblastoma tumor cell sample tested and was relatively specific for such cells within the bone marrow. The ability of S-L 11.14 to eliminate neuroblastoma cells from the bone marrow with an immunomagnetic purging method was evaluated in an experimental model using the LAN.1 and SKNBE neuroblastoma cell lines as targets. Residual malignant cells after the purging procedure were quantified by the Hoechst staining method. The use of S-L 11.14 as a single reagent resulted in a 3-log elimination of malignant cells, a depletion equal to that obtained with a cocktail of five monoclonal antibodies currently used in clinical trials. The addition of the S-L 11.14 antibody to this cocktail did not enhance depletion.

Antibodies, Monoclonal↗
PubMed1987

Recovery of the ability to induce immune resistance against L1210 lymphatic leukemia in semisyngeneic CD2F1 mice after lethal irradiation and reconstitution with bone marrow purged of leukemia with mafosfamide (ASTA Z 7654).

Balb/c x DBA/2 F1 (CD2F1) mice were lethally irradiated (TBI) and reconstituted with syngeneic bone marrow cells (SBMT) untreated or treated with mafosfamide (ASTA Z 7654) for ex vivo purging of semisyngeneic L1210 leukemia (TBI + SBMT or TBI + SBMT-Maf mice, respectively). At various times after irradiation and reconstitution mice were injected intraperitoneally four times at weekly intervals with 10(6) immunogenic L1210-Maf cells (L1210 cells treated in vitro with mafosfamide for inhibition of their growth in vivo). As positive controls we immunized normal (non-irradiated) CD2F1 mice. Full resistance against L1210 leukemia (as compared to normal immunized mice) could be obtained in TBI + SBMT and TBI + SBMT-Maf mice when the immunization procedure was started from day +28 or day +56 after transplantation, respectively. Earlier immunization of TBI + SBMT mice (from day +14) or TBI + SBMT-Maf mice (from day +14 or +28) caused only partial resistance against the leukemia.

Animals↗
PubMed1994

Is bone marrow purging proving to be of value?

Although the role of hematopoietic stem-cell transplantation (HSCT) in cancer treatment is rapidly expanding, decreasing the side effects of stem-cell infusion is a major challenge. Cancer cells present in the stem-cell collection can cause relapse after autologous transplantation. In allogeneic transplantation. T lymphocytes contribute to graft-versus-host disease. Various methods of purging have been used to remove these unwanted cells, and there is some evidence that such manipulations are clinically useful. Nevertheless, the inability to detect minimal disease makes it difficult to determine whether relapse is caused by incomplete disease eradication in the patient or by the infused cells. This makes it hard to justify the clinical benefit of ex vivo purging. Researchers can focus on this issue by designing studies with minimal variation in other factors that affect the success of stem-cell transplantation.

Bone Marrow Purging↗