No preferential sensitivity of clonogenic AML cells to ASTA-Z-7557

Preferential photoinactivation of leukemia cells by aluminum phthalocyanine

The efficacy of chloroaluminum phthalocyanine (AlPc) for photodynamic therapy (PDT) has been evaluated in vitro on acute myeloid leukemia (AML) cells, normal peripheral blood leukocytes (PBL) and mobilized peripheral blood stem cells (mPBSC). The selectivity of the treatment has been evaluated by mixing PBL and TF-1, an erythroleukemic cell line. Upon photoradiation, this photosensitizer leads to a significant and preferential photokilling of leukemia cells in comparison to normal cells. The use of stimulated lymphocytes in PBL/TF-1 mixtures instead of resting cells also leads to a preferential killing towards TF-1 although activated PBL are more affected than resting PBL. The analysis of AlPc intracellular emission by flow cytometry shows that the uptake of the dye by leukemia cells is faster. This good efficacy towards AML and the observed lower phototoxicity towards normal cells (PBL, normal progenitors) suggest that this phthalocyanine is a potential bone marrow purging agent.

High-dose therapy in acute leukemia

The use of intensive induction chemotherapy, primarily with combinations of an anthracycline and cytarabine, allows complete remission rates of greater than 70% in patients with acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL). However, with currently available standard-dose therapy, only 20% of young adults are cured. In order to substantially increase the cure rate, adequate post-remission therapeutic strategies are mandatory. Three different therapeutic options are currently available: (i) dose-intensified chemotherapy; (ii) allogeneic stem cell transplantation; (iii) autologous stem cell transplantation. These therapeutic options should be carefully evaluated according to prognostic information, including cytogenetic and molecular abnormalities as well as phenotypic characterization. Randomized trials of intensive postremission therapy have now confirmed improved leukemia-free survival with the use of allogeneic or autologous transplantation. Autologous transplantation appears to be the most promising treatment modality in AML. Improved preparative regimens and purging techniques may be critical factors in determining the effectiveness of autologous transplantation in AML patients. In adult ALL, the role and optimal methods of stem cell transplantation are still under investigation.

Sensitivity of primary clonogenic blasts from acute lymphoblastic leukemia patients to an activated cyclophosphamide, viz., mafosfamide

Primary cyclophosphamide-naive clonogenic blasts from 32 patients with newly diagnosed acute lymphoblastic leukemia (ALL) were tested for their in vitro sensitivity to an "activated" cyclophosphamide, viz., mafosfamide, using leukemic progenitor cell (LPC) colony assays. Marked interpatient variation in the responses of LPC from newly diagnosed patients to mafosfamide prompted assessment of mafosfamide sensitivity in relation to more frequently measured parameters of newly diagnosed ALL. Only immunophenotype and sex showed a significant association with the intrinsic mafosfamide sensitivity of LPC. LPC from T-lineage ALL patients were more resistant to mafosfamide than LPC from B-lineage ALL patients, as reflected by 1.8-fold and 4.3-fold higher mean SF10 and SF20 (surviving fractions of ALL LPC of 10 and 20 microM mafosfamide, respectively) values. LPC from male patients were more resistant to mafosfamide than LPC from female patients, as reflected by 1.9-fold and 4.8-fold higher mean SF10 and SF20 values. In comparison to T-lineage ALL patients, a significantly greater fraction of B-lineage ALL patients had mafosfamide-sensitive LPC with SF10 values of < 0.25 (61% vs 11%, P = 0.01). Notably, all four cases exhibiting resistance to mafosfamide, i.e., SF20 > or = 0.5, were males with T-lineage ALL. In order to exclude the influence of sex as a confounding factor in the observed immunophenotype-mafosfamide sensitivity association, we also compared the mafosfamide sensitivities of LPC from male patients only. The means of SF10, and SF20 values of LPC from male T-lineage ALL patients were 1.5- and 3.2-fold higher than those of LPC from male B-lineage ALL patients (P < 0.1). Thus, in the male patient subgroup, the immunophenotype-mafosfamide sensitivity association remained significant.

Effect of recombinant human stem cell factor on mafosfamide-treated bone marrow clonogenic cells

The availability of early-acting cytokines could allow the establishment of new approaches to chemical marrow purging. It was the aim of the present study to investigate the capability of recombinant human stem cell factor (SCF) in combination with other growth factors to support the in vitro growth of mafosfamide-treated progenitor cells such as mixed colony forming units (CFU-GEMM), erythroid burst forming units (BFU-E) and granulocyte-macrophage CFU (CFU-GM). When marrow cells were incubated (30 min, 37 degrees C) with increasing doses of mafosfamide (30-120 micrograms/ml) a statistically significant (p < or = .05), dose-dependent suppression of colony growth was observed. Addition of SCF (50 ng/ml) to marrow cultures stimulated with the standard mixture of growth factors (interleukin 3 or IL-3, granulocyte-macrophage colony stimulating factor or GM-CSF, and erythropoietin or Epo) significantly increased the mean (+/- SD) concentration of mafosfamide inducing 95% inhibition of CFU-GM (106 +/- 17 versus 130 +/- 29, p < or = .0005), but not granulocyte/erythroid/macrophage/megakaryocyte CFU (CFU-GEMM) (85 +/- 4 versus 90 +/- 1, p < or = .1) and BFU-E (90 +/- 5 versus 92 +/- 5, p < or = .1). SCF induces a dose-dependent, statistically significant enhancement of colony formation by CD34+, mafosfamide-treated cells. As shown by single colony transfer experiments, mafosfamide-resistant clones promoted by SCF have a significantly higher replating capacity as compared with mafosfamide-resistant clones grown without SCF.(ABSTRACT TRUNCATED AT 250 WORDS)

Normal hematopoietic reconstitution following ASTA-Z 7557-purged grafts in the absence of in vitro CFU-GM colony growth

Hematopoietic reconstitution was assessed in 26 consecutive patients who underwent autologous bone marrow transplantation (ABMT) with ASTA-Z 7557 purged bone marrows. Of the 26, 17 had acute non-lymphoblastic leukemia (ANLL), 7 had acute lymphoblastic leukemia (ALL), 1 had non-Hodgkin's lymphoma (NHL) and 1 had multiple myeloma (MM). Twelve patients had practically no CFU-GM growth after ASTA-Z treatment. No statistical difference was observed in hematopoietic reconstitution between patients with or without in vitro CFU-GM colony growth. No significant linear correlation was observed between CFU-GM content in the treated graft and day of engraftment. In vitro CFU-GM growth has no predictive value in assessing hematopoietic recovery in vivo. Patients with no CFU-GM growth demonstrated normal engraftment.

Biological aspects and clinical results of autologous bone marrow transplantation for acute myeloid leukemia

Autologous bone marrow transplantation is a therapeutic approach that permits the administration of high-dose chemo-radiotherapy followed by the infusion of the patient's own marrow, previously collected during remission and cryopreserved. In recent years, autologous bone marrow transplantation has been increasingly used as a treatment for acute leukemias. The mechanisms underlying leukemic relapse represent the most exciting and controversial aspects of autologous bone marrow transplantation. At least three factors may be responsible for leukemic relapse in patients receiving autologous bone marrow transplantation: (1) minimal residual disease; (2) leukemic cells reinfused with the graft; (3) the lack of a graft-versus-leukemia effect. In this paper, the techniques for pharmacological marrow decontamination and the clinical results obtained with autologous bone marrow transplantation will be reviewed.

In vitro drug sensitivity of normal peripheral blood lymphocytes and childhood leukaemic cells from bone marrow and peripheral blood

In vitro drug sensitivity of leukaemic cells might be influenced by the contamination of such a sample with non-malignant cells and the sample source. To study this, sensitivity of normal peripheral blood (PB) lymphocytes to a number of cytostatic drugs was assessed with the MTT assay. We compared this sensitivity with the drug sensitivity of leukaemic cells of 38 children with acute lymphoblastic leukaemia. We also studied a possible differential sensitivity of leukaemic cells from bone marrow (BM) and PB. The following drugs were used: Prednisolone, dexamethasone, 6-mercaptopurine, 6-thioguanine, cytosine arabinoside, vincristine, vindesine, daunorubicin, doxorubicin, mafosfamide (Maf), 4-hydroperoxy-ifosfamide, teniposide, mitoxantrone, L-asparaginase, methotrexate and mustine. Normal PB lymphocytes were significantly more resistant to all drugs tested, except to Maf. Leukaemic BM and PB cells from 38 patients (unpaired samples) showed no significant differences in sensitivity to any of the drugs. Moreover, in 11 of 12 children with acute leukaemia of whom we investigated simultaneously obtained BM and PB (paired samples), their leukaemic BM and PB cells showed comparable drug sensitivity profiles. In one patient the BM cells were more sensitive to most drugs than those from the PB, but the actual differences in sensitivity were small. We conclude that the contamination of a leukaemic sample with normal PB lymphocytes will influence the results of the MTT assay. The source of the leukaemic sample, BM or PB, does not significantly influence the assay results.

Practical aspects and diagnostic significance of in vitro manipulation of progenitors in human acute myeloid and lymphoid leukaemia

Since their introduction in the early seventies, in vitro culture techniques for human acute leukaemia cells have been modified and improved considerably. Primarily, this is the result of the availability of the recombinant haematopoietic growth factors (HGFs). It is now possible to evaluate HGF responses of acute leukaemia cells in colony and DNA synthesis assays under fully defined conditions. In this chapter we summarize the current insights into the growth properties of human acute leukaemia progenitor cells and evaluate the potential significance of the application of in vitro clonogenic assays for refining the diagnosis of acute leukaemia, for detecting minimal residual disease and for monitoring therapy.

Bone marrow purging with mafosfamide--a critical survey

Autologous bone marrow transplantation (ABMT) is increasingly used to consolidate remissions, primarily in hematological disease. Various purging strategies have been developed to minimize the risk of reimplantation of tumor cells with the bone marrow autotransplant. Pharmacological purging with the oxazaphosphorine derivative mafosfamide has been studied extensively, and recent clinical data suggest that purging with mafosfamide may translate into superior remission duration if compared to nonpurged ABMT in acute leukemia. Chemical and experimental data relevant to mafosfamide-purging and clinical results are reviewed, with special emphasis on safety aspects.

Differential phthalocyanine photosensitization of acute myeloblastic leukaemia progenitor cells: a potential purging technique for autologous bone marrow transplantation

The potential value of sulphonated aluminium phthalocyanine (AISPc) as a purging agent for bone marrow autografts in acute myeloblastic leukaemia (AML) has been studied using in vitro clonogenic assays for normal (GM-CFC) and leukaemic (AML-CFC) progenitor cells. In nine out of 13 cases, the leukaemic blasts were found to be highly sensitive to AISPc. In six of the sensitive cases clonogenic assays revealed that only 2 +/- 1% of AML progenitor cells survived AISPc treatment under conditions which permitted a GM-CFC recovery of 60 +/- 11%. AISPc photosensitization was also shown to selectively eliminate the leukaemic cell line K562 from an in vitro model of minimal residual disease. Thus photosensitization using AISPc may be an effective method of purging marrow autografts in some cases of AML. Evaluation of the sensitivity of AML clonogenic cells at diagnosis may identify those patients in whom AISPc photo-purging may be of benefit at the time of an autologous bone marrow transplant.

Regrowth of granulocyte-macrophage progenitor cells (GM-CFC) in suspension cultures of bone marrow depleted of GM-CFC with 4-hydroperoxycyclophosphamide (4-HC)

The hematopoietic capacity of bone marrow treated with 4-hydroperoxycyclophosphamide (4-HC) was studied using long-term suspension cultures. It was shown that, in the presence of a previously established marrow adherent cell layer (ACL), the 4-HC treated bone marrow, deprived of GM-CFC, generates GM-CFC in long-term suspension cultures in vitro. The kinetics of GM-CFC reappearance in in vitro cultures indicate their origin from more primitive progenitors rather than from surviving GM-CFC. In the presented modification, the suspension culture system is useful in evaluating the transplantation potential of bone marrow purged in vitro with chemotherapeutic or biologic agents.

B-cell colony growth of malignant and normal B-cells

B-cell colony growth of malignant and normal B-cells has been studied in a double layer (agar-fluid) colony assay. Stimulatory factors consisted of irradiated blood leukocytes, phytohaemagglutinin (PHA), interleukin 2 (IL2) and 12-0-tetradecanoylphorbol-13-acetate (TPA) in various combinations. B-cell colonies have been obtained in all cases tested, i.e., 7/7 cases with chronic lymphocytic leukaemia, 7/7 cases with non-Hodgkin's lymphoma, 5/5 cases with hairy cell leukaemia and 7/7 normal B-cell suspensions, obtained from blood (X 3), bone marrow (X 2) and spleen (X 2). The plating efficacy ranged from 0.02-0.35, with a median of 0.07. Colony formation was found to be linear (r = 0.96) in the plating range of 0.5-8 X 10(5) cells. Secondary colonies could be obtained in 2 cases tested. DNA synthesizing cells in colonies were determined in 4 cases using monoclonal antibodies against DNA-incorporated bromodeoxyuridine (BrdUrd). In most cases the combination of PHA (with or without IL2) and irradiated leukocytes yielded the highest number of colonies, but in some experiments stimulation with TPA + IL2 was found to be optimal.

Hairy cell leukemia: in-vitro proliferation and pseudo-colony formation

In an established double layer clonogenic assay, the PHA-leukocyte feeder colony assay, hairy cell leukemia (HCL) cells formed strong aggregates simulating colonies. After irradiation with 50 Gy, colony formation persisted. Even in a modified colony assay consisting of agar 0.5% overlayered by methylcellulose 0.9%, cell aggregation was still possible due to increasing fluidity of the methylcellulose during the culture period. Time-lapse video recordings confirmed prominent cell motility leading to pseudo-colony formation. Studies with bromodeoxyuridine incorporation showed a low proliferation index (up to 13%) of hairy cells. In conclusion, any assay that facilitates cell motility is unsuitable to study HCL colony growth.

Comparison of the sensitivity of normal and leukaemic myeloid progenitors to in-vitro incubation with cytotoxic drugs: a study of pharmacological purging

The sensitivity of myeloid leukaemic colony forming cells (AML-CFC), to five cytotoxic drugs has been compared in two culture systems with the sensitivity of normal myeloid progenitor cells (GM-CFC). No increased sensitivity was found for AML-CFC to any of the chemotherapeutic agents studied. AML-CFC were significantly less sensitive than normal GM-CFC to mafosfamide at the doses commonly used to purge bone marrow autografts. It is suggested that AML cells probably display similar sensitivity to cytotoxic agents as normal myelopoietic cells at a similar stage of differentiation. Hence complete elimination of the leukemic clone by pharmacological purging may be incompatible with bone marrow re-engraftment. We conclude that purging AML autografts with any of the agents examined has little scientific basis.

Autologous bone marrow transplantation in acute myeloid leukemia after in-vitro purging with an anti-lacto-N-fucopentaose III antibody and rabbit complement

Two AML patients, whose leukemic clonogenic cells totally reacted to the anti-lactofucopentaose III S4-7 monoclonal antibody (MoAb), underwent autologous bone marrow transplantation, in first complete remission, after in-vitro purging with S4-7 MoAb and complement. After ablative chemotherapy (BAVC regimen) and reinfusion of S4-7 purged cells, regeneration of marrow cells occurred with prompt recovery of granulopoiesis and erythropoiesis. A more delayed platelet recovery was observed. The two patients are in complete remission at 20 and 11 months from ABMT. The results indicate that immunologic purging with S4-7 MoAb is safe and suitable for selected AML patients undergoing ABMT.

Autologous bone marrow transplantation (ABMT) for acute leukaemia in complete remission: a pilot study of 33 cases

Thirty-three leukaemic patients in CR were treated by high-dose therapy followed by ABMT: 18 of them had acute non-lymphoblastic leukaemia (ANLL) in first remission (CR1) with a mean age of 23.7 years (3-44). All but one of them were conditioned with a polychemotherapy regimen including 6-thioguanine, Ara-C, CCNU, and cyclophosphamide. The marrow cells were purged by chemical means in 16 cases. Five transplant-related deaths were observed: three cardiac failures, one interstitial pneumonitis and one aspergillus pneumonia. At the time of analysis (October 1984), four patients had relapsed and eight were still in unmaintained CR1 (44+, 46+, 30+, and five between 2.5+ and 8+ months post transplant). Fifteen patients had acute lymphoblastic leukaemia: four were autografted in CR1 and 11 children were grafted in CR2; the conditioning regimen was fractionated total body irradiation followed by cyclophosphamide for all but one patient who was conditioned with BACT (Burkitt leukaemia); the marrow was purged by a chemical agent in 11 patients and by monoclonal antibodies and C' in four: four out of 15 patients relapsed (two grafted in CR1 and two grafted in CR2); 10 patients are still in unmaintained CR: two adults grafted in CR1 (26+; 12+ months) and eight children with a mean follow-up of 13.4 months post graft (2 + -45+ months). The clinical study leads to the following conclusions: in adult patients the marrow should be harvested during CR1 and at the time of minimal residual disease. The quality of previous chemotherapy and conditioning regimen prior to ABMT play a prominent role in the in vivo eradication of the leukaemic cells. The real impact of marrow purging is still unknown and a larger series of homogeneous patients, conditioned with the same protocols and the same transplant timing, is required before any conclusions can be drawn.

4-Hydroperoxycyclophosphamide inhibits proliferation by human granulocyte-macrophage colony-forming cells (GM-CFC) but spares more primitive progenitor cells

Despite its considerable toxicity to haemopoietic colony-forming cells, 4-hydroperoxycyclophosphamide (4-HC) has successfully been used to purge marrow of leukaemic cells before it is used to rescue patients from high-dose chemoradiotherapy. These conflicting observations indicate that haemopoietic progenitor cells that are not detected by the established colony-forming assays survive exposure to 4-HC and repopulate the marrow. The recent finding that murine spleen colony-forming cells (CFU-S) are resistant to 4-HC [Porcellini A, et al. (1983) Expl Hemat. 11 (suppl 14) 331 (abstract)] [14] also indicates that sensitivity to 4-HC can be used to distinguish primitive progenitor cells from committed progenitor cells. As part of a study on the nature of a population of blast colony-forming cells in human bone marrow, we tested their sensitivity to 4-HC to see whether they also are spared by the drug. We found that 4-HC had much less effect on the blast colony-forming cells than on the granulocyte-macrophage colony-forming cells (GM-CFC). This result suggests that the blast-colony-forming cells may be early human haemopoietic progenitor cells.