Autologous transplantation of chemotherapy-purged PBSC collections from high-risk leukemia patients: a pilot study

Factors for PBPC collection efficiency and collection predictors

Factors affecting collection efficiency of peripheral blood stem cells (PBSCs) include patient's age, diagnosis, preceding chemoradiotherapy, disease invasion of the bone marrow and mobilizing chemotherapy in PBSC collection for autologous transplants. Mobilizing cytokines, timing for apheresis, machines and operating software would affect mobilization and collection of PBSCs both for autologous and allogeneic transplantation. Also donor's age and gender would affect PBSC yield for allogeneic transplantation. Surrogate markers including peripheral blood CD34+ cell counts before mobilization and on day of collection have been reported to predict the yield of PBSC harvest. A number of standard procedures have been developed based on these findings. Newer agents for PBSC mobilization are being evaluated and still other factors affecting mobilization are being sought to better predict and cope with poor mobilization.

NK-cell purging of leukemia: superior antitumor effects of NK cells H2 allogeneic to the tumor and augmentation with inhibitory receptor blockade

Natural killer (NK) cells are composed of subsets characterized by the expression of inhibitory or activating receptors, or both, specific for different major histocompatibility complex (MHC) class I determinants. We have previously shown that inhibitory receptor blockade of syngeneic NK cells was an effective means of ex vivo purging of leukemia-contaminated bone marrow and that the transplantation of mice with the purged bone marrow cells (BMCs) resulted in long-term, relapse-free survival. We have extended the investigation to assess the antitumor effects mediated by NK cells H2-allogeneic to tumor cells. We demonstrate that various tumor cell lines are more susceptible to lysis by H2-allogeneic NK cells than by syngeneic NK cells in vitro even though comparable percentages of Ly49 NK cells were present. Using allogeneic NK cells to purge leukemia-contaminating BMCs before transplantation resulted in a higher proportion of mice with long-term survival than using syngeneic NK cells. Allogeneic NK cells did not suppress hematopoietic reconstitution as measured by granulocyte/monocyte-colony-forming unit (CFU-GM), complete blood count (CBC), and donor chimerism at various days after transplantation. Inhibitory receptor blockade of allogeneic NK cells also significantly increased these antitumor effects at lower NK/tumor ratios compared with those of syngeneic NK cells. These results demonstrate that H2-allogeneic NK cells mediate more potent antitumor effects than syngeneic NK cells without adverse hematologic effects and thus may be useful in cancer therapy.

Autologous peripheral blood stem cell transplantation in first remission adult acute myeloid leukaemia--an intention to treat analysis and comparison of outcome using a predictive model based on the MRC AML10 cohort

The role of autologous peripheral blood stem cell transplantation (APBSCT) in acute myeloid leukaemia (AML) remains controversial. The current study evaluated the application of APBSCT in a large consecutive series of patients with untreated AML, and compared outcome with a predictive model based on MRC AML10 data. Of 148 evaluable patients, 118 patients entered complete remission (CR) after induction therapy comprising three cycles of daunorubicin, cytosine arabinoside and oral 6-thioguanine. Of these patients, 68 (57%) proceeded to consolidation therapy with two courses of intermediate dose cytosine arabinoside, and stem cell mobilisation, and 40 of these patients (34%) underwent the APBSCT procedure after high dose busulphan conditioning. Harvest quality was the main factor precluding APBSCT. Five-year event-free survival (EFS) in patients who achieved CR was 38% and in APBSCT patients was 57%. There were no transplant-related deaths. No significant differences were demonstrated between observed and expected outcomes at 1 and 2 years, based on the predictive model derived from the MRC AML10 study. These data therefore indicate that only a third of eligible adult patients will undergo APBSCT. However, the results demonstrate favourable survival in such patients, with no transplant-related mortality.

Autologous stem cell transplantation and purging in adult acute lymphoblastic leukaemia

The prognosis for adult acute lymphoblastic leukaemia (ALL) is poor. Only 20-30% of patients will be cured with conventional chemotherapy. Haematopoietic progenitor transplantation is thus an attractive option in these patients. Even if allogeneic transplantation allows a better control of the disease, autologous transplantation remains an important alternative for patients lacking a suitable donor or when allogeneic transplants imply excessive risk. Relapse is the main drawback of autologous transplants, but many strategies are being explored to overcome this problem. We focus here on transplant modality, the source of haematopoietic progenitors, and the best timing to apply the procedure. Also reviewed are the current situation and future strategies for improving results in this setting, such as ex vivo purging; immunotherapy and maintenance chemotherapy.

New approaches to hematopoietic cell transplantation in oncology

The use of high-dose chemotherapy followed by autologous HCT and the use of allogeneic HCT in children and adolescents with high-risk ALL, AML, and NBL has successfully improved outcomes. For other diseases, however, the role of HCT in treatment remains a subject of further research. The availability of HCT was significantly expanded by developing alternative graft sources that currently include BM, peripheral blood, and UCB from autologous and allogeneic related or unrelated donors. Progress in autologous HCT has been achieved by the identification of more effective and less toxic preparative regimens and by ex vivo purging of stem cell products. In allogeneic HCT, graft-versus-leukemia or graft-versus-tumor effects are being exploited increasingly to lower relapse rates. In addition, immunomodulation to promote tolerance, as well as allogeneic antitumor reactions have been achieved by antibody therapy, cytokine therapy, or cell-based immunotherapy. Future improvements are likely, as evidenced by promising preliminary results in the development of stem cell collection techniques, in vitro stem cell expansion, and purging techniques of stem cell grafts. The development of less intensive or nonmyeloablative preparative regimens may further reduce regimen-related morbidity and mortality Specific immunotherapy may facilitate tolerance induction in mismatched allogeneic HCT and support allogeneic HCT in the setting of donor-host HLA disparity. Ultimately, advances in cytokine therapy, tumor-specific vaccines, and gene therapy may decrease or even eradicate recurrence of the malignant disease after HCT.

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.

Double reinforcement with fludarabine/high-dose cytarabine enhances the impact of autologous stem cell transplantation in acute myeloid leukemia patients

Reinforced chemotherapy based on a double high-dose consolidation regimen could be a different way to enhance in vivo purging prior to autologous stem cell transplantation (auto-SCT) in acute myeloid leukemia (AML). We investigated the impact on outcome of auto-SCT after two different strategies of early intensification performed after an identical induction regimen in adult patients with AML. Between January 1993 and December 1998, 140 consecutive AML patients were enrolled in a program consisting of an identical anthracycline-based induction (ICE) and two different consolidation regimens: one cycle, cytarabine-based (single-NOVIA: 91 patients); two cycles, fludarabine-based (double-FLAN: 49 patients). Seventy out of 91 patients received single-NOVIA consolidation: 60 underwent a transplantation procedure (allogeneic bone marrow transplantation (allo-BMT):16 patients; auto-SCT: 44). Thirty-five out of 49 patients received double-FLAN consolidation: 31 underwent a transplantation procedure (allo-BMT: 10; auto-SCT: 21). The double consolidation regimen was well-tolerated with only minor side-effects. Median follow-up observation time for surviving patients was 38 months (range, 17-71) for the double-FLAN consolidation group and 70 months (range: 48-93) for the single-NOVIA consolidation group. Among the patients who received auto-SCT, the double consolidation strategy produced a superior disease-free survival curve at 36 months (78.6% (95%CI: 59.4-97.8) vs 47.7% (95%CI: 33-62.4)) compared with the single-NOVIA group. This difference was confirmed when the patients were analyzed for intention to treat (P = 0.04). In addition, the double-FLAN consolidation group showed a superior overall survival and lower relapse rate (P = 0.02). We conclude that the double-FLAN reinforcement strategy is safe and enhances the clinical impact of auto-SCT for AML patients in first complete remission. It may provide specific clinical benefit for patients undergoing auto-SCT.

Tumor necrosis factor-alpha and TNF-beta inhibit clonogenicity of mobilized human hematopoietic progenitors

We studied the effect of tumor necrosis factors (TNF-alpha and TNF-beta) on the clonogenicity of peripheral blood progenitor cells (PBPC) mobilized by granulocyte colony-stimulating factor (G-CSF). The cells were obtained by nine leukaphereses in patients with malignancies undergoing peripheral blood stem cell transplantation (PBSCT). Flow cytometry was performed to evaluate the number of CD34+ cells in peripheral blood and leukapheresis products. PBPC were grown in semisolid medium supplemented with human growth factors in the absence or presence of TNF at concentrations ranging from 0.1 to 10 ng/ml. Colonies were scored on day 14. TNF-alpha and TNF-beta suppressed colony formation in all cases studied. TNF-alpha inhibited the growth of colony-forming units-granulocyte-macrophage (CFU-GM) at 1 and 10 ng/ml and burst-forming units-erythroid (BFU-E) at 10 ng/ml (p < 0.05), and TNF-beta inhibited the growth of CFU-GM and BFU-E at 1 and 10 ng/ml (p < 0.05). Thus, G-CSF-mobilized hematopoietic PBPC are highly sensitive to both TNF-alpha and TNF-beta. This finding should be taken in account when PBPC are handled ex vivo.

Ex vivo pharmacological purging of leukapheresis collections with nitrogen mustard: amifostine pretreatment improves both early and late peripheral blood progenitor cell recovery

Ex vivo pharmacological purging of bone marrow has been used to eliminate clonogenic tumor cells contaminating the autograft and potentially responsible of relapse. A considerable improvement of pharmacological purging would be achieved only if normal marrow progenitor cells could be selectively protected by the cytotoxicity of these agents. Amifostine (WR-2721; Ethyol), a phosphorylated aminothiol compound, has been shown to have this property both in vivo and in vitro. We describe here, an experimental model for ex vivo purging of peripheral blood progenitor cell (PBPC) collections based on the combination of 3 mg/ml of amifostine and the alkylating agent nitrogen mustard. Amifostine pretreatment resulted in a statistically significant protection of normal late and early progenitor cells. Under the same experimental conditions, we observed a 4-6 log reduction of contaminating leukemic cells (i.e., K-562 and CEM) and in contrast to the protection of normal peripheral blood progenitor cells, preincubation of contaminating K-562 or CEM with amifostine did not significantly alter the LD95 nitrogen mustard concentration. Moreover, when we tested fresh human leukemia progenitor cells, amifostine pretreatment sensitized the leukemic cells to the cytotoxic effects of NM.

Fludarabine-containing regimens severely impair peripheral blood stem cells mobilization and collection in acute myeloid leukaemia patients

We studied the effects of an intensified induction/consolidation treatment containing fludarabine (ICE/FLAN/FLAN) on the mobilization and collection of peripheral blood stem cells (PBSC) in 31 consecutive untreated acute myeloid leukaemia (AML) patients. The complete remission (CR) rate was comparable to classic inductions (68% after ICE; 84% after ICE-FLAN I). To mobilize PBSC, 19 patients received 10 microg/kg/d of granulocyte-colony stimulating factor (G-CSF) starting at day 13 after FLAN, 13 (69%) of whom were found to be nonmobilizers. When a second G-CSF administration was performed in 10/13 patients mobilization was either not achieved (8/10) or was considered insufficient (<1 x 106 CD34+ cells/kg) (2/10) and all 13 were subsequently submitted to bone marrow harvest. The harvest was considered adequate in 12/13 (92%) patients and autologous BMT (ABMT) has so far been performed in 10/12 cases with a mean of 8.6 x 108/kg nucleated reinfused cells. The median times to neutrophil and platelet recovery after ABMT did not significantly differ from those of two previous series of patients treated with ABMT without fludarabine-containing regimens. Adequate amounts of PBSC were obtained in 6/19 (31%) patients, who were then reinfused. Median times for platelet recovery were significantly longer than in a previous series of 26 AML cases reinfused with PBSC after treatment with the ICE-NOVIA induction/consolidation regimen (125 v 20 d to 20 x 109 plt/l, P < 0.02; 218 v 37 d to 50 x 109 plt/l, P < 0.02). In addition, times for platelet recovery after ICE/FLAN/FLAN were not significantly different from those in a previous group treated with ABMT performed after ICE/NOVIA,without fludarabine. We conclude that fludarabine-containing regimens severely impair mobilization and collection of PBSC in AML patients and seem unsuitable when PBSC autotransplantation is programmed.