Peripheral blood stem cell (PBSC) mobilization with chemotherapy followed by sequential IL-3 and G-CSF administration in extensively pretreated patients

Feasibility study of IL-11 and granulocyte colony-stimulating factor after myelosuppressive chemotherapy to mobilize peripheral blood stem cells from heavily pretreated patients

PURPOSE

Pediatric patients with solid tumors treated with prolonged dose-intensive chemoradiotherapy are poor mobilizers of peripheral blood stem cells (PBSC). We have conducted a pilot study to mobilize PBSC in eight pediatric patients with relapsed solid tumors using ifosfamide, carboplatin, and etoposide (ICE) followed-up by IL-11 plus granulocyte colony-stimulating factor (G-CSF).

PATIENTS AND METHODS

Patients received ifosfamide 1.8 g/m2 per day for 5 days, carboplatin 400 mg/m2 per day for 2 days, and etoposide 100 mg/m2 per day for 5 days. After completion of ICE chemotherapy, patients received daily subcutaneous injections of G-CSF (5 microg/kg per day) and IL-11 (50-100 microg/kg per day) until peripheral stem cell apheresis.

RESULTS

The median age was 11 years. Diagnosis included three relapsed Hodgkin disease, three relapsed central nervous system tumors, one relapsed Wilms tumor, and one relapsed rhabdomyosarcoma. The median number of apheresis procedures required to obtain 5 x 10(6) CD34+ cells/kg was one. The mean +/- standard error of mean (SEM) total CD34+ cells collected was 14.0+/-2.7 x 10(6)/kg. The mean +/- SEM total CD34+/CD41+ cells collected was 4.6+/-1.9 x 10(6)/kg. Seven of the eight patients have subsequently undergone myeloablative chemotherapy with autologous PBSC transplantation and have reconstituted hematopoiesis with a median time to neutrophil recovery of 10 days and platelet recovery of 15.5 days.

CONCLUSIONS

We conclude that the regimen of ICE/IL-11 plus G-CSF is successful in mobilizing large numbers of CD34+ PBSC cells with a limited number (one) of apheresis collections in patients that have previously been heavily pretreated with chemotherapy/radiotherapy.

Mobilization of hematopoietic stem cells

Hematopoietic stem cell transplantation has been extensively exploited as a therapeutic and research modality and has revolutionized current patient care. At present, more and more medical centers use peripheral blood progenitor cells for transplantation by mobilizing hematopoietic stem cells from bone marrow to peripheral blood because of potential advantages of peripheral blood stem cell transplantation over bone-marrow transplantation. Different effective mobilization regimens have been developed recently with chemotherapeutic agents, hematopoietic growth factors or their combination. This article reviews current developments related to hematopoietic stem cell mobilization including the biology of hematopoietic stem cells, strategies for mobilization, management for mobilization failure, mechanisms of mobilization, and side effects during mobilization. Finally, the Initiation-Amplification-Emigration-Adaptation Model is proposed to help aid understanding of the mechanisms of hematopoietic stem cell mobilization and to stimulate development of novel and optimal mobilization strategies for patient care.

Characterization and outcome of "hard to mobilize"' lymphoma patients undergoing autologous stem cell transplantation

A "hard to mobilize" patient was defined as one in whom >or= 1x10(6) CD 34+ cells/kg cannot be obtained after two consecutive large volume aphereses. Forty-four consecutive Hodgkin's and non-Hodgkin's lymphoma patients who underwent autologous peripheral blood stem cell (PBSC) transplant treatment between June 1996 and June 1998 were included in this study. Twenty-one patients (48%) met the definition of "hard to mobilize" (Group I). All the rest of the patients (n=23) were the good mobilizers (Group II). The initial mobilization protocol for most patients was 10 microg/kg of G-CSF alone for both groups. For Group I, 7/21 (33%) patients were unable to achieve a minimal dose of >or= 1x10(6) CD34+ cells/kg even after a second mobilization attempt and/or bone marrow (BM) harvest (n=5). Overall, 11/21 (52%) required an additional mobilization and/or BM harvest. Only 3/21 (14%) patients were able to meet the target cell dose of >or= 2.5x10(6) CD34+ cells/kg (median of 4 apheresis). In contrast, 87% of Group II achieved the target dose with a median of 2 aphereses. Predictors of poor mobilization were greater than two prior treatment regimens (p=0.038) and the WBC count (<25,000/microL) on the first day of apheresis (p=0.053). Nineteen patients in Group I and all Group II completed treatment with a median time to engraftment of ANC>500/microl of 12 and 11 days, and platelet >20x10(3)/microl of 31 and 13 days, respectively. Outcome analysis revealed that 6/19 patients in Group I died of relapse within one year from transplant compared with only 2/23 of Group II who died of relapse (p=0.005, log rank test). There were no treatment related deaths in either group. Independent predictive features for "hard to mobilize" patients are a lack of significant increase in WBC count on the first day of apheresis and the number of prior treatment regimens. Poor mobilization appears to predict a worse outcome after autografting for lymphoma patients.

Cytokine-mobilized peripheral blood progenitor cells for allogeneic reconstitution of miniature swine

BACKGROUND

Because of the relative ease of acquisition, increased yield, and improved engraftment characteristics, mobilized peripheral blood progenitor (stem) cells (PBSCs) have recently become the preferred source for hematopoietic stem cell transplantation. In our laboratory, procurement of a megadose of PBSCs is necessary for on-going studies evaluating non-myelosuppressive transplant regimens for the induction of mixed chimerism and allograft tolerance. To exploit hematopoietic growth factor synergy, we have sought to combine growth factors with proven utility to improve PBSC mobilization and maximize our PBSC procurement through an automated collection procedure.

METHODS

Mobilization characteristics of PBSCs were determined in 2-5-month-old miniature swine. Animals received either swine recombinant stem cell factor (pSCF, 100 microg/kg) and swine recombinant interleukin 3 (pIL-3, 100 microg/kg), administered intramuscularly for 8 days, or pSCF, pIL-3, and human recombinant granulocyte-colony stimulating factor (hG-CSF), at 10 microg/kg. Leukapheresis was performed beginning on day 5 of cytokine treatment and continued daily for 3 days.

RESULTS

Collection of PBSCs from cytokine-mobilized animals via an automated leukapheresis procedure demonstrated a 10-fold increase in the number of total nucleated cells (TNC) (20-30 x 10(10) TNC) compared to bone marrow harvesting (2-3 x 10(10) total TNC). A more rapid rise in white blood cells (WBCs) was seen after administration of all three cytokines compared to pSCF and pIL-3 alone. An increase in colony-forming unit granulocyte-macrophage frequency measured daily from peripheral blood during cytokine treatment, was seen with the addition of hG-CSF to pSCF/pIL-3 correlating well with the rise in WBCs. Similarly, the addition of hG-CSF demonstrated a notable increase in the median progenitor cell yield from the 3-day leukapheresis procedure. Cytokine-mobilized PBSCs were capable of hematopoietic reconstitution. PBSCs mobilized with pSCF/pIL-3 were infused into an SLA-matched recipient conditioned with cyclophosphamide (50 mg/kg) and total body irradiation 1150 cGy. Neutrophil and platelet engraftment occurred on days 5 and 7, respectively, with minimal evidence of graft-versus-host disease. Complete donor chimerism has been demonstrated 331 days after transplant.

CONCLUSIONS

Our preliminary results show that in this well-defined miniature swine model, recombinant swine cytokine combinations (pSCF, pIL-3 with or without hG-CSF) successfully mobilize a high yield of progenitor cells for allogeneic transplantation. Furthermore, these cytokine-mobilized PBSCs demonstrate the potential to reconstitute hematopoiesis and provide long-term engraftment in miniature swine.