Defining a therapeutic dose of peripheral blood stem cells

The ISHAGE guidelines for CD34+ cell determination by flow cytometry. International Society of Hematotherapy and Graft Engineering

The increased use of Peripheral Blood Stem Cells (PBSC) to reconstitute hematopoiesis in autotransplant and, more recently, allotransplant settings has not been associated with a consensus means to quality control the PBSC product. Since the small population of cells that bear the CD34 antigen are thought to be responsible for multilineage engraftment, graft assessment by flow cytometric quantitation of CD34+ cells should provide a rapid, reliable, and reproducible assay. Unfortunately, although a number of flow cytometric assays for CD34 enumeration have been described, the lack of a standardized method has led to the generation of widely divergent data. Furthermore, none of these assays has been validated as to interlaboratory reproducibility and suitability for widespread clinical application. In early 1995, the International Society of Hematotherapy and Graft Engineering (ISHAGE) established a Stem Cell Enumeration Committee, the mandate of which was to validate a simple, rapid, and sensitive flow cytometric method to quantitate CD34+ cells in peripheral blood and apheresis products. We also sought to establish its utility on a variety of flow cytometers in clinical laboratories and its reproducibility between transplant centers. Here, we describe the four-parameter flow methodology adopted by ISHAGE for validation in a multicenter study in North America.

Blood stem cell collection: factors influencing the recovery of granulocyte-macrophage colony forming cells

We evaluated data from all blood cell (BC) collections performed in our institution between 1989 and 1995 to determine factors influencing the outcome of collection. One hundred and thirty-three collections were performed on 106 patients. Malignant diagnoses were: non-Hodgkins lymphoma (NHL) in 35%, multiple myeloma in 31%, breast cancer in 26%, and Hodgkin's disease in 8%. Collections were obtained routinely in myeloma and breast cancer and due to bone marrow involvement with malignancy or inaspirable bone marrow in lymphoma patients. Collections were obtained on a Cobe Spectra or Baxter-Fenwall CS3000+. Engraftment potential was determined by methylcellulose colony assay (CFU-GM), with a target of > 10 x 10(4) CFU-GM/kg. Apheresis nucleated cell count correlated significantly, albeit weakly (r = 0.26), with CFU-GM with a cell count of > 5 x 10(8)/kg resulting in an adequate number of CFU-GM in 78% of patients. In univariant analysis outcome of collection was significantly influenced by the patients age (p = 0.01), malignant diagnosis (p < 0.001), reason for collection (p = 0.002), and the mobilization regimen (p = 0.01). The nature of the apheresis device used did not influence outcome. Only malignant diagnosis was significant (p < 0.001) in multivariate analysis. We conclude that the outcome of BC is most strongly influenced by patient factors such as malignant diagnosis. These factors must be considered when comparing the outcome of different mobilization regimens and when planning collection strategies.

Ex vivo manipulation of cell subsets for cell therapies

Large-scale cell separation and ex vivo expansion technologies will form the basis for development of new cellular products for the treatment of cancer and fatal viral diseases. The cell subsets that are likely to play a significant role in cellular therapy include hematopoietic stem cells, platelet and granulocyte precursors, cytotoxic lymphocytes, and genetically modified hematopoietic or lymphoid precursors. Cell enrichment techniques are required to eliminate tumor cells from autologous stem cell grafts and to reduce the size of culture systems required for expansion or gene transfection. The consumption of expensive culture components such as cytokines and serum may be reduced by the use of perfusion bioreactor devices. Methods that have been developed for the production of cell subsets for cellular therapy are reviewed.

Transfusion and stem cell support in cancer treatment

Intensification of therapeutic regimens, improved patient survival, and advances in cytokine and cellular therapies have led to increasingly complex requirements for transfusion and stem cell support in cancer treatment. This article focuses on current and evolving issues in red blood cell, platelet, and granulocyte transfusion support, as well as measures to avoid increasingly important complications of transfusion therapy, such as alloimmunization, graft-versus-host disease, cytomegalovirus infection, and immunomodulation. Issues concerning current applications of hematopoietic stem cell transplantation and future prospects also are discussed.

Bone marrow and blood cells as alternative sources of hematopoietic progenitors after failure of a first collection. A single institution retrospective study

From October 1992 through October 1994, we retrospectively identified 12 patients who underwent two collections of hematopoietic progenitors because the first one was considered inadequate. Five patients had bone marrow harvest first and underwent apheresis later. Seven patients underwent apheresis first and had bone marrow harvest later. Most patients had advanced cancer and had been heavily pretreated at time of harvesting. The second harvest yielded an appropriate number of progenitors for a proportion of patients. Nine of 12 patients received both cryopreserved marrow and blood cells. Hematopoietic recovery in these patients was somewhat longer than in patients currently receiving blood cells as a support for high dose chemotherapy at our institution; however, except for 2 patient, neutrophil and platelet recovery was observed within a reasonable delay. We conclude that patients who have poor blood cell collection may benefit from bone marrow harvesting, and vice versa.

G-CSF-induced mobilization of peripheral blood stem cells from healthy adults for allogeneic transplantation

We investigated a dose-escalation effect of G-CSF (5, 10, and 15 micrograms/kg) on mobilization of committed and primitive hemopoietic progenitor cells, including CFU-GM, BFU-E, and long-term culture-initiating cells (LTC-IC) in addition to CD34+ cells and yields of progenitor cells in PBSC harvests obtained by leukapheresis of healthy adult donors. Results indicate that the mobilization of these progenitor cells is both dose and time dependent. Despite the very small number of healthy donors studied, it is estimated from our data that a sufficient number of CD34+ cells for allogeneic PBSC transplant (PBSCT) could be collected using a 5 day administration of 10 micrograms/kg of G-CSF to normal adult donors. Adverse effects include general fatigue and bone pain in most of the donors and fever and headache in some. These symptoms were well tolerated in most instances. Laboratory test abnormalities, including transient thrombocytopenia, increased platelet aggregation, and increased serum levels of some liver enzymes, were induced by G-CSF administration, but all were reversible within a short time. These observations suggest that hemopoietic stem cells for allogeneic PBSCT can be mobilized by short-term administration of a relatively high-dose G-CSF.

Optimization of peripheral blood stem cell mobilization

Peripheral blood stem cells (PBSC) are increasingly utilized in lieu of marrow for hematopoietic support due to the ease of collection and the rapid kinetics of recovery relative to bone marrow (BM). Neutrophil and platelet recovery times after PBSC transplantation average less than 8-12 days after infusion in contrast to the usual two to four weeks experienced after BM transplantation. This has simplified autologous transplantation and made it safer because patients require fewer days of antibiotic and blood component support and are discharged earlier from the hospital. The administration of hematopoietic growth factors during recovery from high-dose chemotherapy increases the number of circulating hematopoietic progenitor cells to levels as much as 1,000-fold greater than levels normally found in blood and 10-50 times greater than with chemotherapy alone. More recently, it has been shown that adequate numbers of PBSC can be collected using growth factors alone without prior chemotherapy. Although not yet universally accepted, the CD34+ cells content of PBSC appears to be the single most powerful predictor of recovery kinetics in patients receiving myeloablative therapy and PBSC infusion. Infusion of > 5 x 10(6) CD34+ cells/kg is associated with a rapid engraftment of neutrophils and platelets, although successful engraftment has also been reported with the infusion of 2.5-5 x 10(6) CD34+ cells/kg. By measuring the CD34 or colony forming units-granulocyte-macrophage (CFU-GM) content of PBSC collections, mobilization chemotherapy and cytokine regimens, age, marrow disease, prior radiation and prior chemotherapy treatment have been found to be important factors influencing the numbers of stem cells collected. The current challenge for clinical investigators is to improve methods of identifying patients who will fail to mobilize sufficient numbers of PBSC prior to collection and to utilize new strategies for stem cell mobilization. The relative ease of collection and the rapid engraftment after myeloablative therapy suggest that PBSC will likely supplant marrow for both allogeneic and autologous transplantation in the next five years.

Purging of peripheral blood stem cell grafts

The shortage of HLA-matched sibling donors for bone marrow transplant patients has stimulated interest in the use of alternative donors. As a result, there has been a dramatic increase in the use of autologous marrow transplantation, which avoids the complications of graft-versus-host disease, but may deprive the patient of a potentially beneficial graft-versus-disease response and runs the risk of returning occult tumor cells with the graft. There is increasing evidence that these cells may be associated with disease relapse post-transplant, and many methods have been developed for their removal ex vivo. Combinations of negative and positive selection may achieve elimination of tumor cells to the limits of detection of the most sensitive assays currently available. The marked trend toward the use of autologous grafts derived from blood rather than marrow has raised the question as to whether peripheral blood stem cell (PBSC) preparations should be purged of tumor. Data indicate that these grafts generally contain a lower tumor burden, although the stem cell mobilization procedure may recruit tumor cells into the peripheral circulation. Enrichment of CD34+ cells from apheresis products appears, at present, to be less efficient than from marrow and provides at best about a 2-3 log depletion of tumor. This has prompted proposals to follow positive selection by a small-scale purging procedure. Technical issues, such as preprocessing and pooling of collections prior to purging, remain to be addressed. Ultimately, the development of successful purging procedures for PBSC grafts will simply reemphasize the necessity of improving the efficacy of high-dose therapy.

Autologous bone marrow transplantation

Autologous bone marrow transplantation has become a very popular and successful treatment for many patients with lymphomas and other malignancies. The current indications, pretreatment regimes, and laboratory manipulations are discussed as well as the application of gene transfer to eliminate selected genetic diseases and detect disease relapse.

G-CSF-mobilized peripheral blood progenitor cells for allogeneic transplantation: safety, kinetics of mobilization, and composition of the graft

Allogeneic transplantation of peripheral blood progenitor cells (PBPC) makes the general anaesthesia of the donor unnecessary and may result in more rapid engraftment and faster recovery of the immune system. We have studied G-CSF-mediated PBPC mobilization in healthy donors and analysed the cellular composition of the resulting PBPC grafts. PBPC grafts were obtained from nine healthy donors (18-67 years old) for allogeneic or syngeneic transplantation. Six donors received 10 micrograms/kg G-CSF per day, the others 5-6 micrograms/kg. Mobilization and harvesting were well tolerated except for moderate bone pain which occurred in all donors primed with 10 micrograms/kg. With 10 micrograms/kg, a 31-fold (9-62) enrichment of circulating CD34+ cells was observed with peak values constantly occurring on day 5 after the start of G-CSF administration. Starting harvest on day 5, one to three collections on consecutive days yielded 5.5 x 10(6)/kg (0.9-10.7) CD34+ cells, 219 x 10(6)/kg (106-314) T cells, and 34 x 10(6)/kg (23-67) NK cells per 10 litres leukapheresis volume. Altogether, PBPC grafts contained 3 times more CD34+ cells, 7 times more T cells, and 20 times more NK cells than five allogeneic marrow grafts that were analysed for comparison. The yield of CD34+ cells per 10 litres apheresis volume as well as the height of the CD34+ peak in peripheral blood were inversely correlated to the age of the donor. In the donors primed with 5-6 micrograms/kg G-CSF the increase of circulating CD34+ cells (4-7-fold enrichment) and the CD34+ cell yield per 10 litres leukapheresis volume (1 x 10(6)/kg [0.8-2.2]) was much smaller compared with the 10 micrograms/kg group. In conclusion, sufficient amounts of PBPC capable of restoring haemopoiesis in allogeneic recipients can be mobilized safely by administration of G-CSF (10 micrograms/kg s.c. for 5 d) in healthy donors, and harvested with one or two leukapheresis procedures. Whether the large numbers of T-cells and NK cells that are contained in the collection products may influence graft-versus-host and graft-versus-leukaemia reactivities of PBPC grafts remains to be determined.

The use of the APAAP technique as a rapid indicator of peripheral blood progenitor cell levels

Rapid and sustained engraftment following autotransplantation with peripheral blood stem cells (PBSC) depends on adequate numbers of stem cells and progenitor cells. In this study we have compared the number of myeloid progenitor cells quantitated using the colony forming units-granulocyte macrophage (CFU-GM) clonogenic assay with the number of CD34+ cells estimated both by flow cytometry and by the alkaline phosphatase anti-alkaline phosphatase (APAAP) technique. We have analysed 15 peripheral blood mononuclear cells (PBMNC) samples from 13 normal subjects and 179 PBMNC from 32 patients undergoing PBSC harvests during the recovery phase of high dose cyclophosphamide chemotheraphy. The number of CD34+ cells measured by the APAAP technique correlated well with the number of CD34+ cells measured by flow cytometry (r = 0.727, p = 0.0001), and also with the number of CFU-GM measured in the clonogenic assay (r = 0.721, p = 0.0001). The APAAP method provides a rapid, reliable measure of progenitor cell levels that can be used to monitor the optimal time to harvest peripheral blood stem cells (PBSC), and to estimate the marrow repopulating ability (MRA) of stem cell preparations used for transplantation.

Growth factors and hematopoietic recovery

Availability of hematopoietic growth factors (GC-SF, GM-CSF, erythropoietin, etc.) has started a new arena of dose-intensification. The use of such growth factors has resulted in faster hematopoietic recovery of cancer patients and now offers several new treatment modifications. These include: (1)dose-intensification without hematopoietic stem cell support, (2) speedier hematopoietic recovery after hematoablative therapy and stem cell transplantation (allogeneic or autologous); (3) use of combination of growth factors, and (4) improvement in the delivery of anti-microbial drugs which are toxic towards hematopoietic cells (Gancyclovir, Bactrim, etc.). The above treatment strategies are under active clinical trials and can provide improved, cost-effective methods of treating patients with cancer.

The combined use of soybean agglutinin and immunomagnetic beads for T lymphocyte subset depletion of bone marrow allografts: a laboratory analysis

The prevention of graft-versus-host disease by T-lymphocyte depletion of allografts prior to bone marrow transplantation has resulted in an increase in graft failure/rejection and relapse of disease. Evidence for the selective roles of specific T-lymphocyte subsets in each of the engraftment, graft-versus-host disease, and disease relapse processes has been presented, but sufficient clinical verification to support any hypothesis in this regard is lacking. In this paper we describe a convenient and highly flexible clinical laboratory method for depletion of specific T-lymphocytes in controllable quantities by the use of select monoclonal antibodies. Almost 3 log10 removal of CD2+ and CD8+ cells without significant loss of hematopoietic progenitors (CFU-GM, BFU-E, and CD34+ cells) can be reproducibly achieved. This method, employing soybean agglutination and immunomagnetic beads, is potentially adaptable to depletion of any cell subset or any tumor cell for which unique cell-surface antigen characteristics have been defined. In addition, our protocol is equally suited to the positive selection of stem cells and hematopoietic progenitors bearing the CD34 surface antigen.

Sequential transplants using mobilized peripheral blood progenitor cells

Modest success has been achieved with the use of high-dose cytotoxic therapy and bone marrow transplantation in solid tumors. Patient outcome can potentially be improved with further intensification of the therapy. The rapid hematologic recovery achieved with mobilized peripheral blood progenitor cells (PBPC) may reduce the toxicity of transplantation enabling the use of sequential courses of myeloablative therapy. We report on 42 patients with solid tumors enrolled in a tandem transplant protocol involving the use of PBPC mobilized with cyclophosphamide (4 g/m2), etoposide (1 g/m2), and granulocyte-colony-stimulating factor (G-CSF: 10 micrograms/kg/day). This regimen significantly increased the number of circulating progenitor cells; only 1-2 aphereses were sufficient to collect 2.5 x 10(8)/kg mononuclear cells, our goal for each transplant course. The median number of circulating colony-forming units (CFU) and CD34+ cells obtained for each transplant course were 70.3 x 10(4)/kg, and 11.7 x 10(6)/kg, respectively. There was a significant correlation between the numbers of CD34+ cells and CFU measured in the apheresis product (r = 0.49, P = .003). The first transplant regimen given to 38 patients consisted of thiotepa, carboplatin, and cyclophosphamide. The second transplant regimen given to 29 patients consisted of busulfan and etoposide. Hematologic recovery was comparable after each of the two transplant courses. The median time to neutrophil recovery over 0.5 x 10(9)/L and to platelet transfusion independence was 9 and 8 days, respectively. There was no difference in engraftment rates after transplant with PBPC only (n = 28 courses) compared to transplant with PBPC plus bone marrow (n = 39 courses).(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization and measurement of CD34-expressing hematopoietic cells

Because of availability of anti-CD34 monoclonal antibodies, multiparameter flow cytometry has become the tool of choice for determination of hematopoietic stem and progenitor cells. This report describes general techniques for quantitation and characterization of CD34-expressing cells by flow cytometry.

Measurement of CD34+ cells in bone marrow by flow cytometry

A procedure is described for the measurement of the %CD34+ progenitor cells in bone marrow using directly conjugated antibodies. Staining cells with anti-CD45.FITC in conjunction with anti-CD34.PE allows the CD45- nucleated red blood cells and the CD45++ lymphocytes and monocytes to be separated from the CD45+ progenitor cells. Granulocytes are separated from the CD34+ cells based on differences in side scatter properties. A gated acquisition of CD34+ cells is used to define the boundaries of the CD34+ population in a plot of forward scatter vs side scatter and in a plot of anti-CD45.FITC vs anti-CD34.PE. Use of these regions during analysis reduces background staining and allows for a consistent identification of a CD34+ population. Acquisition of 50,000 cells provides adequate precision of the %CD34+ measurement. Acquisition and analysis procedures are presented for use of both a Becton Dickinson FACScan flow cytometer and a Coulter EPICS Profile II flow cytometer.