Peripheral blood stem cell transplantations: past, present and future

Peripheral Blood Stem Cell Transplantation: Critical Review

Autologous blood stem cell transplantations have been increasingly performed worldwide for almost ten years in place of autologous bone marrow transplantation and even of allogenic bone marrow transplantation. Several crucial issues were the subjects of impassioned controversies. Some of them are now satisfactorily answered while others still remain unresolved. First, it is now possible to conclude today that peripheral blood stem cells (PBSC) are undoubtedly capable of restoring short term hematopoiesis when reinfused after myeloablative therapy as well and even more rapidly than bone marrow stem cells, provided that they have been previously collected in sufficient amounts. On the opposite, it is still impossible to firmly prove that their very immature CD34+ cell subset, although in vitro functionally and phenotypically almost identical to their marrow counterpart, is actually responsible for sustained long term hematopoietic recovery, even if it is likely that these cells play a key role.

Most of the time, using chemotherapy alone or a combination of chemotherapy and cytokine(s), mobilizing regimens allow collection of appropriate yields of PBSC with only a small number of apheresis cycles, provided that a sufficient number of residual stem cells remains to be stimulated, when, on the contrary, collection in steady-state is time-consuming and does not provide further accelerated post transplant hematopoietic recovery.

It was initially hypothesized that PBSC could have a lower likelihood of tumoral contamination compared with bone marrow. In fact, biological as well as clinical data are discordant and probably depend largely on the type of disease, its evolutive history and its way of dissemination. Furthermore, the respective impact on the development of further relapse of graft contamination and of residual tumor cells into patient remains to be determined.

Finally, although it has often been claimed that the cost of mobilization, collection and cryopreservation of PBSC would be much higher than the cost of bone marrow harvesting, it is now possible to assert that the whole ABSCT procedure, including this preliminary phase, as well as the post-transplant period, allows an indisputable saving compared with ABMT.

These advantages are already sufficient reasons “per se” to propose ABSCT in place of ABMT or alloBMT in many indications even if their clinical benefit, in terms of disease-outcome, remains to be prospectively explored.

Pharmaceutical care and the cancer patient

Purpose. The primary objective of this paper is to discuss pharmaceutical care of the oncology patient in the context of recent recommendations made by the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) and recent changes in Health Care Reform.

Data Sources. We reviewed the literature through a MEDLINE search from 1985 to 1995. We searched the following terms: pharmaceutical care, cancer, patient, and pharmacist. We restricted the search to the English language. We also have incor porated several of our practice guidelines as examples of tools that can be used in the implementation of pharmaceutical care. We also focused on areas that the JCAHO guidelines specify as important pharma ceutical care issues in the cancer patient.

Data Extraction. Within the framework of drug prescribing, drug administration, drug monitoring, and patient education, we have provided interven tions that may potentially improve outcomes in can cer patients.

Data Synthesis. The advent of managed care will require that the pharmacist be more involved in the care and management of the cancer patient. This activity will necessitate that the pharmacist document the impact of interventions on patient outcomes. Although tumor response and survival are classic outcomes that are assessed in the cancer patient, other outcome indicators may be used to evaluate interventions made by the pharmacist.

Conclusions. This review offers strategies for implementing pharmaceutical care in the cancer pa tient. Because we did not present study results on patient outcomes, it is unknown which of these proposed pharmacist interventions are important fac tors in the implementation of pharmaceutical care in this patient population. Although pharmaceutical care is the new paradigm in pharmacy practice, we must perform prospective studies to determine its value to the cancer community.

Finding the needle in the hay stack: hematopoietic stem cells in Fanconi anemia

Fanconi anemia is a rare bone marrow failure and cancer predisposition syndrome. Childhood onset of aplastic anemia is one of the hallmarks of this condition. Supportive therapy in the form of blood products, androgens, and hematopoietic growth factors may boost blood counts temporarily. However, allogeneic hematopoietic stem cell transplantation (HSCT) currently remains the only curative treatment option for the hematologic manifestations of Fanconi anemia (FA). Here we review current clinical and pre-clinical strategies for treating hematopoietic stem cell (HSC) failure, including the experience with mobilizing and collecting CD34+ hematopoietic stem and progenitor cells as target cells for somatic gene therapy, the current state of FA gene therapy trials, and future prospects for cell and gene therapy.

Symptom management and successful outpatient transplantation for patients with multiple myeloma

This retrospective descriptive study compared symptoms and symptom management in patients who completed autologous peripheral blood stem cell transplantation without hospital admission with those of patients who required unplanned hospital admission during the transplantation period. The sample consisted of 87 patients with multiple myeloma treated as outpatients during a 16-month period. Medical records and electronic database records review for each patient provided data on patient characteristics, medical factors, and symptoms/symptom management. Neither age, gender, religion, payer source, treatment on or off protocol, nor positive blood culture made a difference in hospital admission. The percentage of outpatient visits that included documented teaching on self-care made a significant difference (P = .008). Longitudinal analyses of patients' documented symptoms before admission compared with nonadmitted patients captured changes over time in symptoms/symptoms management. Overall, the patients' symptoms were managed well. Significant differences were fatigue, measured as the percentage of usual energy (P = .017), and the amount of oral hydration in a 24-hour period (P < .001). Results call attention to the role that fatigue and the amount of oral hydration may have in unplanned hospital admissions and to the importance of teaching on self-care.

Mobilization of dendritic cells from patients with breast cancer into peripheral blood stem cell leukapheresis samples using Flt-3-Ligand and G-CSF or GM-CSF

Treatment with myeloablative chemotherapy and autologous peripheral blood stem cell (PBSC) transplantation followed by vaccination with autologous dendritic cells (DCs) treated with tumor antigens is a promising therapeutic strategy for several types of cancer. Obtaining sufficient numbers of both PBSCs and DCs is central to this approach. Previously, it has been shown that administration of Flt-3-Ligand (FL) combined with either G-CSF or GM-CSF mobilizes large numbers of PBSCs in patients with cancer. In the current study, we sought to determine whether these same cytokines could simultaneously mobilize DCs into the PBSC leukapheresis collection. DCs were analysed in PBSC leukapheresis samples obtained from five patients with high-risk breast cancer who received G-CSF alone as priming prior to leukapheresis, four patients who received FL+G-CSF and five patients who received FL+GM-CSF. DCs were defined as cells with a lin(dim/-) HLA-DR+ CD11c+ phenotype. The proportions of DCs in the FL+G-CSF and FL+GM-CSF samples were significantly higher than in pre-mobilization peripheral blood and G-CSF leukapheresis samples. The mean yield of DCs/kg in the FL+GM-CSF samples was also significantly higher than the mean yield of DCs in the G-CSF samples. The FL+G-CSF and FL+GM-CSF mobilized DCs were immature by morphologic and phenotypic criteria but stimulated allogeneic T-cells at levels similar to DCs generated in culture from PBMCs. Overnight culture?of the immature DCs obtained from patients receiving either FL+G-CSF or FL+GM-CSF in TNF-alpha?resulted in the generation of mature DCs. In summary, administration of FL in combination with GM-CSF and G-CSF to patients with breast cancer can mobilize large numbers of immature DCs into PBSC leukapheresis collections.

Role of the CD34+ 38- cells in posttransplant hematopoietic recovery

Using three different statistical tests in parallel, we showed in a preliminary study that neither mononuclear cells, CD34+ 33+ or 33- cells, nor CD34+ 38+ cells significantly correlated with engraftment kinetics following autologous blood cell transplantation (ABCT). We additionally demonstrated here, in a series of patients suffering from malignant diseases, that the graft content in CD34+ 38- cells is individually a more sensitive indicator of the earliest, as well as the latest post-ABCT trilineage hematopoietic recovery than the colony-forming units-granulocyte-macrophage and even the total CD34+ cell content. This suggests that the CD34+ 38- cell population is itself subdivided into two more subsets, one being already lineage-committed and responsible for short-term engraftment, the other containing only very primitive hematopoietic cells responsible for sustained engraftment. Strong arguments favor the probability that these subsets correspond to HLA-DR+ and DR cells, respectively. We also defined an optimal threshold value of 0.05 x 10(6) CD34+ 38- cells/kg of the patient's body weight (b.w.) above which a rapid and sustained trilineage engraftment safely occurs. In fact, infusion of lower numbers of cells seems to have a more significant impact on long-term compared to short-term neutrophil recovery and on platelet kinetics engraftment. We additionally looked for the eventual influence on engraftment time of the type of disease, and of post-ABCT administration of hematopoietic growth factors (HGF). When the type of disease appeared to have no influence on the engraftment time, posttransplant HGF administration significantly reduced the time to trilineage engraftment in patients transplanted with < 0.05 x 10(6) CD34+ 38- cells, thus justifying it in case of reinfusion of low numbers of CD34+ 38- cells. On the other hand, the administration of HGF after infusion of more than 0.05 x 10(6) CD34+ 38- cells/kg b.w. did not hasten more, or only very little, the engraftment time, thus becoming not only unprofitable for the patients but costly as well.

Reduction of intra- and interlaboratory variation in CD34+ stem cell enumeration using stable test material, standard protocols and targeted training. DK34 Task Force of the European Working Group of Clinical Cell Analysis (EWGCCA)

The European Working Group on Clinical Cell Analysis (EWGCCA) has, in preparation for a multicentre peripheral blood stem cell clinical trial, developed a single-platform flow cytometric protocol for the enumeration of CD34+ stem cells. Using this protocol, stabilized blood and targeted training, the EWGCCA have attempted to standardize CD34+ stem cell enumeration across 24 clinical sites. Results were directly compared with participants in the UK National External Quality Assessment Scheme (NEQAS) for CD34+ Stem Cell Quantification that analysed the same specimens using non-standardized methods. Two bead-counting systems, Flow-Count and TruCount, were also evaluated by the EWGCCA participants during trials 2 and 3. Using Flow-Count, the intralaboratory coefficient of variation (CV) was </= 5% in 39% of the laboratories (trial 1), increasing to 65% by trial 3. Interlaboratory variation was reduced from 23.3% (trial 1) to 10.8% in trial 3. In trial 2, 70% of laboratories achieved an intralaboratory CV </= 5% using TruCount, increasing to 74% for trial 3; the interlaboratory CV was reduced from 23.4% to 9.5%. Comparative analysis of the EWGCCA and the UK NEQAS cohorts revealed that EWGCCA laboratories, using the standardized approach, had lower interlaboratory variation. Thus, the use of a common standardized protocol and targeted training significantly reduced intra- and interlaboratory CD34+ cell count variation.

Identification of a peptide directed against the anti-CD34 antibody, 9C5, by phage display and its use in hematopoietic stem cell selection

A peptide sequence was identified by phage display technology that could be used as an alternative to chymopapain for the release of hematopoietic progenitor cells captured by anti-CD34 monoclonal antibodies. This was achieved by affinity selection screening (biopanning) of a random hexapeptide sequence phage display library. Four rounds of biopanning were performed to enrich for phage clones with specific affinity for anti-CD34 monoclonal antibody, 9C5. DNA sequence analyses of these phage clones revealed an enrichment of two predominant sequences, QQGWFP and TQGSFW. These two clones also shared a consensus sequence motif, QGxF, that exhibited 50% and 67% homology with a region spanning amino acids 14-19 of the mature CD34 antigen. Based on these data, synthetic peptides were generated and assessed for their ability to release 9C5 from CD34+ cells. Using a flow cytometric assay, it was found that the synthetic peptide, 9069N, effectively released 9C5 from the CD34-expressing cell line, KG1a, in a concentration-dependent manner (77% and 99% release of 9C5 at 0.14 and 0.70 mM peptide concentrations, respectively). In the Isolex 300i immunomagnetic selection system, this peptide was shown to be effective at releasing 9C5 sensitized CD34+ hematopoietic progenitors from sheep anti-mouse IgG Dynabeads. Thus, a synthetic peptide, which specifically and efficiently released immunomagnetically selected hematopoietic progenitor cells from paramagnetic beads, was identified. This reagent is a significant advance in the selection of hematopoietic progenitors in that it does not alter cell surface antigens. As such, further phenotypic characterization or immunoselection can be performed.

Primordial role of CD34+ 38- cells in early and late trilineage haemopoietic engraftment after autologous blood cell transplantation

In order to better define which cell subset contained in graft products might be the most predictive of haemopoietic recovery following autologous blood cell transplantation (ABCT), the relationships between the amounts of reinfused mononuclear cells (MNC), CFU-GM, total CD34+ cells and their CD33 and CD38 subsets. and the successive stages of trilineage engraftment kinetics, were studied in 45 cancer patients, using the Spearman correlation test, a linear regression model and a log-inverse model. No relationship was found between the infused numbers of MNC, CD33+ and CD33- subsets observed and the numbers of days to reach predetermined absolute neutrophil (ANC), platelet and reticulocyte counts. The infused numbers of CFU-GM, CD34+ and CD34+ 38+ cells correlated inconstantly with haemopoietic recovery parameters. The strongest and the most constant correlations were significantly observed between the infused numbers of CD34+ 38- cells and each trilineage engraftment parameter. The log-inverse model determined a threshold dose of 0.05 x 10(6) (= 5 x 10(4)) CD34+ 38- cells/kg, below which the trilineage engraftment kinetics were significantly slower and unpredictable. Post-transplant TBI-conditioning regimens increased the low cell dose-related delay of engraftment kinetics whereas post-transplant administration of haemopoietic growth factors (HGF) seemed to abrogate this delay. This would justify clinical use of HGF only in patients transplanted with CD34+ 38- cell amounts lower than the proposed threshold value. This study suggests that the CD34+ 38- subpopulation, although essentially participating in late complete haemopoietic recovery, is also composed of committed progenitor cells involved in early trilineage engraftment.

Difference between expression of adhesion molecules on CD34+ cells from bone marrow and G-CSF-stimulated peripheral blood

Three-color immunofluorescence cytometry was used to quantify the expression of different adhesion molecules on CD34+ cells of steady-state bone marrow (BM) and peripheral blood stem cells (PBSC) after mobilizing with G-CSF (10 micrograms/kg/body weight) in nine cancer patients undergoing high-dose chemotherapy with subsequent autologous blood stem cell rescue. The expression rate of each adhesion molecule on CD34+ cells showed great inter-individual variations. High expression (> 50%) on CD34+ cells from PBSC and BM was found for CD58 (leukocyte function-associated antigen-3), CD31 (platelet-endothelial cell adhesion molecule-1), CD11a (leukocyte function-associated antigen-1) and CD49d (very late activation antigen-4); a moderate expression (20%-40%) was seen for CD49e (very late activation antigen-5), CD62L (leukocyte-endothelial cell adhesion molecule), CD54 (ICAM-1) and CD117 (c-kit). c-kit, CD58, CD62L and CD49d were less expressed on CD34+ cells of PBSC than of BM, the difference being statistically significant for CD49d (p < 0.05). CD49e and CD37 were expressed more in PBSC than BM without being statistically significant. The mean fluorescence intensity for all adhesion molecules on CD34+ cells did not differ significantly between PBSC and BM. The significantly lower expression of CD49d on G-CSF-mobilized PBSCs might suggest that downregulation of this molecule may be involved in the process of peripheral stem cell mobilization.

FLT-3 ligand mobilizes hematopoietic primitive and committed progenitor cells into blood in mice

We investigated the effects of the administration of FLT-3 ligand (FL) on mobilization of primitive and committed progenitor cells in mice. C57bl/6J mice were injected subcutaneously with FL once a day for 5 d at doses of 20, 100 and 200 microg/kg. After the collection of peripheral blood, we determined the number of white blood cells (WBCs) with the differential counts. The formation of colony-forming cells (CFCs) in peripheral blood, bone marrow and spleen was evaluated. Although the administration of FL, 20 microg/kg, did not stimulate leukocytosis, its administration at doses of 100 and 200 microg/kg increased the number of WBC up to 1.7- and 2.4-fold, respectively. Committed progenitor cells were mobilized into the peripheral blood dose-dependently and the number of CFCs was increased up to 5.5-fold by the administration of FL at 200 microg/kg on d 5. The number of CFCs in the bone marrow increased, but not dose-dependently. The number of CFCs in the spleen also increased up to 32-fold at a dose of 200 microg/kg FL. Mobilized peripheral blood mononuclear cells were transplanted into lethally irradiated mice and the number of CFU-S (d 12) was scored. A dose-dependent mobilization of CFU-S (d 12) into peripheral blood was also observed. These observations suggest that FL can mobilize hematopoietic primitive and committed progenitor cells into the peripheral blood of mice and those cells mobilized by FL may be applicable to peripheral blood stem cell transplantation.

Mobilisation and reinfusion of Philadelphia negative peripheral blood mononuclear cells in chronic myeloid leukaemia with hydroxyurea and G-CSF

Unmanipulated autologous transplantation of marrow of peripheral blood stem cells has been performed in small numbers of patients with CML for many years. More recently there has been interest in attempting to 'purge' the autograft of clonal cells as defined by the presence of the Philadelphia chromosome or BCR-ABL rearrangement. One method by which this might be achieved in vivo has been developed in Genoa and involves the administration of high dose chemotherapy and G-CSF followed by peripheral blood stem cell collection. These collections are frequently devoid of Philadelphia positive cells and the hope is that this will enhance the effects of subsequent autograft. We have investigated the use of a less toxic regimen for this procedure using oral hydroxyurea and G-CSF. In this review we describe the background to autografting in CML and the development of strategies to mobilise Philadelphia negative cells into the peripheral blood. We go on to present an update of our data using hydroxyurea and discuss some of the practical and theoretical issues behind the procedure.

Intratibial injection of an anti-doxorubicin monoclonal antibody prevents drug-induced myelotoxicity in mice

With few exceptions, the major limit to high-dose chemotherapeutic treatments is the severity and duration of drug-induced myelosuppression. We have recently developed a monoclonal antibody, MAD11, which reacts with the potent anti-tumour antibiotic doxorubicin and other anthracyclines. To protect directly pluripotent stem cells and cells of the haematopoietic microenvironment in the bone marrow against doxorubicin cytotoxicity, the monoclonal antibody MAD11 was injected into the tibial bone of mice before chemotherapeutic treatment. All mice pretreated intratibially with MAD11 and injected with 14 mg kg(-1) body weight of doxorubicin survived, whereas 41% of mice treated with doxorubicin alone died. At a higher dose of doxorubicin (18 mg kg(-1)), early mortality (first 6 days) was similar in the groups, but no deaths were observed thereafter in the intratibially MAD11-treated group, whereas most of the mice treated with doxorubicin alone died. Data obtained in mice injected with P388 leukaemia cells showed that the intratibial injection of MAD11 did not compromise the anti-tumoral activity of doxorubicin. Moreover, the administration of the anti-doxorubicin monoclonal antibody before chemotherapeutic treatment effectively reduced apoptosis induced by doxorubicin in the bone marrow cells. These data suggest the usefulness of monoclonal antibodies against chemotherapeutic drugs in the local protection of bone marrow without influencing the anti-tumour properties of the drug.

Development of a method of thymocyte differentiation of bone marrow-enriched CD34+CD38- cells in postnatal allogeneic cultured thymic epithelia to evaluate immunodeficiency disorders

An in vitro model of CD34+CD38- stem cell (SC) differentiation in postnatal cultured thymic epithelia fragment (CTEF) cocultures is described. Sequential phenotypic analysis of the progeny of the SC-CTEF demonstrated predominantly thymocytes and minor populations of promyelocytes, monocytes and natural killer cells. Triple-positive CD3+CD4+CD8+, double-positive CD4+CD8+, and mature single-positive CD4+ and CD8+ T cells, which were TCR alpha beta+, were identified indicating normal thymocyte maturation. In kinetic studies, mature single-positive CD4+ T cells increased from 29% of total cells at one week to 54% at four weeks of coculture. These findings demonstrate that coculture of bone marrow-derived SC and allogeneic cultured thymic epithelia in vitro results in continuous normal predominantly thymocyte differentiation. The SC-CTEF cocultures were then infected with two different strains of human immunodeficiency virus. CD4+ thymocytes were markedly decreased. However, inhibition of early thymocyte maturation steps was also suggested by the presence of increased triple-negative and CD44+CD25-CD3-thymocytes and decreased CD44+CD25+ thymocytes. This model system of thymocyte maturation will be useful in the evaluation of primary T cell immunodeficiency disorders, gene therapy of SC and pharmacological augmentation of thymic function.

The significance of microbial cultures of the hematopoietic support for patients receiving high-dose chemotherapy

The use of hematopoietic support for patients receiving high-dose chemotherapy has increased over the past 10 years. Various quality controls are performed on the hematopoietic cells, including microbiologic cultures. There is considerable expense associated with the serial cultures performed at different times during the collection, processing, and use of the cells. We reviewed all the microbiologic cultures performed on bone marrow harvests and leukaphereses over a 17 month period. Of the 227 bone marrow harvests, 16 cultures were positive, but only 3 (1.3%) were repeat positives with the same organism after processing or at the time of reinfusion. Of the 560 leukaphereses, 4 (0.7%) were cultured positive at the time of collection and reinfusion. Two patients were bacteremic with gram-negative bacilli at the time of leukaphereses despite being asymptomatic, and these were the only two products that had to be collected again. No patient suffered an adverse clinical result after receiving culture-positive cells. Bone marrow and peripheral blood progenitor cells can be safely collected, and a culture after processing is adequate to ensure the safety of the product.

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.

CD34+Thy-1+Lin- stem cells from mobilized peripheral blood

Over the last ten years there has been increasing use of mobilized peripheral blood (MPB) progenitor cells as grafts for autologous transplantation. Among the cells comprising these MPB autografts is a subpopulation of CD34+Thy-1+Lineage (Lin)- cells, which is enriched for hematopoietic stem cell (HSC) activity. The percentage of CD34+ cells which express Thy-1 is higher in some samples of MPB than in bone marrow (BM). Using myeloid and erythroid cell depletion prior to high speed cell sorting, it is possible to purify sufficient numbers of CD34+Thy-1+Lin-HSCs from a MPB leukapheresis sample for use as an autograft. CD34+Thy-1+Lin-cells will potentially provide a tumor-depleted autograft for cancer patients. This HSC population is also being studied as a potential target for gene transfer for the treatment of patients with HIV, cancer and a variety of genetic disorders.

LW/SO cell line: a tool for studying the phenotypical characterization and commitment of hematopoietic stem cells

We report our observations with the cell line LW/SO, which was recently derived from the bone marrow of a patient with acute myeloid leukemia. Based on the morphological and histochemical examination, the leukemic cells were classified primarily as FAB type M4. However, 2 years later, in relapse, the cells changed their morphology and were hence specified as FAB type M2 (slightly positive for acid phosphatase and Sudan black). The cells established have now been in culture for approximately 11 months and display nearly 100% CD4/5/7/15/25/71/120a,b at varying densities. Some of them spontaneously and reversibly become either CD34 + /38- or CD34 - /38+, yet the majority of the cells remain negative for both. All attempts to separate the cells with a distinct phenotype by limiting dilution or sorting through a flow cytometer failed repeatedly. The subsets, enriched up to 98% (regardless of their primary immunophenotype CD34 - / 38-, CD34 + /38-, or CD34 - /38+), soon displayed a phenotypical constellation similar to that before sorting. The ratio of CD34- to CD34+ seems to be influenced by the cell density: The greater the cell-to-cell contact, the lower the percentage of CD34-expressing cells. Some of the cells apparently differentiate into T-cell phenotype and acquire CD3 and T-cell receptor (TCR) alpha/beta molecules. While the quantity of CD34-expressing cells significantly increased in the presence of dexamethasone (10(-7) M), and some of them additionally acquired CD33 antigen, the percentage of CD3-positive cells was enhanced by adding 1% DMSO in medium. In contrast, cytokines such as IL-1, IL-2, IL-3, IL-4, IL-6, G-CSF, GM-CSF, or SCF (c-kit ligand) altered neither the proliferation capacity nor the phenotypical constellation of LW/SO cells (each tested alone). Although normal karyotype was obtained from the bone marrow cells, the LW/SO cells revealed a homogeneous chromosomal composition of 45, X, -X, der(9) inv(9) (p12q13) del(9) (p22?). These data suggested that LW/SO cells might be the leukemic counterpart of putative pre-CD34-positive progenitors. In order to substantiate this assumption, we analyzed the expression of other so-called T-cell markers on CD34+ cells from peripheral blood stem cell aphereses of five patients who later underwent high-dose chemotherapy and subsequent stem cell retransfusion. These data clearly revealed that a considerable amount of CD34+ hematopoietic progenitors co-express CD2/4/(5)/(7)/25 at an early stage of differentiation, and support the notion that CD34-negative LW/SO cells with the surface markers CD4/5/7/25 are probably phenotypical representatives of pluripotent stem cell. Hence, not all CD34-negative populations with so-called T-cell surface markers should be considered T-cells; some may constitute the ancestor of CD34 antigen-expressing progenitors.

Development of a clinically applicable high-speed flow cytometer for the isolation of transplantable human hematopoietic stem cells

A high-speed cell sorter capable of a throughput speed 4-5-fold greater than commercially available systems was developed and evaluated as a processing tool for isolating purified hematopoietic stem cell grafts. The clinical high-speed sorter (CHSS) serves as a single-pass, multiparameter processing tool that provides the means to isolate a highly purified population of cells from starting cell populations with extremely low frequencies. The sorter incorporates environmental barriers to create a sterile environment for cell processing. Monoclonal antibodies and reagents produced under good manufacturing practices (GMP) are used to isolate hematopoietic stem cells by means of the CHSS. Using this technology, the CD34+Thy-1+Lin- hematopoietic stem cell population has been isolated from normal adult bone marrow and mobilized peripheral blood. The sorted cells have been shown to be sterile and viable and to retain hematopoietic function.

The VLA4/VCAM-1 adhesion pathway defines contrasting mechanisms of lodgement of transplanted murine hemopoietic progenitors between bone marrow and spleen

Selective lodgement or homing of transplanted hemopoietic stem cells in the recipient's bone marrow (BM) is a critical step in the establishment of long-term hemopoiesis after BM transplantation. However, despite its biologic and clinical significance, little is understood about the process of homing. In the present study, we have concentrated on the initial stages of homing and explored the functional role in vivo of some of the adhesion pathways previously found to mediate in vitro adhesion of hemopoietic cells to cultured BM stroma. We have found that homing of murine hemopoietic progenitors of the BM of lethally irradiated recipients at 3 h after transplant was significantly reduced after pretreatment of the donor cells with an antibody to the integrin very late antigen 4 (VLA4). This inhibition of marrow homing was accompanied by an increase in hemopoietic progenitors circulating in the blood and an increased uptake of these progenitors by the spleen. Similar results were obtained by treatment of the recipients with an antibody to vascular cell adhesion molecule 1 (VCAM-1), a ligand for VLA4. Furthermore, we showed that administration of the same antibodies (anti-VLA4 or anti-VCAM-1) to normal animals causes mobilization of hemopoietic progenitors into blood. These data suggest that hemopoietic cell lodgement in the BM is a regulatable process and can be influenced by VLA4/VCAM-1 adhesion pathway. Although additional molecular pathways are not excluded and may be likely, our data establish VCAM-1 as a BM endothelial addressin, analogous to the role that mucosal addressin cell adhesion molecule (MAdCAM) plays in lymphocyte homing. Whether splenic uptake of hemopoietic progenitors is passive or controlled through different mechanisms remains to be clarified. In addition, we provide experimental evidence that homing and mobilization are related phenomena involving, at least partly, similar molecular pathways.

Broad inter-individual variations in circulating progenitor cell numbers induced by granulocyte colony-stimulating factor therapy

The elevated white cell counts (WCC) and myeloid progenitor cell levels in the blood induced by granulocyte colony-stimulating factor (G-CSF) treatment were studied in three settings: cancer patients previously treated with chemo/radiotherapy (n = 13), untreated cancer patients (n = 5) and normal volunteers (n = 9). The inter-individual variations in progenitor cell mobilization responses to G-CSF and the impact of previous chemo/radiotherapy were investigated. The absolute levels of circulating progenitor cells, but not total white cells, were reduced significantly in the pretreated cancer patients (median 961, range 289-3355 per ml blood) as compared to untreated cancer patients (median 9891, range 2219-16625 per ml blood). In each setting, wide ranges of circulating progenitor cell numbers were observed, and the variation in progenitor cell numbers was considerably greater than observed for the WCC. However, progenitor cell numbers in normal volunteers (942-25296 per ml blood) demonstrated as much variance as observed in pretreated cancer patients. This broad physiological variation in progenitor cell levels induced by G-CSF needs to be considered when designing strategies for allogeneic peripheral blood stem cell transplantation.

Mixed haematopoietic colony formation via immature blast cell clusters on foetal mesenchymal cell layers distinguishes stem cells from peripheral blood, cord blood, bone marrow and blood stem cells mobilized by granulocyte-macrophage colony-stimulating factor

Multilineage colony formation was evaluated from healthy donors' bone marrow (BM), peripheral blood (PB) and cord blood (CB) and compared with blood stem cell (BSC) harvests of sarcoma patients mobilized with granulocyte-macrophage colony-stimulating factor (GM-CSF). The test was a modified CFU-blast assay performed with and without an irradiated foetal mesenchymal cell layer (HFFF). These non-transformed mesenchymal cells served as a good source of haematopoietically active stroma cells in that cytokine expression patterns (interleukin (IL)-6, granulocyte (G)-CSF, GM-CSF) and adhesion molecules on HFFF cells were qualitatively identical to BM-derived fibroblasts, but the expression density of adhesion receptors was significantly higher. This HFFF layer stimulated blood stem cells of GM-CSF-treated patients significantly more than a cocktail of exogenous growth factors with IL-1, IL-6, and stem cell factor (SCF). The reverse was true for multilineage colonies from healthy donors' PB, BM, and CB. According to these results, stem cells of GM-CSF-treated patients are functionally distinct due to their dependence on stroma-derived factors and/or matrix-adhesion interactions and can be reproducibly evaluated on these mesenchymal cells.

Mobilization of peripheral blood stem cells with chemotherapy and cytokines in multiple myeloma

In an attempt to offset the impaired hematopoietic progenitors' mobilization and collection which are frequently encountered in multiple myeloma (MM), we have started a pilot study to evaluate the ability of a combination of high-dose melphalan (HDM) and sequential s.c. administration of recombinant human interleukin 3 (rhIL-3) and rh-granulocyte colony-stimulating factor (G-CSF) to mobilize blood cells (BC) in MM patients. Two different schedules for administration were successively tested. Schedule A consisted of IL-3 (5 micrograms/kg/d) from day 7 to day 11 after HDM followed by G-CSF (5 micrograms/kg/d) from day 12 to day 20. Under schedule B, HDM was followed by IL-3 alone at the same dosage from day 1 to day 3, IL-3 and G-CSF (idem) from day 4 to day 7 and G-CSF alone from day 8 until completion of apheresis. Two patients (one previously untreated, one having received prior chemotherapy for one year) underwent schedule A; three patients (one previously untreated, two pretreated) underwent schedule B. The post-HDM aplasia was not shortened in schedule A patients in comparison to what we usually observed following HDM alone (25 days) correlated with a very moderate two- to three-fold CD34+ cell increase. Only one patient was further transplanted with apheresis products: the post-transplant granulocyte recovery was slower than usual (16 days versus 12 days) while platelet count never recovered over 20 x 10(9)/l. In contrast, the post-HDM aplasia was significantly shortened in two of the schedule B patients (3 to 10 days) and was followed by a 25- to 165-fold increase in CD34+ cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased peripheral blood normal myeloid progenitor cells (CFU-GM) in chronic lymphocytic leukemia: a perspective for autologous peripheral blood stem cell transplantation

We assayed granulocyte-macrophage committed progenitor cells (CFU-GM) in the peripheral blood of 34 patients with chronic lymphocytic leukemia (CLL) and 12 normal individuals. The patients were divided into separate groups on the basis of previous therapy (i.e. analysis performed at diagnosis, during and after chemotherapy) and clinical features of the disease (i.e. disease stage, pattern of bone marrow infiltration, peripheral blood lymphocytosis). The mean CFU-GM colony count of the patients was 30 times higher than that of the controls (206.4 +/- 197.8 (SD) CFU-GM per 5 x 10(5) cells plated versus 6.5 +/- 3.6). There was no statistical difference in the numbers of circulating CFU-GM between the patients studied at diagnosis (257 +/- 215.4 CFU-GM/5 x 10(5) cells) and those studied during (117.6 +/- 169.2 CFU-GM/5 x 10(5) cells) or after chemotherapy (207.5 +/- 105.9 CFU-GM/5 x 10(5) cells), although a trend towards a higher recovery of myeloid progenitors was observed as a function of time elapsing from the last treatment. In addition, we found no significant difference in the in vitro CFU-GM growth of patients grouped according to their disease stage, pattern of bone marrow infiltration and degree of peripheral blood lymphocytosis. In conclusion, our data indicate that intensification with peripheral blood stem cell support may be feasible in CLL, since progenitor cells of myeloid-monocytic series are markedly increased in the peripheral blood of these patients. Moreover, it is possible to extend this kind of therapy to patients who have undergone previous extensive chemotherapy and who might have persisting bone marrow infiltration.

Hemopoietic-initiating cells

Primordial germ cells are cells which can be detected first in the epiblast of the day 3 blastocyst and later as alkaline phosphate positive cells in the extraembryonic mesoderm at the base of the allantois prior to day 7 p.c. At this time there are probably less than ten such cells in the embryo cylinder. After migrating back into the embryo, primordial germ cells migrate along the wall of the hind gut, through the para-aortic splanchnopleura, and reach the genital ridges on day 10.5 p.c. Their growth factor requirements, together with their coincident presence not only at the time definitive hemopoiesis begins, but probably also when primitive hemopoiesis is initiated, lends support for the hypothesis that the cells called primordial germ cells could actually be hemopoietic-initiating cells.

Biological and clinical aspects of hematopoietic stem cells

Recent advances in cell isolation techniques have greatly enhanced our understanding of the phenotype and function of hematopoietic stem cells in mice and humans. Many clinical studies have established the efficacy of using peripheral blood stem cells to supplement or replace bone marrow transplantation as a therapeutic modality for several types of malignancies. This new approach to malignant disease management, perhaps in combination with posttransplantation cytokine therapy, promises to completely alter the clinical course of bone marrow transplantation.

Automated enumeration of CD34+ cells in peripheral blood and bone marrow

We have developed a rapid and accurate method to enumerate the number of CD34+ cells in peripheral blood, bone marrow, and leukopheresis samples. The method consists of a two-tube assay and a dedicated software program for data acquisition and analysis. The first reagent combination consists of (a) a nucleic acid dye to identify nucleated cells, (b) a CD45 monoclonal antibody labeled with PE/CY5 to discriminate progenitor cells from mature lymphoid, neutrophil, erythroid, and monocytic cells, (c) an IgG1 control antibody labeled with PE to establish the boundary between specific and nonspecific staining, and (d) a known number of fluorescent beads to determine an absolute count of cells. In the second reagent combination the IgG1 control antibody is replaced by a CD34 antibody labeled with PE that is used to identify the CD34+ cells in the location established by the control reagent combination. The software program uses the fluorescent beads to adjust the forward light scatter, orthogonal light scatter, and three fluorescence detectors of the flow cytometer. The expected location of the CD34+ cells is then established with the control reagent combination followed by the enumeration of the CD34+ cells per microliter of sample with the reagent combination containing the CD34 antibody. This method is sensitive enough to detect CD34+ cells in peripheral blood of normal donors and can reliably determine an increase in CD34+ cells in the peripheral blood of patients treated with chemotherapy and/or growth factors. The method alleviates some of the difficulties encountered when small numbers of CD34+ cells are enumerated. The system allows for more precise evaluations of the grafts used for bone marrow transplantation.