Biomedical subjects
Publications and source records attributed to S Heimfeld.
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The activity of two peptidases was determined in immortalized lines of thymic stromal cells. A line of total stromal cells (T-TG-St) was grown from transgenic mouse expressing temperature-sensitive SV40 T antigen under the control of the regulatory elements of the mouse major histocompatibility complex class I gene. From these cells we isolated a subset (DP-TG-St) that binds thymocytes which are mainly CD4+8+. We also assayed a clone of fetal thymic epithelial cells (BA/10) that binds CD4+8+ thymocytes. Both lines of double -positive cell-binding stroma exhibited strong activity of two peptidases, neutral endopeptidase (NEP; EC 3.4.24.11) and aminopeptidase N (APN; EC 3.4.11.2). In contrast, the activity of both enzymes was very low in the total thymic stromal line. Use of the specific inhibitors confirmed that these two enzymes were responsible for the activity observed but also suggested the presence of additional unidentified aminopeptidase(s) in the same stromal cells. The high activity of the two peptidases on stromal cells that bind thymocytes at the double-positive stage raises the possibility that they might contribute to the microenvironment of the developing thymocytes.
A unique avidin-biotin immunoadsorption system (CellPro CEPRATE SC) has been developed for the rapid clinical scale purification of CD34+ cells from bone marrow, mobilized peripheral blood (PBSC), or cord blood. This system has been used to treat more than 2500 patients worldwide in a variety of clinical studies. In the autologous transplantation setting, selection for CD34+ cells results in significant reduction (2- > 5 logs) of contaminating tumor cells in the enriched fractions, as documented using sensitive immunocytochemistry staining techniques or quantitative PCR analyses. In the allogeneic bone marrow or PBSC transplant setting, using the CEPRATE SC system as a method for T cell depletion has shown a 3-log reduction in overall T cell content, with more rapid hematopoietic recovery after PBSC reinfusion as compared with bone marrow. CD34+ enrichment is required for efficient ex vivo expansion of progenitor cells as well as for gene therapy applications involving the genetic modification of stem cells.
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We have developed an avidin-biotin immunoadsorption technique in conjunction with a monoclonal anti-CD34 antibody that is capable of selecting CD34+ progenitor cells from marrow and mobilized peripheral blood. Clinical studies with these CD34+ selected cells have shown that the cells are capable of rapid and durable engraftment. In addition, there is significantly less infusional toxicity to the patient because the volume in which the CD34+ selected cells are contained is much less than that of a typical marrow or apheresis buffy coat. Selection of CD34+ progenitor cells also offers other potential advantages, including T-cell depletion of allografts and tumor cell depletion of autografts. CD34+ selection can also be used to facilitate other manipulations of marrow and peripheral blood, including gene transfection, ex vivo stem cell expansion, tumor purging, and progenitor cell banking. Future graft engineering studies are expected to clarify these relationships and enable refinement of the graft to the point at which GVHD can be minimized, graft survival maximized, and relapse-free survival prolonged.
A simple rare event detection method utilizing dual-parameter flow cytometry is described, which allows quantitation of specific cellular events at the level of two cells in 10(7) total cells. Using a standard unmodified single laser flow cytometer sampling at a rate of 25,000 events/sec and a fluorescence discriminator, 10(7) total cells are processed in 7 min. The assay involves precise characterization of instrument flow rates to calculate total events processed by the cytometer rather than accumulate total events in computer memory. This method of detecting rare events is demonstrated by using a model system of breast cancer cells labeled with a metabolically activated dye and serially diluted into normal peripheral blood. Potential applications include validation of methods to detect minimum residual disease following myeloablative therapy, detection of any remaining tumor cells following purging methods, and validation of methods to detect circulating fetal cells in maternal blood.
BACKGROUND: Autologous peripheral-blood progenitor cells can restore hematopoiesis after high-dose chemotherapy in patients with solid tumors or hematologic cancers. We investigated the ability of peripheral-blood progenitor cells generated ex vivo to restore hematopoiesis in patients with cancer who have undergone high-dose chemotherapy. METHODS: Ten patients who had received high-dose chemotherapy were given transplants of autologous progenitor cells that had been generated ex vivo. We used 11 million CD34+ hematopoietic progenitor cells as the starting population for the cell growth. This number corresponds to less than 10 percent of the usual preparation of peripheral-blood CD34+ mononuclear cells used in leukapheresis. The CD34+ cells were grown in medium containing autologous plasma, recombinant human stem-cell factor, interleukin-1 beta, interleukin-3, interleukin-6, and erythropoietin. RESULTS: No toxic effects were observed with the infusion of the generated cells. The cells promoted a rapid and sustained hemopoietic recovery when transplanted after treatment with high-dose etoposide (1500 mg per square meter of body-surface area), ifosfamide (12 g per square meter), carboplatin (750 mg per square meter), and epirubicin (150 mg per square meter). The pattern of hematopoietic reconstitution was identical to that in historical controls treated with unseparated mononuclear cells or positively selected CD34+ cells. CONCLUSIONS: A small number of peripheral-blood CD34+ cells, when grown ex vivo, can supply a population of hematopoietic precursors that have the ability to restore blood formation in patients treated with high doses of chemotherapy. This method, which requires only a small volume of the patient's blood, may reduce the risk of tumor-cell contamination, circumvent the need for leukapheresis, and allow repeated cycles of high-dose chemotherapy.
Dendritic antigen-presenting cells are considered to be the most effective stimulators of T cell immunity. The use of dendritic cells has been proposed to generate therapeutic T cell responses to tumor antigens in cancer patients. One limitation is that the number of dendritic cells in peripheral blood is exceedingly low. Dendritic cells originate from CD34+ hematopoietic progenitor cells (HPC) which are present in the bone marrow and in small numbers in peripheral blood. CD34+ HPC can be mobilized into the peripheral blood by in vivo administration of granulocyte-colony-stimulating factor. The aim of the current study was to determine whether functional dendritic cells could be elicited and grown in vitro from CD34+ HPC derived from bone marrow or granulocyte-colony-stimulating factor-mobilized peripheral blood. Culture of CD34+ HPC with granulocyte-macrophage-colony-stimulating factor and tumor necrosis factor alpha yielded a heterogeneous cell population containing cells with typical dendritic morphology. Phenotypic studies demonstrated a loss of the CD34 molecule over 1 week and an increase in cells expressing surface markers associated with dendritic cells, CD1a, CD80 (B7/BB1), CD4, CD14, HLA-DR, and CD64 (Fc gamma RI). Function was validated in experiments showing that cultured cells could stimulate proliferation of allogeneic CD4+ and CD8+ T lymphocytes. Antigen-presenting capacity was further confirmed in experiments showing that cultured cells could effectively stimulate tetanus toxoid-specific responses and HER-2/neu peptide-specific responses. The derivation and expansion of dendritic cells from cultured bone marrow or granulocyte-colony-stimulating factor-mobilized CD34+ HPC may provide adequate numbers for testing of dendritic cells in clinical studies, such as vaccine and T cell therapy trials.
A large volume culture system was developed for the ex vivo expansion of CD34 positive (+) hematopoietic progenitors, using cell donated by 15 patients receiving high-dose chemotherapy with autologous hematopoietic progenitor cell support (AHPCS). Substantial expansion of myeloid (181-fold) and megakaryocyte (41-fold) progenitors cells was demonstrated, using the conditions that we determined to be optimal: CD34+ progenitors cultured unperturbed for 7 (marrow) or 10 (blood) days in Teflon-coated bags with X-Vivo-10 medium containing 10% autologous plasma, 100 ng/ml, respectively, of recombinant stem cell factor (SCF), interleukin 3 (IL-3), interleukin 6 (IL-6), and granulocyte colony-stimulating factor (G-CSF). The studies demonstrated that (a) CD34 selection was necessary to obtain large, clinically relevant numbers of hematopoietic progenitors, (b) the addition of G-CSF to the baseline regimen of SCF/IL-3/IL-6 significantly enhanced the expansion of myeloid progenitors, (c) the addition of IL-1 to SCF/IL-3/IL-6 did not significantly enhance myeloid progenitor cell expansion, (d) CD34+ G-CSF-mobilized peripheral blood progenitor cells (PBPC) produced higher numbers of myeloid progenitors in culture than CD34+ marrow cells, and (e) long-term tissue culture (LTC) assays demonstrate the preservation of long-term initiating cells in ex vivo culture. The short-term and long-term reconstituting capability of CD34+ PBPC cultured in this system remains to be determined and will be evaluated in a clinical trial where they will be used as the sole source of AHPCS following high-dose therapy.
Retroviral-mediated gene transfer is the most attractive modality for gene transfer into hematopoietic stem cells. However, transduction efficiency has been low using amphotropic Moloney murine leukemia virus (MoMLV) vectors. In this study, we investigated modifications of gene transfer using amphotropic MoMLV vectors in cell-free supernatant for their ability to increase the currently low transduction of both committed hematopoietic progenitors, granulocyte-macrophage colony-forming units (CFU-GMs), and their precursors, long-term culture-initiating cells (LTC-IC). First, based on the observation that bone marrow cells express more gibbon ape leukemia virus (GALV) receptor (Glvr-1) than amphotropic receptor (Ram-1), PG13/LN, which is a MoMLV vector pseudotyped with the GALV envelope, was compared with the analogous amphotropic envelope vector (PA317/LN). Second, progenitor cell transduction efficiency was compared between CD34 enriched and nonenriched progenitor populations. Third, the duration of transduction in vitro was extended to increase the proportion of progenitor cells that entered cell cycle and could thereby integrate vector cDNA. In 20 experiments, 1 x 10(6) marrow or peripheral blood mononuclear cells (PBMCs)/mL were exposed to identical titers of pseudotyped PG13/LN vector or PA317/LN vector in the presence of recombinant human interleukin-1 (IL-1), IL-3, IL-6, and stem cell factor (SCF; c-kit ligand) for 5 days. 50% of fresh vector supernatant was refed daily. Hematopoietic progenitor cells as measured by G418-resistant granulomonocytic colony (CFU-GM) formation were transduced more effectively with PG13/LN (19.35%) than with PA317/LN (11.5%, P = .012). In 11 further experiments, enrichment of CD34 antigen positive cells significantly improved gene transfer from 13.9% G418-resistant CFU-GM in nonenriched to 24.9% in CD34-enriched progenitor cells (P < .01). To analyze gene transfer after extended growth factor-supported long-term culture, 1 x 10(6) marrow cells/mL were cultured with IL-1, IL-3, IL-6, and SCF (50 ng/mL each) for 1, 2, and 3 weeks. Fifty percent of PG13/LN supernatant with growth factors was refed on 5 days per week. Five percent of marrow CFU-GM and 67% of LTC-IC were G418 resistant at 1 week (n = 4), 60% of CFU-GM and 100% of LTC-IC were resistant at 2 weeks (n = 2) and 74% of CFU-GM (n = 4) and 82% of LTC-IC (n = 2) were resistant at three weeks.(ABSTRACT TRUNCATED AT 400 WORDS)
To investigate the feasibility of peripheral blood CD34+ cell selection and to analyze CD34+ cell-mediated engraftment after high-dose chemotherapy, we performed a phase I/II trial in 21 patients with advanced malignancies. The rationale for the selection of CD34+ cells from peripheral blood progenitor cell (PBPC) collections is based on the observation that contaminating tumor cells can be depleted approximately 3 logs using this procedure. CD34+ cells from chemotherapy+granulocyte colony-stimulating factor-mobilized PBPCs were positively selected with an avidin-biotin immunoadsorption column (CEPRATE SC system). One leukapheresis product with a median number of 2.8 x 10(6) CD34+ cells/kg was labeled with a biotinylated anti-CD34 monoclonal antibody and subsequently processed over the column. The yield of selected CD34+ cells was 73% +/- 24.6%. The purity of the CD34+ cell fraction was 61.4% +/- 19.7%. CD34+ cells were shown to represent predominantly committed progenitors coexpressing CD33, CD38, and HLA-DR molecules (lin+). They gave rise to myeloid as well as erythroid and multilineage colonies in vitro. In addition, positively selected CD34+ cells also comprised early hematopoietic progenitor cells, as shown by the presence of CD34+/lin- cells. Transfusion of positively selected CD34+ cells (2.5 x 10(6) CD34+/kg; range, 0.45 to 5.1) after high-dose VP16 (1,500 mg/m2), ifosfamide (12 g/m2), carboplatin (750 mg/m2), and epirubicin (150 mg/m2) (VIC-E) in 15 patients resulted in a rapid and stable engraftment of hematopoiesis without any adverse events. As compared with 13 historical control patients reconstituted with a comparable number of unseparated PBPCs, time to neutrophil and platelet recovery was identical in both groups (absolute neutrophil count > 500/microL, day + 12; platelet count > 50,000/microL, day + 15). These data indicate that autologous peripheral blood CD34+ cells and unseparated PBPCs mediate identical reconstitution of hematopoiesis after high-dose VIC-E chemotherapy. Because positive selection of CD34+ cells from mobilized blood results in a median 403-fold depletion of T cells, allogeneic CD34+ cells from mobilized blood should be investigated as an alternative to bone marrow cells for allotransplantation.
Recombinant adeno-associated virus 2 (AAV) virions were constructed containing a gene for resistance to neomycin (neoR), under the control of either the herpesvirus thymidine kinase (TK) gene promoter (vTK-Neo), or the human parvovirus B19 p6 promoter (vB19-Neo), as well as those containing an upstream erythroid cell-specific enhancer (HS-2) from the locus control region of the human beta-globin gene cluster (vHS2-TK-Neo; vHS2-B19-Neo). These recombinant virions were used to infect either low density or highly enriched populations of CD34+ cells isolated from human umbilical cord blood. In clonogenic assays initiated with cells infected with the different recombinant AAV-Neo virions, equivalent high frequency transduction of the neoR gene into slow-cycling multipotential, erythroid, and granulocyte/macrophage (GM) progenitor cells, including those with high proliferative potential, was obtained without prestimulation with growth factors, indicating that these immature and mature hematopoietic progenitor cells were susceptible to infection by the recombinant AAV virions. Successful transduction did not require and was not enhanced by prestimulation of these cell populations with cytokines. The functional activity of the transduced neo gene was evident by the development of resistance to the drug G418, a neomycin analogue. Individual high and low proliferative colony-forming unit (CFU)-GM, burst-forming unit-erythroid, and CFU-granulocyte erythroid macrophage megakaryocyte colonies from mock-infected, or the recombinant virus-infected cultures were subjected to polymerase chain reaction analysis using a neo-specific synthetic oligonucleotide primer pair. A 276-bp DNA fragment that hybridized with a neo-specific DNA probe on Southern blots was only detected in those colonies cloned from the recombinant virus-infected cells, indicating stable integration of the transduced neo gene. These studies suggest that parvovirus-based vectors may prove to be a useful alternative to the more commonly used retroviral vectors for high efficiency gene transfer into slow or noncycling primitive hematopoietic progenitor cells, without the need for growth factor stimulation, which could potentially lead to differentiation of these cells before transplantation.
Sixty-six stage IV breast cancer patients received high dose chemotherapy followed by autologous transplantation of CD34-positive(+) cells obtained from the bone marrow and/or granulocyte colony stimulating factor (G-CSF)-mobilized peripheral blood. Grafts were examined for the presence of tumor using conventional histology and immunocytochemical staining. Patients achieved a granulocyte count of 500 x 10(9)/liter 10-12 days posttransplant, with a platelet count of > 20 x 10(9)/liter in 14-15 days. Enrichment of CD34+ cells from the peripheral blood progenitor cell (PBPC) collections resulted in a 1.3 to 4.0 log depletion of breast cancer cells from the graft.
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Human umbilical cord bloods were fractionated by unit gravity sedimentation in 1% (v/v) dextran, followed by immunoaffinity selection for CD34+ stem and progenitor cells. Dextran sedimentation alone enabled recovery of more than 80% of the nucleated cells present and 90% of the CD34+ cells, as determined by flow cytometry. The addition of an immunoaffinity selection step for CD34+ cells resulted in a 134-fold enrichment for CD34+ cells, with a mean yield of 64 +/- 15%. The resultant CD34+ population contained almost half the CFU-GM activity initially present in the cord bloods and could be expanded ex vivo in liquid culture.
Expansion of stem/progenitor cells has important implications for transplantation. We recently reported that a factor or factors in cord blood (CB), but not adult peripheral blood (PB), plasma enhanced replating of granulocyte erythroid macrophage megakaryocyte colony-forming units (CFU-GEMM) progenitors, a measure of self-renewal capacity. In this context, we evaluated effects of CB plasma, in comparison with PB plasma and fetal bovine serum (FBS), on ex vivo expansion of CD34+ column-separated (72-98% CD34+) CB cells using stroma-free cultures in the absence and presence of either PIXY321 (a granulocyte-macrophage colony-stimulating factor/interleukin-3 [GM-CSF/IL-3] fusion protein), IL-3+IL-6+IL-1, or steel factor (SLF) -/+ PIXY. CB plasma, PB plasma, or FBS alone did not sustain cell numbers. Combinations of CB plasma +SLF+PIXY induced maximal cumulative nucleated cell expansion (1044-fold), which was greater than that of PB plasma plus cytokines (633-fold) and FBS plus cytokines (142-fold). Total CD34+ cells peaked by day 7 with 7-fold expansion in the presence of CB plasma+SLF+PIXY compared with PB plasma or FBS with these same cytokines (threefold each). By day 7, total CFU-GEMM production in the presence of either PIXY, SLF+PIXY, or IL-3+IL-6+IL-1 was greater with CB plasma (maximum 11.4-fold average increases) than with PB plasma (6.8-fold increase). These increases were greater than with FBS. However, PB plasma was at least as good as CB plasma for expansion of immature and mature subsets of CFU-GM. The frequency of progenitors decreased with time, and expansion was coupled with differentiation. Although the proliferative capacity of CFU-GEMM was maintained, the capacity of CFU-GEMM to be replated decreased after time in suspension culture, suggesting age-related commitment of cells. Moreover, with plasma +SLF+PIXY for 7 days, expansion of more mature CFU-GM (responsive to GM-CSF) was greater (16-146-fold with CB plasma and 31-208-fold with PB plasma) than immature CFU-GM (responsive to GM-CSF+SFL) (4- to 14-fold with CB plasma and 6- to 17-fold with PB plasma). The results suggest that CB plasma enhances expansion of CFU-GEMM to a greater extent than PB plasma or FBS, but expansion in these cultures favors more mature subsets of cells.
To provide sufficient numbers of peripheral blood progenitor cells (PBPCs) for repetitive use after high-dose chemotherapy, we investigated the ability of hematopoietic growth factor combinations to expand the number of clonogenic PBPCs ex vivo. Chemotherapy plus granulocyte colony-stimulating factor (G-CSF) mobilized CD34+ cells from 18 patients with metastatic solid tumors or refractory lymphomas were cultured for up to 28 days in a liquid culture system. The effects of interleukin-1 beta (IL-1), IL-3, IL-6, granulocyte-macrophage-CSF (GM-CSF), G-CSF, macrophage-CSF (M-CSF), stem cell factor (SCF), erythropoietin (EPO), leukemia inhibitory factor (LIF), and interferon-gamma, as well as 36 combinations of these factors were tested. A combination of five hematopoietic growth factors, including SCF, EPO, IL-1, IL-3, and IL-6, was identified as the optimal combination of growth factors for both the expansion of total nucleated cells as well as the expansion of clonogenic progenitor cells. Proliferation peaked at days 12 to 14, with a median 190-fold increase (range, 46- to 930-fold) of total clonogenic progenitor cells. Expanded progenitor cells generated myeloid (colony-forming unit-granulocyte-macrophage), erythroid (burst-forming unit-erythroid), as well as multilineage (colony-forming unit-granulocyte, erythrocyte, monocyte, megakaryocyte) colony-forming units. The number of multilineage colonies increased 250-fold (range, 33- to 589-fold) as compared with pre-expansion values. Moreover, the absolute number of early hematopoietic progenitor cells (CD34+/HLA-DR-; CD34+/CD38-), as well as the number of 4-HC-resistant progenitors within expanded cells increased significantly. Interferon-gamma was shown to synergize with the 5-factor combination, whereas the addition of GM-CSF significantly decreased the number of total clonogenic progenitor cells. Large-scale expansion of PB CD34+ cells (starting cell number, 1.5 x 10(6) CD34+ cells) in autologous plasma supplemented with the same 5-factor combination resulted in an equivalent expansion of progenitor cells as compared with the microculture system. In summary, our data indicate that chemotherapy plus G-CSF-mobilized PBPCs from cancer patients can be effectively expanded ex vivo. Moreover, our data suggest the feasibility of large-scale expansion of PBPCs, starting from small numbers of PB CD34+ cells. The number of cells expanded ex vivo might be sufficient for repetitive use after high-dose chemotherapy and might be candidate cells for therapeutic gene transfer.