Stem cell factor enhances interleukin-3 dependent induction of 68-kD calmodulin-binding protein and thymidine kinase activity in NFS-60 cells

Stem cell factor (SCF) is known to act synergistically with other hematopoietic factors in increasing the colony formation of hematopoietic progenitor cells. We have shown that interleukin-3 (IL-3)-dependent proliferation of NFS-60 cells is associated with the induction of a specific calmodulin-binding protein of about 68 kD (CaM-BP68). To evaluate the relationship between proliferative stimulation and the induction of CaM-BP68 by cytokines, we examined whether the increased proliferative potential of NFS-60 cells in response to SCF is reflected in an increased induction of the CaM-BP68. We observed that SCF alone has a limited effect on proliferative stimulation and on the induction of CaM-BP68 in factor-deprived NFS-60 cells. However, when combined with IL-3, granulocyte colony-stimulating factor (G-CSF), or IL-6, it caused a significant increase in cytokine-dependent proliferative stimulation, as well as in the induction of CaM-BP68. Furthermore, an increase in IL-3-dependent induction of CaM-BP68 in the presence of SCF coincided with a corresponding increase in thymidine kinase activity, whose expression is linked to G1/S transition of the cells. At low concentrations SCF caused a synergistic increase in IL-3-dependent induction of both CaM-BP68 and thymidine kinase activity. In contrast to the changes in CaM-BP68 and thymidine kinase activity, no significant changes in DNA polymerase alpha were observed in factor-deprived NFS-60 cells in response to IL-3 and/or SCF. These observations suggest an increased expression of CaM-BP68 and thymidine kinase are associated with the synergistic effect of SCF on factor-dependent proliferation of hematopoietic progenitor cells.

Umbilical cord blood as a new and promising source of unrelated-donor hematopoietic stem cells for transplantation

A rapidly accelerating number of transplantations of hematopoietic stem cells from human umbilical cord blood have been performed for malignancies and for congenital disorders. Umbilical cord blood presents multiple advantages over bone marrow as a source of stem cells. Harvesting presents no donor risk or discomfort, the product carries less likelihood of infectious disease transmission, and collection can be targeted to include minority groups underrepresented in bone marrow donor registries. Furthermore, the interval from initiation of a search to the transplantation procedure has been much shorter than for bone marrow, and the lack of mature T lymphocytes in cord blood reduces the incidence and severity of graft-versus-host disease in transplant recipients. Potential problems under current investigations include whether cord blood provides a sufficient quantity of stem cells for adult recipients or an effective level of "graft-versus-leukemia" effect.

Deletion variants within the NF-kappa B activation domain of the LMP1 oncogene prevail in acquired immunodeficiency syndrome-related large cell lymphomas and human immunodeficiency virus-negative atypical lymphoproliferations

This sequencing study of 17 acquired immunodeficiency syndrome-related lymphomas (9 primary brain, 8 systemic) and 8 human immunodeficiency virus-negative atypical lymphoproliferations expressing large amounts of the latent membrane protein 1 (LMP1) of Epstein-Barr virus was performed to characterize the carboxy terminal NF-kappa B activation domain of LMP1 at the molecular level in an immunocompromised host. In-frame deletions within the NF-kappa B activation domain were identified in all but 2 primary brain lymphomas, 4 systemic lymphomas, and 4 atypical lymphoproliferations, ie, in 60% of cases. In addition, non silent point mutations (range 1 to 5, mean 3.3) were detected in all cases. Although all changes occurred within the first 100 nucleotides of the carboxy terminal NF-kappa B activation domain--a critical sequence for the protein half-life--not a single point mutation was found in the remaining 62 nucleotides, necessary for malignant transformation. Such a clustering of nonrandom sequence variations, associated with a high oncoprotein expression in immunocompromised hosts, suggests that this part of the LMP1 oncogene behaves as a hypervariable region with natural selection of growth-promoting variants through prolongation of the protein half-life.

Improved engraftment of human cord blood stem cells in NOD/LtSz-scid/scid mice after irradiation or multiple-day injections into unirradiated recipients

Human lymphoematopoietic stem cells engraft in irradiated immunodeficient mice that are homozygous for the severe combined immunodeficiency (scid) mutation. Engraftment levels in C.B-17-scid/scid mice, however, have been low and transient, decreasing the utility of this model for investigation of the development potential and function of human stem cells. In the present study, we have used NOD/LtSz-scid/scid mice as recipients and human cord blood as a source of donor stem cells. Our results demonstrate that NOD/LtSz-scid/scid mice support approximately fivefold higher levels of human stem cell marrow engraftment than do C.B-17-scid/scid mice. Human CD34+ cells are present in the marrow of recipient mice, and the engrafted cells readily peripheralize to the circulation of the host. Terminal differentiation of the stem and progenitor cells into mature progeny is limited. Using a multiple-day injection protocol developed in mice, which allows engraftment of stem cells between congenic mice in the absence of irradiation preconditioning, we observed high levels of human cell engraftment in unirradiated NOD/LtSz-scid/scid recipients after three or five consecutive-day injections. These results demonstrate that NOD/LtSz-scid/scid mice support high levels of human stem cell engraftment and that xenogeneic lymphohematopoietic stem cells can engraft in unirradiated hosts without the need for ablative reconditioning. This model will be useful for the in vivo investigation of human stem cells and for the preclinical analysis of human stem cells for transplantation.

Ex vivo expansion of murine marrow cells with interleukin-3 (IL-3), IL-6, IL-11, and stem cell factor leads to impaired engraftment in irradiated hosts

In vitro incubation of bone marrow cells with cytokines has been used as an approach to expand stem cells and to facilitate retroviral integration. Expansion of hematopoietic progenitor cells has been monitored by different in vitro assays and in a few instances by in vivo marrow renewal in myeloablated hosts. This is the first report of studies, using two competitive transplant models, in which cytokine-treated cells, obtained from nonpretreated donors (eg, 5-fluorouracil), were competed with normal cells. A basic assumption is that the expansion of progenitors assayed in vitro as high- and low-proliferative potential colony-forming cells (HPP- and LPP-CFCs) indicates an expansion of stem cells which will repopulate in vivo. This study shows that culture of marrow cells with four cytokines (stem cell factor, interleukin-3 [IL-3], IL-6, IL-11) induces significant expansion and proliferation of HPP-CFC and LPP-CFC. Cell-cycle analysis showed that these hematopoietic progenitors were induced to actively cell cycle by culture with these cytokines. In the first competitive transplant model, which uses Ly5.2/Ly5.1 congenic mice, cytokine-cultured Ly5.2 cells competed with noncultured Ly5.1 cells led to 5% +/- 1% engraftment at 12 weeks and to 4% +/- 2% engraftment at 22 weeks posttransplantation for the cytokine exposed cells. Noncultured Ly5.2 cells competed with cultured Ly5.1 cells led to 70% +/- 1% engraftment at 12 weeks and to 93% +/- 2% engraftment at 22 weeks posttransplantation. In the second model, which uses BALB/c marrow of opposite genders, cultured male cells lead to 13% +/- 9% engraftment at 10 weeks and 2% +/- 1% engraftment at 14 weeks posttransplantation; noncultured male cells lead to 70% +/- 2% and 95% +/- 2% engraftment at 10 and 14 weeks posttransplantation, respectively. Data presented here from two different competitive transplant studies show a defect of cytokine expanded marrow related to cell cycle activation which manifests as defective long-term repopulating capability in irradiated host mice. The engraftment defect is more profound at longer time intervals, suggesting that the most striking effect may be on long-term repopulating cells.

High levels of engraftment with a single infusion of bone marrow cells into normal unprepared mice

Repetitive infusion of 40 million male murine marrow cells (total 200 million cells) into normal unprepared female BALB/c hosts for 5 consecutive days results in high levels of engraftment at 1-25 months postinfusion, as determined by Southern blot analysis using a Y chromosome-specific probe. We investigated the importance of the schedule of injections in this engraftment model. Surprisingly, a single infusion of 200 x 10(6) male BALB/c bone marrow cells analyzed at 7-14 weeks postinfusion resulted in engraftment levels in individual female mice of over 50% with mean values of 25 +/- 2% for 44 individual transplant points. Engraftment levels in spleen and thymus were 14 +/- 1% and 18 +/- 3%, respectively. Including heparin in the infusion increased engraftment in marrow, spleen, and thymus. Administration of the cells over five or 10 separate infusions, rather than in one injection, did not increase engraftment levels. If the infused bone marrow cells seeded equally between host spleen, thymus, and bone marrow, and if all cells engrafted, the bone marrow engraftment seen here approaches the theoretical maximum. This suggests either a large number of available "niches" or the displacement of host marrow cells by infused marrow. The latter possibility is upheld by cell counts per tibia/femur and total seven-factor HPP-CFC/tibia, which were not increased. These data suggest that a single infusion of marrow homes quantitatively to spleen, thymus, and bone marrow, possibly displacing host cells in the process.

The ski/sno protooncogene family in hematopoietic development

The ski/sno protooncogenes encode nuclear proteins that may act as transcription factors. We examined ski and sno mRNA expression in hemolymphopoietic lineages. The ski protooncogene is expressed in B- and T-lineage cells, mature macrophages, and mast cells. In normal murine marrow-derived progenitors analyzed by single-cell reverse transcription-polymerase chain reaction (RT-PCR), ski expression is limited to dual-lineage megakaryocyte/erythrocyte colony-starts. Expression of sno is more limited than ski in mature cells; it is expressed in T lymphopoietic cells, but not in B-lineage cells. The sno protooncogene is expressed more widely than ski in myeloid progenitors, as it is found consistently in tri-, dual-, and single-lineage progenitors. Both ski and sno are cell cycle-regulated in synchronized factor-dependent mouse myeloid cells. Expression of ski mRNA peaks in mid G1 in cells synchronized by isoleucine deprivation in the presence of growth factor, but falls off rapidly when growth factor is withdrawn. Expression of sno mRNA is maximal in early to mid G1 and then oscillates as the cells continue through cycle. These results suggest that the ski/sno protooncogenes play a role in hematopoiesis, growth factor responses, and cell cycle-regulation, with the two members of the family showing differing properties.

The high-proliferative-potential megakaryocyte mixed (HPP-Meg-Mix) cell: a trilineage murine hematopoietic progenitor with multiple growth factor responsiveness

Megakaryocyte progenitors are notable for their response to synergistic cytokine combinations and apparently early position in the hematopoietic differentiation pathway. Although high-proliferative-potential murine megakaryocyte progenitors have been described, they have previously been primarily observed as unilineage colonies. We describe a subclass of agar-based high-proliferative-potential colony forming cells (HPP-CFC) derived from populations enriched for early hematopoietic progenitors which, when stimulated with the combination of CSF-1, G-CSF, GM-CSF, IL-1 alpha, IL-3 and SCF, produces colonies with trilineage potential for macrophages, granulocytes, and megakaryocytes. The high proliferative potential megakaryocyte mixed (HPP-Meg-Mix) colony-forming cell is defined as a cell meeting traditional criteria for HPP-CFC but additionally containing 20 or more megakaryocytes per colony. The combination of high-proliferative-potential, multilineage differentiation, and megakaryocytic lineage capacity suggests that the HPP-Meg-Mix marks a very early hematopoietic progenitor cell.

Engraftment of bone marrow cells into normal unprepared hosts: effects of 5-fluorouracil and cell cycle status

Bone marrow from animals treated with 5-fluorouracil (5FU) competes equally with normal marrow when assessed in vivo in an irradiated mouse, but shows markedly defective engraftment when transplanted into noncytoablated hosts. Using Southern Blot analysis and a Y-chromosome specific probe, we determined the level of engraftment of male donor cells in the bone marrow, spleen, and thymus of unprepared female hosts. We have confirmed the defective engraftment of marrow harvested 6 days after 5FU (FU-6) and transplanted into unprepared hosts and shown that this defect is transient; by 35 days after 5FU (FU-35), engraftment has returned to levels seen with normal marrow. FU-6 marrow represents an actively cycling population of stem cells, and we hypothesize that the cycle status of the stem cell may relate to its capacity to engraft in the nonirradiated host. Accordingly, we have evaluated the cycle status of engrafting normal and FU-6 marrow into normal hosts using an in vivo hydroxyurea technique. We have shown that those cells engrafting from normal marrow and over 70% of the cells engrafting from FU-6 marrow were quiescent, demonstrating no killing with hydroxyurea. We have also used fluorescent in situ hybridization (FISH) analysis with a Y-chromosome probe and demonstrated that normal and post-5FU engraftment patterns in peripheral blood were similar to those seen in bone marrow, spleen, and thymus. Altogether these data indicate that cells engrafting in normal, unprepared hosts are dormant, and the defect that occurs after 5FU is concomitant with the induction of these cells to transit the cell cycle.

Concept and organization of a clinical gene therapy lab

Designing a dedicated clinical facility to meet the needs of existing and developing Gene Therapy Protocols presents a unique challenge. Here, we review some of the issues we faced and share some of our design concepts. An optimal Clinical Gene Therapy Lab must meet relevant regulatory guidelines, interface with other hospital labs as well as the clinic and patient care areas, be efficient and flexible in utilization of space, and have the potential to meet future needs without continual renovation. As clinical science expands to include more gene transfer approaches, specific laboratory areas for this type of work will become increasingly necessary.

Murine marrow cells expanded in culture with IL-3, IL-6, IL-11, and SCF acquire an engraftment defect in normal hosts

Stimulatory cytokines may induce murine hematopoietic progenitor cells (HPCs) to survive, self-renew, proliferate, or differentiate. We studied the role of active cell cycling induced by the cytokines interleukin-3 (IL-3), IL-6, IL-11, and Steel factor (SF) on murine progenitor cell frequency and cell cycle status in an in vitro system and on engraftment potential in nonmyeloablated mice. Marrow exposure to IL-3, IL-6, IL-11, and SF in in vitro liquid culture maintained or expanded seven factor-responsive high and low proliferative potential colony-forming cells (HPP-CFC and LPP-CFC). The HPP-CFC and LPP-CFC were dormant at the initiation of culture, as determined by 3H-thymidine suicide. There was an increase in the number and proliferation of HPP-CFC and LPP-CFC at 48 hours; by 48 hours, 62% of HPP-CFC and 56% of LPP-CFC were killed by 3H-TdR exposure. In engraftment studies of cytokine-stimulated marrow cells into normal hosts, female BALB/c mice received the equivalent of 40 x 10(6) starting male marrow cells exposed to cytokines in vitro for 48 hours for 3 consecutive days and were sacrificed 8 weeks after transplantation. Control groups received either 40 x 10(6) male uncultured marrow cells, 40 x 10(6) starting marrow cells cultured in medium without growth factors for 48 hours, or phosphate-buffered saline (PBS) for 3 days. Engraftment of male cytokine-treated cells was analyzed by Southern blot analysis using the Y-chromosome-specific pY2-cDNA probe. There was minimal engraftment (approaching background levels) in marrow, spleen, and thymus of nonmyeloablated female recipients. Transplant recipients that had received uncultured marrow directly after sacrifice showed engraftment levels of 21% (11 mice; range = 8 to 44%) into marrow, of 9% (range = 0 to 22%) into spleen, and 13% (range = 2 to 43%) into thymus. We conclude that active cell cycling of marrow cells induced by cytokine stimulation is associated with an engraftment defect in the normal host.

The 68 kDa calmodulin-binding protein is tightly associated with the multiprotein DNA polymerase alpha-primase complex in HeLa cells

Calcium and its receptor protein calmodulin function in the regulation of proliferation of mammalian cells. A 68 kDa calmodulin-specific binding protein was shown previously to be associated with growth factor-dependent progression of a variety of mammalian cells from G1 to S phase and to stimulate DNA synthesis in permeabilized hematopoietic progenitor cells. In this report we show that the 68 kDa calmodulin-specific binding protein in HeLa cells is tightly associated with the DNA polymerase alpha-primase component of the 21S complex of enzymes for DNA synthesis. The 68 kDa calmodulin-binding protein and the DNA polymerase alpha-primase complex cofractionate during Q-Sepharose chromatography to isolate the 21S enzyme complex, native and denatured DNA-cellulose to dissociate the 21S complex, and DEAE-Bio-Gel chromatography to isolate the multiprotein DNA polymerase alpha-primase complex. The 68 kDa calmodulin-specific binding protein and DNA polymerase alpha also bind and coelute during affinity chromatography on calmodulin-agarose. They also coprecipitate with C10-agarose-linked monoclonal antibody SJK 132-20 to human DNA polymerase alpha. The tight association of the 68 kDa calmodulin-binding protein to the DNA polymerase alpha-primase complex supports a function for this protein in the regulation of DNA synthesis in vivo.

Growth factor modulated calmodulin-binding protein stimulates nuclear DNA synthesis in hemopoietic progenitor cells

A specific calmodulin-binding protein of 68 kDa (CaM-BP68) is modulated in response to growth factors that induce proliferative stimulation in a variety of hemopoietic progenitor cells. The nuclear localization of the CaM-BP68 coincided temporally with interleukin 3 (IL-3)-dependent progression of synchronized FDC-P1 cells from G1 to S phase [Reddy et al. (1992) Blood 79, 1946-1956]. To delineate the role of the CaM-BP68 in the onset of DNA synthesis (S phase), this protein was purified to an apparent homogeneity from FDC-P1 cells and its effects on DNA replication in permeabilized FDC-P1 cells were examined. Purified CaM-BP exhibited a single silver-stained protein band of 68 kDa on SDS-polyacrylamide gels. This purified protein, when incubated with permeabilized log-growing FDC-P1 cells, caused a 3-4-fold increase in the rate of [3H]dTTP incorporation into DNA as compared to the controls. There was a direct correlation between the increase in the rate of [3H]dTTP incorporation into DNA and the concentration of the added CaM-BP68 in the incubation mixture. These observations suggest that the CaM-BP68, whose nuclear localization is associated with growth factor dependent proliferative stimulation of myeloid progenitor cells, is involved in the regulation of nuclear DNA synthesis.

Engraftment of normal murine marrow into nonmyeloablated host mice

When 200 x 10(6) male BALB/c cells are given by tail vein injection to female nonmyeloablated hosts in one injection, a relatively low engraftment percentage is seen, but when the same total number of cells is given over five injections (separated by 24 hours), the observed engraftment is much higher. A further increase in engraftment appears to occur when the same number of cells is given in 10 injections separated by at least 24 hours. These data suggest that somewhere between 5 and 10% of marrow niches are available at intervals of 24 or more hours and that the keys to high levels of engraftment are the cell cycle status of the engrafting stem cell and the schedule of engraftment.

Long-term engraftment of normal and post-5-fluorouracil murine marrow into normal nonmyeloablated mice

We report the successful long-term engraftment of normal male donor bone marrow (BM) transfused into noncytoablated female mice, challenging the assumption that "niches" need to be created for marrow to engraft. We have used chromosomal banding and Southern blot analysis to identify transplanted male marrow cells, and shown the long-term stability of the chimeric marrows. Balb/C, BDF1, or CBA-J female hosts (no irradiation) received for 5 consecutive days 40 x 10(6) male cells (per day) of the same strain, and repopulation patterns were observed. Parallel studies were performed using tibia/femur equivalents of normal marrow or marrow from Balb/C mice pretreated 6 days previously with 150 mg/kg 5-fluorouracil (5-FU). Chromosome banding techniques showed that 5% to 46% of marrow cells were male 3 to 9 months posttransplant with normal donor marrow. Southern blot analysis, using the pY2 probe, showed continued engraftment at 21 to 25 months posttransplant, ranging from 15% to 42% male engrafted cells in marrow. Normal donor male marrow engrafted significantly better than 5-FU-pretreated male marrow as shown 1 to 12 months posttransplant in non-cytoablated female recipients. Percentages of male engrafted cells in BM ranged from 23% to 78% for recipients of normal donor marrow and from 0.1% to 39% for recipients of 5-FU marrow. Mean engraftment for 6 mice receiving normal marrow was 38%, whereas that for 6 mice receiving post-5-FU marrow was 8%, as assayed 1 to 3 months posttransplant. At 10 to 12 months, mean engraftment for the normal donor group was 46%, compared with 16% for the 5-FU group. The patterns of engraftment with normal and 5-FU marrow were similar for spleen and thymus. These results show that long-term chimerism can be established after transplantation of normal donor marrow to normal nonirradiated host mice and indicate that marrow spaces do not have to be created for successful engraftment. They suggest that transplanted marrow competes equally with host marrow for marrow space. Finally, these data show that post-5-FU Balb/C male marrow is markedly inferior in the repopulation of Balb/C female host marrow, spleen, and thymus, and suggest that this population of cells may not be the ideal population for gene transfer studies.

Post-5-fluorouracil human marrow: stem cell characteristics and renewal properties after autologous marrow transplantation

The effect of 5-fluorouracil (5-FU) pretreatment on human bone marrow (BM) progenitor/stem cells and recovery of hematopoiesis after autologous marrow transplant was studied. Twenty-one patients were treated with 5-FU (15 mg/kg to 45 mg/kg) intravenously (IV) for 1 to 3 days administered 6 to 22 days before BM harvest. Post-FU marrow was infused into 15 patients after high-dose cyclophosphamide, carmustine (BCNU), and VP-16 (CBV). Seventeen patients (historical controls) were treated with CBV and autologous BM transplantation but did not receive 5-FU before marrow harvest. The groups were comparable for diagnosis and prior therapy. In the 5-FU-treated group and control group, median recovery times for platelet count to 50,000/mm3 were 20 and 30 days, respectively (P = .007), and for platelet count to 100,000/mm3, 23 and 38 days, respectively (P = .007), while neutrophil recovery was not significantly altered. In vitro cultures with 1 to 7 growth factors (interleukin-1 [IL-1], IL-3, IL-4, IL-6, colony-stimulating factor-1 [CSF-1], granulocyte-macrophage colony-stimulating factor [GM-CSF], and G-CSF) were performed. In 8 of 10 patients whose marrow was studied before and after 5-FU treatment, the numbers of CFU-C responsive to the combination of GM-CSF and IL-3 was increased 6.15-fold by 5-FU pretreatment. In 4 of these patients, thymidine suicide of GM-CSF- and IL-3-stimulated CFU-C ranged from 17% to 42%. High proliferative potential colony-forming cell (HPP-CFC) was observed in low frequency in normal marrow and patient's marrow before 5-FU treatment. In 11 of 16 patients pretreated with 5-FU, increased numbers of HPP-CFC were noted. GM-CSF and IL-3 interacted synergistically to stimulate HPP-CFC. Multifactor combinations, especially GM-CSF + G-CSF + IL-3 + IL-6 + IL-1 + CSF-1 did not increase total colony count or classic HPP-CFC but did result in altered morphology, producing huge, loose colonies. The marrow from patients pretreated with 5-FU is enriched with multifactor-responsive HPP-CFC, renews in vivo granulopoiesis in a manner comparable with marrow harvests without 5-FU pretreatment, and provides accelerated in vivo platelet recovery. This marrow may be an appropriate target marrow for gene insertion in gene-therapy protocols.

Interleukin-3/erythropoietin fusion proteins: in vitro effects on hematopoietic cells

Erythropoietin (Epo) acts synergistically with interleukin-3 (IL-3) to induce proliferation and differentiation of erythroid progenitors. This synergy occurs at IL-3 concentrations that have little or no effect alone. To determine whether optimal expansion of erythroid cells results when they are targeted by a molecule with both IL-3 and Epo activities, fusion proteins were generated and analyzed. Expression vectors were constructed in which the coding regions of human IL-3 and Epo cDNAs were joined by either a short (2 to 3 amino acids) or long (23 amino acids) linker sequence and expressed in Chinese hamster ovary (CHO) cells. Analysis of equilibrium binding properties of the IL-3 and Epo moieties revealed that in all fusion proteins each retained the ability to bind receptor. When IL-3 was connected to Epo by a short linker, the binding affinity of the IL-3 moiety was lower. In vitro proliferative activity of each moiety was observed on cell lines responsive to IL-3, Epo or a combination of the two cytokines. Fusion of IL-3 to Epo through its amino terminus was found to result in partial loss of its function. All the fusion proteins were biologically active on human bone marrow. When IL-3 was located at the amino domain of the protein, induction of erythroid colonies was similar to that of a mixture of IL-3 and Epo. These results indicate that biological integrity of both IL-3 and Epo can be maintained when these cytokines are fused, but that enhancement of erythropoiesis over that observed with a mixture of the two cytokines cannot be achieved by their fusion alone. Other requirements such as the coexpression of the IL-3 and Epo receptors and the sharing of a receptor subunit are likely to be needed for an optimal cell response to the fusion growth factors.