Individual clones of hemopoietic cells in murine long-term bone marrow culture

Forty-seven individual hemopoietic cell clones bearing unique radiation markers were studied in long-term bone marrow cultures. Throughout cultivation clones appeared at different times, from 1 to 12 weeks after explantation, survived during 1-10 more weeks, and were characterized by marked variability in size. Usually, the number of metaphases peculiar to an individual clone rapidly increased, achieved maximum, and then underwent a decline. Cells of reliably disappearing clones were never seen again. The experimental results provide further evidence for the model of hemopoiesis by clonal succession.     

Lack of development of thermotolerance in early progenitors of murine bone marrow cells

We have studied the sensitivities of four hematopoietic stem cell types to heat stress as well as their abilities to develop thermotolerance. Granulocyte-macrophage colony forming units were the most heat resistant bone marrow progenitors tested. Of the erythroid progenitors tested, erythrocyte colony forming units were more resistant than the two more primitive erythrocyte burst forming units. To determine their ability to develop thermotolerance, hematopoietic precursors were heated in vivo at 43 degrees C for 30 min. At various times thereafter the hematopoietic stem cells were flushed from female C3Hf/Sed mouse preheated tibia. The bone marrow cell suspensions were then heated in vitro and plated for colony formation. The four stem cell precursors differed markedly in their abilities to develop thermotolerance. The thermotolerance induced in granulocyte-macrophage colony forming units reached a maximum at 3-6 h after heating and disappeared by 24-48 h. The thermotolerance in erythrocyte colony forming units (0.5 units erythropoietin/ml media) reached a maximum at 3-6 h and disappeared by 48-72 h. The maximum level of thermotolerance reached by granulocyte-macrophage colony forming units and erythrocyte colony forming units was approximately the same. On the contrary, the two more primitive erythrocyte precursors which were grown by the addition of 2.5 and 5 units erythropoietin/ml of media do not develop thermotolerance.     

Leucovorin antagonizes the effects of trimetrexate on mouse hemopoietic progenitors.

Trimetrexate (2, 4, diamino -5- methyl - 6 [3, 4, 5, trimethoxyanilino) methyl] quinazoline) (TMQ) is a non-classic folate antagonist that is used as an antineoplastic and antipneumocystis agent with promising results. TMQ and methotrexate (MTX) toxicities are comparable. Leucovorin (N-5-formyltetrahydrofolate) (LV) is used to prevent the toxic effects of MTX. In this study the effects of LV on TMQ induced hemopoietic progenitor damage are studied in a murine model. Changes of pluripotent stem cells (colony forming units spleen, CFU-S), granulocyte-macrophage committed progenitors (GM-CFC), erythroid committed progenitor (BFU-E) levels in the bone marrow were followed after administration to mice of a single dose of TMQ or of simultaneous injection of TMQ and LV. Results show that the latter significantly reduces the effects of the former on peripheral blood cells and on hemopoietic progenitors.     

Effects of cancer immunotherapy with indomethacin and interleukin-2 on murine hemopoietic stem cells.

We examined: (a) whether in vitro-generated lymphocyte-activated killer (LAK) cells from normal mice and splenic killer cells from tumor-bearing mice subjected to interleukin-2 (IL-2) therapy alone or in combination with chronic indomethacin therapy have any detrimental effects on the spleen colony-forming units (CFU-S) of the normal bone marrow (BM); and (b) the effects of these immunotherapy protocols on CFU-S numbers in host hemopoietic organs. Effects of in vitro-generated LAK cells (normal C3H/HeN mouse splenocytes cultured with 1000 units IL-2/10(6) cells for 72 h) on BM CFU-S were examined by incubating macrophage-depleted BM cells with LAK cells at 1:2.5 and 1:5 BM:LAK cell ratios or with LAK cell supernatant for 4 h. The cells were washed and subsequently injected into irradiated mice. Irradiated mice were also reconstituted with BM cells or LAK cells incubated alone. Spleen colonies were scored macroscopically and microscopically on day 7 after reconstitution of lethally irradiated mice with the various cell combinations. A comparison of colony numbers produced by LAK and BM cell mixture revealed that LAK cells at either dose had no suppressive effect on the colony-forming ability of BM at the macroscopic and microscopic levels of analysis. The supernatant of cultured LAK cells had a minor suppressive effect on colony formation at the macroscopic but not the microscopic level of analysis, indicating the presence of one or more suppressive factors capable of mediating a short-term inhibitory effect. In the immunotherapy experiment, C3H/HeN mice transplanted s.c. with 5 x 10(5) C3L5 mammary adenocarcinoma cells received either vehicle alone (controls), IL-2 (1.5 x 10(4) Cetus units i.p. every 8 h on days 10-14 and days 20-25), or chronic indomethacin therapy (10 micrograms/ml in drinking water from day 5 onwards) plus IL-2 as above. Animals were killed 24-25 days after tumor transplantation to examine: (a) the number of metastatic lung nodules; (b) the effects of co-incubating therapy-generated splenic effector cells with normal BM cells for 4 h on BM CFU-S, and (c) the CFU-S content of host BM and spleen. Results revealed a drop in spontaneous lung metastases from a mean of 50 in control mice to 18 with IL-2 therapy alone, and to 5 with chronic indomethacin therapy plus IL-2 therapy. Splenocytes from normal and tumor-bearing control or treated mice, when incubated with normal BM, had no effect on spleen colony formation at the macroscopic level.(ABSTRACT TRUNCATED AT 400 WORDS)     

Phenotypically distinct target cells for murine sarcoma virus and murine leukemia virus marrow transformation in vitro.

An in vitro hematopoietic microenvironment was established from explained fragments of bone marrow from adult noninbred NIH Swiss mice with the use of corticosteroid-reconstituted horse serum. Infection with Kirsten murine sarcoma virus (Ki-MuSV) with either a Rauscher murine leukemia virus (R-MuLV) or Balb:virus-1 helper virus coat reduced proliferation of granulocytic and pluripotent hematopoietic stem cells and produced neoplastic transformation of both macrophages and preadipocytes in the adherent cell population within a 4-week period. Ki-MuSV-transformed, virus-releasing macrophages formed clusters of 4-49 cells in 0.8% methylcellulose-containing medium in the absence of added colony-stimulating factor (CSF), synthesized lysozyme, ASD-chloroacetate substrate-specific esterase-M, and CSF, and produced tumors following inoculation iv into adult NIH Swiss mice or ip into newborn NIH Swiss mice. In cultures infected with helper leukemia viruses R-MuLV or Balb:virus-1, gradual transformation of a distinct cell phenotype was observed over a 9-week period with generation of increasing numbers of atypical myeloblasts and promyelocytes which showed dyssynchronous nuclear-cytoplasmic maturation, basophilic granulation, cytoplasmic vacuolation, and formation of incompletely maturing CSF-dependent granulocyte-macrophage colonies in vitro and small spleen colonies in vivo. These data demonstrated that rapid biologic expression of the murine sarcoma virus genome in specific adherent "stromal" marrow cells prevents detection of a more subtle helper-virus-induced dysmyelopoiesis in a distinct nonadherent cell population.     

Suppressive effect of LD78 on the proliferation of human hemopoietic progenitors.

LD78 is a cDNA newly isolated from human stimulated tonsillar lymphocytes. The expression of LD78 is related to inflammatory responses and its structure has a homology with macrophage inflammatory protein 1-alpha, which is known to have an inhibitory effect on murine CFU-S. Using a colony assay technique, we examined the effects of LD78 on human hemopoietic progenitors. The addition of doses of 100 ng/ml or more of LD78 suppressed the colony formation of KMT-2, a factor-dependent myelomonocytic cell line established from cord blood cells; this suppressive activity was neutralized by the addition of antibody against LD78. The same doses of LD78 suppressed the formation of neutrophil, macrophage, and megakaryocytic colonies which were supported by human interleukin-3 and erythropoietin; however, LD78 did not affect colony formation by either non-phagocytic mononuclear cells or sorted CD34+ cells. The conditioned medium of KMT-2 cells or peripheral blood mononuclear cells cultured with LD78 suppressed colony formation by CD34+ cells. From these findings, it is suggested that LD78 affects phagocytic cells and induces factors that are inhibitory for hemopoiesis. We consider LD78 to be a new cytokine that plays an inhibitory role in hemopoiesis.     

Growth of normal hemopoietic cells in cultures of bone marrow from leukemic mice

Bone marrow from mice with spontaneous leukemia was studied in long-term culture in the presence of 10⁻⁷M hydrocortisone. These conditions resulted in a complete loss of leukemia cells from marrows which initially showed 95% or greater replacement with lymphoblasts. The culture conditions were also found to favor the growth of hemopoietic stem cells and the surviving cultured cells produced sufficient numbers of these cells to protect lethally irradiated (950 rads) synegeneic mice. The irradiated recipients of the cultured marrow did not develop leukemia during the 180 days of observation post-irradiation, indicating the absence of leukemia cells in the inocula. A loss of leukemia cells in vitro occurred in cultures with and without the addition of hydrocortisone to the medium. Hydrocortisone was shown to have a stimulating effect on maintenance of hemopoietic stem cells, granulocyte progenitors and granulopoiesis in these cultures.     

In vitro cloning of hemopoietic cells.

Semisolid cloning systems are now available to detect the specific progenitor cells of neutrophilmacrophages, eosinophils, megakaryocytes and erythroid cells. Colony proliferation in vitro with the production of mature progeny requires stimulation by glycoprotein regulators specific for each hemopoietic class. Two of these, erythropoietin and GM-CSF have been purified. A new cloning system has been developed using spleen conditioned medium that detects multipotential hemopoietic cells in the mouse.     

Differentiation pathways of pluripotent hemopoietic stem cells in long-term mouse bone marrow culture

Differentiation pathways of CFU-S were examined in mouse bone marrow long-term culture system. E/G ratios of non-adherent CFU-S in this system increased from 2 to 7-9 by 2-3 weeks of culture and then fluctuated during the culture period. On the other hand, E/G ratios of adherent CFU-S were lower than that of non-adherent CFU-S, and always remained under 2. Some of the supernatants collected from culture flasks at weekly intervals increased E/G ratios of normal bone marrow CFU-S after 18-20 h of incubation. These results suggest that the differentiation of CFU-S is controlled by humoral factors, secreted from yet unknown cells in bone marrow, in this system.     

An immature immunophenotype of bone marrow mast cells predicts for multilineage D816V KIT mutation in systemic mastocytosis

D816V KIT mutation of bone marrow (BM) mast cells (MC) is a common feature to systemic mastocytosis (SM) patients. Nevertheless, occurrence of the KIT mutation in BM cell compartments other than MC is associated with progression to more aggressive forms of the disease and poor outcome in indolent SM (ISM). Here, we assessed the potential association between the immunophenotype of MC and multilineage KIT mutation in the BM of SM patients through the investigation of the flow cytometric protein expression profile (PEP) of bone marrow mast cells (BMMC) from 70 control individuals and 206 SM patients, classified according to the WHO (World Health Organization), and the degree of involvement of BM hematopoiesis by the D816V KIT mutation; additionally, we developed a score-based class prediction algorithm for the detection of SM cases with multilineage mutation. Our results show that aberrant expression of CD25 with a Fc?RI(lo), FSC(lo), SSC(lo) and CD45(lo) immature phenotype of BMMC, in the absence of coexisting normal MC in the BM, was associated with multilineage involvement by the D816V KIT mutation, regardless of the diagnostic subtype of the disease (for example, indolent vs aggressive SM), which supports the utility of the immunophenotype of BMMC as a surrogate marker to screen for multilineage KIT mutation in ISM.     

Clonal analysis of the actions of the murine leukemia inhibitory factor on leukemic and normal murine hemopoietic cells

The in vitro actions of leukemia inhibitory factor (LIF) purified from Krebs tumor conditioned medium, were analyzed on murine leukemic M1 and WEHI-3B D+ cells and on normal hemopoietic progenitor cells. LIF has no observable effects on WEHI-3B D+ cells but rapidly induced macrophage differentiation and loss of clonogenicity in M1 cells, resulting in the formation of abortive clones or differentiating colonies of reduced size and number. These effects were observable within one to two cell divisions in the presence of LIF and were irreversible. Addition of macrophage-colony-stimulating factor (CSF) but not granulocyte/macrophage-CSF, granulocyte-CSF, or multi-CSF reduced the LIF-induced suppression of colony numbers and size. G-CSF had a slower differentiation-inducing action on M1 cells than LIF but potentiated the differentiation-inducing effects of low concentrations of LIF. LIF had no colony-stimulating activity for normal granulocyte-macrophage progenitor cells and did not alter their quantitative responsiveness to CSF. However, culture of normal progenitor cells in the presence of LIF, but initial absence of CSF, reduced the survival of these cells. The differing actions of LIF and G-CSF on M1 leukemic cells suggest the existence of distinct mechanisms for inducing macrophage differentiation in these leukemic cells.     

Early disappearance of murine plasmocytoma stem cells in long-term bone marrow culture.

Long-term bone marrow culture (LTBMC) was evaluated as a purging procedure in the murine plasmocytoma MOPC-315s system. MOPC-315s cells injected in Balb-c mice rapidly proliferate both in marrow and spleen, where macroscopic tumor colonies develop. A linear relationship between the number of injected cells and spleen colonies was observed, consistent with the presence of 1 clonogenic myeloma stem cell out of 1800 cells. In vitro, MOPC-315s cells are easily identifiable as rosette-forming cells (RFC+) with trinitrophenil acid (TNP) coated sheep red blood cells. When bone marrow (BM) cells containing 20-40% RFC+ were seeded in LTBMC, RFC+ rapidly decreased and were no longer detectable by day 14 of culture. Clonal Ig gene rearrangement was evident at time 0, but it was no more detectable later on. In addition, cells taken at days 14 and 21 of culture were no more tumorigenic when injected in vivo. The results suggest the efficacy of the LTBMC for the in vitro elimination of myeloma cells, including the neoplastic stem cells.     

Retroviral src gene expression in continuous marrow culture increases the self-renewal capacity of multilineage hematopoietic stem cells

To define the action of the retroviral src gene on hematopoietic stem cells, C57BL/6 x DBA/2 (B6D2F1) mouse long-term marrow cultures were infected at initiation with Moloney murine leukemia virus (MuLV) pseudotypes of src-recombinant retroviruses with the src gene inserted in the env region of an amphotropic MuLV (src-Ampho), or in the gag region of Moloney MuLV (src-Mo). Other cultures were infected with Friend spleen focus-forming virus polycythemia-inducing strain (SFFVp), Moloney MuLV, or amphotropic MuLV, or were uninfected controls. Harvested nonadherent cells were tested weekly for multilineage, granulocyte-erythroid-megakaryocyte macrophage (CFU-GEMM) colony formation in vitro in recombinant murine IL-3 and erythropoietin, and individual colonies were removed, split 1:2, with half of each replated for in vitro self-renewal and the other half examined morphologically for number of hematopoietic cellular lineages, or tested for release of MuLV and src virus. Cultures infected with src-Ampho, src-Mo, or SFFVp demonstrated a significant increase in cumulative nonadherent cell and CFU-GEMM production. There was prolonged self-renewal over seven serial transfers of individual CFU-GEMM from src virus-infected cultures over seven serial transfers, and five of 61 individual colonies from the second or third generations contained detectable v-src gene sequences, but none released detectable src virus. Self-renewal of CFU-GEMM was similar to that with permanent IL-3-dependent cell line B6SUtA. In contrast, MuLV-infected or control uninfected cultures produced fewer cells, and self-renewal of CFU-GEMM did not exceed three generations. IL-3-dependent clonal hematopoietic progenitor cell lines, derived from each culture group, formed no detectable tumors in vivo; however, each released the original helper and/or transforming virus. Adherent cell lines, derived from src-Ampho-infected cultures released src virus and formed fibro-sarcomas in vivo. The data support the conclusion that src-recombinant virus expression in long-term marrow cultures increases the self-renewal capacity of multilineage hematopoietic stem cells.     

CBFbeta-SMMHC slows proliferation of primary murine and human myeloid progenitors.

CBFbeta-SMMHC is expressed in 8% of acute myeloid leukemias and inhibits AML1/RUNX1. In this study, murine marrow or human CD34(+) cells were transduced with retroviral or lentiviral vectors expressing CBFbeta-SMMHC or two mutant variants. CBFbeta-SMMHC reduced murine or human myeloid cell proliferation three- to four-fold in liquid culture relative to empty vector-transduced cells, during a period when vector-transduced cells accumulated five-fold and human cells 20-fold. CBFbeta-SMMHC decreased the formation of myeloid, but not erythroid, colonies two- to four-fold, and myeloid colonies expressing CBFbeta-SMMHC were markedly reduced in size. However, CBFbeta-SMMHC did not slow differentiation to granulocytes or monocytes. Neither CBFbeta-SMMHC(Delta2-11), which does not bind AML1, nor CBFbeta-SMMHC(DeltaACD), which does not multimerize or efficiently bind corepressors, slowed proliferation or reduced myeloid colonies. CBFbeta-SMMHC increased the G1/S ratio 1.4-fold. AML1 had an effect opposite to CBFbeta-SMMHC, stimulating proliferation of murine myeloid progenitors 2.0-fold in liquid culture. Thus, CBFbeta-SMMHC directly inhibits the proliferation of normal myeloid progenitors via inhibition of AML1 and dependent upon the integrity of its assembly competence domain. These findings support the development of therapeutics that target the ability of CBFbeta-SMMHC to interact with AML1 or to multimerize via its assembly competence domain.     

The sensitivities of human and murine hemopoietic cells exposed to cytotoxic drugs in an in vivo culture system.

An agar diffusion chamber technique has been used to measure the sensitivities of human and murine hemopoietic colony-forming cells to cytotoxic drugs. The cells were held in i.p. diffusion chambers and exposed to the cytotoxic drugs by i.v. injection of the host mice. This method allows some account to be taken of the continuous changes in activity during the metabolic degradation of the drug. To determine how far this system provides a valid measure of the sensitivity of the cells in hemopoietic tissue, the responses of mouse bone marrow exposed to the drugs in situ in the donor mouse were compared with those of mouse cells exposed in diffusion chambers. The dose-response curves for cyclophosphamide and 5-fluorouracil were exponential in all cases. Exponential survival curves were also seen when human and mouse colony-forming cells were exposed to vinblastine or methotrexate in diffusion chambers. The plateaus seen when mouse cells were exposed to these drugs in situ could, however, be regained by omitting agar from the chambers during the exposure period. The results indicate that there are differences between the sensitivities of human and mouse marrow cells to cytotoxic drugs and that any extrapolation from mouse to humans must be viewed with caution.     

Differential seeding of injected hemopoietic precursor cells in the bone marrow and spleen of irradiated mice

The seeding efficiency was determined of syngeneic granulocyte, macrophage, erythroid/mixed and megakaryocyte colony-forming cells (G-GFC, GM-CFC, M-CFC, E/Mix-CFC, MEG-CFC) in the femoral bone marrow and spleen of lethally-irradiated C57BL mice. The overall seeding efficiency of CFC's was similar to that for multipotential stem cells (CFU-S) in the marrow but in the spleen CFC seeding efficiency was ten-fold lower than for CFU-S. Two and a half hours after transplantation of 10⁷ bone marrow cells, the relative frequencies of E/Mix-CFC's and M-CFC's recovered from the recipient marrow were higher than in the injected marrow population. However the relative frequencies of CFC's recovered from the spleen corresponded closely to those of the injected marrow population.     

Recombinant interleukin 2 and anti-Tac influence the growth of enriched multipotent hemopoietic progenitors: proposed hypotheses for different responses in early and late progenitors

Experiments were designed to evaluate the effect of recombinant IL-2 on growth of hemopoietic precursors from different sources (normal cord blood and bone marrow, and PB from CGL patients). For this purpose, combined cell sorting techniques and multipotent colony forming cell assays were used. A monoclonal antibody BI-3C5, which recognizes an antigen present on early lympho-myeloid cells as well as on all colony forming cells (CFU-GEMM assay), was used to enrich the studied populations. Double colour immunofluorescence techniques were performed to analyse the expression of Tac antigen on early progenitors. The results showed that rIL-2 had a stimulatory effect on growth of enriched progenitors from the three sources and surprisingly that addition of anti-Tac did not abolish this effect. On the contrary, anti-Tac enhanced even more growth of these sorted BI-3C5 precursors, suggesting a ligand action of the antibody. More interestingly, a low percentage of cord cells (1 in 1000) expressed both BI-3C5 and Tac antigens. The vast majority of cells did not concomitantly express both markers. The double labelled cells had a lymphoid-like morphology, high nucleus/cytoplasmic ratio and 2-3 nucleoli. The results will be discussed focusing on early and late "stem" cell growth.     

Rapid and complete hemopoietic reconstitution following combined transplantation of autologous blood and bone marrow cells. A changing role for high dose chemo-radiotherapy?

The role of high dose chemo-radiotherapy with autologous bone marrow transplantation in the treatment of neoplasia remains to be clearly defined. Because of the iatrogenic morbidity, mortality and high cost of the supportive care required during the post-transplantation period of prolonged marrow aplasia, intensive therapy remains a sophisticated procedure lacking proper evaluation in clinical trials. We report here that when autologous bone marrow cells are supplemented with a small number of peripheral blood nucleated cells collected after prior myelosuppressive chemotherapy, complete hematological recovery is so prompt that myeloid toxicity appears no longer the major limiting factor of high-dose chemo-radiotherapy. The increased therapeutic index made possible by the procedure will allow us to address the issue of whether intensive cytoreductive therapy can be useful as initial treatment of selected tumors with curative intent.