Further studies on mechanisms of abnormal prostaglandin response by chronic myelogenous leukaemia granulocyte/macrophage progenitors

Prostaglandins of the E series (PGE) have varying effects in vitro on normal granulocyte/macrophage (CFU-GM) progenitors. When added directly to cultures, PGE inhibits growth of normal 7 and 14 day bone marrow CFU-GM in a dose-dependent manner, while CML CFU-GM are refractory to PGE inhibition. The plant diterpene forskalin, a potent activator of intracellular cyclic AMP, inhibited normal and CML CFU-GM, indicating that the response of CML cells to increased intracellular cyclic AMP is normal. Low dose forskalin, which potenfiates activators of adenyl cyclase, showed additive effects with PGE on normal CFU-GM cells, however, showed no additive effects of PGE and forskalin, suggesting that PGE failed to activate adenyl cyclase. Normal CFU-GM incubated with PGE for two hours showed a significant increase in CFU-GM growth, and removal of adherent cells prior to exposure to PGE abrogated this effect. CML cells did not respond to a 2-h exposure to PGE, and removal of adherent cells from these cultures had no effect. Normal and CML CFU-GM showed dose-dependent increases in proliferation in the presence of PGF₂. These studies confirm that CML CFC-GM are refractory to inhibition by PGE, and show that these cells respond normally to increased levels of intracellular cyclic AMP. Response of CML cells to PGF_2α is normal, and conversion of PGE to PGF could result in increased granulocyte progenitor proliferation.     

Defect of Stromal Microenvironment in Long Term Bone Marrow Cultures of Patients with Acute and Chronic Myelogenous Leukemias

Inhibition of normal hemopoiesis is a regular finding in acute (AML) and chronic (CML) myelogenous leukemias and functional abnormalities of the hemopoietic microenvironment may be involved in this regard. In order to evaluate this possibility we studied the formation of adherent stromal cell layers (ASCL) in long term bone marrow cultures (LTBMC) of 7 patients with CML and 7 patients with AML and examined the ability of these ASCLs to support hemopoiesis after irradiation and a second inoculation of bone marrow cells. The formation of ASCLs was significantly impaired in CML and AML. These CML patients and 3 AML patients did not form typical ASCLs and the cellularity of these layers was greatly reduced. Colony forming unit granulocyte-macrophage (CFU-GM) production from bone marrow cells seeded on normal irradiated ASCLs peaked at week 3 and then gradually decreased by week 8. In CML and AML cocultures CFU-GM numbers decreased rapidly to zero by weeks 4-6 and did not differ Significantly from the control cultures which did not contain preestablished ASCLs beginning from week 3. It is suggested that there may be a functional microenvironmental defect in CML and AML that may play a role in the pathogenesis of inhibition of normal hemopoiesis in these diseases.     

Recombinant interferon-alpha-2C in chronic myelogenous leukaemia: relationship of sensitivity of committed haematopoietic precursor cells in vitro (BFU-E, CFU-GM, CFU-Meg) and clinical response

In an ongoing phase-II trial we aimed to predict clinical responsiveness of Philadelphia chromosome positive (Ph1+) chronic myelogenous leukaemia (CML) to recombinant IFN-alpha-2C (rIFN-alpha-2C) by pretesting in vitro. From five normal controls and 14 CML patients in chronic phase, bone marrow samples were taken before treatment and tested for antiproliferative activity by rIFN-alpha-2C, using a microagar culture system for BFU-E, CFU-GM, and CFU-Meg. Light-density nucleated bone marrow cells were stimulated for BFU-E and CFU-Meg colony formation with Alpha medium containing 20% serum obtained from a patient with severe aplastic anaemia. CFU-GM growth was induced with conditioned medium from the cell line GCT. In normal controls BFU-E, CFU-GM and CFU-Meg colony formation was inhibited by rIFN-alpha-2C in a dose-dependent manner. BFU-E proved to be the most sensitive cell lineage (IC50: 65; range: 53-116 U/ml) whereas CFU-GM was about 20 times less sensitive (IC50: 643; range: 480-897 U/ml). The sensitivity of CFU-Meg ranged between these two colony types with 50% growth inhibition at an IFN concentration of 160 (range: 68-246 U/ml). A heterogeneous response to rIFN-alpha-2C in vitro was seen in CML patients. Three of the 14 patients were 'resistant' to rIFN-alpha-2C in vitro with IC50 values for BFU-E, CFU-GM and/or CFU-Meg colony formation greater than 10(4) U/ml. Patients were subsequently treated with a daily dose of rIFN-alpha-2C of 5 x 10(6) U. Four patients achieved a complete and six achieved a partial haematological response. Of the four non-responders three rapidly progressed into blastic crisis. Thus it was seen that treatment failure to interferon was accompanied by IFN-resistance in vitro of BFU-E, CFU-GM and/or CFU-Meg colony formation by bone marrow precursors (p less than 0.01). These results suggest a predictive value of IFN-sensitivity testing in vitro in Ph1 + CML.     

Growth advantage of chronic myeloid leukemia CFU-GM in vitro: survival to growth factor deprivation, possibly related to autocrine stimulation, is a more common feature than hypersensitivity to GM-CSF/IL3 and is efficiently counteracted by retinoids +- alpha-interferon.

Bcr/abl fusion gene, in experimental models, induces survival to growth factor deprivation and hypersensitivity to IL3. However, conflicting data were reported about chronic myeloid leukemia (CML) progenitors. We investigated the responsiveness of purified CML CFU-GM to GM-CSF/IL3 and their survival to growth factor deprivation. CFU-GM hypersensitivity to IL3 and/or GM-CSF was found in 3/11 CML cases only. CML CFU-GM survived well in stroma-free 'mass' culture (5 x 10(4) cells/ml) without cytokine addition, up to day 11, average recovery being around 95% in medium + 10% fetal bovine serum and 67-81% in serum-free medium. Conversely, normal progenitors declined steadily, particularly after extensive purification (18 +/- 10% recovery at the 7th day), and in serum-free medium (4 +/- 6% recovery). By contrast, normal and CML CFU-GM declined in a similar way in limiting dilution cultures (1-10 cells/50 microl). We also investigated the effects of retinoic acid and alpha-interferon on CFU-GM survival. Both all-trans- and 13-cis retinoic acid, particularly in combination with alpha-interferon, reduced CML CFU-GM recovery down to normal progenitors' values. In conclusion, hypersensitivity to CSFs is rare in CML, whereas resistance to growth factor deprivation has been confirmed in mass, but not in limiting, dilution cultures. Both stereoisomers of retinoic acid, at therapeutic concentrations and in combination with alpha-interferon, can overcome the survival advantage of CML progenitors.     

c-abl function in normal and chronic myelogenous leukemia hematopoiesis: in vitro studies with antisense oligomers.

By using antisense oligomers the functional role of the c-abl proto-oncogene in the in vitro growth of bone marrow hematopoietic progenitors from normal subjects and patients with chronic myelogenous leukemia (CML) has been evaluated. Light density bone marrow cells (LDBMs) were depleted of adherent cells, pre-incubated for 15 h with the appropriate oligomer at a concentration of 14 microns, and then plated in methylcellulose for the evaluation of colony formation. Both anti-exon Ia and anti-exon Ib antisense oligomers produced a significant inhibition of normal day 14 CFU-GM growth in vitro (n = 5, 41 +/- 11%, and 36 +/- 7%, respectively; p less than 0.01). In contrast, normal BFU-E growth was not significantly influenced by antisense oligomers (n = 5, 14 +/- 21% and 7 +/- 19%, respectively; p less than 0.05). These findings were confirmed by plating CD34 positive progenitors. When interleukin 3 (IL-3) (100 ng/ml) was added to the culture medium during the preincubation of LDBMCs, the inhibitory effects of antisense oligomers on normal CFU-GM growth were abolished. Seven patients with CML were also studied, all of whom had cytogenetic evidence of 100% clonal hematopoiesis. In five patients in the chronic phase, antisense oligomers were inhibitory on in vitro growth of both day 14 CFU-GM (37 +/- 20% and 37 +/- 15%, p less than 0.05) and BFU-E (45 +/- 15% and 41 +/- 11%, p less than 0.05), and this inhibition was not removed by pre-incubation with IL-3. No significant effect was observed on cluster or colony formation in two patients with CML in accelerated or blastic phase, and on in vitro growth of clonogenic cells from the Ph1-positive K-562 cell line. These findings (i) confirm previous observations showing a lineage specific requirement of c-abl function in normal hematopoiesis, and (ii) suggest that the residual c-abl expression has a role in chronic phase CML hematopoiesis, as its inhibition impairs both myeloid and erythroid colony formation in vitro.     

All-trans-retinoic acid effects the growth, differentiation and apoptosis of normal human myeloid progenitors derived from purified CD34+ bone marrow cells.

We have previously shown that all-trans retinoic acid (ATRA) increases the number of CFU-GM colonies grown from unseparated human bone marrow cells with crude sources of colony stimulating factors. In this study, we further characterized the effect of ATRA on the growth of CFU-GM stimulated by individual cytokines from multiple samples of CD34+ enriched or purified human bone marrow cells. The number of IL-3- or GM-CSF-induced CFU-GM with 3 x 10(-7) M ATRA was 3.25+/-1.13, and 2.17+/-0.8-fold greater respectively, compared to controls without ATRA, while G-CSF had no effect and the ratio of colony-induced with or without ATRA was 1.06+/-0.17 (P = 0.00012). No colonies grew with ATRA + IL-6 or ATRA without a cytokine. Maximum enhancing effect on IL-3-induced CFU-GM occurred when ATRA was added on day 2, gradually diminished when delaying ATRA, and in cultures of day 9 or older adding ATRA had no effect. In 14 days liquid cultures of purified CD34+ cells with IL-3, ATRA increased the number of myeloid differentiated cells to 91-95%, compared to 37-70% with IL-3 alone. In addition, the number of apoptotic cells using the annexin V method increased after 14 days from 5.1% with IL-3 to 17.1% with IL-3 + ATRA and by the TUNEL in situ method from 10-26% to 60-95%, respectively. This study demonstrates that ATRA consistently enhances the growth of myeloid progenitors from CD34+ cells. This effect is dependent on the stimulating cytokine, suggesting the myeloid cells responding to ATRA are the less mature CFU-GMs that are targets of IL-3 and GM-CSF and not the G-CSF-responding mature progenitors. The growth stimulation by ATRA and IL-3 is also associated with granulocyte differentiation and increased apoptosis. These studies further suggest a potential role of pharmacological doses of ATRA on the development of normal human hematopoietic cells.     

Studies on chronic myeloid leukemia cell populations with colony-forming abilities in PHA-leukocyte feeder and robinson assays

Investigation of leukemic colony-forming cells (CFC) in PHA-supplemented cultures requires removal of T lymphocyte precursors prior to culture. Using a method of discontinuous density gradient centrifugation with concurrent depletion of E-rosette forming cells, T lymphocytes were effectively separated from light density CML bone marrow and blood cell fractions. Consequently, in light density fractions (1.056 and 1.059 g/ml) pure leukemic colony growth was obtained in the PHA-leukocyte feeder (PHA-l.f.) assay. Fraction 1.062 g/ml also yielded pure leukemic colonies in most experiments. Comparison of the density distributions of leukemic PHA-l.f. CFC and Robinson CFC revealed that both CFC populations had congruent density profiles in most patients. In others PHA-l.f. CFC were found to be of somewhat higher density than Robinson CFC. The most striking divergence was apparent in a patient in blast crisis. The findings suggest that different subsets of precursor cells within the CML population proliferate in PHA-l.f. and Robinson colony methods. Both colony techniques are thus potentially useful for discriminating subpopulations of colony-forming cells in chronic myeloid leukemia.     

Comparative Effect of Heme Analogues on Hematopoiesis in Lymphoproliferative Disorders

Anemia is a common characteristic of lymphoproliferative disorders (LPD) and the impairment of blood formation in these disorders is not fully understood. Heme synthesis and the heme degradative enzyme heme oxygenase are critical to hematopoietic differentiation and disturbances may contribute to anemic states. Tin protoporphyrin (SnPP) is a potent inhibitor of heme oxygenase, and has proven to be a useful clinical agent. Bone marrow cells from seven patients with LPD were studied for their in vitro hemopoietic response to growth factors and SnPP. Heme oxygenase mRNA levels were determined by Northern blot analysis of bone marrow samples. Quantitation of hematopoiesis in cultures with erythropoietin or GM-CSF revealed adequate CFU-E, BFU-E and CFU-GM growth by LPD bone marrow. Inclusion of 10 μM SnPP in cultures was found to significantly enhance CFU-E/BFU-E growth by LPD marrows, whereas Zinc protoporphyrin had a marked inhibitory effect. Little or no effect by SnPP was seen on CFU-GM. In contrast, normal bone marrow cultures failed to show an enhanced response to 10 μM SnPP. Analysis of heme oxygenase mRNA levels revealed that LPD marrows had elevated expression of heme oxygenase mRNA as contrasted with normals. Furthermore, measurements revealed that heme oxygenase activity was markedly suppressed by SnPP in the LPD bone marrow cultures. Results lend further support to the importance of heme oxygenase in the differentiation process. Although LPD bone marrow cells may respond to erythropoietin in vitro, in stressed conditions where heme oxygenase is elevated, suppression of heme oxygenase may potentiate the erythropoietic response in this disease.     

Opposite effect of tumor necrosis factor alpha on granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor-dependent growth of normal and leukemic hemopoietic progenitors.

The effect of recombinant human tumor necrosis factor alpha (TNF-alpha) on normal and chronic myeloid leukemia granulocyte-macrophage progenitors (CFU-GM) growing in semisolid agar cultures in the presence of recombinant granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor was studied. Granulocyte-macrophage colony-stimulating factor-dependent growth of normal and chronic myeloid leukemia bone marrow CFU-GM was greatly enhanced by TNF-alpha at doses of 0.1 to 100 units/ml. Growth enhancement included neutrophil, eosinophil, and monocyte-macrophage colonies and clusters at 7 and 14 days of culture. Since similar results were achieved with highly enriched progenitor cell populations, devoid of accessory cells, an indirect effect on CFU-GM growth through the release by accessory cells of other cytokines upon TNF-alpha stimulation was thus ruled out. By contrast, the same doses of TNF-alpha inhibited the growth of normal CFU-GM in granulocyte colony-stimulating factor-dependent cultures. Taken together, our findings indicate that the final effect of TNF-alpha on normal bone marrow granulocyte-macrophage progenitor growth is dependent on the specific growth factor interacting with it, and that both normal and chronic myeloid leukemia CFU-GM are equally responsive to the combined effects of TNF-alpha and a given colony-stimulating factor.     

Neuropilin-1某因在髓细胞白血病和正常人骨髓基质细胞中的表达(英文)

目的了解 neuropilin-1(NP-1)基因在髓细胞白血病(AML 和 CML)患者及正常人骨髓基质细胞中的表达情况。方法收集12例 AML、14例 CML 和20例正常对照骨髓标本,分离单个核细胞。进行体外长期培养,收集贴壁细胞(骨髓基质细胞)。利用逆转录-聚合酶链反应分别检测3组骨髓基质细胞中 NP-1基因的表达。结果成功建立了 AML、CML 和正常人骨髓基质细胞培养方法,NP-1基因在 AML、CML 骨髓基质细胞中的表达率分别为47.1%和50%,明显低于正常对照(85%)。结论 NP-1基因可表达于部分 AML、CML 和大部分正常人的骨髓基质细胞中,其在髓细胞白血病患者骨髓基质细胞中的低表达,可能与其调节造血功能异常有关。     

Neuropilin-1基因在髓细胞白血病和正常人骨髓基质细胞中的表达

目的了解neuropilin-1(NP-1)基因在髓细胞白血病(AML和CML)患者及正常人骨髓基质细胞中的表达情况。方法收集12例AML、14例CML和20例正常对照骨髓标本,分离单个核细胞。进行体外长期培养,收集贴壁细胞(骨髓基质细胞)。利用逆转录-聚合酶链反应分别检测3组骨髓基质细胞中NP-1基因的表达。结果成功建立了AML、CML和正常人骨髓基质细胞培养方法,NP-1基因在AML、CML骨髓基质细胞中的表达率分别为47.1%和50%,明显低于正常对照(85%)。结论NP-1基因可表达于部分AML、CML和大部分正常人的骨髓基质细胞中,其在髓细胞白血病患者骨髓基质细胞中的低表达, 可能与其调节造血功能异常有关。     

Comparative effect of heme analogues on hematopoiesis in lymphoproliferative disorders

Anemia is a common characteristic of lymphoproliferative disorders (LPD) and the impairment of blood formation in these disorders is not fully understood. Heme synthesis and the heme degradative enzyme heme oxygenase are critical to hematopoietic differentiation and disturbances may contribute to anemic states. Tin protoporphyrin (SnPP) is a potent inhibitor of heme oxygenase, and has proven to be a useful clinical agent. Bone marrow cells from seven patients with LPD were studied for their in vitro hemopoietic response to growth factors and SnPP. Heme oxygenase mRNA levels were determined by Northern blot analysis of bone marrow samples. Quantitation of hematopoiesis in cultures with erythropoietin or GM-CSF revealed adequate CFU-E, BFU-E and CFU-GM growth by LPD bone marrow. Inclusion of 10 μM SnPP in cultures was found to significantly enhance CFU-E/BFU-E growth by LPD marrows, whereas Zinc protoporphyrin had a marked inhibitory effect. Little or no effect by SnPP was seen on CFU-GM. In contrast, normal bone marrow cultures failed to show an enhanced response to 10 μM SnPP. Analysis of heme oxygenase mRNA levels revealed that LPD marrows had elevated expression of heme oxygenase mRNA as contrasted with normals. Furthermore, measurements revealed that heme oxygenase activity was markedly suppressed by SnPP in the LPD bone marrow cultures. Results lend further support to the importance of heme oxygenase in the differentiation process. Although LPD bone marrow cells may respond to erythropoietin in vitro, in stressed conditions where heme oxygenase is elevated, suppression of heme oxygenase may potentiate the erythropoietic response in this disease.     

The effect of the leukemic cell line HL60 and acute myeloblastic leukemic cells before and after induction of differentiation on normal pluripotent hematopoietic progenitors (CFU-GEMM)

A leukemic cell line (HL60) and acute myeloblastic leukemia (AML) cells from six patients were co-cultured with normal marrow cells to assess their effects on growth of normal CFU-GEMM. The effects of the following inducers: 12-0-tetradecanoyl-phorbol-13-acetate (TPA), retinoic acid (RA), dimethylsulphoxide (DMSO), 1-25 (OH) D3 (Vitamin D3) and PHA-LCM on both the HL60 and AML cells, were studied. Inhibition of growth of normal CFU-GEMM was observed in the co-cultures in the presence of 1 X 10(4) HL60 or AML leukemic cells/ml. This inhibition was reversed by pretreating the HL60 line with vitamin D3, TPA and RA. No effect on growth of CFU-GEMM was noted when DMSO and PHA-LCM were used. AML cells were morphologically induced to differentiate by TPA or RA in all six cases. In three cases, reversal of inhibition of growth of normal pluripotent hemopoietic progenitors occurred and in three the inhibition of growth persisted. Regulation of inhibition by different inducers did not seem to correlate in all cases with morphological differentiation.     

No preferential sensitivity of clonogenic AML cells to ASTA-Z-7557

ASTA-Z-7557, an in vitro active metabolite of cyclophosphamide, has recently been introduced to purge autologous bone marrow grafts of patients with AML. The rationale of this approach assumes a relatively higher sensitivity of leukemic cells to the drug as compared to that of normal marrow precursors. We have investigated in direct comparison the sensitivity to ASTA-Z-7557 of normal bone marrow progenitors (GM-CFC and BFU-E) and clonogenic leukemic cells (L-CFC). Normal bone marrow cells and purified leukemic blast cells were exposed to varying concentrations of the drug. Dose-response relationships did not indicate a selective cytotoxic susceptibility of L-CFC to ASTA-Z-7557. The recovery of bone marrow precursors following exposure to ASTA-Z-7557 depended on the cell concentration during exposure and was higher for 2 X 10(7) cells/ml than for 1 X 10(6)/ml. To mimic minimal residual leukemia cell mixtures of 95% irradiated normal bone marrow cells with 5% leukemic blast cells were exposed to ASTA-Z-7557. In this mixture killing of L-CFC was largely decreased. These data suggest that in vitro incubation of autologous bone marrow grafts of patients with minimal residual leukemia with ASTA-Z-7557 might not offer a therapeutic advantage.     

PHA-induced colony formation in acute non-lymphocytic and chronic myeloid leukemia

A method which has previously been introduced for growing colonies in vitro from T-lymphocytic cells in normal subjects, has been applied to studying the growth of colonies from the bone marrow and blood of patients with acute non-lymphocytic leukemia and chronic myeloid leukemia. The technique consists of an underlayer of agar containing irradiated leukocytes and a liquid overlayer containing PHA. In leukemic patients, the assay permitted the formation of T-lymphocytic as well as leukemic colonies. Removal of the E-rosette forming cells before culture resulted in the appearance of mainly leukemic colonies. Cytogenetic analysis demonstrated the presence of the acquired karyotypic changes characteristic of the leukemic cells of these patients in the colony cells. Study of eight cases of acute non-lymphocytic leukemia, four cases of blast crisis of CML, and seven cases of CML chronic phase revealed the assay to be efficient in growing large numbers of leukemic blast colonies, as compared to the Robinson culture assay where large colony formation is only found in chronic leukemia [10]. Removal of the progenitors of lymphocytic colonies was sometimes incomplete in acute leukemia but not in CML.     

Butyric acid: Inhibition of non-leukemic and chronic myeloid leukemia granulocyte macrophage clonal growth

Butyric acid has been shown to inhibit the growth of several established tumor cell lines and to induce either granulocytic or erythroid differentiation in different human and murine leukemic cell lines. The dose-dependent effect of butyric acid was testedin vitro on the clonal growth of granulocyte macrophage progenitors in 13 patients with chronic myeloid leukemia (CML) and compared with control bone marrow and peripheral blood responses. The growth of myeloid progenitors from both healthy donors and non-leukemic and leukemic patients was almost completely inhibited by 1.0 mM butyric acid. At 0.5 mM butyric acid, inhibition of CML progenitors, both from chronic phase and blastic phase patients, was significantly greater (P < 0.01) than bone marrow from non-leukemic patients and peripheral blood controls. Butyric acid, a 4-carbon compound, was the most potent inhibitor of six short chain fatty acids tested on CML myeloid progenitors.     

Effect of lymphokine-activated killer cell fraction on the development of human hematopoietic progenitor cells

Lymphokine-activated killer (LAK) cells from cultures of human peripheral blood mononuclear cells with recombinant interleukin-2 (rIL-2) have been clinically used in adoptive immunotherapy for cancer patients. To study their influence on human hematopoiesis, the LAK cell fraction was cocultured with marrow nonphagocytic cells from normal subjects in an assay system of hematopoietic progenitors. The fraction suppressed colony growth from relatively mature erythroid progenitors in a dose-dependent manner. Although unactivated cells, which were produced without IL-2, augmented the growth of early erythroid progenitors, the LAK cell fraction did not. This fraction suppressed colony growth from mature granulocyte-macrophage progenitors (day 7 CFU-GM) especially with an 18-h preincubation prior to coculture. It also suppressed both immature granulocyte-macrophage progenitors (day 14 CFU-GM) and multipotential hematopoietic progenitors. The suppressive effects were observed on colony growth from autologous marrow cells as well as allogeneic marrow cells. The suppression of day 7 CFU-GM colony growth by supernatants due to preincubation with marrow cells and the LAK cell fraction suggested that the humoral factor contributes to the suppression by the LAK cell fraction. These data suggest that the LAK cell fraction suppresses the development of human hematopoietic progenitor cells.     

Acidic isoferritins do not suppress differentiation of mouse myeloid leukemic M1 cells

The differentiation of mouse myeloid leukemia line cells (M1) into macrophages or granulocytes has been reported. Resistant M1 cells which did not differentiate even with a high concentration of inducer of differentiation were isolated from M1 cells. The conditioned medium of the resistant M1 cells (RCM) inhibited the induction of differentiation of M1 cells and the formation of macrophage and granulocyte colonies of normal mouse bone marrow cells. Acidic isoferritins known as negative regulators of normal bone marrow cells (CFU-GM) failed to inhibit the induction of differentiation and growth of M1 cells. The RCM treated with anti-acidic isoferritin serum could inhibit the induction of differentiation of M1 cells as did the untreated RCM. The activities, in RCM, inhibiting growth and differentiation of the normal bone marrow cells were partly neutralized by treatment with the antiserum but most of the activities remained. These results suggest that growth and differentiation of the mouse myeloid leukemia M1 cells are not regulated by acidic isoferritins and other inhibitory activities affecting normal bone marrow colony formation, in addition to acidic isoferritins, are released from M1 cells.     

Antigenic characteristics of circulating CFU-GM in chronic granulocytic leukaemia resemble those of CFU-GM in normal marrow and differ from those in normal blood

We studied the surface antigenic determinants of myeloid progenitor cells (Day 7 CFU-GM, Day 14 CFU-GM and BFU-E) in the peripheral blood and bone marrow of patients with chronic granulocytic leukaemia (CGL) and normal subjects by complement-mediated cytotoxicity with a panel of 8 selected murine monoclonal antibodies (McAbs) followed by culture in methyl cellulose. All classes of progenitor cell studied expressed HLA-DR antigens and also expressed other antigens recognized by two of the McAbs (S3-13 and S17-25) with myeloid specificity. Two other McAbs (R1.B19 and WGHS.29.1). Recognized antigens on Day 14 CFU-GM derived from normal marrow but not on those from normal blood. The pattern of reactivity of Day 14 CFU-GM from the blood of patients with CGL resembled to a considerable extent that of CFU-GM from normal marrow and differed from that of CFU-GM from normal blood. BFU-E from the blood of patients with CGL reacted with these McAbs in a manner very similar to that of BFU-E from normal blood; however the same two McAbs (R1.B19 and WGHS.19.1) reacted with a much higher proportion of the BFU-E from the marrows of CGL patients than of normal subjects. Our data are consistent with the hypothesis that normal blood-derived CFU-GM are more primitive than marrow-derived CFU-GM; however the CFU-GM in the circulation in CGL differ from those in normal blood, perhaps because they reflect overflow from or exchange with a hyperplastic marrow population.