Contribution of mutant HSC clones to immature and mature cells in MDS and CMML, and variations with AZA therapy

Myelodysplastic neoplasms (MDSs) and chronic myelomonocytic leukemia (CMML) are clonal disorders driven by progressively acquired somatic mutations in hematopoietic stem cells (HSCs). Hypomethylating agents (HMAs) can modify the clinical course of MDS and CMML. Clinical improvement does not require eradication of mutated cells and may be related to improved differentiation capacity of mutated HSCs. However, in patients with established disease it is unclear whether (1) HSCs with multiple mutations progress through differentiation with comparable frequency to their less mutated counterparts or (2) improvements in peripheral blood counts following HMA therapy are driven by residual wild-type HSCs or by clones with particular combinations of mutations. To address these questions, the somatic mutations of individual stem cells, progenitors (common myeloid progenitors, granulocyte monocyte progenitors, and megakaryocyte erythroid progenitors), and matched circulating hematopoietic cells (monocytes, neutrophils, and naïve B cells) in MDS and CMML were characterized via high-throughput single-cell genotyping, followed by bulk analysis in immature and mature cells before and after AZA treatment. The mutational burden was similar throughout differentiation, with even the most mutated stem and progenitor clones maintaining their capacity to differentiate to mature cell types in vivo. Increased contributions from productive mutant progenitors appear to underlie improved hematopoiesis in MDS following HMA therapy.

RAS mutations drive proliferative chronic myelomonocytic leukemia via a KMT2A-PLK1 axis

Proliferative chronic myelomonocytic leukemia (pCMML), an aggressive CMML subtype, is associated with dismal outcomes. RAS pathway mutations, mainly NRASG12D, define the pCMML phenotype as demonstrated by our exome sequencing, progenitor colony assays and a Vav-Cre-NrasG12D mouse model. Further, these mutations promote CMML transformation to acute myeloid leukemia. Using a multiomics platform and biochemical and molecular studies we show that in pCMML RAS pathway mutations are associated with a unique gene expression profile enriched in mitotic kinases such as polo-like kinase 1 (PLK1). PLK1 transcript levels are shown to be regulated by an unmutated lysine methyl-transferase (KMT2A) resulting in increased promoter monomethylation of lysine 4 of histone 3. Pharmacologic inhibition of PLK1 in RAS mutant patient-derived xenografts, demonstrates the utility of personalized biomarker-driven therapeutics in pCMML.

Mast cell differentiation of leukemic blasts in diverse myeloid neoplasms: A potential pre-myelomastocytic leukemia condition

INTRODUCTION

Myeloid neoplasm with blasts showing mast cell (MC)-differentiation and MC-component less than 10% of all nucleated cells but not fulfilling the criteria for systemic mastocytosis with associated hematological neoplasm (SM-AHN) or myelomastocytic leukemia (MML) has not been described in the literature. Herein, we report a study of diverse myeloid malignancies with blasts showing MC-differentiation but not meeting the criteria for SM-AHN or MML. We also evaluated the utility of flow-cytometric immunophenotyping (FCI) in the characterization of immature-MCs (iMCs).

METHODS

We identified nine patients of myeloid neoplasms and studied their morphological, FCI, immunohistochemistry, cytogenetic and molecular characteristics. We also compared the immunophenotypic features of MCs from patient samples with control samples.

RESULTS

The study included patients with newly-diagnosed acute myeloid leukemia (n = 4), chronic myelomonocytic leukemia (n = 1), and chronic myeloid leukemia on follow-up (n = 4) showing MC differentiation in leukemic-blasts. These patients had mildly increased MCs (range, 0.5%-3%) in bone-marrow morphology, including immature-forms and did not meet the criteria for either SM-AHN or MML. On FCI, iMCs were positive for bright-CD117, heterogeneous-CD34, dim-to-negative-HLADR, and moderate-CD203c expression. Expression-levels of CD123 and CD38 were higher (p < 0.001) but CD33 and CD45 were lower in iMCs compared to mature-MC from control samples (p = 0.019 and p = 0.0037).

CONCLUSION

We reported a rare finding of MC differentiation of leukemic blasts in diverse myeloid neoplasms and proposed it as a potential pre-myelomastocytic leukemia condition. We described the distinct immunophenotypic signature of immature-MCs using commonly used markers and highlighted the utility of FCI for the diagnosis of this entity.

Cut-like homeobox 1 (CUX1) tumor suppressor gene haploinsufficiency induces apoptosis evasion to sustain myeloid leukemia

While oncogenes promote tumorigenesis, they also induce deleterious cellular stresses, such as apoptosis, that cancer cells must combat by coopting adaptive responses. Whether tumor suppressor gene haploinsufficiency leads to such phenomena and their mechanistic basis is unclear. Here, we demonstrate that elevated levels of the anti-apoptotic factor, CASP8 and FADD-like apoptosis regulator (CFLAR), promotes apoptosis evasion in acute myeloid leukemia (AML) cells haploinsufficient for the cut-like homeobox 1 (CUX1) transcription factor, whose loss is associated with dismal clinical prognosis. Genome-wide CRISPR/Cas9 screening identifies CFLAR as a selective, acquired vulnerability in CUX1-deficient AML, which can be mimicked therapeutically using inhibitor of apoptosis (IAP) antagonists in murine and human AML cells. Mechanistically, CUX1 deficiency directly alleviates CUX1 repression of the CFLAR promoter to drive CFLAR expression and leukemia survival. These data establish how haploinsufficiency of a tumor suppressor is sufficient to induce advantageous anti-apoptosis cell survival pathways and concurrently nominate CFLAR as potential therapeutic target in these poor-prognosis leukemias.

Correlation of RAS-Pathway Mutations and Spontaneous Myeloid Colony Growth with Progression and Transformation in Chronic Myelomonocytic Leukemia-A Retrospective Analysis in 337 Patients

Although the RAS-pathway has been implicated as an important driver in the pathogenesis of chronic myelomonocytic leukemia (CMML) a comprehensive study including molecular and functional analyses in patients with progression and transformation has not been performed. A close correlation between RASopathy gene mutations and spontaneous in vitro myeloid colony (CFU-GM) growth in CMML has been described. Molecular and/or functional analyses were performed in three cohorts of 337 CMML patients: in patients without (A, n = 236) and with (B, n = 61) progression/transformation during follow-up, and in patients already transformed at the time of sampling (C, n = 40 + 26 who were before in B). The frequencies of RAS-pathway mutations (variant allele frequency ≥ 20%) in cohorts A, B, and C were 30%, 47%, and 71% (p < 0.0001), and of high colony growth (≥20/10⁵ peripheral blood mononuclear cells) 31%, 44%, and 80% (p < 0.0001), respectively. Increases in allele burden of RAS-pathway mutations and in numbers of spontaneously formed CFU-GM before and after transformation could be shown in individual patients. Finally, the presence of mutations in RASopathy genes as well as the presence of high colony growth prior to transformation was significantly associated with an increased risk of acute myeloid leukemia (AML) development. Together, RAS-pathway mutations in CMML correlate with an augmented autonomous expansion of neoplastic precursor cells and indicate an increased risk of AML development which may be relevant for targeted treatment strategies.

Transcriptomic analysis implicates necroptosis in disease progression and prognosis in myelodysplastic syndromes

Myelodysplastic syndromes (MDS) are characterized by ineffective hematopoiesis and cytopenias due to uncontrolled programmed cell death. The presence of pro-inflammatory cytokines and constitutive activation of innate immunity signals in MDS cells suggest inflammatory cell death, such as necroptosis, may be responsible for disease phenotype. We evaluated 64 bone marrow samples from 55 patients with MDS or chronic myelomonocytic leukemia (CMML) obtained prior to (n = 46) or after (n = 18) therapy with hypomethylating agents (HMAs). RNA from sorted bone marrow CD34+ cells was isolated and subject to amplification and RNA-Seq. Compared with healthy controls, expression levels of MLKL (CMML: 2.09 log2FC, p = 0.0013; MDS: 1.89 log2FC, p = 0.003), but not RIPK1 or RIPK3, were significantly upregulated. Higher expression levels of MLKL were associated with lower hemoglobin levels at diagnosis (-0.19 log2FC per 1 g/dL increase of Hgb, p = 0.03). Significant reduction in MLKL levels was observed after HMA therapy (-1.06 log2FC, p = 0.05) particularly among nonresponders (-2.89 log2FC, p = 0.06). Higher RIPK1 expression was associated with shorter survival (HR 1.92, 95% CI 1.00-3.67, p = 0.049 by Cox proportional hazards). This data provides further support for a role of necroptosis in MDS, and potentially response to HMAs and prognosis. This data also indicate that RIPK1/RIPK3/MLKL are potential therapeutic targets in MDS.

Oligo-monocytic CMML and other pre-CMML states: Clinical impact, prognostication and management

Chronic myelomonocytic leukemia (CMML) is defined by myelodysplasia, pathologic accumulation of monocytes and a substantial risk to transform to secondary acute myeloid leukemia (sAML). In recent years, minimal diagnostic criteria for classical CMML and CMML-variants were proposed. Moreover, potential pre-stages of CMML and interface conditions have been postulated. Oligomonocytic CMML is a condition where the absolute peripheral blood monocyte count does not reach a diagnostic level but all other criteria for CMML are fulfilled. Among potential pre-stages of CMML, clonal and non-clonal conditions have been described, including idiopathic monocytosis (IMUS) and clonal monocytosis of unknown significance (CMUS). Patients with myelodysplastic syndromes (MDS), clonal cytopenia of unknown significance (CCUS), clonal hematopoiesis of indeterminate potential (CHIP) and idiopathic cytopenia of undetermined significance (ICUS) may also progress to CMML. The current article provides an overview of pre-CMML conditions and oligomonocytic CMML, with special reference to diagnostic criteria, differential diagnoses, clinical outcomes and management.

Somatic SETBP1 mutations in myeloid neoplasms

SETBP1 is a SET-binding protein regulating self-renewal potential through HOXA-protein activation. Somatic SETBP1 mutations were identified by whole exome sequencing in several phenotypes of myelodysplastic/myeloproliferative neoplasms (MDS/MPN), including atypical chronic myeloid leukemia, chronic myelomonocytic leukemia, and juvenile myelomonocytic leukemia as well as in secondary acute myeloid leukemia (sAML). Surprisingly, its recurrent somatic activated mutations are located at the identical positions of germline mutations reported in congenital Schinzel-Giedion syndrome. In general, somatic SETBP1 mutations have a significant clinical impact on the outcome as poor prognostic factor, due to downstream HOXA-pathway as well as associated aggressive types of chromosomal defects (-7/del(7q) and i(17q)), which is consistent with wild-type SETBP1 activation in aggressive types of acute myeloid leukemia and leukemic evolution. Biologically, mutant SETBP1 attenuates RUNX1 and activates MYB. The studies of mouse models confirmed biological significance of SETBP1 mutations in myeloid leukemogenesis, particularly associated with ASXL1 mutations. SETBP1 is a major oncogene in myeloid neoplasms, which cooperates with various genetic events and causes distinct phenotypes of MDS/MPN and sAML.

Cytogenetic and molecular abnormalities in chronic myelomonocytic leukemia

Chronic myelomonocytic leukemia (CMML) is a clonal stem cell disorder associated with peripheral blood monocytosis and an inherent tendency to transform to acute myeloid leukemia. CMML has overlapping features of myelodysplastic syndromes and myeloproliferative neoplasms. Clonal cytogenetic changes are seen in ~30%, whereas gene mutations are seen in >90% of patients. Common cytogenetic abnormalities include; trisomy 8, -Y, -7/del(7q), trisomy 21 and del(20q), with the Mayo-French risk stratification effectively risk stratifying patients based on cytogenetic abnormalities. Gene mutations frequently involve epigenetic regulators (TET2 ~60%), modulators of chromatin (ASXL1 ~40%), spliceosome components (SRSF2 ~50%), transcription factors (RUNX1 ~15%) and signal pathways (RAS ~30%, CBL ~15%). Of these, thus far, only nonsense and frameshift ASXL1 mutations have been shown to negatively impact overall survival. This has resulted in the development of contemporary, molecularly integrated (inclusive of ASXL1 mutations) CMML prognostic models, including Molecular Mayo Model and the Groupe Français des Myélodysplasies model. Better understanding of the prevalent genetic and epigenetic dysregulation has resulted in emerging targeted treatment options for some patients. The development of an integrated (cytogenetic and molecular) prognostic model along with CMML-specific response assessment criteria are much needed future goals.

Specific molecular signatures predict decitabine response in chronic myelomonocytic leukemia

Myelodysplastic syndromes and chronic myelomonocytic leukemia (CMML) are characterized by mutations in genes encoding epigenetic modifiers and aberrant DNA methylation. DNA methyltransferase inhibitors (DMTis) are used to treat these disorders, but response is highly variable, with few means to predict which patients will benefit. Here, we examined baseline differences in mutations, DNA methylation, and gene expression in 40 CMML patients who were responsive or resistant to decitabine (DAC) in order to develop a molecular means of predicting response at diagnosis. While somatic mutations did not differentiate responders from nonresponders, we identified 167 differentially methylated regions (DMRs) of DNA at baseline that distinguished responders from nonresponders using next-generation sequencing. These DMRs were primarily localized to nonpromoter regions and overlapped with distal regulatory enhancers. Using the methylation profiles, we developed an epigenetic classifier that accurately predicted DAC response at the time of diagnosis. Transcriptional analysis revealed differences in gene expression at diagnosis between responders and nonresponders. In responders, the upregulated genes included those that are associated with the cell cycle, potentially contributing to effective DAC incorporation. Treatment with CXCL4 and CXCL7, which were overexpressed in nonresponders, blocked DAC effects in isolated normal CD34+ and primary CMML cells, suggesting that their upregulation contributes to primary DAC resistance.

Gingival Involvement in a Patient with CD56+Chronic Myelomonocytic Leukemia

Leukemic infiltration of the gingiva is most commonly reported to be associated with monocytic subtypes of acute myeloblastic leukemia (AML) but rarely with myelodysplastic syndromes (MDS). Here we report a case of CD56+ chronic myelomonocytic leukemia (CMML) who developed gingival involvement simultaneously when the leukocyte count elevated. At that time no increase in peripheral or bone marrow blasts were observed. Gingival hypertrophy regressed with the treatment of hydroxyurea. Three months later, bone marrow blast count elevated and the patient was treated with two courses of AML-like regimen and then one course of consolidation therapy. The patient is in complete hematological remission for one and a half years. Similar to other extramedullary involvements, gingival hypertrophy in CMML can be a harbinger of the disease entering a more aggressive phase requiring systemic chemotherapy.

FLT3 mutations confer enhanced proliferation and survival properties to multipotent progenitors in a murine model of chronic myelomonocytic leukemia

Despite their known transforming properties, the effects of leukemogenic FLT3-ITD mutations on hematopoietic stem and multipotent progenitor cells and on hematopoietic differentiation are not well understood. We report a mouse model harboring an ITD in the murine Flt3 locus that develops myeloproliferative disease resembling CMML and further identified FLT3-ITD mutations in a subset of human CMML. These findings correlated with an increase in number, cell cycling, and survival of multipotent stem and progenitor cells in an ITD dose-dependent manner in animals that exhibited alterations within their myeloid progenitor compartments and a block in normal B cell development. This model provides insights into the consequences of constitutive signaling by an oncogenic tyrosine kinase on hematopoietic progenitor quiescence, function, and cell fate.

Chronic myelomonocytic leukemia: The role of bone marrow biopsy immunohistology

The World Health Organization criteria for diagnosing chronic myelomonocytic leukemia (CMML) are largely based on findings observed in the peripheral blood and bone marrow aspirate. A specific diagnostic role for the bone marrow biopsy has not been adequately explored. We examined whether bone marrow biopsy supplemented by immunohistochemistry may be helpful in distinguishing CMML from cases of chronic myelogenous leukemia and atypical chronic myeloid leukemia (aCML). We immunostained 25 cases of CMML with paraffin reactive antibodies which included CD68 (KP1), CD68R (PG-M1), and CD163, and compared the results with those observed in six cases of chronic myelogenous leukemia and in three cases of atypical CML. In addition, we examined whether CD34 immunohistochemistry could be useful in separating cases of CMML with less than 10% blasts (type-1) from cases of CMML with blasts accounting for 10-19% (type-2), and cases of CMML in acute transformation to acute myeloid leukemia (blasts > or = 20%). The presence of nodules of plasmacytoid monocytes was investigated by CD123 staining. CD42b was used to highlight abnormal megakaryocytes. Our results demonstrate significant differences between the groups. CD34 analysis allowed separating CMML type-1 from type-2 and the former from CMML in acute transformation. CD123-positive plasmacytoid monocyte nodules were found only in CMML and not in the other two disease groups. Overlap between CMML and the other two groups were observed with CD68 immunostaining. CD68R was more restricted to bone marrow macrophages and monocytes than CD68, but the differences between CMML and chronic myelogenous leukemia or atypical CML were still not significant. Although CD42b immunostaining facilitated the detection of dwarf megakaryocytes often present in CMML, the distinction between those and the small forms seen in chronic myelogenous leukemia was still problematic.

Oncogenic NRAS rapidly and efficiently induces CMML- and AML-like diseases in mice

Activating mutations in RAS, predominantly NRAS, are common in myeloid malignancies. Previous studies in animal models have shown that oncogenic NRAS is unable to induce myeloid malignancies effectively, and it was suggested that oncogenic NRAS might only act as a secondary mutation in leukemogenesis. In this study, we examined the leukemogenicity of NRAS using an improved mouse bone marrow transduction and transplantation model. We found that oncogenic NRAS rapidly and efficiently induced chronic myelomonocytic leukemia (CMML)- or acute myeloid leukemia (AML)- like disease in mice, indicating that mutated NRAS can function as an initiating oncogene in the induction of myeloid malignancies. In addition to CMML and AML, we found that NRAS induced mastocytosis in mice. This result indicates that activation of the RAS pathway also plays an important role in the pathogenesis of mastocytosis. The mouse model for NRAS leukemogenesis established here provides a system for further studying the molecular mechanisms in the pathogenesis of myeloid malignancies and for testing relevant therapies.

Survivin expression, apoptosis and proliferation in chronic myelomonocytic leukemia

We analyzed the expression of the inhibitor of apoptosis survivin by immunocytochemistry in bone marrow cells from patients with chronic myelomonocytic leukemia (CMML) to evaluate possible abnormalities in comparison with other myelodysplastic (MDS) and myeloproliferative syndromes, and to investigate a possible correlation between survivin expression and altered apoptosis or proliferation, or relevant laboratory and clinical findings. Thirty-four patients with CMML [18 MDS-CMML and 16 myeloproliferative disorder (MPD)-CMML], 90 with MDS, 41 with acute myeloid leukemia (AML), 19 with chronic MPD and 25 control subjects were studied. In normal samples survivin was never detectable. In CMML survivin levels higher than in MDS and AML (P < 0.0001), but similar to those found in MPD were observed. In CMML and MDS apoptosis was significantly higher compared to normal controls and all other subtypes of leukemias (P < 0.0001). Proliferation did not differ significantly in normal controls, MDS and CMML; the lowest levels were observed in AML and MPD (P < 0.0001). In CMML there was no correlation between survivin expression and blast cell percentage, apoptosis or proliferation, FAB or WHO subgroup. Proliferation was higher in MDS-CMML and tended to correlate with overall survival. CMML-2 cases with higher survivin expression showed higher evolution rate and shorter survival. In conclusion, CMML is characterized by high proliferation and apoptosis. Survivin overexpression, by disrupting the balance between cell proliferation/differentiation and apoptosis, may play an important role in its pathophysiology. The detection of survivin-deregulated expression may provide a useful tool for diagnosis, prognosis and a possible target for experimental treatments.

Refractory anemia with ringed sideroblasts and chronic myelomonocytic leukemia: myelodysplastic/myeloproliferative disease

Here is reported the case of an elderly woman that, after surgical intervention, showed an important anemia, leucocytosis and thrombocytopenia. The leucocytosis was accompanied with clean increase of the monocytes. The morphological appearances, both peripheral blood and bone marrow, showed an evident overlapping of myelodysplastic and myeloproliferative picture, characterized from the presence of refractory anemia with ringed sideroblasts (RARS) and chronic myelomonocytic leukemia (CMML). The case has been reported because it is not frequent, besides, the CMML, until from the beginning of French-American-British (FAB) classification application, has raised problems of classification. Currently, the World Health Organization (WHO) has given an arrangement to the hematological picture with myelodysplastic and myeloproliferative morphological appearances, including this pathology in a new category: myelodysplastic/myeloproliferative diseases (MDS/MPD).

A Role for Proapoptotic BID in the DNA-Damage Response

The BCL-2 family of apoptotic proteins encompasses key regulators proximal to irreversible cell damage. The BH3-only members of this family act as sentinels, interconnecting specific death signals to the core apoptotic pathway. Our previous data demonstrated a role for BH3-only BID in maintaining myeloid homeostasis and suppressing leukemogenesis. In the absence of Bid, mice accumulate chromosomal aberrations and develop a fatal myeloproliferative disorder resembling chronic myelomonocytic leukemia. Here, we describe a role for BID in preserving genomic integrity that places BID at an early point in the path to determine the fate of a cell. We show that BID plays an unexpected role in the intra-S phase checkpoint downstream of DNA damage distinct from its proapoptotic function. We further demonstrate that this role is mediated through BID phosphorylation by the DNA-damage kinase ATM. These results establish a link between proapoptotic Bid and the DNA-damage response.

RAS-blocking bisphosphonate zoledronic acid inhibits the abnormal proliferation and differentiation of juvenile myelomonocytic leukemia cells in vitro

Juvenile myelomonocytic leukemia (JMML) is a clonal myeloproliferative/myelodysplastic disorder of early childhood with a poor prognosis. JMML cells are characterized by hypersensitivity to granulocyte-macrophage colony-stimulating factor (GM-CSF) caused by a continuously activated GM-CSF receptor-retrovirus-associated sequence (RAS) signal transduction pathway through various molecular mechanisms, resulting in spontaneous GM colony formation in vitro. Bisphosphonate zoledronic acid (ZOL), a RAS-blocking compound, suppressed colony formation from bone marrow (BM) cells of 8 patients with JMML and 5 healthy control subjects without and with GM-CSF (10 ng/mL), respectively, in a dose-dependent manner in clonal culture. At 10 microM ZOL, however, spontaneous GM colony formation from JMML BM cells decreased to 3%, but the formation of G colonies containing granulocytes, but no macrophages, was enhanced, whereas 40% of GM colonies were retained and G colony formation was not affected in culture of normal BM cells with GM-CSF. In suspension culture, cytochemical and flow cytometric analyses showed that 10 microM ZOL also inhibited spontaneous proliferation and differentiation along monocyte/macrophage lineage of JMML BM cells but not the development of normal BM cells by GM-CSF. The inhibitory effect of ZOL on JMML cells was confirmed at a single-clone level and observed even at 3 microM. The current result offers a novel approach to therapy in JMML.

Comparative study of myelodysplastic syndromes and normal bone marrow biopsies with conventional staining and immunocytochemistry

OBJECTIVE

To study the histomorphometric features of megakaryocytic elements in bone marrow trephine biopsies of various subtypes of myelodysplastic syndrome (MDS).

STUDY DESIGN

Comparative image morphometry using hematoxylin-eosin-stained and CD 61-stained trephine biopsies was carried out on 40 cases of MDS and 10 normal subjects to analyze the megakaryocytes objectively. The various variables analyzed were number of megakaryocytes and micromegakaryocytes, area, perimeter and diameter of the megakaryocytic elements.

RESULTS

The mean number of megakaryocytes was lower in cases of MDS as compared to the normals in all except for a single case of hypoplastic MDS, in which the megakaryocytes were more abundant (3.6 per high-power field [hpf]). No micromegakaryocytes were observed in the 2 cases of chronic myelomonocytic leukemia. The mean area, perimeter and diameter of megakaryocytes decreased significantly on immunostaining with CD 61.

CONCLUSION

The mean number of megakaryocytes per hpf was lower in the cases of MDS as compared to normal cases on hematoxylin-eosin. However, on CD 61 staining the number of megakaryocytes per hpf increased in cases of MDS. Micromegakaryocytes were seen in scanty numbers in the normals but increased in MDS cases and increased significantly on CD 61 immunostaining. The mean area, perimeter and diameter of megakaryocytes decreased significantly on immunostaining with CD 61, indicating the increased numbers of micromegakaryocytes in MDS. Hence, immunostaining is an efficient method of detecting increased numbers of megakaryocytes and micromegakaryocytes that would ordinarily be missed by using routine hematoxylin-eosin staining.

Methylation status of the p15 and p16 genes in paediatric myelodysplastic syndrome and juvenile myelomonocytic leukaemia

Aberrant DNA methylation is frequently observed in adults with myelodysplastic syndrome (MDS), and is recognized as a critical event in the disease's pathogenesis and progression. This is the first report to investigate the methylation status of p15 and p16, cell cycle regulatory genes, in children with MDS (n = 9) and juvenile myelomonocytic leukaemia (JMML; n = 18) by using a methylation-specific polymerase chain reaction. The frequency of p15 hypermethylation in paediatric MDS was 78% (7/9), which was comparable to that in adult MDS. In contrast, p15 hypermethylation in JMML was a rare event (17%; 3/18). In JMML, clinical and laboratory characteristics including PTPN11 mutations and aberrant colony formation were not different between the three patients with hypermethylated p15 and the others. Aberrant methylation of p16 was not detected in children with either MDS or JMML. Since p15 and p16 genes were unmethylated in two children with JMML, in whom the disease had progressed with an increased number of blasts, a condition referred to as blastic crisis, we infer that the aberrant methylation of these genes is not responsible for the progression of JMML. The results suggest that demethylating agents may be effective in most children with MDS and a few patients with JMML.

Human somatic PTPN11 mutations induce hematopoietic-cell hypersensitivity to granulocyte-macrophage colony-stimulating factor

Juvenile myelomonocytic leukemia (JMML) is a lethal disease of young children characterized by hypersensitivity of hematopoietic progenitors to granulocyte-macrophage colony-stimulating factor (GM-CSF). Mutations in PTPN11, which encodes the protein tyrosine phosphatase Shp-2, are common in JMML. We hypothesized that PTPN11 mutations induce hypersensitivity of hematopoietic progenitors to GM-CSF and confer increased GM-CSF-stimulated phospho-extracellular signal-regulated kinase (Erk) levels. To test this hypothesis, the wild-type (WT) and 3 mutant Ptpn11 cDNAs (E76K, D61V, and D61Y) were transduced into murine bone marrow cells to examine GM-CSF-stimulated granulocyte-macrophage colony-forming unit (CFU-GM) growth, macrophage progenitor proliferation, and activation of the Ras signaling pathway. Expression of the Shp-2 mutants induced progenitor cell hypersensitivity to GM-CSF compared with cells transduced with vector alone or WT Shp-2. Macrophage progenitors expressing the Shp-2 mutants displayed both basal and GM-CSF-stimulated hyperproliferation compared with cells transduced with vector alone or WT Shp-2. Consistently, macrophage progenitors transduced with the Shp-2 mutants demonstrated constitutively elevated phospho-Erk levels and sustained activation of phospho-Erk following GM-CSF stimulation compared with vector alone or WT Shp-2. These data support the hypothesis that PTPN11 mutations induce hematopoietic progenitor hypersensitivity to GM-CSF due to hyperactivation of the Ras signaling axis and provide a basis for the GM-CSF signaling pathway as a target for rational drug design in JMML.

A case of chronic myelomonocytic leukemia with severe eosinophilia having t(5;12)(q31;p13) with t(1;7)(q10;p10)

We describe an unusual case of chronic myelomonocytic leukemia with severe eosinophilia having t(5;12)(q31;p13) with t(1;7)(q10;p10). The eosinophilic proliferation was severe in peripheral blood and bone marrow, and they revealed marked dysplastic features. We performed fluorescence in situ hybridization (FISH) and immunohistochemistry to evaluate the clonality of eosinophils. The eosinophils were stained positively to platelet-derived growth factor receptor-beta. By FISH using chromosome 1 satellite probe and chromosome 1q telomere probe, the eosinophils were proved to belong to the malignant clone.

Positive and negative regulatory roles of the WW-like domain in TEL-PDGFbetaR transformation

TEL-platelet-derived growth factor-beta receptor (TEL-PDGFbetaR) is expressed in chronic myelomonocytic leukemias associated with t(5;12)(q33;p13), and the fusion tyrosine kinase retains a conserved WW-like domain in the PDGFbetaR autoinhibitory juxtamembrane region. Here we report that mutation of the 2 conserved tryptophan residues of the WW-like domain has opposing effects on TELPDGFbetaR kinase activation. Alanine substitution of W593, essential for protein-protein interaction in the context of other WW domains, impaired TEL-PDGFbetaR-mediated transformation of hematopoietic cells due to inhibition of TEL-PDGFbetaR kinase activity. In contrast, alanine substitution of W566, essential for structural integrity of WW domain in other contexts, had no effect on TEL-PDGFbetaR activation and oncogenic activity. Surprisingly, however, the W566A mutation suppressed the W593A phenotype. Double mutant W566A/W593A was indistinguishable from the wild-type fusion protein with regard to kinase activity, ability to confer factor-independent growth to Ba/F3 cells, or ability to induce a myeloproliferative disease in mice. Additional mutational analysis identified other substitutions within the WW-like domain in addition to W566A that could also suppress the W593A phenotype, including mutations predicted to diminish the autoinhibitory function of the juxtamembrane region. Therefore, the WW-like domain in the context of TELPDGFbetaR may have both positive and negative regulatory roles in kinase activation.

Neutrophil-specific reduction in the expression of granulocyte--macrophage colony-stimulating factor receptor subunits in myelodysplastic syndromes

The proliferative and differentiative response of neutrophils to granulocyte-macrophage colony-stimulating factor (GM-CSF) is known to be impaired in patients with myelodysplastic syndromes (MDS). To investigate the mechanisms of the defective response in MDS, we examined expression levels of GM-CSF receptor alpha (GMR alpha) and common beta (beta c) subunits on CD16(+) neutrophils, CD14(+) monocytes and CD3(+) T cells from 26 MDS patients and 10 healthy controls using flow cytometry. Expression of GMR alpha was significantly decreased on the neutrophils of five out of 26 patients and was not specific for any FAB subtype. In contrast, beta c expression on neutrophils was significantly reduced in 14 out of 26 patients with a higher proportion occurring in the advanced stages of MDS including refractory anaemia with excess of blasts (RAEB), RAEB in transformation (RAEBt) and overt leukaemia compared with refractory anaemia (RA)/RA with ringed sideroblasts (RARS) or healthy controls. Decreased beta c also correlated with the degree of hypogranular neutrophil morphology and increased infection. Expression of both subunits on T cells and monocytes in MDS was similar to normal controls. Polymerase chain reaction amplification of reverse-transcribed mRNA isolated from the affected neutrophils suggests that the reduction of beta c may result from decreased message levels. The observed reduction in GM-CSF receptor expression could account for the impaired proliferative and maturational responses in MDS.

Detection of TNFalpha expression in the bone marrow and determination of TNFalpha production of peripheral blood mononuclear cells in myelodysplastic syndrome

TNFalpha is a highly active cytokine which plays an important role in the regulation of apoptotic cell death, a mechanism involved in the pathophysiology of myelodysplastic syndrome (MDS). In this study we investigated the expression of TNFalpha of the bone marrow trephine biopsies by immunohistochemical method and the TNFalpha production of peripheral blood mononuclear cells by ELISA method in 15 patients affected by MDS. Five of seven patients without excess of blasts showed high or intermediate TNFalpha expression in the bone marrow biopsies, whereas two patients with excess of blasts were negative and one had low expression. The five CMML patients revealed low or intermediate expression. The production of TNFalpha by the PBMC was analysed in 10 patients, four patients with RA and two with CMML produced higher level of TNFalpha which increased after stimulation with phorbol myristic acetate, but none of the RAEB patients revealed increase in TNFalpha production. In conclusion we suppose that increased TNFalpha expression and production by PBMC may be an indirect evidence of the role of increased apoptosis in low risk MDS patients.

Expression of interferon regulatory factor 1 and 2 in hematopoietic cells of children with juvenile myelomonocytic leukemia

Interferon regulatory factor 1 (IRF-1) is a transcriptional activator in the interferon system and acts as a tumor suppressor. The structurally related IRF-2 represses the effects of IRF-1 by competitive binding to the same DNA sequence elements. Changes in the relative balance between IRF-1 and IRF-2 lead to dysregulation of cell growth and may play a role in the development of neoplasias. The loss of functional IRF-1 has been observed in a number of patients with myelodysplastic syndrome (MDS) and leukemia, suggesting a potentially critical role of IRF-1 in leukemogenesis. We studied the expression of both transcription factors in peripheral blood (PB) and bone marrow (BM) cells of children with juvenile myelomonocytic leukemia (JMML) using RT-PCR and Southern blot hybridization. No significant difference between the expression levels of IRF-1 and IRF-2 could be detected in PB and BM of patients with JMML and normal donors. Although our results are preliminary they suggest that neither the tumor suppressor gene IRF-1 nor the oncogene IRF-2 is involved in the pathogenesis of JMML.

Study of p53 in elderly patients with myelodysplastic syndromes by immunohistochemistry and DNA analysis

We analyzed the tumor suppressor gene product, p53, in elderly patients with myelodysplastic syndromes (MDS) and in overt leukemia patients after transformation from MDS using immunohistochemical techniques. We examined 52 MDS patients (mean age 79 years, range 68 to 96) from the time of initial diagnosis to death or development of overt leukemia. p53 protein was detected by immunohistochemistry (IHC) in 8/52 patients (15%) at initial diagnosis: 1/26 with refractory anemia (RA), 0/4 with RA with ringed sideroblasts, 3/11 with RA with an excess of blasts (RAEB), 3/8 with RAEB in transformation, and 1/3 with chronic myelomonocytic leukemia. We also analyzed gene mutations in patients with positive IHC. p53 mutations were detected in 3/8 (38%) patients. IHC-positive patients had a significantly higher incidence of leukemic transformation and the presence of a complex karyotype with monosomy 17. IHC-positive cells included blasts as well as mature myeloid cells, erythroblasts, and megakaryocytes. Scrutiny of our data in combination with previous data revealed that patients with positive IHC in multilineage cells were older than those in whom positivity was noted mostly in myeloblasts. This suggests that p53 IHC positivity with a multilineage pattern may be a characteristic of MDS in older patients.

Troglitazone suppresses cell growth of myeloid leukemia cell lines by induction of p21WAF1/CIP1 cyclin-dependent kinase inhibitor

In a human eosinophilic leukemia cell line, EoL-1, cell proliferation was suppressed by 2-day treatment with troglitazone. EoL-1 cells treated with troglitazone were arrested and maintained in the G0/G1 phase in the cell cycle. This suppression correlated with the up-regulation of mRNA for p21WAF1/CIP1 cyclin-dependent kinase (Cdk) inhibitor. The inhibitory effects of troglitazone on cell proliferation and expression of p21 mRNA were observed in a human myelomonocytic cell line, U937, and a human myelomonoblastic cell line, KPB-M15. In addition, in EoL-1 cells, p21 protein was induced by troglitazone treatment and the induction was inhibited by protein synthesis inhibitor, cycloheximide. These data suggest that troglitazone inhibits cell proliferation in myeloid leukemia cell lines at least in part by induction of p21 Cdk inhibitor.

Splenic pathology in myelodysplasia: a report of 13 cases with clinical correlation

Splenomegaly is uncommon in myelodysplasia (MDS) and, although cytopenias may be severe, therapeutic splenectomy is rarely performed. We report the histologic, histochemical, and immunophenotypic findings of nine cases of surgical splenectomy and four postmortem spleens from MDS patients. Four histologic patterns were identified: one dominated by erythrophagocytosis, one characterized by red pulp plasmacytosis, one with extramedullary hematopoiesis as the only salient finding, and one with marked red pulp expansion caused by a monocytic proliferation. Wright-Giemsa and histochemical stains were performed on touch preparations in three cases and played a critical role in the precise subclassification of one MDS patient's hematologic disorder, which ultimately proved to be chronic myelomonocytic leukemia. Splenectomy led to sustained improvement of cytopenias in three cases, but did not eliminate transfusion dependence for the remaining patients. Three splenectomy cases exhibited clustered Leder-negative mononuclear elements: two of these patients experienced disease progression to refractory anemia with excess blasts in transformation or acute myelogenous leukemia during post-splenectomy follow-up, whereas none of the three splenectomy patients without clustered mononuclear elements did. We conclude that splenomegaly in MDS usually reflects the sequelae of dyspoiesis rather than evidence of a proliferative phase, that clustering of Leder-negative large cells may correlate with either a substantial monocytic component or, possibly, increased risk of disease progression, and that the spleen can provide diagnostic as well as prognostic information in MDS patients with splenomegaly.

Expression of lung resistance protein and correlation with other drug resistance proteins and outcome in myelodysplastic syndromes

The major vault lung resistance protein LRP is a cytoplasmic protein involved in drug resistance, especially in acute myeloid leukemia. We looked for LRP overexpression, using immunocytochemistry with LRP 56 monoclonal antibody, on marrow slides from 41 cases of myelodysplastic syndromes (MDS). LRP overexpression (LRP+) was defined by expression of LRP 56 in at least 20% of marrow blasts. LRP overexpression was seen in 19 (46%) cases. Concordant results between LRP overexpression and P-glycoprotein (PGP) expression were seen in 66% of the cases (p = 0.03), and discordant results (LRP+ and PGP-, or LRP- and PGP+) in 33% of the cases. No correlation was seen between LRP overexpression and FAB type, karyotype, CD34, p53 expression and bcl2 overexpression in blasts. Furthermore, in the 18 cases treated with anthracycline-AraC intensive chemotherapy and the 7 cases treated with low dose AraC, the response rate was not significantly different in LRP+ and LRP- patients. Survival was also similar in LRP+ and LRP- patients. In conclusion, LRP overexpression is probably more frequent in MDS than in de novo AML and, as in AML, is only partially correlated with PGP expression. In our experience, however, LRP was not a prognostic factor for response to chemotherapy and survival in MDS.

Juvenile chronic myelomonocytic leukemias: molecular and novel therapeutic basis

Myelomonocytic leukemias of children represent a distinct disorder from chronic myelogenous leukemia and adult myelomonocytic leukemias. The prognosis is poor and no therapy has proved to be yet effective. This review summarizes the molecular and cellular characteristics of this disease which may allow to design more targetted therapeutic agents.

Interleukin (IL)-10, but not IL-4 or IL-13, inhibits cytokine production and growth in juvenile myelomonocytic leukemia cells

Juvenile myelomonocytic leukemia (JMML) carries a poor prognosis. The endogenous production of cytokines by the JMML cells contributes to their growth and therapeutic resistance. Interleukin (IL)-4, IL-10, and IL-13 inhibit cytokine production in monocytes. We have now studied whether these cytokines can inhibit JMML cell cytokine production, thereby potentially reducing the malignant cell load in this disorder. We found that IL-10, but not IL-4 or IL-13, dose dependently inhibited JMML cell production of the hemopoietic growth factors granulocyte-macrophage colony-stimulating factor, tumor necrosis factor alpha, and IL-1beta. Similarly, IL-10, but not IL-4 or IL-13, suppressed JMML colony formation and cell viability. This was not due to the absence of receptors because we could detect mRNAs for the IL-4 and the IL-13 receptor alpha subunits and the IL-2 common gamma subunit in JMML cells. Furthermore, the receptors were active since both IL-4 and IL-13 up-regulated surface expression of MHC class II and down-regulated CD14 antigens on JMML cells and monocytes. Unlike activated monocytes, the JMML cells did not produce IL-10. It is suggested that the loss of cytokine inhibitory effects of IL-4 and IL-13 could play a role in the pathogenesis of this disorder. On the other hand, the inhibition of cytokine production, growth, and viability of JMML cells by IL-10 suggests that this cytokine may have a therapeutic potential in JMML.

The TEL/platelet-derived growth factor beta receptor (PDGF beta R) fusion in chronic myelomonocytic leukemia is a transforming protein that self-associates and activates PDGF beta R kinase-dependent signaling pathways

The TEL/PDGF beta R fusion protein is the product of the t(5;12) translocation in patients with chronic myelomonocytic leukemia. The TEL/PDGF beta R is an unusual fusion of a putative transcription factor, TEL, to a receptor tyrosine kinase. The translocation fuses the amino terminus of TEL, containing the helix-loop-helix (HLH) domain, to the transmembrane and cytoplasmic domain of the PDGF beta R. We hypothesized that TEL/PDGF beta R self-association, mediated by the HLH domain of TEL, would lead to constitutive activation of the PDGF beta R tyrosine kinase domain and cellular transformation. Analysis of in vitro-translated TEL/ PDGF beta R confirmed that the protein self-associated and that self-association was abrogated by deletion of 51 aa within the TEL HLH domain. In vivo, TEL/PDGF beta R was detected as a 100-kDa protein that was constitutively phosphorylated on tyrosine and transformed the murine hematopoietic cell line Ba/F3 to interleukin 3 growth factor independence. Transformation of Ba/F3 cells required the HLH domain of TEL and the kinase activity of the PDGF beta R portion of the fusion protein. Immunoblotting demonstrated that TEL/PDGF beta R associated with multiple signaling molecules known to associate with the activated PDGF beta R, including phospholipase C gamma 1, SHP2, and phosphoinositol-3-kinase. TEL/PDGF beta R is a novel transforming protein that self-associates and activates PDGF beta R-dependent signaling pathways. Oligomerization of TEL/PDGF beta R that is dependent on the TEL HLH domain provides further evidence that the HLH domain, highly conserved among ETS family members, is a self-association motif.

Differential expression of receptors for hemopoietic growth factors on subsets of CD34+ hemopoietic cells

The production of peripheral blood cells is regulated by hemopoietic growth factors (HGF) which promote the survival of stem cells and stimulate the proliferation and maturation of progenitors as well as effector functions of mature blood cell subsets. The actions of HGF's are determined by the cellular distribution of receptors for these HGF's within the hemopoietic tissues and by the functional program that receptor-expressing cells can execute after growth factor stimulation. Identification of stem cells and their progeny and delineation of the growth factor receptor phenotype of these cells will establish target cell range and functions of individual growth factors in hemopoiesis. Cells with specific HGF receptors can be detected and isolated by flow cytometric methods, e.g., by staining with biotinylated ligand and fluorescently-tagged streptavidin. Receptor-expressing cells can be classified on the basis of expression of the CD34 antigen and other markers that distinguish immature progenitors from more differentiated cells. Using this approach distinct expression patterns have been shown for the receptors for interleukin-3 (IL-3), IL-6, granulocyte/macrophage colony-stimulating factor (GM-CSF) and Steel Factor (SF) on subsets of CD34+ and CD34- cells in bone marrow. Expression of the IL-3 receptor (R), IL-6R and GM-CSFR appears to be very low on the most immature subsets of CD34+ cells, but increases progressively during successive stages, of in particular myelomonocytic differentiation. In contrast, the receptor for SF, i.e., Kit, is highly expressed on very immature CD34-bright/HLA-DR-dull cells, which include stem cells. Kit levels decline during myelomonocytic and B-lymphoid differentiation whereas they increase to maximal levels during early stages of erythropoiesis. The heterogeneity in receptor expression, together with other immunophenotypic characteristics, allows for the identification of distinct progenitor cell subsets and differentiation stages within the CD34+ cell compartment. By selecting appropriate phenotypic criteria it will be possible to further dissect the stem cell compartment and eventually establish the, possibly heterogeneous, HGF receptor phenotype of pluripotent stem cells.

Juvenile myelomonocytic leukemia: molecular understanding and prospects for therapy

Juvenile myelomonocytic leukemia is a rare but deadly myeloproliferative disorder of early childhood that infrequently progresses to acute leukemia. The pathogenesis of this leukemia has been linked to deregulated signal transduction, resulting in growth factor hypersensitivity. Several other myeloproliferative disorders appear to share growth factor hypersensitivity as a common pathophysiological mechanism and thus this leukemia serves as an important model. New treatment modalities, such as retinoid therapy, are emerging for juvenile myelomonocytic leukemia. Further understanding of deregulated signal transduction should pave the way for even more rationally designed therapy for this leukemia and related disorders.

Interleukin 10 inhibits growth and granulocyte/macrophage colony-stimulating factor production in chronic myelomonocytic leukemia cells

Autonomous release of hematopoietic growth factors may play a crucial role in the pathogenesis of certain hematological malignancies. Because of its cytokine synthesis-inhibiting action, interleukin 10 (IL-10) could be a potentially useful molecule to affect leukemic cell growth in such disorders. Chronic myelomonocytic leukemia (CMML) cells spontaneously form myeloid colonies (colony-forming units-granulocyte/macrophage) in methylcellulose, suggesting an autocrine growth factor-mediated mechanism. We studied the effect of recombinant human IL-10 (rhIL-10) on the in vitro growth of mononuclear cells obtained from peripheral blood or bone marrow of patients with CMML. IL-10 specifically binding to leukemic cells had a profound and dose-dependent inhibitory effect on autonomous in vitro growth of CMML cells. IL-10 significantly inhibited the spontaneous growth of myeloid colonies in methylcellulose in 10/11 patients, and autonomous CMML cell growth in suspension in 5/5 patients tested. Spontaneous colony growth from CMML cells was also markedly reduced by addition of antigranulocyte/macrophage colony-stimulating factor (GM-CSF) antibodies, but not by addition of antibodies against G-CSF, IL-3, or IL-6, IL-10-induced suppression of CMML cell growth was reversed by the addition of exogenous GM-CSF and correlated with a substantial decrease in GM-CSF production by leukemic cells, both at the mRNA and protein levels. Our data indicate that IL-10 profoundly inhibits the autonomous growth of CMML cells in vitro most likely through suppression of endogenous GM-CSF release. This observation suggests therapeutic evaluation of rhIL-10 in patients with CMML.

Glucocorticoid-induced modulation of cytokine secretion from normal and leukemic human myelomonocytic cells

Since glucocorticoid effects on inflammatory processes may be mediated via modulation of cytokine release, different types of myelomonocytic cells were stimulated in vitro with lipopolysaccharide (50 ng/ml) or phorbol myristate acetate (25 ng/ml) plus the ionophore A23187, 2 x 10(-7) M, and release of interleukin (IL)-1 beta, IL-8 and tumor necrosis factor (TNF)-alpha was measured after 24 h by ELISA. Peripheral blood mononuclear cells from two allergic and two normal human donors released similarly large quantities of IL-8 and lower amounts of IL-1 beta and TNF-alpha. This also held for myelomonocytic cell lines, with THP-1 cells being most active, followed by U-937 and HL-60 cells. All potent glucocorticoids studied caused a dose-dependent inhibition of cytokine release from donor cells, being most marked for IL-1 beta and lowest for IL-8. Inhibition of cytokine release was also noted with U-937 cells, with clear differences in potency between the glucocorticoids, whereas release was enhanced in all experiments with THP-1 cells. These results were confirmed with Northern blot analysis. Modulating effects of glucocorticoids on cytokine release are thus complex, and are particularly dependent on the cell type studied.

Relative cytokine-stimulating activities of surface components of the oral periodontopathogenic bacterium Actinobacillus actinomycetemcomitans

The purpose of this study was to determine whether bacterial surface components other than lipopolysaccharide (LPS) could stimulate pro-inflammatory cytokine synthesis by mesenchymal and myelomonocytic cells in vitro. LPS, lipid A-associated proteins (LAP) and saline-extractable surface-associated material (SAM) were isolated from the periodontopathogenic bacterium Actinobacillus actinomycetemcomitans and added to cultures of human gingival fibroblasts (HGFs), human PBMCs and the human myelomonocytic MonoMac-6 cell line. Pro-inflammatory cytokine release into culture supernatants was determined by two-site ELISAs. Contrary to expectation, the highly purified LPS extracted from this bacterium was significantly less potent than the other surface extracts in stimulating release of IL-1 beta, IL-6 and TNF-alpha by all three cell types. The SAM was the most potent cytokine-stimulating agent showing equivalent activity to highly purified E. coli LPS in stimulating IL-6 release by PBMCs. LAP also had cytokine-stimulating activity although it was generally significantly less potent than the SAM. Thus in the case of this organism, which is involved in the pathology of chronic inflammatory diseases the LPS does not appear to be the major cytokine-stimulating component.

Induction of differentiation of WEHI-3B D+ leukemic cells transfected with differentiation-stimulating factor/leukemia inhibitory factor receptor cDNA

Differentiation-stimulating factor (D-factor)/leukemia inhibitory factor can induce the differentiation of mouse myeloid leukemia M1 cells and also stimulate proliferation of the interleukin-3 (IL-3)-dependent cell line, DA-1a. To determine whether D-factor can induce the differentiation of leukemia cells other than M1 cells, WEHI-3B D+ mouse myelomonocytic leukemia cells were transfected with a plasmid containing mouse D-factor receptor cDNA. Expression of D-factor receptor in transfected cells was determined by binding of [125]D-factor and analyzed by Scatchard's method. The transfected cells had high-affinity D-factor receptors with a dissociation constant of 100 to 200 pmol/L and binding sites per cell varied from 67 to 1,500 among several clones. The cells expressing a high level of D-factor receptor were induced to differentiate by D-factor; about 60% of the cells exhibited the ability to reduce nitroblue tetrazolium and expression of the differentiation antigen Mac-1 (CD11b) on the cell surface increased. The effect of cytokines, which induce the differentiation of M1 cells, on the transfected WEHI-3B cells was examined. The sensitivity to oncostatin M was identical to that against D-factor in the cells of each clone. Expression of D-factor receptor in WEHI-3B cells promoted sensitivity to IL-6 and granulocyte colony-stimulating factor (G-CSF). Induction of differentiation of the cells accompanied the suppression of proliferation. Treatment of the cells with D-factor for longer than 5 days resulted in 50% inhibition of growth. These results indicate that the stimulating effect of D-factor on the differentiation of malignant myeloid cells is not unique to M1 cells.

Surface-associated plasminogen activation in leukemic cells: interaction with extracellular matrix

In WEHI-3B murine leukemic cells, plasminogen activator and plasminogen binding sites are associated with the cell membrane. The putative receptor for the zymogen exhibits low affinity for the ligand (dissociation constant of 0.38 microM and a high binding capacity (40,000 sites per cell). Plasminogen also binds in a cooperative fashion to type I collagen with an affinity which is higher than that displayed by cells. Collagen-bound plasminogen can be activated by cells preincubated with plasminogen in a manner that cells develop the capacity to adhere to type I collagen. The activation of collagen-bound plasminogen by cellular urokinase-like plasminogen activator (u-PA) was 60% more efficient than the activation of the soluble (not bound) form of plasminogen. These results suggest that in the invasive phenomena, WEHI cells operate as carriers of plasminogen from plasma to tissue. In addition, collagen can serve as a reservoir of zymogen in the extracellular matrix milieu through direct binding to plasminogen and at the same time allow more efficient plasminogen activation.

Different effects of various hematopoietic growth factors on myelomonocytic cell line (KY-821) and its drug-resistant sublines

Human myelomonocytic leukemic cell line, designated as KY-821, and its sublines KY-Ra, KY-VCR, and KY-MTX, which were resistant to cytosine arabinoside, vincristine, and methotrexate, respectively, were compared for response to various hematopoietic growth factors. Cells of KY-Ra and KY-VCR proliferated in response to natural interleukin-1 (nIL-1), whereas the proliferation of KY-821 and KY-MTX was inhibited. Unexpectedly, recombinant IL-1 alpha and IL-1 beta had no effect on the proliferation of each cell line. The effect of nIL-1 was partially deleted by an addition of optimal anti-IL-1. Supernatants of each cell line had no IL-1 activity. Interferon gamma (IFN gamma) and tumor necrosis factor alpha (TNF alpha) also had an inhibitory effect for KY-821 and KY-MTX, but lacked such effect in KY-RA and KY-VCR. nIL-1, IFN gamma and TNF alpha could not differentiate between any of the cell lines but IFN gamma and TNF alpha induced monocytic surface antigens. In addition, there was no difference in the number of IL-1 and TNF alpha receptors in each cell line. These results indicate that there is a difference in biological effects between nIL-1 and recombinant IL-1 species and acquirement of resistance for some types of drugs may associate closely with different responses to hematopoietic growth factors, probably through altered postmembranous transduction.

[Differentiating agents in myelodysplastic syndromes. Analysis of personal cases]

The Myelo-Dysplastic Syndromes are a heterogeneous group of diseases which includes patients with different prognosis. There is no agreement about the management and the therapeutic strategy must be based on many individual parameters, particularly the age of the patients and their performance status. The therapeutic options range from no cytotoxic therapy for low-risk patients up to more aggressive treatment for high-risk patients, with disappointing results except for the very few cases eligible for allogenic bone marrow transplantation. The leukaemic cell can be induced to differentiate, so losing its self-maintenance potential; different drugs such as Interferon, vitamin D3, retinoids and arabinosyl-cytosine (low doses) have shown a differentiating action on myeloid blasts in "vitro". We summarize the general strategy in the treatment of myelo-dysplastic syndromes based on literature data, and on our results about the efficacy and tolerance of a combination of the above mentioned differentiating drugs, in a group of 27 elderly patients affected by myelodysplastic syndrome with poor prognosis. We obtained 14 objective responses (52%), and the median overall survival of these patients have been compared with that of 25 patients with severe myelodysplastic syndrome treated with a conventional regimen. In the 27 patients receiving the differentiating combination the median survival was found to be 14.7 months, versus 8.4 months for the control group. The results obtained are encouraging about the tolerance and the efficacy of this combination in elderly patients with a poor MDS prognosis. Further randomized studies are necessary to establish whether this treatment can really improve the survival in this group of patients.

Expression of the hyaluronan-binding glycoprotein hyaluronectin in leukemias

Hyaluronectin (HN), a hyaluronan (hyaluronic acid, HA)-binding glycoprotein is normally expressed in the nervous system, found in the desmoplasia of tumours, and is also produced in vitro by peripheral blood mononuclear cells. We have therefore investigated the expression and the production of HN by leukemic cells, with the hypothesis that HN would be expressed in leukemias of the myeloid lineage. Fresh and frozen leukemic cells were studied from 70 patients of whom 53 had acute myeloblastic leukemia (AML). HN was strongly expressed (> 80% blood cells) in two out of 13 M4 AMLs and four out of four M5B AMLs. One further M4 AML displayed 25% positive cells and two 20% cell positivity cases were seen, in one case of M4 AML and in one case of chronic myelomonocytic leukemia (CMML). The rest of the cases of AML as well as all cases of acute lymphoblastic leukemia (ALL) showed almost no positivity (< 1%). The residual positive cells appeared to be normal blood promonocytes. Taken together > or = 20% positive cells was seen in eight out of 56 (14%) examined myeloid leukemias. The HN production was significantly higher (p < 0.0001) in cell culture media of M4 and M5 AML cells than in other AML or ALL cell culture media. A significant correlation was found (p < 0.0001) between the number of HN-positive leukemic cells and the number of cells with a monocytic morphology, suggesting that HN is a marker for the promonocyte.

Low frequency of ras oncogene mutations in Philadelphia-positive acute leukemia and report of a novel mutation H61 Leu in a single case

Activating ras mutations are frequent (25-60%) in chronic myelomonocytic leukemia (CMML) and in acute myeloid leukemia (AML) (30%), in contrast to chronic myeloid leukemia (CML) in which the incidence is very low (0-3%). This might reflect that the leukemic cell in CML is at a level of differentiation in which ras gene activation is not involved or, alternatively, might be due to the presence in CML of the bcrlabl fused gene. We have analyzed the presence of point mutations in codons 12, 13, 59, 61 and 63 of N-, K-, and H-ras genes, in 26 cases of Philadelphia-chromosome-positive, bcrlabl-positive acute leukemia (Ph+ AL), and in eight CMML cases by using the polymerase chain reaction. Aberrant ras genes were detected in a single Ph+ AL case, and in four out of eight CMML patients. The Ph+ AL showing altered ras allele had an unusual point mutation in H-ras gene, substituting leucine for glutamine. This mutation has not been previously found in any hematological disease. Our findings suggest that ras mutations are probably not involved in the pathogenesis of those leukemias in which blast cells contain bcrlabl oncogene activation.

The role of interleukin-1 and granulocyte-macrophage colony-stimulating factor in the paracrine stimulation of an in vivo-derived murine myeloid leukemia

WEHI-274.3 is a cell line isolated from an in vivo-derived, murine myelomonocytic leukemia. Although the survival and growth of WEHI-274.3 cells in vitro is absolutely dependent on the addition of exogenous growth factors such as interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), or colony-stimulating factor-1, when injected into syngeneic mice the cell line is tumorigenic. Sera from normal mice contain low levels of an activity that sustains survival of WEHI-274.3 but does not stimulate growth. In contrast, sera from mice bearing the WEHI-274.3 leukemia contained levels of CSF-1 and GM-CSF that stimulated the growth of WEHI-274.3 cells. Supernatants of cultures of WEHI-274.3 cells contained an activity that stimulated 3T3 fibroblasts to release an activity that stimulated the growth of the WEHI-274.3 cells. The 3T3-stimulatory activity released by the WEHI-274.3 cells was neutralized completely with an antiserum specific for murine IL-1 alpha, but not with antiserum specific for IL-1 beta. Moreover, WEHI-274.3 cells both in vitro and in vivo contained high levels of IL-1 alpha and IL-1 beta mRNAs. The leukemia-stimulatory activity released by the 3T3 cells was neutralized by an antiserum specific for GM-CSF. We postulate that the IL-1 alpha constitutively released by the WEHI-274.3 cells stimulates the production of GM-CSF from host cells such as fibroblasts or endothelial cells. A similar paracrine mechanism of growth stimulation may occur in acute myeloid leukemias in humans.