Pluripotent stem cell model of early hematopoiesis in Down syndrome reveals quantitative effects of short-form GATA1 protein on lineage specification

Children with Down syndrome (DS) are susceptible to two blood disorders, transient abnormal myelopoiesis (TAM) and Down syndrome-associated acute megakaryocytic leukemia (DS-AMKL). Mutations in GATA binding protein 1 (GATA1) have been identified as the cause of these diseases, and the expression levels of the resulting protein, short-form GATA1 (GATA1s), are known to correlate with the severity of TAM. On the other hand, despite the presence of GATA1 mutations in almost all cases of DS-AMKL, the incidence of DS-AMKL in TAM patients is inversely correlated with the expression of GATA1s. This discovery has required the need to clarify the role of GATA1s in generating the cells of origin linked to the risk of both diseases. Focusing on this point, we examined the characteristics of GATA1 mutant trisomy-21 pluripotent stem cells transfected with a doxycycline (Dox)-inducible GATA1s expression cassette in a stepwise hematopoietic differentiation protocol. We found that higher GATA1s expression significantly reduced commitment into the megakaryocytic lineage at the early hematopoietic progenitor cell (HPC) stage, but once committed, the effect was reversed in progenitor cells and acted to maintain the progenitors. These differentiation stage-dependent reversal effects were in contrast to the results of myeloid lineage, where GATA1s simply sustained and increased the number of immature myeloid cells. These results suggest that although GATA1 mutant cells cause the increase in myeloid and megakaryocytic progenitors regardless of the intensity of GATA1s expression, the pathways vary with the expression level. This study provides experimental support for the paradoxical clinical features of GATA1 mutations in the two diseases.

Pro-inflammatory cytokinemia is frequently found in Down syndrome patients with hematological disorders

Down syndrome (DS) patients are frequently complicated with infections, autoimmune phenomena and hematological disorders, including transient abnormal myelopoiesis (TAM) in infancy and acute megakaryoblastic leukaemia (AMKL) in later life. In this study, serum levels of cytokines from 23 TAM and 15 AMKL patients were examined using the highly sensitive microsphere fluorescence system. Statistical differences between DS neonates with or without TAM were found in IL-1beta [median 7.0 pg/ml (0.34-271.6) verses 0.05 pg/ml (0.0-2.4), p=0.034], TNF-alpha [8.11 pg/ml (0.1-253.0) verses 0.41 pg/ml (0.1-1.5), p=0.041], and IFN-gamma [20.0 pg/ml (0.14-406.3) verses 1.5 pg/ml (0.14-5.79), p=0.036]. Moreover, abnormal inflammatory cytokinemia was also found in myelodysplastic syndrome (MDS) and AMKL with DS. These abnormal cytokinemia may have a role in the pathophysiology of TAM, MDS and AMKL in DS, especially in liver fibrosis or myelofibrosis.

[Acute leukemia relapse of donor origin in two cases after haploidentical bone marrow transplantation]

To investigate the leukemia relapse of AL patients after HLA haploidentical bone marrow transplantation (HLA HBMT), 2 relapsed leukemia patients received HLA HBMT were studied, peripheral blood simples and bone marrow smear were examined, morphologic change of bone marrow cells was observed, while the HLA genotype and chromosome karyotye were analyzed by PCR and routine G-banding methods, respectively. The results indicated that the two cases were diagnosed primarily as acute lymphocytic leukemia (common cell subtype) and acute megakaryocytic leukemia, in which chromosome abnormalities or activation of protooncogene in leukemic cells were observed. The complete hematopuietie reconstitution of donor origin was obtained in these 2 cases after HLA HBMT, but the leukemic cells in these 2 leukemia patients were confirmed to be donor origin after relapse, their blood groups and HLA genotype were found to be originated from donor. These 2 relapsed leukemia patients were diagnosed as acute lymphocytic leukemia (B cell subtype) and acute megakaryocytic leukemia. It is suggested that high-dose of immunosuppressive agents used in transplantation may contribute to leukemia relapse of donor origin in these patients. Abnormalities in hematopoietic microenvironment may be also involved in the leukemia development. Donor-cell leukemia after allogeneic hematopoietic stem cell transplantation can be an ideal model to investigate the related events in human leukemogenesis.

A prospective study of the natural history of transient leukemia (TL) in neonates with Down syndrome (DS): Children's Oncology Group (COG) study POG-9481

A unique transient leukemia (TL) has been described in newborns with Down syndrome (DS; or trisomy 21 mosaics). This leukemia has a high incidence of spontaneous remission; however, early death and subsequent development of acute megakaryoblastic leukemia (AMKL) have been reported. We prospectively evaluated 48 infants with DS and TL to determine the natural history and biologic characteristics of this disease, identify the clinical characteristics associated with early death or subsequent leukemia, and assess the incidence of subsequent leukemia. Blast cells associated with TL in DS infants exhibited FAB M(7) morphology and phenotype. Most infants (74%) had trisomy 21 (or mosaicism) as the only cytogenetic abnormality in the blast cells. Most children were able to spontaneously clear peripheral blasts (89%), normalize blood counts (74%), and maintain a complete remission (64%). Early death occurred in 17% of infants and was significantly correlated with higher white blood cell count at diagnosis (P < .001), increased bilirubin and liver enzymes (P < .005), and a failure to normalize the blood count (P = .001). Recurrence of leukemia occurred in 19% of infants at a mean of 20 months. Development of leukemia was significantly correlated with karyotypic abnormalities in addition to trisomy 21 (P = .037). Ongoing collaborative clinical studies are needed to determine the optimal role of chemotherapy for infants at risk for increased mortality or disease recurrence and to further the knowledge of the unique biologic features of this TL.

Acute megakaryoblastic leukemia with erythrophagocytosis and thrombosis in a dog

A 7-year-old, intact male Dachshund was presented to the Lyon veterinary school for lethargy and anorexia of several weeks duration. The main clinical signs were pale and icteric mucous membranes, hepatomegaly, splenomegaly, and lymphadenopathy. Results of a CBC and plasma biochemistry tests revealed severe nonregenerative anemia, thrombocytopenia, and increased alanine aminotransferase and alkaline phosphatase activities. Blood smear evaluation and cytologic examination of lymph node and bone marrow aspirate specimens revealed a large population of poorly differentiated blast cells with morphologic features suggesting megakaryocytic lineage. A low number of well-differentiated but dysplastic megakaryocytes also were observed in lymph node and bone marrow smears. A few blast cells were erythrophagocytic. Blast cells were positive for glycoprotein IIIa, factor VIII-related antigen, and factor XIII using immunocytochemistry. The dog was euthanized and necropsied. Histologic findings consisted of diffuse, massive infiltration of lymph nodes, liver, and spleen by megakaryoblasts and atypical megakaryocytes, with widespread thrombosis. This case confirms the usefulness of immunochemistry, including for factor XIII, in the diagnosis of megakaryoblastic leukemia, and demonstrates the unique features of tumor cell erythrophagocytosis and marked fibrinous thrombosis, which have not been reported previously in dogs.

Acute megakaryoblastic leukaemia with extreme thrombocytosis and p190 bcr/abl rearrangement

Acute megakaryoblastic leukaemia (AML-M7) is an uncommon disease, composing 0.5-1.2% of newly diagnosed adult acute myeloid leukaemias (AML). It is characterised by higher incidence and complexity of cytogenetic abnormalities. We report a rare case of Philadelphia (Ph) chromosome-positive AML-M7, presenting with extreme thrombocytosis and having a poor outcome. The diagnosis was established on the basis of morphological and flow cytometry data for megakaryoblastic proliferation in the bone marrow. Cytogenetics revealed 47,XX,+8,t(9;22)(q34;q11), and p190(BCR-ABL)-rearrangement was detected. MDR1-gene overexpression was not demonstrated; however, the patient was resistant to therapy and died in 6 months. The reported case contributes to the overt heterogeneity of Ph-positive AMLs, which warrants further investigation and understanding.

Acute megakaryoblastic leukaemia: a clinico-haematological profile of five cases

Herein we are presenting the clinical, morphological and cytochemical characteristics of five cases of acute megakaryoblastic leukaemia (AML-M7) seen by us over a period of five years (Jan 1996-Dec 2000). Morphological assessment revealed marked polymorphism of blast cells and platelets both in the peripheral blood and bone marrow smears in all cases. Size of the blast cells ranged from very small to very large multinucleated cells, with variable chromatin pattern and number of nucleoli. More differentiated megakaryocytic cells showing cytoplasmic blebs, protrusions and platelet budding with bizarre platelet morphology were characteristic features suggesting the diagnosis. Cytochemical stains like myeloperoxidase, sudan black and PAS were positive in 5-15% of blast cell. Coagulation studies revealed a normal coagulation profile, whereas platelet studies showed marked impairment in aggregation of platelets with ADP and adrenalin with a normal PF-3 availability.

Biology, clinical, and hematologic features of acute megakaryoblastic leukemia in children

To assess the incidence, clinical features at presentation, hematologic, immunophenotypic, and cytogenetic characteristics of AMKL in children we prospectively studied 834 consecutive non selected children with newly diagnosed acute leukemia (AL) admitted to the Hematology Department at the Instituto Nacional de Pediatría (INP), Mexico, D.F. We found 682 cases (81.8%) with a typical ALL immunophenotype, and the remaining 152 (18.2%) were considered to have AML. In 29 of the 152 patients with AML studied, a diagnosis of AMKL was established. These 29 cases represented 19.1% of the cases of AML and 3.48% of the total cases of AL during the time span covered by the study. Twenty-four percent of the cases occurred in infants 2 years old or younger and 41.4% occurred in children 41 months of age or younger. In contrast, in only 18.6% of the patients with AML (M0-M6), the diagnosis was established before 42 months of age and in 17% before their second year of life. Clinical presentation was not strikingly different than that observed in patients with other types of AML, and the time interval from onset of symptoms to diagnosis was also similar, though in a small subset of patients, the clinical course was characterized by a chronic slowly progressive disorder extending over weeks or months resembling smoldering leukemia or chronic myelofibrosis with agnogenic myeloid metaplasia. Bone marrow (BM) fibrosis was a constant features in our patients; 75% of the patients studied showed this complication at the time of diagnosis. Some rather unusual findings in this study were intense skeletal pains from multiple osteolytic lesions, the presence of soft-tissue tumor, and the presence of cohesive scanty clusters of primitive-looking blast cells in BM aspirates. Several interesting cytogenetic findings in our study were t(1;22)(p13;q13) in a 14-year-old boy, t(9;22)(q34;q11) in one patient, and monosomy 7 in two patients. Another important finding in our study was the clinical association with colonic adenocarcinoma in one patient, an association that to our knowledge has not been reported previously. In conclusion, our data suggest that the incidence of AMKL in Mexico might be higher than those reported in Caucasian white pediatric population, and that biologic and cytogenetic profile may differ from those of western countries, but more studies are needed to corroborate cytogenetic heterogeneity, ethnic and geographic diversity. Early onset of the disease, low WBC counts, slight thrombocytopenia or normal platelet counts, and BM fibrosis were characteristic distinctive features of at least half of the patients with this subtype of AML.

Megakaryoblastic transformation of polycythemia vera with hypercalcemia

Polycythemia vera (PV) is known to occasionally transform into acute leukemia. Administration of alkylating agents seems to be associated with an increased risk of leukemic transformation of PV. Hypercalcemia is a serious complication of malignancies, but it is uncommon in acute leukemia. In the majority of malignancies with hypercalcemia, elevated parathyroid hormone-related protein (PTHrP) is thought to be the main cause of hypercalcemia. We report a rare case of megakaryoblastic transformation of PV with hypercalcemia. A 62-year-old man was diagnosed as having PV in 1983, and he had received ranimustine and busulfan. He developed acute megakaryoblastic leukemia 17 years after the initial diagnosis of PV. Serum calcium was elevated, the serum level of intact parathyroid hormone (PTH) was suppressed, and the level of intact PTHrP was slightly elevated. He had no lytic bone lesions; however, uncoupling of bone turnover due to an increase in bone resorption and a decrease in bone formation was detected by using biochemical markers. Since the level of PTHrP was slightly elevated from the normal value, we speculated that PTHrP produced in the local field by leukemic cells might have been more abundant than circulating PTHrP. Pamidronate and adrenocortical hormone were effective in reducing the serum calcium level. However, the patient died shortly after the start of induction chemotherapy. The prognosis of cases of PV that has transformed into acute leukemia is generally poor because the majority of such cases are refractory to chemotherapy.

Acute megakaryoblastic leukemia after transient myeloproliferative disorder with clonal karyotype evolution in a phenotypically normal neonate

We report a case of transient myeloproliferative disorder (TMD) in a neonate without features of Down syndrome (DS) with clonal karyotype evolution, after apparent spontaneous resolution of TMD, but eventually progressing to acute megakaryoblastic leukemia (AMKL). The patient had petechiae, thrombocytopenia, and blastemia. Trisomy 21 with a satellited Y chromosome (Yqs) was found in proliferating blasts. A stimulated peripheral blood culture confirmed the constitutional origin of the Yqs, but did not reveal the presence of any trisomic 21 cell. By the age of 3 months, clonal chromosome evolution in the form of an interstitial deletion of the long-arm of chromosome 13 [del(13)(q13q31)] was detected along with trisomy 21 in unstimulated bone marrow cultures. However, remission was achieved without treatment at the age of 4 months. Trisomy 21 and del(13)(q13q31) were not identified in either cytogenetics or fluorescence in situ hybridization studies at that time. The child was asymptomatic until the age of 20 months when anemia and thrombocytopenia prompted a bone marrow biopsy, revealing changes consistent with AMKL. The remission proceeded by clonal karyotype evolution in a neonate with TMD demonstrates that clonal karyotype evolution does not indicate an immediately progressive disease. However, the development of AMKL after TMD in this case illustrates the increased risk for leukemia in TMD cases, even without DS. The gradual clonal evolution of the blasts in our patient suggests that "multiple hits" oncogenesis applies to TMD progression to acute leukemia.

Telomerase and the benign and malignant megakaryoblastic leukemias of Down syndrome

The most common form of leukemia in Down syndrome patients is megakaryoblastic leukemia. There are two forms of the disease. Transient leukemia (TL) is a form of megakaryoblastic leukemia that occurs in newborns with Down syndrome and usually disappears spontaneously within the first 3 months of life. Acute megakaryoblastic leukemia (AMKL) occurs in Down syndrome children within the first 4 years of life and is fatal without treatment. The megakaryoblasts of TL and AMKL are indistinguishable by light and electron microscopy; yet, TL is benign and AMKL is malignant. One of the hallmarks of many malignancies is the expression of telomerase. It is therefore hypothesized that the transient, benign form of megakaryoblastic leukemia (TL) would not contain telomerase activity, whereas telomerase would be demonstrable in the malignant form of the disease. Telomerase activity was determined in the blood and/or bone marrow aspirates in 29 cases of AMKL and 34 cases of TL. The authors found telomerase activity in 15 of 29 (52%) cases, of AMKL and in only 4 of 34 (12%) cases of TL (P < 0.001). Furthermore, three of the four telomerase-positive TL cases were particularly severe, of which two were fatal. Telomerase activity is found frequently in the leukemic cells of the malignant form of megakaryoblastic leukemia but rarely in the benign form of the disease (TL). Observations provide evidence that telomerase may be a critical factor for the malignant conversion of leukemic cells.

Hypercalcemia complicating leukemic transformation of agnogenic myeloid metaplasia-myelofibrosis

Hypercalcemia is a common and potentially life-threatening metabolic derangement associated with many malignancies, especially solid tumors and multiple myeloma. Hypercalcemia has been reported only rarely with acute myelogenous leukemia. We describe a patient who developed hypercalcemia in association with transformation of agnogenic myeloid metaplasia into M7 acute myelogenous leukemia. Laboratory investigation revealed low levels of serum parathyroid hormone, undetectable levels of parathyroid hormone-related peptide, and normal levels of 25-hydroxyvitamin D. These observations suggest that another mediator was responsible for hypercalcemia in this patient. Awareness of this rare complication of acute myelogenous leukemia is essential for prompt diagnosis and management.

Mutational analysis of the tumor suppressor Smad2 in acute lymphoid and myeloid leukemia

Smad4 is a tumor suppressor that is inactivated in about 50% of pancreatic carcinomas. Mutations in this gene have also been found with variable, yet much lower frequency in other tumor types and were absent from a large number of samples from patients with hematological malignancies. Smad2 shows considerable sequence similarity with Smad4 and cooperates with it in the growth inhibitory TGF-beta pathway. Smad2 mutations have been found in a fraction of colon carcinomas and have been shown to impair the function of the corresponding proteins. However, only a few other tumor types have been screened for Smad2 mutations so far. Therefore, we analyzed 50 primary tumor samples from patients with acute lymphoid or myeloid leukemia (ALL or AML) and five cell lines of hematopoietic origin for alterations in the Smad2 gene. None of the specimens tested carried mutations in the conserved MH1 or MH2 domains of Smad2.

Platelet-like particle formation in the human megakaryoblastic leukaemia cell lines, MEG-01 and MEG-01s

The platelet-sized particle formation in the human megakaryoblastic leukaemia cell line MEG-01 and its subline MEG-01s was examined. MEG-01 and MEG-01s cells spontaneously released platelet-sized particles into the culture medium, in which the cells occasionally extended cytoplasmic processes similar to those of megakaryocyte proplatelets. Scanning electron microscopic images showed cytoplasmic processes elongated from blebs on the MEG-01 and MEG-01s cell surface and were constricted between segments of platelet size. Immunofluorescence staining with anti-tubulin antibody showed that the cytoplasmic processes contained microtubules that were organized into a ring, which is a characteristic of circulating platelets. Some platelet-sized particles, probably released by ruptures at the sites of the process constriction, were metabolically active in an MTT assay (about 50%). Some particles also expressed the platelet-specific glycoproteins GPIIb, IIIa and GMP-140. Rarely, in response to thrombin, particles underwent a shape change from spherical to a shape with irregular membrane protrusions and fine filopodia, and aggregating with one another. The particles also had increased GMP-140 (P-selectin) expression with the addition of thrombin. These results show the usefulness of the MEG-01 and MEG-01s cell lines for the study of thrombopoiesis.

CD34+ megakaryoblastic leukaemic cells are CD38-, but CD61+ and glycophorin A+: improved criteria for diagnosis of AML-M7?

The aim of this flow cytometry study in acute megakaryoblastic leukaemia (AML-M7) was to describe the membrane phenotype of CD34+ progenitor subsets and compare these with the phenotypes expressed by other AML FAB types. Following conventional histopathological diagnosis mononuclear cells from bone marrow and blood were examined in seven patients with AML-M7 and compared with results from 26 sequential patients with AML-M0 to AML-M6. The CD34+ subsets in AML-M7 patients differed from that of patients with AML-M0 to AML-M6 as the CD34+ CD61+ and the CD34+ Glycophorin A+ subsets were median 31% and 20%, respectively, compared to 4% and 2% in the AML-M0 to AML-M6 (P = 0.0005). Only 1% of the CD34+ progenitors were CD34+ CD38+ in AML-M7 compared to 72% in other AML subtypes (P < 0.000). These findings suggest that the CD34+ cell compartment in AML-M7 consists of early lineage-specific progenitors. In conclusion, flow cytometry analysis of CD34+ subsets may improve the diagnostic safety in AML-M7 and consequently the prognostic significance of immunophenotyping in acute leukaemia.

Chronic myeloid leukemia manifested during megakaryoblastic crisis

We describe a 38-year-old man with a chronic myeloproliferative syndrome characterized by elevated white blood cell and platelet counts and increased blasts in the peripheral blood. Bone marrow aspiration was a "dry tap" and the biopsy specimen was hypercellular with numerous blasts, atypical megakaryocytes, and increased reticulin fibrosis. The blasts exhibited cytochemical reactivity for nonspecific esterase and PAS and immunohistochemically were positive for factor VIII, supporting megakaryoblastic lineage. Cytogenetic studies of peripheral blood revealed the t(9;22)(q34;q11). We interpreted these findings to be most consistent with chronic myeloid leukemia (CML) manifested at the time of megakaryoblastic crisis. Although the initial complete blood count showed leukocytosis and thrombocytosis, the patient subsequently had pancytopenia with clinical and pathologic findings consistent with acute myelofibrosis (AMF). Cytosine arabinoside and etoposide chemotherapy induced remission of the acute leukemia. We conclude that CML infrequently presents itself in megakaryoblastic crisis and that such cases may result in the clinicopathologic syndrome of AMF. The success of chemotherapy in this case also suggests that intensive antileukemic therapy may be useful in other patients with either CML-blast crisis or the clinicopathologic syndrome of AMF.

A case of megakaryoblastic leukemia in a dog

An 8-year-old intact female Maltese was presented with anorexia and weight loss. Severe anemia, leukocytosis, and marked thrombocytosis were noticed. Blast cells resembled to megakaryoblasts were observed in peripheral blood smear. Based on bone marrow biopsy and histopathological examination, it was diagnosed as megakaryoblastic leukemia. Canine megakaryoblastic leukemia is very rare, however this is the first case report in Japan.

Acute megakaryoblastic leukaemia with mediastinal tumor

Acute megakaryoblastic leukemia (AMKL) is a rare myeloproliferative syndrome with a fulminant clinical course characterized by progressive pancytopenia, pallor, weakness and severe hemorrhage. We present a 18-year old male with pancytopenia and massive hemorrhage, lymphadenopathy, organomegaly, and with unusual presentation of retrocardial mediastinal tumor on the right side. The diagnosis of AMKL was established by combining cytological and immunocytochemical analyses of peripheral blood cells (blasts were GPIIIa and GPIb positive); by immunohistochemical analysis of lymph node (dysplastic megakaryocytes were GPIIIa and F VIII positive); in vitro culture studies confirmed enormous growth of CFU-Mk with high proliferative capacity. In spite of therapy, the patient died 3 months after the first signs of the disease.

Demonstration of feline and canine platelet glycoproteins by immuno- and lectin histochemistry

Canine and feline platelet cytocentrifuge preparations (CCPs), cryostat and paraffin-embedded bone marrow sections were used in this study. We evaluated whether platelets, megakaryocytes and megakaryocyte precursor cells could be labelled by monoclonal antibodies (Y2/51, CLB-thromb/1, HPL1) against human platelet membrane glycoprotein GP IIIa and the GP IIb/IIIa complex or by the following 10 biotinylated lectins: concanavalin A (Con A), Lens culinaris agglutinin (LCA), Pisum sativum agglutinin (PsA), wheat germ agglutinin (WGA), peanut agglutinin (PNA), Phaseolus vulgaris lectin (PHA-L), Ricinus communis agglutinin 120 (RCA120), Ulex europaeus agglutinin-I(UEA-1), soybean agglutinin (SBA) and Dolichos biflorus agglutinin (DBA). Monoclonal antibodies Y2/51 and HPL1 cross reacted with platelets and megakaryocytic cells from both species, whereas CLB-thromb/1 was unreactive with canine preparations. Only Y2/51 labelled megakaryocytic cells in paraffin-embedded samples. LCA, PSA, WGA and PHA-L labelled feline and canine platelets and different numbers of morphologically identifiable megakaryocytes and numerous other, mostly myeloid, cells. Immunoblots of dog and cat platelet lysates using Y2/51 visualized a single protein of 95 kDa (unreduced), a mol.wt value within the range of those reported for GP IIIa. Some of the platelet (but not necessarily megakaryocyte) glycoproteins reacting with LCA, PSA and WGA could be identified in lectin blots following one- or two (nonreduced/reduced)-dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Thus in dogs and cats, the immunohistochemical detection of GP IIIa (and eventually GP IIb/IIIa) rather than lectin binding patterns could be important for the diagnosis of megakaryoblastic leukaemias.

Acute megakaryoblastic leukemia in children and adolescents: a retrospective analysis of 24 cases

In order to characterize the clinical, cytogenetic, and outcome features of childhood acute megakaryoblastic leukemia (AMKL), we reviewed 24 cases; 14 were identified among 150 consecutive newly diagnosed acute myelogenous leukemia (AML) patients at St. Jude Children's Research Hospital, and 10 were cases referred to the National Institute of Cancer in Rio de Janeiro, Brazil. There were 5 Down syndrome patients and one patient with chronic myeloid leukemia (Ph+) in blastic crisis. Twelve patients had significant hepatosplenomegaly. Leukemic cell morphology and cytochemistry were consistent with the M7 classification in 17 cases, and all cases tested expressed megakaryocytic surface antigens. AMKL patients were significantly younger than other AML patients (P = 0.0001) and had poorer responses to therapy (P = 0.03, univariate analysis only). Ten of 24 failed induction, and only 5 are disease-free at 6 months to 4.5+ years. We conclude that AMKL usually affects young children, frequently producing marked organomegaly. It comprises approximately 10% of pediatric AML cases, and responds poorly to intensive AML therapies.

Acute megakaryoblastic leukemia in one cat and two dogs

The clinical, hematologic, and histologic features of acute megakaryoblastic leukemia are described for an 8-year-old female Domestic Shorthair cat, a 3-year-old female mixed-breed dog, and a 3-year-old male German Shepherd Dog. The neoplastic cells were characterized as belonging to the megakaryocytic lineage. The following techniques were used: electron microscopy; detection of antibodies against human von Willebrand factor (vWF) and human platelet glycoprotein GP IIIa using a modified avidin biotin peroxidase complex technique on formalin-fixed paraffin sections; and enzyme histochemical methods on plastic sections for alkaline phosphatase, acid phosphatase, myeloperoxidase, alpha-naphthyl acetate esterase, alpha-naphthyl butyrate esterase, naphthol AS acetate esterase, and naphthol AS-D chloroacetate esterase. In addition, benign megakaryocytic cells, platelets, and neoplastic cells were labeled with lectins that have partially been shown to bind to platelet glycoproteins of other species. In healthy cats and dogs, the megakaryocytes and platelets reacted with lectins PSA, LCA, PHA-L, and WGA. Megakaryocytes and platelets from healthy cats were also labeled by lectin PNA. The lectins PHA-L and WGA reacted with neoplastic cells from the cat and both dogs. Lectin PNA bound to neoplastic cells from the cat, and lectins PSA, LCA, and SBA bound to neoplastic cells from both dogs. For the retrospective examination of paraffin-embedded material, the detection of vWF and GP IIIa appears to be the most reliable method for the identification of megakaryocytic cells.

Characterization of an acute micromegakaryocytic leukaemia: evidence for the pathogenesis of myelofibrosis

The current hypothesis for the pathogenesis of myelofibrosis involves the intramedullary release of growth factors from defective or abnormal megakaryocytes. We describe a case of an acute micromegakaryocytic leukaemia, in a patient with chronic myelofibrosis, that provides additional evidence for this concept. The micromegakaryocytes, which reached 223 x 10(9)/l, were characterized morphologically by both light and electron microscopy, immunocytochemically and by platelet peroxidase activity. The cells were shown to have a mature cytoplasm, containing alpha granules and the associated proteins; vWF:Ag, fibrinogen, fibronectin and protein S. DNA analysis, by both a Seescan Solitaire Plus image analysis system and flow cytometry, revealed nuclear immaturity, with 92% of cells being diploid. Serum markers of connective tissue synthesis, namely carboxy terminal peptide of procollagen I (PICP), procollagen terminal peptide III (PIIIP) and laminin all increased significantly following transformation and were associated with an increase in platelet-derived growth factor (PDGF) and transforming growth factor-beta (TGF-beta). These observations support the current hypothesis for bone marrow fibrosis formation and provide, for the first time, a link between in vivo growth factor release, bone marrow stromal turnover and megakaryocyte mass. In addition, the release of biologically active TGF-beta may explain both the increased fibronectin and angiogenesis characteristic of myelofibrotic bone marrow.

Serum CD4, CD8, and interleukin-2 receptor levels in childhood acute myeloid leukemia

Leukemic cell expression and serum levels of CD4, CD8, and interleukin-2 receptor (IL-2R) were determined at diagnosis for children or adolescents with acute myeloid leukemia (AML). Cellular expression of CD4 was detected in 18 of 62 cases, CD8 in none of 60 cases, and IL-2R in one of 33 cases tested. Myeloblasts of the M4 and M5 subtypes expressed CD4 significantly more frequently than other FAB subtypes (p = 0.0001). Serum levels of the three soluble factors (tested for 91 patients) were positively correlated with each other. Increased serum CD4 levels were significantly associated with cellular CD4 expression, high leukocyte count, M5 leukemia, spleen enlargement, and age less than 1 year. High serum CD8 levels correlated significantly with splenomegaly, extramedullary disease, absence of Auer rods, and high leukocyte count. Cases with high serum IL-2R levels were less likely to have Auer rods and more likely to have splenomegaly and M5 leukemia; serum levels greater than 750 U/ml were associated with a higher probability of treatment failure (p = 0.05), even after adjustment for other potential prognostic factors. Further studies of serum CD4, CD8, and IL-2R levels may help to clarify the immunoregulatory role of T-cells in patients with AML.

Signal transduction of the human granulocyte-macrophage colony-stimulating factor and interleukin-3 receptors involves tyrosine phosphorylation of a common set of cytoplasmic proteins

Human granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-3 (IL-3) exert multiple effects on the proliferation, differentiation, and function of myeloid lineage cells through their interaction with specific cell-surface receptors. There is a considerable degree of overlap in the biological effects of these two growth factors, but little is known about the mechanisms of postreceptor signal transduction. We have investigated the effects of GM-CSF and IL-3 on protein tyrosine-kinase activity in a human cell line, MO7E, which proliferates in response to either factor. Tyrosine-kinase activity was detected using immunoblotting with a monoclonal antibody (MoAb) specific for phosphotyrosine. GM-CSF and IL-3 were found to induce a nearly identical pattern of protein tyrosine phosphorylation using both one- and two-dimensional gel electrophoresis. Tyrosine phosphorylation of two cytosolic proteins in particular was increased more than 10-fold, a 93-Kd protein (pp93) and a 70-Kd protein (pp70). Tyrosine phosphorylation of pp93 and pp70 was observed within 1 minute, reached a maximum at 5 to 15 minutes, and gradually decreased thereafter. Other proteins of 150, 125, 63, 55, 42, and 36 Kd were also phosphorylated on tyrosine in response to both GM-CSF and IL-3, although to a lesser degree. Tyrosine phosphorylation was dependent on the concentration of GM-CSF over the range of 0.1 to 10 ng/mL and on IL-3 over the range of 1 to 30 ng/mL. Stimulation of MO7E cells with 12-0-tetradecanoyl-phorbol-13-acetate (TPA) or cytokines such as G-CSF, M-CSF, interleukin-1 (IL-1), interleukin-4 (IL-4), interleukin-6 (IL-6), interferon gamma, tumor necrosis factor (TNF), or transforming growth factor-beta (TGF-beta) did not induce tyrosine phosphorylation of pp93 or pp70, suggesting that these two phosphoproteins are specific for GM-CSF-or IL-3-induced activation. The extent and duration of phosphorylation of all the substrates were increased by pretreatment of cells with vanadate, an inhibitor of protein-tyrosine phosphatases. Importantly, culture of MO7E cells with vanadate (up to 10 mumol/L) resulted in a dose-dependent increase in GM-CSF-or IL-3-induced proliferation of up to 1.8-fold. These results suggest that tyrosine phosphorylation may be important for GM-CSF and IL-3 receptor-mediated signal transduction and that cell proliferation may be, at least partially, regulated by a balance between CSF-induced protein-tyrosine kinase activity and protein-tyrosine phosphatase activity.

[Beta-thromboglobulin and platelet factor 4 in a follow-up of acute myelofibrosis (megakaryoblastic leukemia)]

We report a patient with acute myelofibrosis (AM) in whom a megakaryocytic origin was demonstrated after conventional microscopy, investigation with monoclonal antibodies directed against the glycoprotein complex IIb/IIIa (CD41a) and the platelet peroxidase (PPO) reaction. Thus, a diagnosis of acute megakaryoblastic leukemia (AMGL) was made. It is now known that this megakaryoblastic proliferation is responsible for myelofibrosis as an increased release of platelet-derived growth factor (PDGF), beta-thromboglobulin (BTG), and platelet factor 4 (PF4) develops because ineffective megakaryocytopoiesis and failure of these clonal populations to store the mentioned substances in their alpha granules. At the time of diagnosis, the plasma concentrations of BTG and PF4 were measured and were found to be high. Thus, an increased PDGF level was indirectly assumed, with the subsequent fibroblast stimulation. After treatment with low dose cytosine arabinoside, a clinical, analytical and histological remission was achieved, with a return of BTG and PF4 values to the normal range. It was therefore concluded that the follow up of these parameters is useful for the diagnosis and the establishment of remission criteria in these patients.

Childhood acute megakaryoblastic leukemia with internalization of hemic cells

Two atypical cases of acute megakaryoblastic leukemia (AMKL) in infants diagnosed by immunophenotying are described. In both cases, the leukemic cells at diagnosis resembled monoblasts with reniform nuclei, fine reticular chromatin, and abundant grey-blue cytoplasm with pseudopods. In addition, these blasts frequently showed internalization of hemic cells. Therefore, the diagnosis of acute monocytic leukemia (AMOL) or malignant histiocytosis (MH) was initially suggested. However, alpha-naphthyl butyrate esterase stain was negative and immunologic studies determined megakaryocytic lineage of the blasts. Our observation in two consecutive cases of AMKL implies that there is a potential risk of misdiagnosing AMKL as AMOL or MH in infants. The incidence and significance of internalization of hemic cells by blast cells of AMKL in infancy are unknown and we cannot be certain whether these cases constitute a subgroup of AMKL in infancy.

Platelet vacuoles in acute megakaryoblastic leukemia

The case of a 53-year-old man with acute megakaryoblastic leukemia (M7) was studied. At time of diagnosis, the platelet count was 980 X 10(9)/L and abnormal platelet vacuoles were present. The vacuoles were periodic acid-Schiff (PAS) positive. Electron microscopic examination showed large aggregates of glycogen. Findings of qualitative platelet function studies were abnormal. The authors' study and review of the literature indicates that thrombocytosis with large platelet vacuoles accompanying a blast cell population suggests a diagnosis of M7 and indicates the need for appropriate confirmatory studies.

[Megakaryocytic myelosis--clinical aspects, morphology and platelet function]

The study reviews 22 patients, aged between 19 to 73 years, with megakaryocytic myelosis. In the course of the disease 11 patients presented haemorrhagic manifestations, 12 patients thrombotic complications, and 6 patients the association of haemorrhage and thrombosis. The maximum platelet counts ranged from 524 to 2700 x 10(9)/l. The bone marrow showed a conspicuous megakaryocytic proliferation with polyploidy of the nuclei, giant forms and clusters. Marked alterations of erythro- and granulopoiesis were excluded. There was no evidence for a reactive thrombocytosis in any case. Patients with thrombocythaemia due to megakaryocytic myelosis (n = 14), with secondary thrombocytosis of various origin (n = 16), and a control group of healthy donors (n = 20) were investigated with respect to the aggregation behaviour and the total calcium content of blood platelets. In 9 of 14 patients with megakaryocytic myelosis platelet rich plasma did not respond to epinephrine (15 mumol/l), a concentration which induced at least weak aggregation in 14 of 16 patients with secondary thrombocytosis and also in healthy subjects. In patients with megakaryocytic myelosis the mean extent of aggregation induced by epinephrine, collagen or adenosine diphosphate was significant lower as compared to controls whereas in patients with secondary thrombocytosis in most cases this parameter did not differ significantly from that of controls. The total calcium content of platelets was significantly lower in both groups of patients as compared to controls. In 14 patients with megakaryocytic myelosis the concentration of the glycoprotein (GP) IIb-IIIa complex was estimated by crossed- and rocket-immunoelectrophoresis and found to be decreased in 8 of them.(ABSTRACT TRUNCATED AT 250 WORDS)

Platelet dysfunction in acute megakaryoblastic leukemia

Platelet function profiles were studied in 3 patients with megakaryoblastic leukemia. All patients had a moderate decrease in platelet counts with abnormal platelet retention. One patient who developed hemorrhagic diathesis had prolonged bleeding time. In all patients platelet aggregation was defective after the addition of ADP, collagen, adrenaline, or U46619, a thromboxane A2 agonist. Malondialdehyde was reduced in all patients, as was platelet serotonin. Plasma beta-thromboglobulin levels were normal in all cases whereas PF4 was markedly elevated in one. Platelet dysfunction was not reversed by clinical remission. These studies confirm that megakaryoblastic leukemia is associated with a thrombocytopathy which may play a role in hemorrhagic diathesis and should be taken into account in the management of these patients.

Refractory anemia terminating in acute megakaryoblastic leukemia (M7)

A 72-year-old man with refractory anemia (RA) developed overt megakaryoblastic leukemia after the course of RA with excess of blasts. The blasts were positive for platelet peroxidase activity and had platelet glycoproteins (GPs) such as GPIIb/IIIa and GPIIIa. The bone marrow biopsy at terminal stage disclosed marked fibrosis. The nature of the megakaryoblasts was investigated. The blasts did not differentiate morphologically into mature megakaryocytes with TPA addition. In vitro colony assay showed the failure of colony-forming unit, megakaryocyte growth in peripheral blood. The pathogenesis of myelofibrosis in our patient is discussed.

Leukemias with megakaryoblastic involvement: clinical, hematologic, and immunologic characteristics

The clinical, hematologic, and phenotypic features of 28 patients with acute leukemia with megakaryocytic involvement (AMKL) were analyzed. The prevalence of this type of leukemia in the entire series was 11.6%, with a higher incidence among patients with acute transformation of a previous myeloproliferative disorder (MPD) (24%) than among the transformed myelodysplastic syndrome (13%) patients. The incidence in the "de novo" ANLL was 8% and 16% among secondary leukemias. The presence of bone marrow fibrosis together with low WBC and normal or increased platelet counts despite a severe anemia are the most relevant features in these patients who otherwise displayed an apparently poor prognosis. Megakaryoblasts were morphologically recognized more frequently in the acute transformations of MPD than in de novo ANLL. Only two cases were considered pure AMKL, and in the remaining 26 patients, megakaryoblasts coexisted with other granulomonocytic and/or erythroid populations. Antiglycoprotein IIIa (anti-GPIIIa) (C17) and anti-GPIIb/IIIa (CDw41-, J15-) antibodies are probably the best markers for AMKL, although the monoclonal antibody against GPIX (FMC25) was also positive in a majority of cases but in a lower percentage of cells. On the other hand, megakaryoblasts were generally negative for granulocytic or monocytic markers (CD13, CD14, CD15); the expression of HLA-DR antigens in these cells was variable. Our present results indicate that megakaryoblastic involvement is more common than previously recognized. This is true not only in acute transformed leukemias but also in de novo ANLL. Although the diagnosis of these cases should be based on megakaryocytic markers, it is often possible to suspect a diagnosis according to certain clinical and hematologic features.

Hypercalcemia complicating a megakaryoblastic crisis of chronic myelocytic leukemia

A 38-year-old woman with megakaryoblastic chronic myelocytic leukemia (CML) crisis developed recurrent episodes of severe hypercalcemia, manifested by nausea and vomiting and later by dyspnea and hypoxia. The levels of serum parathyroid hormone and serum and urine cyclic AMP were normal. Autopsy revealed widespread metastatic calcifications in various organs, including the lungs. The case suggests that hypercalcemia complicating blast crisis of CML is not related to blast cell phenotype, can cause severe pulmonary malfunction, and is a terminal event. The hypercalcemia most probably resulted from bone resorption, either directly by the megakaryoblasts or by secretion of osteolytic substances.

Cytochemical characterization of leukemic cells with numerous cytoplasmic granules

Ten cases in which leukemic cells contained numerous cytoplasmic granules were examined by using a panel of cytochemical reactions. The diagnoses in the 10 cases were mast cell leukemia, chronic basophilic leukemia, and acute myeloid leukemia with basophilic differentiation in one case each, acute promyelocytic leukemia in two cases, acute megakaryoblastic leukemia in two cases, and blastic hairy cell leukemia in three cases. The cytochemical panel consisted of peroxidase, toluidine blue, chloroacetate esterase, aminocaproate esterase, tartrate-resistant acid phosphatase, and immunoalkaline phosphatase for platelet/megakaryocyte-specific antigen. The unusual cytologic features of leukemic cells in cases similar to our 10 cases have caused considerable diagnostic difficulties. In our 10 cases, however, the effective use of cytochemical studies helped to achieve accurate identification of the various types of leukemic cells. We conclude that the intelligent application of cytochemical techniques continues to be useful for the accurate cytodiagnosis of hematopoietic neoplasms.

Philadelphia chromosome-positive thrombocythemia and megakaryoblast leukemia

A case of well-documented and -illustrated megakaryoblastic transformation is described in a patient with thrombocythemia passing through a stage of myelofibrosis without features of chronic granulocytic leukemia. Immunocytologic studies with the use of conventional and monoclonal antibodies against platelet membrane glycoproteins and electron microscopic investigations, demonstrating bull's-eye granules and platelet peroxidase positivity, proved the megakaryocytic differentiation of the blast cells. From the onset of the disease as well as during the megakaryoblastic transformation, the Philadelphia (Ph1) karyotype, 46XX t(9:22) (q34:q11), was found in peripheral blood and bone marrow cells as the only clonal abnormality. Southern blot analysis of DNA extracted from the blast cells revealed a rearrangement within the bcr on chromosome 22 similar to findings in chronic granulocytic leukemia. The presentation with excessive small and abnormal megakaryocytes in the initial and subsequent bone marrow and the rapid progressive myelofibrosis and splenomegaly differentiate the Ph1 chromosome-positive thrombocythemia from the chronic myeloproliferation of thrombocythemia in its primary form or associated with polycythemia vera.