CCAAT/enhancer-binding protein alpha (CEBPA) gene haploinsufficiency does not alter hematopoiesis or induce leukemia in Lck-CALM/AF10 transgenic mice.

Although rare, CALM/AF10 is a chromosomal rearrangement found in immature T-cell acute lymphoblastic leukemia (T-ALL), acute myeloid leukemia, and mixed phenotype acute leukemia of T/myeloid lineages with poor prognosis. Moreover, this translocation is detected in 50% of T-ALL patients with gamma/delta T cell receptor rearrangement, frequently associated with low expression of transcription factor CCAAT/enhancer-binding protein alpha (CEBPA). However, the relevance of CEBPA low expression for CALM/AF10 leukemogenesis has not yet been evaluated. We generated double mutant mice, which express the Lck-CALM/AF10 fusion gene and are haploinsufficient for the Cebpa gene. To characterize the hematopoiesis, we quantified hematopoietic stem cells, myeloid progenitor cells, megakaryocyte-erythrocyte progenitor cells, common myeloid progenitor cells, and granulocyte-macrophage progenitor cells. No significant difference was detected in any of the progenitor subsets. Finally, we tested if Cebpa haploinsufficiency would lead to the expansion of Mac-1+/B220+/c-Kit+ cells proposed as the CALM/AF10 leukemic progenitor. Less than 1% of bone marrow cells expressed Mac-1, B220, and c-Kit with no significant difference between groups. Our results showed that the reduction of Cebpa gene expression in Lck-CALM/AF10 mice did not affect their hematopoiesis or induce leukemia. Our data corroborated previous studies suggesting that the CALM/AF10 leukemia-initiating cells are early progenitors with lymphoid/myeloid differentiating potential.

CCAAT/enhancer-binding protein alpha (CEBPA) gene haploinsufficiency does not alter hematopoiesis or induce leukemia in Lck-CALM/AF10 transgenic mice

Although rare, CALM/AF10 is a chromosomal rearrangement found in immature T-cell acute lymphoblastic leukemia (T-ALL), acute myeloid leukemia, and mixed phenotype acute leukemia of T/myeloid lineages with poor prognosis. Moreover, this translocation is detected in 50% of T-ALL patients with gamma/delta T cell receptor rearrangement, frequently associated with low expression of transcription factor CCAAT/enhancer-binding protein alpha (CEBPA). However, the relevance of CEBPA low expression for CALM/AF10 leukemogenesis has not yet been evaluated. We generated double mutant mice, which express the Lck-CALM/AF10 fusion gene and are haploinsufficient for the Cebpa gene. To characterize the hematopoiesis, we quantified hematopoietic stem cells, myeloid progenitor cells, megakaryocyte-erythrocyte progenitor cells, common myeloid progenitor cells, and granulocyte-macrophage progenitor cells. No significant difference was detected in any of the progenitor subsets. Finally, we tested if Cebpa haploinsufficiency would lead to the expansion of Mac-1+/B220+/c-Kit+ cells proposed as the CALM/AF10 leukemic progenitor. Less than 1% of bone marrow cells expressed Mac-1, B220, and c-Kit with no significant difference between groups. Our results showed that the reduction of Cebpa gene expression in Lck-CALM/AF10 mice did not affect their hematopoiesis or induce leukemia. Our data corroborated previous studies suggesting that the CALM/AF10 leukemia-initiating cells are early progenitors with lymphoid/myeloid differentiating potential.

Telomere length analysis in monoclonal B-cell lymphocytosis and chronic lymphocytic leukemia Binet A.

Monoclonal B-cell lymphocytosis (MBL) is an asymptomatic clinical entity characterized by the proliferation of monoclonal B cells not meeting the diagnosis criteria for chronic lymphocytic leukemia (CLL). MBL may precede the development of CLL, but the molecular mechanisms responsible for disease progression and evolution are not completely known. Telomeres are usually short in CLL and their attrition may contribute to disease evolution. Here, we determined the telomere lengths of CD5+CD19+ cells in MBL, CLL, and healthy volunteers. Twenty-one CLL patients, 11 subjects with high-count MBL, and 6 with low-count MBL were enrolled. Two hundred and sixty-one healthy volunteers aged 0 to 88 years were studied as controls. After diagnosis confirmation, a flow cytometry CD19+CD5+-based cell sorting was performed for the study groups. Telomere length was determined by qPCR. Telomere length was similar in the 3 study groups but shorter in these groups compared to normal age-matched subjects that had been enrolled in a previous study from our group. These findings suggest that telomere shortening is an early event in CLL leukemogenesis.

Biological X-ray irradiator characterization for use with small animals and cells.

This study presents the characterization of an X-ray irradiator through dosimetric tests, which confirms the actual dose rate that small animals and cells will be exposed to during radiobiological experiments. We evaluated the linearity, consistency, repeatability, and dose distribution in the positions in which the animals or cells are placed during irradiation. In addition, we evaluated the performance of the X-ray tube (voltage and tube operating current), the radiometric survey (leakage radiation) and safety devices. The irradiator default setting was established as 160 kV and 25 mA. Tests showed that the dose rate was linear overtime (R2=1) and remained stable for long (constant) and short (repeatability) intervals between readings. The mean dose rate inside the animal cages was 1.27±0.06 Gy/min with a uniform beam of 95.40% (above the minimum threshold guaranteed by the manufacturer). The mean dose rate inside the cell plates was 0.92±0.19 Gy/min. The dose rate dependence with tube voltage and current presented a quadratic and linear relationship, respectively. There was no observed mechanical failure during evaluation of the irradiator safety devices and the radiometric survey obtained a maximum ambient equivalent dose rate of 0.26 mSv/h, which exempts it from the radiological protection requirements of the International Atomic Energy Agency. The irradiator characterization enables us to perform radiobiological experiments, and assists or even replaces traditional therapy equipment (e.g., linear accelerators) for cells and small animal irradiation, especially in early research stages.

35 years of the Brazilian Journal of Medical and Biological Research.

The authors pay homage to the three founders of the Brazilian Journal of Medical and Biological Research Profs. Lewis Joel Greene, Sérgio Henrique Ferreira and Eduardo Moacyr Krieger for their vision and commitment to divulge the scientific production of developing countries.

FLORENCE: a randomized, double-blind, phase III pivotal study of febuxostat versus allopurinol for the prevention of tumor lysis syndrome (TLS) in patients with hematologic malignancies at intermediate to high TLS risk.

BACKGROUND: Serum uric acid (sUA) control is of key relevance in tumor lysis syndrome (TLS) prevention as it correlates with both TLS and renal event risk. We sought to determine whether febuxostat fixed dose achieves a better sUA control than allopurinol while preserving renal function in TLS prevention. PATIENTS AND METHODS: Patients with hematologic malignancies at intermediate to high TLS risk grade were randomized to receive febuxostat or allopurinol, starting 2 days before induction chemotherapy, for 7-9 days. Study treatment was blinded, whereas daily dose (low/standard/high containing allopurinol 200/300/600 mg, respectively, or fixed febuxostat 120 mg) depended on the investigator's choice. The co-primary end points, sUA area under curve (AUC sUA1-8) and serum creatinine change, were assessed from baseline to day 8 and analyzed through analysis of covariance with two-sided overall significance level of 5%. Secondary end points included treatment responder rate, laboratory and clinical TLS incidence and safety. RESULTS: A total of 346 patients (82.1% intermediate TLS risk; 82.7% assigned to standard dose) were randomized. Mean AUC sUA1-8 was 514.0 ± 225.71 versus 708.0 ± 234.42 mgxh/dl (P < 0.0001) in favor of febuxostat. Mean serum creatinine change was -0.83 ± 26.98% and -4.92 ± 16.70% for febuxostat and allopurinol, respectively (P = 0.0903). No differences among secondary efficacy end points were detected. Drug-related adverse events occurred in 6.4% of patients in both arms. CONCLUSION: In the largest adult trial carried out in TLS prevention, febuxostat achieved a significant superior sUA control with one fixed dose in comparison to allopurinol with comparable renal function preservation and safety profile. CLINICAL TRIAL REGISTRATION: NCT01724528.

Synthetic phosphoethanolamine has in vitro and in vivo anti-leukemia effects.

BACKGROUND: We recently showed that synthetic phosphoethanolamine reduces tumour growth and inhibits lung metastasis in vivo. Here, we investigated its anti-leukaemia effects using acute promyelocytic leukaemia (APL) as a model. METHODS: Cytotoxic effects of Pho-s on leukaemia cells were evaluated by MTT assay. Leukaemic cells obtained from hCG-PML-RARa transgenic mice were transplanted to NOD/SCID mice. After the animals were diagnosed as leukaemic, treatment started with Pho-s using all-trans retinoid acid or daunorubicin as positive control or and saline control. Cell morphology and immunophenotyping were used to detect the undifferentiated blast cells in the spleen, liver and bone marrow. The induction of apoptosis in vitro and in malignant leukaemic clones was evaluated. RESULTS: Synthetic phosphoethanolamine is cytotoxic and induces apoptosis through the mitochondrial pathway in vitro to leukaemia cell lines. In vivo Pho-s exhibits anti-proliferative effects in APL model reducing the number of CD117(+) and Gr-1(+) immature myeloid cells in the BM, spleen and liver. Synthetic phosphoethanolamine impairs the expansion of malignant clones CD34(+)/CD117(+), CD34(+) and Gr-1(+) in the BM. In addition, Pho-s induces apoptosis of immature cells in the spleen and liver, a notable effect. CONCLUSION: Synthetic phosphoethanolamine has anti-leukaemic effects in an APL model by inhibiting malignant clone expansion, suggesting that it is an interesting compound for leukaemia treatment.

Inhibition of NF- κ B by Dehydroxymethylepoxyquinomicin Suppresses Invasion and Synergistically Potentiates Temozolomide and γ -Radiation Cytotoxicity in Glioblastoma Cells.

Despite advances in neurosurgery and aggressive treatment with temozolomide (TMZ) and radiation, the overall survival of patients with glioblastoma (GBM) remains poor. Vast evidence has indicated that the nuclear factor NF- κ B is constitutively activated in cancer cells, playing key roles in growth and survival. Recently, Dehydroxymethylepoxyquinomicin (DHMEQ) has shown to be a selective NF- κ B inhibitor with antiproliferative properties in GBM. In the present study, the ability of DHMEQ to surmount tumor's invasive nature and therapy resistance were further explored. Corroborating results showed that DHMEQ impaired cell growth in dose- and time-dependent manners with G2/M arrest when compared with control. Clonogenicity was also significantly diminished with increased apoptosis, though necrotic cell death was also observed at comparable levels. Notably, migration and invasion were inhibited accordingly with lowered expression of invasion-related genes. Moreover, concurrent combination with TMZ synergistically inhibited cell growth in all cell lines, as determined by proliferation and caspase-3 activation assays, though in those that express O(6)-methylguanine-DNA methyltransferase, the synergistic effects were schedule dependent. Pretreatment with DHMEQ equally sensitized cells to ionizing radiation. Taken together, our results strengthen the potential usefulness of DHMEQ in future therapeutic strategies for tumors that do not respond to conventional approaches.

Disrupting membrane raft domains by alkylphospholipids.

Using phase contrast and fluorescence microscopy we study the influence of the alkylphospholipid, ALP, 10-(octyloxy) decyl-2-(trimethylammonium) ethyl phosphate, ODPC, in giant unilamellar vesicles, GUVs, composed of DOPC (1,2-dioleoyl-sn-glycero-3-phosphocholine), brain sphingomyelin (SM) and cholesterol (Chol). The results show that adding 100µM ODPC (below CMC) to the outer solution of GUVs promotes DOPC membrane disruption over a period of 1h of continuous observation. On the other hand, the presence of SM and Chol in homogeneous fluid lipid bilayers protects the membrane from disruption. Interestingly, by adding 100µM ODPC to GUVs containing DOPC:SM:Chol (1:1:1), which display liquid ordered (Lo)-liquid disordered (Ld) phase coexistence, the domains rapidly disappear in less than 1min of ODPC contact with the membrane. The lipids are subsequently redistributed to liquid domains within a time course of 14-18min, reflecting that the homogenous phase was not thermodynamically stable, followed by rupture of the GUVs. A similar mechanism of action is also observed for perifosine, although to a larger extent. Therefore, the initial stage of lipid raft disruption by both ODPC and perifosine, and maybe other ALPS, by promoting lipid mixing, may be correlated with their toxicity upon neoplastic cells, since selective (dis)association of essential proteins within lipid raft microdomains must take place in the plasma membrane.

Comparative analysis of the pathological events involved in immune and non-immune TRALI models.

BACKGROUND AND OBJECTIVES: Transfusion-related acute lung injury (TRALI) is characterized by leukocyte transmigration and alveolar capillary leakage shortly after transfusion. TRALI pathogenesis has not been fully elucidated. In some cases, the infusion of alloantibodies (immune model), whereas in others the combination of neutrophil priming by proinflammatory molecules with the subsequent infusion of biological response modifiers (BRMs) in the hemocomponent (non-immune model) have been implicated. Our aim was to compare the pathological events involved in TRALI induced by antibodies or BRMs using murine models. MATERIALS AND METHODS: In the immune model, human HNA-2(+) neutrophils were incubated in vitro with a monoclonal antibody (anti-CD177, clone 7D8) directed against the HNA-2 antigen and injected i.v. in NOD/SCID mice. In the non-immune model, BALB/c mice were treated with low doses of lipopolysaccharide (LPS) followed by platelet-activating factor (PAF) infusion 2 h later. Forty minutes after PAF administration, or 6 h after neutrophil injection, lungs were isolated and histological analysis, determination of a variety of cytokines and chemokines including keratinocyte-derived chemokine (KC), MIP-2, the interleukins IL-1ß, IL-6, IL-8 as well as TNFα, cell influx and alveolar capillary leakage were performed. RESULTS: In both models, characteristic histological findings of TRALI and an increase in KC and MIP-2 levels were detected. In contrast to the immune model, in the non-immune model, there was a dramatic increase in IL-1ß and TNFα. However, capillary leakage was only detected if PAF was administrated. CONCLUSIONS: Regardless of the triggering event(s), KC, MIP-2 and integrins participate in TRALI pathogenesis, whereas PAF is essential for capillary leakage when two events are involved.

(+)α-Tocopheryl succinate inhibits the mitochondrial respiratory chain complex I and is as effective as arsenic trioxide or ATRA against acute promyelocytic leukemia in vivo.

The vitamin E derivative (+)α-tocopheryl succinate (α-TOS) exerts pro-apoptotic effects in a wide range of tumors and is well tolerated by normal tissues. Previous studies point to a mitochondrial involvement in the action mechanism; however, the early steps have not been fully elucidated. In a model of acute promyelocytic leukemia (APL) derived from hCG-PML-RARα transgenic mice, we demonstrated that α-TOS is as effective as arsenic trioxide or all-trans retinoic acid, the current gold standards of therapy. We also demonstrated that α-TOS induces an early dissipation of the mitochondrial membrane potential in APL cells and studies with isolated mitochondria revealed that this action may result from the inhibition of mitochondrial respiratory chain complex I. Moreover, α-TOS promoted accumulation of reactive oxygen species hours before mitochondrial cytochrome c release and caspases activation. Therefore, an in vivo antileukemic action and a novel mitochondrial target were revealed for α-TOS, as well as mitochondrial respiratory complex I was highlighted as potential target for anticancer therapy.

Differentiation syndrome in promyelocytic leukemia: clinical presentation, pathogenesis and treatment.

Differentiation syndrome (DS) represents a life-threatening complication in patients with acute promyelocytic leukemia (APL) undergoing induction therapy with all-trans retinoic acid (ATRA) or arsenic trioxide (ATO). It affected about 20-25% of all patients and so far there are no definitive diagnostic criteria. Clinically, DS is characterized by weight gain, fever not attributable to infection, respiratory distress, cardiac involvement, hypotension, and/or acute renal failure. At the histological point of view, there is an extensive interstitial and intra-alveolar pulmonary infiltration by maturing myeloid cells, endothelial cell damage, intra-alveolar edema, inter-alveolar hemorrhage, and fibrinous exsudates. DS pathogenesis is not completely understood, but it is believed that an excessive inflammatory response is the main phenomenon involved, which results in increased production of chemokines and expression of adhesion molecules on APL cells. Due to the high morbidity and mortality associated with DS, its recognition and the prompt initiation of the treatment is of utmost importance. Dexamethasone is considered the mainstay of treatment of DS, and the recommended dose is 10 mg twice daily by intravenous route until resolution of DS. In severe cases (respiratory or acute renal failure) it is recommended the discontinuation of ATRA or ATO until recovery.

Epidemiology and treatment of acute promyelocytic leukemia in latin america.

Distinct epidemiological characteristics have been described in Acute Promielocytic Leukemia (APL). Populations from Latin America have a higher incidence of APL and in some geographic areas a distinct distribution of the PML-RARA isoforms is present. Here, we review the main differences in APL epidemilogy in Latin America as well as treatment outcomes.

Analysis of five polymorphic DNA markers for indirect genetic diagnosis of haemophilia A in the Brazilian population.

Hemophilia A is an X-linked, inherited, bleeding disorder caused by the partial or total inactivity of the coagulation factor VIII (FVIII). Due to difficulties in the direct recognition of the disease-associated mutation in the F8 gene, indirect diagnosis using polymorphic markers located inside or close to the gene is used as an alternative for determining the segregation of the mutant gene within families and thus for detecting carrier individuals and/or assisting in prenatal diagnosis. This study characterizes the allelic and haplotype frequencies, genetic diversity, population differentiation and linkage disequilibrium of five microsatellites (F8Int1, F8Int13, F8Int22, F8Int25.3 and IKBKG) in samples of healthy individuals from São Paulo, Rio Grande do Sul and Pernambuco and of patients from São Paulo with haemophilia A to determine the degree of informativeness of these microsatellites for diagnostic purposes. The interpopulational diversity parameters highlight the differences among the analyzed population samples. Regional differences in allelic frequencies must be taken into account when conducting indirect diagnosis of haemophilia A. With the exception of IKBKG, all of the microsatellites presented high heterozygosity levels. Using the markers described, diagnosis was possible in 10 of 11 families. The F8Int22, F8Int1, F8Int13, F8Int25.3 and IKBKG microsatellites were informative in seven, six, five and two of the cases, respectively, demonstrating the effectiveness of using these microsatellites in prenatal diagnosis and in carrier identification in the Brazilian population.

The role of micro-ribonucleic acids in normal hematopoiesis and leukemic T-lymphogenesis

Micro-ribonucleic acids (microRNAs) are small molecules containing 20-23 nucleotides. Despite their small size, it is likely that almost every cellular process is regulated by them. Moreover, aberrant microRNA expression has been involved in the development of various diseases, including cancer. Although many data are available about the role of microRNAs in various lymphoproliferative disorders, their impact on the development of acute lymphoblastic leukemia of T-cell progenitors is largely unknown. In this review, we present recent information about how specific microRNAs are expressed and regulated during malignant T-lymphopoiesis and about their role during normal hematopoiesis.

The role of micro-ribonucleic acids in normal hematopoiesis and leukemic T-lymphogenesis.

Micro-ribonucleic acids (microRNAs) are small molecules containing 20-23 nucleotides. Despite their small size, it is likely that almost every cellular process is regulated by them. Moreover, aberrant microRNA expression has been involved in the development of various diseases, including cancer. Although many data are available about the role of microRNAs in various lymphoproliferative disorders, their impact on the development of acute lymphoblastic leukemia of T-cell progenitors is largely unknown. In this review, we present recent information about how specific microRNAs are expressed and regulated during malignant T-lymphopoiesis and about their role during normal hematopoiesis.

Interaction of 10-(octyloxy) decyl-2-(trimethylammonium) ethyl phosphate with mimetic membranes and cytotoxic effect on leukemic cells.

10-(Octyloxy) decyl-2-(trimethylammonium) ethyl phosphate (ODPC) is an alkylphospholipid that can interact with cell membranes because of its amphiphilic character. We describe here the interaction of ODPC with liposomes and its toxicity to leukemic cells with an ED-50 of 5.4, 5.6 and 2.9 microM for 72 h of treatment for inhibition of proliferation of NB4, U937 and K562 cell lines, respectively, and lack of toxicity to normal hematopoietic progenitor cells at concentrations up to 25 microM. The ED-50 for the non-malignant HEK-293 and primary human umbilical vein endothelial cells (HUVEC) was 63.4 and 60.7 microM, respectively. The critical micellar concentration (CMC) of ODPC was 200 microM. Dynamic light scattering indicated that dipalmitoylphosphatidylcholine (DPPC) liposome size was affected only above the CMC of ODPC. Differential calorimetric scanning (DCS) of liposomes indicated a critical transition temperature (T(c)) of 41.5 degrees C and an enthalpy (H) variation of 7.3 kcal mol(-1). The presence of 25 microM ODPC decreased T(c) and H to 39.3 degrees C and 4.7 kcal mol(-1), respectively. ODPC at 250 microM destabilized the liposomes (36.3 degrees C, 0.46 kcal mol(-1)). Kinetics of 5(6)-carboxyfluorescein (CF) leakage from different liposome systems indicated that the rate and extent of CF release depended on liposome composition and ODPC concentration and that above the CMC it was instantaneous. Overall, the data indicate that ODPC acts on in vitro membrane systems and leukemia cell lines at concentrations below its CMC, suggesting that it does not act as a detergent and that this effect is dependent on membrane composition.

Outcome of acute myeloid leukemia patients with hyperleukocytosis in Brazil.

Acute myeloid leukemia (AML) with a high white blood cell (WBC) count at presentation has been associated with an increased early mortality rate, usually secondary to leukostasis. However, the value of the WBC count at which there is a high risk of early death (ED) and the efficiency of supportive treatments remain unclear. In this report, a series of 187 consecutive adult patients with AML in our institution was reviewed. The outcome of 40 patients with WBC above 50×10(9) L(-1) (hyperleukocytosis) was compared to 147 patients with a leukocyte count lower than 50×10(9) L(-1). The group with hyperleukocytosis showed a significantly shorter OS (P<0.0001) and a higher rate of ED (P=0.0008). Even when the data from ED patients were removed from analysis, we still detected a shorter OS in patients with hyperleukocytosis (P=0.0049), which suggests that high WBC number influences long-term survival, and not only ED. We also observed higher lactic dehydrogenase (LDH) and serum creatinine levels in the group of patients with hyperleukocytosis (P=0.0003 and 0.0406, respectively). Besides considering all the patients with ED, we could observe higher levels of lactic dehydrogenase, a serum creatinine and nitrogen urea (P=0.0056, P=0.0008 and P<0.0001, respectively). Pulmonary involvement was more frequent in patients with ED (P=0.0277). In conclusion, hyperleukocytosis confers a poorer prognosis in patients with AML.

Translocations t(X;14)(q28;q11) and t(Y;14)(q12;q11) in T-cell prolymphocytic leukemia.

We report a case of T-cell prolymphocytic leukemia (T-PLL) in a 41-year-old male. Classical cytogenetic, spectral karyotyping (SKY) and fluorescence in situ hybridization (FISH) studies of a blood sample obtained at diagnosis revealed the co-existence of t(X;14)(q28;q11), t(Y;14)(q12;q11) and a ring chromosome derived from i(8)(q10). Immunophenotypic studies revealed involvement of T-cell lineage, with proliferation of CD4(-) CD8+. The co-existence of two translocations involving both sex chromosomes in a case of T-PLL is rare. Chromosomal instability associated with the disease progression may have allowed the emergence of cell clones with translocations involving the sex chromosomes and the ring chromosome observed.

Asynchronous expression of myeloid antigens in leukemic cells in a PML/RARalpha transgenic mouse model.

Acute promyelocytic leukemia (APL) is characterized by the expansion of blasts that resemble morphologically promyelocytes and harbor a chromosomal translocation involving the retinoic acid receptor alpha (RARalpha) and the promyelocytic leukemia (PML) genes on chromosomes 17 and 15, respectively. The expression of the PML/RARalpha fusion gene is essential for APL genesis. In fact, transgenic mice (TM) expressing PML/RARalpha develop a form of leukemia that mimics the hematological findings of human APL. Leukemia is diagnosed after a long latency (approximately 12 months) during which no hematological abnormality is detected in peripheral blood (pre-leukemic phase). In humans, immunophenotypic analysis of APL blasts revealed distinct features; however, the precise immunophenotype of leukemic cells in the TM model has not been established. Our aim was to characterize the expression of myeloid antigens by leukemic cells from hCG-PML/RARalpha TM. In this study, TM (N = 12) developed leukemia at the mean age of 13.1 months. Morphological analysis of bone marrow revealed an increase of the percentage of immature myeloid cells in leukemic TM compared to pre-leukemic TM and wild-type controls (48.63 +/- 16.68, 10.83 +/- 8.11, 7.4 +/- 5.46%, respectively; P < 0.05). Flow cytometry analysis of bone marrow and spleen from leukemic TM identified the asynchronous co-expression of CD34, CD117, and CD11b. This abnormal phenotype was rarely detected prior to the diagnosis of leukemia and was present at similar frequencies in hematologically normal TM and wild-type controls of different ages. The present results demonstrate that, similarly to human APL, leukemic cells from hCG-PML/RARalpha TM present a specific immunophenotype.