Squamous cell carcinoma of the vulva and adjacent lesions treated at Nagoya University Hospital from 1965 to 1997

Japan has a lower incidence of vulvar squamous cell carcinoma (VSCC) than Western nations. To pin-point the reasons for this, we reviewed biopsy samples from all cases treated at Nagoya University Hospital over the past 33 years in order to investigate the background lesions for VSCC. Two of 36 VSCC patients had adjacent or coexisting lichen sclerosus (LS), 5 had squamous cell hyperplasia (SCH), and 16 had vulvar intraepithelial neoplasia (VIN). There were 8 cases in which these lesions were thought to be the origin of the VSCC, 1 in which keratinizing squamous cell carcinoma (KSC) was seen in LS, 1 in which verrucous SCH was the origin, and 6 in which 4 basaloid carcinoma and 2 warty carcinoma developed from basaloid VIN and warty VIN, respectively. Although 8 other cases of keratinizing or non-keratinizing squamous cell carcinomas (NSC) coexisted with VIN NOS (not otherwise specified), differentiated VIN or basaloid VIN, we could not be histologically certain of the origin. Among 22 VSCC patients tested for HPV DNA, only an 84-year-old woman presenting a histological feature of KSC tested positive by in situ hybridization (ISH). It was considered that LS and SCH had little and VIN considerable capacity to cause the malignancy of VSCC. We surmise that in Japan the majority of squamous cell carcinoma is unrelated to HPV. One reason for the low incidence of VSCC is largely due to race; the homogeneous, monoethnic Japanese population, as well as the few cases of HPV-related VSCC.

Important role of energy-dependent mitochondrial pathways in cultured rat cardiac myocyte apoptosis

Recent studies have suggested that apoptosis and necrosis share common features in their signaling pathway and that apoptosis requires intracellular ATP for its mitochondrial/apoptotic protease-activating factor-1 suicide cascade. The present study was, therefore, designed to examine the role of intracellular energy levels in determining the form of cell death in cardiac myocytes. Neonatal rat cardiac myocytes were first incubated for 1 h in glucose-free medium containing oligomycin to achieve metabolic inhibition. The cells were then incubated for another 4 h in similar medium containing staurosporine and graded concentrations of glucose to manipulate intracellular ATP levels. Under ATP-depleting conditions, the cell death caused by staurosporine was primarily necrotic, as determined by creatine kinase release and nuclear staining with ethidium homodimer-1. However, under ATP-replenishing conditions, staurosporine increased the percentage of apoptotic cells, as determined by nuclear morphology and DNA fragmentation. Caspase-3 activation by staurosporine was also ATP dependent. However, loss of mitochondrial transmembrane potential (DeltaPsi(m)), Bax translocation, and cytochrome c release were observed in both apoptotic and necrotic cells. Moreover, cyclosporin A, an inhibitor of mitochondrial permeability transition, attenuated staurosporine-induced apoptosis and necrosis through the inhibition of DeltaPsi(m) reduction, cytochrome c release, and caspase-3 activation. Our data therefore suggest that staurosporine induces cell demise through a mitochondrial death signaling pathway and that the presence of intracellular ATP favors a shift from necrosis to apoptosis through caspase activation.

AML1-ETO expression is directly involved in the development of acute myeloid leukemia in the presence of additional mutations

The t(8;21) is one of the most frequent chromosomal abnormalities associated with acute myeloid leukemia (AML). The translocation, which involves the AML1 gene on chromosome 21 and the ETO gene on chromosome 8, generates an AML1-ETO fusion transcription factor. To examine the effect of the AML1-ETO fusion protein on leukemogenesis, we made transgenic mice in which expression of AML1-ETO is under the control of the human MRP8 promoter (hMRP8-AML1-ETO). AML1-ETO is specifically expressed in myeloid cells, including common myeloid progenitors of hMRP8-AML1-ETO transgenic mice. The transgenic mice were healthy during their life spans, suggesting that AML1-ETO alone is not sufficient for leukemogenesis. However, after treatment of newborn hMRP8-AML1-ETO transgenic mice and their wild-type littermates with a strong DNA-alkylating mutagen, N-ethyl-N-nitrosourea, 55% of transgenic mice developed AML and the other 45% of transgenic mice and all of the wild-type littermates developed acute T lymphoblastic leukemia. Our results provide direct evidence that AML1-ETO is critical for causing myeloid leukemia, but one or more additional mutations are required for leukemogenesis. The hMRP8-AML1-ETO-transgenic mice provide an excellent model that can be used to isolate additional genetic events and to further understand the molecular pathogenesis of AML1-ETO-related leukemia.

The fetal liver counterpart of adult common lymphoid progenitors gives rise to all lymphoid lineages, CD45+CD4+CD3- cells, as well as macrophages

We identified an IL-7Ralpha(+)Sca-1(low)c-Kit(low) population in E14 fetal liver, which is the phenotypical analog of common lymphoid progenitors (CLP) in adult bone marrow. After transfer into newborn mice, the IL-7Ralpha(+)Sca-1(low)c-Kit(low) population rapidly differentiated into CD45(+)CD4(+)CD3(-) cells, which are candidate cells for initiating lymph node and Peyer's patch formation. In addition, this population also gave rise to B, T, NK, and CD8alpha(+) and CD8alpha(-) dendritic cells. The fetal liver precursors expressed a significantly lower level of the myeloid-suppressing transcription factor Pax-5, than adult CLP, and retained differentiation activity for macrophages in vitro. We propose that the transition from fetal liver IL-7Ralpha(+)Sca-1(low)c-Kit(low) cells to adult CLP involves a regulated restriction of their developmental potential, controlled, at least in part, by Pax-5 expression.

Fetal liver myelopoiesis occurs through distinct, prospectively isolatable progenitor subsets

Hematopoietic fate maps in the developing mouse embryo remain imprecise. Definitive, adult-type hematopoiesis first appears in the fetal liver, then progresses to the spleen and bone marrow. Clonogenic common lymphoid progenitors and clonogenic common myeloid progenitors (CMPs) in adult mouse bone marrow that give rise to all lymphoid and myeloid lineages, respectively, have recently been identified. Here it is shown that myelopoiesis in the fetal liver similarly proceeds through a CMP equivalent. Fetal liver CMPs give rise to megakaryocyte-erythrocyte-restricted progenitors (MEPs) and granulocyte-monocyte-restricted progenitors (GMPs) that can also be prospectively isolated by cell surface phenotype. MEPs and GMPs generate mutually exclusive cell types in clonogenic colony assays and in transplantation experiments, suggesting that the lineage restriction observed within each progenitor subset is absolute under normal conditions. Purified progenitor populations were used to analyze expression profiles of various hematopoiesis-related genes. Expression patterns closely matched those of the adult counterpart populations. These results suggest that adult hematopoietic hierarchies are determined early in the development of the definitive immune system and suggest that the molecular mechanisms underlying cell fate decisions within the myeloerythroid lineages are conserved from embryo to adult. (Blood. 2001;98:627-635)

Detection of monocyte chemoattractant protein-1 receptor expression in experimental atherosclerotic lesions: an autoradiographic study

BACKGROUND

Monocytes, a common component of atheroma, are attracted to the lesion site in response to chemotactic signals, particularly expression of monocyte chemoattractant peptide 1 (MCP-1). This study assessed the feasibility of using radiolabeled MCP-1 to identify monocytes and macrophages that have localized at sites of experimental arterial lesions. Methods and Results-- The biodistribution of radiolabeled MCP-1 was determined in normal mice, and localization in experimental atheroma was determined in cholesterol-fed rabbits 4 weeks after arterial injury of the iliac artery (9 rabbits) and the abdominal aorta (1 rabbit). Vessels were harvested and autoradiographed after intravenous administration of (125)I-labeled MCP-1 and Evans blue dye. The arteries were evaluated histologically by hematoxylin and eosin staining and immune staining with a monoclonal antibody specific for rabbit macrophages (RAM-11). (125)I-MCP-1 has a blood clearance half-time of approximately 10 minutes and circulates in association with cells. The liver, lungs, and kidneys had the highest concentration of (125)I-MCP-1 at 5 and 30 minutes after tracer administration. Autoradiograms revealed accumulation of (125)I-MCP-1 in the damaged artery wall, with an average ratio of lesion to normal vessel of 6:1 (maximum 45:1). The accumulation of (125)I-MCP-1 in the reendothelialized (plaque formation) areas was greater than in the deendothelialized (Evans blue-positive) areas (6.55+/-2.26 versus 4.34+/-1.43 counts/pixel, P<0.05). The uptake of (125)I-MCP-1 correlated with the number of macrophages per unit area (r=0.85, P<0.0001).

CONCLUSIONS

Radiolabeled MCP-1 may be a useful tracer for imaging monocyte/macrophage-rich experimental atherosclerotic lesions.

Dendritic cell potentials of early lymphoid and myeloid progenitors

It has been proposed that there are at least 2 classes of dendritic cells (DCs), CD8alpha(+) DCs derived from the lymphoid lineage and CD8alpha(-) DCs derived from the myeloid lineage. Here, the abilities of lymphoid- and myeloid-restricted progenitors to generate DCs are compared, and their overall contributions to the DC compartment are evaluated. It has previously been shown that primitive myeloid-committed progenitors (common myeloid progenitors [CMPs]) are efficient precursors of both CD8alpha(+) and CD8alpha(-) DCs in vivo. Here it is shown that the earliest lymphoid-committed progenitors (common lymphoid progenitors [CLPs]) and CMPs and their progeny granulocyte-macrophage progenitors (GMPs) can give rise to functional DCs in vitro and in vivo. CLPs are more efficient in generating DCs than their T-lineage descendants, the early thymocyte progenitors and pro-T cells, and CMPs are more efficient DC precursors than the descendant GMPs, whereas pro-B cells and megakaryocyte-erythrocyte progenitors are incapable of generating DCs. Thus, DC developmental potential is preserved during T- but not B-lymphoid differentiation from CLP and during granulocyte-macrophage but not megakaryocyte-erythrocyte development from CMP. In vivo reconstitution experiments show that CLPs and CMPs can reconstitute CD8alpha(+) and CD8alpha(-) DCs with similar efficiency on a per cell basis. However, CMPs are 10-fold more numerous than CLPs, suggesting that at steady state, CLPs provide only a minority of splenic DCs and approximately half the DCs in thymus, whereas most DCs, including CD8alpha(+) and CD8alpha(-) subtypes, are of myeloid origin. (Blood. 2001;97:3333-3341)

Dendritic cell development from common myeloid progenitors

Dendritic cells (DCs) are professional antigen-presenting cells which both initiate adaptive immune responses and control tolerance to self-antigens. It has been suggested that these different effects on responder cells depend on subsets of DCs arising from either myeloid or lymphoid hematopoietic origins. In this model, CD8 alpha+ Mac-1- DCs are supposed to be of lymphoid while CD8 alpha- Mac-1+ DCs are supposed to be of myeloid origin. Here we summarize our findings that both CD8 alpha+ and CD8 alpha- DCs can arise from clonogenic common myeloid progenitors (CMPs) in both thymus and spleen. Therefore CD8 alpha expression DCs does not indicate a lymphoid origin and differences among CD8 alpha+ and CD8 alpha- DCs might rather reflect maturation status than ontogeny. On the basis of transplantation studies, it seems likely that most of the DCs in secondary lymphoid organs and a substantial fraction of thymic DCs are myeloid-derived.

Expression of DNA methyltransferases DNMT1, 3A, and 3B in normal hematopoiesis and in acute and chronic myelogenous leukemia

Aberrant hypermethylation of tumor suppressor genes plays an important role in the development of many tumors. Recently identified new DNA methyltransferase (DNMT) genes, DNMT3A and DNMT3B, code for de novo methyltransferases. To determine the roles of DNMT3A, DNMT3B, as well as DNMT1, in the development of leukemia, competitive polymerase chain reaction (PCR) assays were performed and the expression levels of DNMTs were measured in normal hematopoiesis, 33 cases of acute myelogenous leukemia (AML), and 17 cases of chronic myelogenous leukemia (CML). All genes were constitutively expressed, although at different levels, in T lymphocytes, monocytes, neutrophils, and normal bone marrow cells. Interestingly, DNMT3B was expressed at high levels in CD34(+) bone marrow cells but down-regulated in differentiated cells. In AML, 5.3-, 4.4-, and 11.7-fold mean increases were seen in the levels of DNMT1, 3A, and 3B, respectively, compared with the control bone marrow cells. Although CML cells in the chronic phase did not show significant changes, cells in the acute phase showed 3.2-, 4.5-, and 3.4-fold mean increases in the levels of DNMT1, 3A, and 3B, respectively. Using methylation-specific PCR, it was observed that the p15(INAK4B) gene, a cell cycle regulator, was methylated in 24 of 33 (72%) cases of AML. Furthermore, AML cells with methylated p15(INAK4B) tended to express higher levels of DNMT1 and 3B. In conclusion, DNMTs were substantially overexpressed in leukemia cells in a leukemia type- and stage-specific manner. Up-regulated DNMTs may contribute to the pathogenesis of leukemia by inducing aberrant regional hypermethylation. (Blood. 2001;97:1172-1179)

Development of CD8alpha-positive dendritic cells from a common myeloid progenitor

Dendritic cells (DCs) are critical in both initiating adaptive immune responses and maintaining tolerance to self antigens. These apparently contradictory roles have been suggested to depend on different subsets of DCs that arise from either myeloid or lymphoid hematopoietic origins, respectively. Although DC expression of CD8alpha is attributed to a lymphoid origin, here we show that both CD8alpha+ and CD8alpha- DCs can arise from clonogenic common myeloid progenitors in both thymus and spleen. Thus, expression of CD8alpha is not indicative of a lymphoid origin, and phenotypic and functional differences among DC subsets are likely to reflect maturation status rather than ontogeny.

Epstein-Barr virus-infected natural killer cell leukemia

Natural killer cell leukemia (NK leukemia) is an aggressive form of lymphoproliferative disease of granular lymphocytes, and frequently complicates fulminant hemophagocytic lymphohistiocytosis. NK leukemia cells usually possess a single episomal form of Epstein-Barr virus (EBV), and therefore originate from a single EBV-infected NK cell. The NK leukemia cells lack endogenous Bcl-2 expression and are sensitive to apoptotic cell death. However, they constitutively produce interferon-gamma and maintain their survival in an autocrine fashion. The interferon-gamma released from NK leukemia cells may trigger the occurrence of hemophagocytic lymphohistiocytosis through activating macrophages/histiocytes. In the primary infection of EBV, T cells infected with the episomal form of EBV sometimes produce a high amount of interferon-gamma that may lead to the occurrence of hemophagocytic lymphohistiocytosis. Thus, it is important to determine the role of EBV in the increased production of interferon-gamma that occurs in EBV-infected T and NK cells to clarify the developmental mechanism of NK leukemia and its paraneoplastic hemophagocytic lymphohistiocytosis.

[Percutaneous transluminal septal myocardial ablation combined with permanent dual-chamber pacing in hypertrophic obstructive cardiomyopathy: a case report]

A 74-year-old woman suffering from dyspnea on effort and chest pain (New York Heart Association functional class III) was admitted to our hospital. Echocardiography and left ventriculography showed severe hypertrophy of the left ventricular wall and a severe intraventricular pressure gradient of about 150 mmHg. The diagnosis was hypertrophic obstructive cardiomyopathy. The intraventricular pressure gradient was decreased from 157 to 68 mmHg by percutaneous transluminal septal myocardial ablation (PTSMA), but this reduction was not adequate. Thereafter, dual-chamber pacing was additionally performed. The intraventricular pressure gradient was decreased to 26 mmHg with no complication. PTSMA is a certain way to decrease pressure gradient, but has some complications. Permanent dual-chamber pacing also can show the same effect, but is inferior to PTSMA. Combination of these 2 methods succeeded in abolishing the intraventricular pressure gradient with no complication.

Comparative study of perioperative management of hepatic resection

In an attempt to identify the factors that influence outcome after hepatic resection, patient background was reviewed and operative morbidity and mortality rates were assessed during two periods: 1985-1988 (group I: N = 96) and 1995-1998 (group II: N = 109). There were no differences in patient background factors between the two groups, but intraoperative blood loss, operative morbidity, and mortality were significantly reduced in group II compared to group I. There has been a significant reduction in postoperative complications, even in cases complicated by liver cirrhosis or obstructive jaundice. As a result of appropriate surgical procedures, postoperative complications in cirrhosis have been markedly decreased. After preoperative percutaneous biliary drainage in obstructive jaundice, attempts have been made to reduce the volume of blood loss even in extensive hepatectomy, the extent of liver resection in poor risk cases has been reduced without sacrificing radicality, and, by minimizing surgical stress, perioperative management has been greatly improved.

Cell-fate conversion of lymphoid-committed progenitors by instructive actions of cytokines

The primary role of cytokines in haemato-lymphopoiesis is thought to be the regulation of cell growth and survival. But the instructive action of cytokines in haematopoiesis has not been well addressed. Here we show that a clonogenic common lymphoid progenitor, a bone marrow-resident cell that gives rise exclusively to lymphocytes (T, B and natural killer cells), can be redirected to the myeloid lineage by stimulation through exogenously expressed interleukin (IL)-2 and GM-CSF (granulocyte/macrophage colony-stimulating factor) receptors. Analysis of mutants of the beta-chain of the IL-2 receptor revealed that the granulocyte- and monocyte-differentiation signals are triggered by different cytoplasmic domains, showing that the signalling pathway(s) responsible for these unique developmental outcomes are separable. Finally, we show that the endogenous myelomonocytic cytokine receptors for GM-CSF and macrophage colony-stimulating factor (M-CSF) are expressed at low to moderate levels on the more primitive haematopoietic stem cells, are absent on common lymphoid progenitors, and are upregulated after myeloid lineage induction by IL-2. We conclude that cytokine signalling can regulate cell-fate decisions and propose that a critical step in lymphoid commitment is downregulation of cytokine receptors that drive myeloid cell development.

[Is myocardial impairment in idiopathic dilated hypertrophic cardiomyopathy reversible by carvedilol?: a case report]

A 64-year-old woman with dilated hypertrophic cardiomyopathy was treated by beta-blocker, because of recurrent episodes of congestive heart failure. Carvedilol administration was started with a dose of 2.5 mg/day, and gradually increased to the dose of 20 mg/day 3 months later. Her functional class recovered from New York Heart Association stage IV to stage II. Thallium-201 scintigraphy demonstrated advanced myocardial damage: defect/low perfusion in the anteroseptal, infero-posterior and apical regions. Iodine-123 beta-methyl-p-iodophenyl-pentadecanoic acid scintigraphy confirmed these findings. However, the scintigraphic abnormalities had reversed to near normal perfusion and metabolism similar to those of stunned myocardium after an ischemic episode. This case demonstrates the recovery of myocardial impairment during beta-blocker therapy in a patient with dilated hypertrophic cardiomyopathy.

AML1/ETO-expressing nonleukemic stem cells in acute myelogenous leukemia with 8;21 chromosomal translocation

Leukemia-specific AML1/ETO transcripts are detectable in most patients with t(8;21) acute myelogenous leukemia (AML) in long-term remission. To understand the inconsistency between the clinical cure and the presence of "residual disease" at a molecular level, we separated and identified the cells expressing AML1/ETO by phenotype and function. Here we demonstrate that AML1/ETO transcripts are present in a fraction of stem cells, monocytes, and B cells in remission marrow, and in a fraction of B cells in leukemic marrow, but not in T cells. AML1/ETO transcripts also were demonstrated in a fraction of colony-forming cells of erythroid, granulocyte-macrophage, and/or megakaryocyte lineages in both leukemic and remission marrow. These data strongly suggest that the acquisition of the t(8;21) occurs at the level of stem cells capable of differentiating into B cells as well as all myeloid lineages, and that a fraction of the AML1/ETO-expressing stem cells undergo additional oncogenic event(s) that ultimately leads to transformation into AML.

B lymphopoiesis in the thymus

The thymus has been regarded as the major site of T cell differentiation. We find that in addition to alphabeta and gammadelta T cells, a significant number (approximately 3 x 104 per day) of B220+IgM+ mature B cells are exported from the thymus of C57BL/6 mice. Of these emigrating B cells, we estimate that at least approximately 2 x 104 per day are cells which developed intrathymically, whereas a maximum of approximately 0.8 x 104 per day are cells which circulated through the thymus from the periphery. The thymus possesses a significant number of pro-B and pre-B cells that express CD19, VpreB, lambda5, and pax-5. These B cell progenitors were found in the thymic cortex, whereas increasingly mature B cells were found in the corticomedullar and medullary regions. Other lymphoid cells, including NK cells and lymphoid dendritic cells, are not exported from the thymus at detectable levels. Thus, the thymus contributes to the formation of peripheral pools of B cells as well as of alphabeta and gammadelta T cells.

Cytokine-induced nitric oxide production inhibits mitochondrial energy production and impairs contractile function in rat cardiac myocytes

OBJECTIVES

The present study examined whether nitric oxide (NO) produced by inducible nitric oxide synthase (iNOS) can directly inhibit aerobic energy metabolism and impair cell function in interleukin (IL)-1beta,-stimulated cardiac myocytes.

BACKGROUND

Recent reports have indicated that excessive production of NO induced by cytokines can disrupt cellular energy balance through the inhibition of mitochondrial respiration in a variety of cells. However, it is still largely uncertain whether the NO-induced energy depletion affects myocardial contractility.

METHODS

Primary cultures of rat neonatal cardiac myocytes were prepared, and NO2-/NO3- (NOx) in the culture media was measured using Griess reagent.

RESULTS

Treatment with IL-1beta (10 ng/ml) increased myocyte production of NOx in a time-dependent manner. The myocytes showed a concomitant significant increase in glucose consumption, a marked increase in lactate production, and a significant decrease in cellular ATP (adenosine 5'-triphosphate). These metabolic changes were blocked by co-incubation with N(G)-monomethyl-L-arginine (L-NMMA), an inhibitor of NO synthesis. Sodium nitroprusside (SNP), a NO donor, induced similar metabolic changes in a dose-dependent manner, but 8-bromo-cyclic guanosine 3',5'-monophosphate (8-bromo-cGMP), a cGMP donor, had no effect on these parameters. The activities of the mitochondrial iron-sulfur enzymes, NADH-CoQreductase and succinate-CoQreductase, but not oligomycin-sensitive ATPase, were significantly inhibited in the IL-1beta, or SNP-treated myocytes. Both IL-1beta and SNP significantly elevated maximum diastolic potential, reduced peak calcium current (I(Ca)), and lowered contractility in the myocytes. KT5823, an inhibitor of cGMP-dependent protein kinase, did not block the electrophysiological and contractility effects.

CONCLUSIONS

These data suggest that IL-1beta-induced NO production in cardiac myocytes lowers energy production and myocardial contractility through a direct attack on the mitochondria, rather than through cGMP-mediated pathways.

Lymphoid precursors

Lymphopoiesis of mature and diverse populations of T, B and NK (natural killer) cells from multipotent hematopoietic stem cells is an ideal model of tissue generation and regeneration. Identification and isolation of hematolymphoid stem and progenitor cells in several laboratories over the past several years have provided populations that can be studied biologically for lineage commitment and biochemically for receptor function, signal transduction and selective gene expression. These studies may ultimately provide candidate genes involved in lineage commitment, cell death or survival, self-renewal and migratory capacities of progenitors.

Posttranscriptional regulation of Bruton's tyrosine kinase expression in antigen receptor-stimulated splenic B cells

Mutation of Bruton's tyrosine kinase (Btk) causes human X-linked agammaglobulinemia and murine X-linked immunodeficiency syndrome (xid). Quantitative aspects of B lymphocyte development and function have been demonstrated to depend on Btk level in vivo by using a murine transgenic model system. A sensitive intracellular immunofluorescent assay was developed to measure Btk protein on a per cell basis to test the hypothesis that its dosage is dynamically regulated during B cell development or functional responses. Marrow-derived hematopoietic stem cells, common lymphoid progenitor cells, and developing B and myeloid lineages expressed Btk protein at comparable levels. Resting peripheral B lineage cells had a significantly lower amount of Btk than marrow-derived cells in both wild-type and xid mice. Activation of the B cell antigen receptor up-regulated Btk protein level 10-fold within several hours by a phosphatidylinositol 3-kinase-dependent, posttranscriptional mechanism. In contrast, the protein level of Btk R28C in activated B lymphocytes from xid mice remained low. Bypass of the antigen receptor signaling pathways by treatment of cells with phorbol myristic acid and ionomycin rescued up-regulation of Btk protein in xid splenic B cells. These combined results suggest that certain receptor signals mediated by Btk regulate the level of expression of Btk protein in responding B lymphocytes to potentiate signal transduction. Dynamic regulation of Btk protein dosage is an additional mechanism to modulate B lymphocyte immune functions.

A clonogenic common myeloid progenitor that gives rise to all myeloid lineages

Haematopoietic stem cells give rise to progeny that progressively lose self-renewal capacity and become restricted to one lineage. The points at which haematopoietic stem cell-derived progenitors commit to each of the various lineages remain mostly unknown. We have identified a clonogenic common lymphoid progenitor that can differentiate into T, B and natural killer cells but not myeloid cells. Here we report the prospective identification, purification and characterization, using cell-surface markers and flow cytometry, of a complementary clonogenic common myeloid progenitor that gives rise to all myeloid lineages. Common myeloid progenitors give rise to either megakaryocyte/erythrocyte or granulocyte/macrophage progenitors. Purified progenitors were used to provide a first-pass expression profile of various haematopoiesis-related genes. We propose that the common lymphoid progenitor and common myeloid progenitor populations reflect the earliest branch points between the lymphoid and myeloid lineages, and that the commitment of common myeloid progenitors to either the megakaryocyte/erythrocyte or the granulocyte/macrophage lineages are mutually exclusive events.

Aclarubicin induces differentiation of leukemic progenitors in myelodysplastic syndrome cooperating with granulocyte colony-stimulating factor

We have reported that low-dose aclarubicin (ACR) therapy is effective in some patients with myelodysplastic syndrome (MDS). Here, we demonstrate that a low concentration of ACR induces the in vitro differentiation of leukemic progenitor cells from patients with MDS. ACR (0.1 ng/ml) significantly increased the number of granulocyte colony-stimulating factor (G-CSF)-dependent colonies from circulating blast cells in vitro in six out of seven MDS patients with refractory anemia with excess of blast in transformation or chronic myelomonocytic leukemia, but not in all four patients with primary acute myelogenous leukemia. In these MDS patients, the effect of ACR gradually disappeared along with the progression of MDS. Interestingly, the majority of G-CSF/ACR-dependent colonies consisted of rather differentiated myeloid cells such as myelocytes and metamyelocytes, whereas colonies formed by G-CSF alone were composed mainly of immature blastic cells. The number of G-CSF-responding progenitors significantly increased during a 24-48 h incubation with ACR alone. The circulating blasts in MDS patients expressed G-CSF receptors at unchanged levels before and after the incubation with ACR. It is suggested that ACR might increase clonogenic progenitor responsiveness to G-CSF in MDS, probably through modulating downstream signaling cascades associated with G-CSF receptors, and induce these progenitors to differentiate in response to G-CSF.