PU.1 is an Ets family transcription factor, which is important for differentiation of granulocytes, monocytes/macrophages, and B cells. In the Friend leukemia model, it is reported that the failure ...of PU.1 down-regulation in erythroblasts reportedly results in differentiation arrest that leads to erythroleukemia. In conditional knockout mice of the 3.5 kb length of enhancer region located in14 kb 5′ of the PU.1 gene, PU.1 is down-regulated in myeloid cells and B cells down to 20% of that of wild type, and such mice develop acute myeloid leukemia and CLL-like disease. In addition, a deletion of the 3.5 kb enhancer region, which also contains the suppressor region for PU.1 in T cells, results in ectopic expression of PU.1 in T cells, which leads to T cell lymphoma in those mice. Taken together, the failure of up-regulation or down-regulation of PU.1 in certain differentiation stages for each lineage appears to cause differentiation arrest and hematological malignancies. We recently reported that PU.1 is down-regulated in a majority of myeloma cell lines through the methylation of the promoter and enhancer region located in17 kb 5′ of human PU.1 gene which is homologous to that in14 kb 5′ of murine PU.1 gene. Conditionally expressed PU.1 induced cell growth arrest and apoptosis of those PU.1 low-negative myeloma cell lines, U266 and KMS12PE, suggesting that down-regulation of PU.1 is necessary for myeloma cell growth. In addition, we reported that PU.1 is expressed in normal plasma cells and PU.1 is down-regulated in myeloma cells of some myeloma patients. Myeloma patients with low-to-negative PU.1 expression (lower 25th percentile of PU.1 expression level distribution among 30 patients we examined) may have poor prognosis compared to those with high PU.1 expression, although more patient samples have to be examined to define the significance of the relationship of PU.1 expression levels and prognosis. To elucidate the mechanisms of PU.1 induced cell growth arrest and apoptosis of myeloma cells, we next performed DNA microarray analysis to compare gene expression levels before and after PU.1 induction. We utilized Illumina Sentrix® Human-6 Expression BeadChip. Of 47296 genes, 479 genes were up-regulated (>2fold) and 1697 genes down-regulated (<0.5 fold) either day 1 or 3 after PU.1 induction in U266 cells. Among apoptosis related genes, TRAIL was highly up-regulated in both U266 and KMS12PE cell lines. Stably expressed siRNA for TRAIL partially inhibited apoptosis of U266 cells expressing PU.1, suggesting that TRAIL is related to PU.1 induced cell death of U266 cells. Among cell-cycle related genes, p21WAF1/CIP1 was found up-regulated in U266 cells, which was confirmed with protein levels. We are now examining the roles of the observed up-regulated genes in both U266 and KMS12PE myeloma cell lines.
Understanding how multipotent cells commit to each of their terminal fate potentials is an important aspect of stem cell biology. In adult murine hematopoiesis, HSCs with long-term self-renewal ...potential reside within the Lin −Sca-1+c-Kit+ (LSK) fraction having CD34−, Thy1lo, and Flt3/Flk2−phenotypes. The LSK cells having CD34+, Thy1−, and/or Flt3+ phenotypes are capable of multi-lineage reconstitution only for a short-term, and therefore should contain multipotent progenitors (MPPs). In terms of developmental steps downstream of MPPs, there has been a controversy. The existence of prospectively isolatable progenitors capable of generating only myeloerythroid cells (common myeloid progenitor: CMP) or only lymphocytes (common lymphoid progenitors: CLP) outside the LSK fraction suggests that the first commitment step after the MPP stage is the strict bifurcation of lymphoid vs. myeloid pathway. Recently, however, several studies have suggested that the lineage commitment could occur within the LSK fraction, preceding the proposed bifurcation of myeloid and lymphoid pathways. For example, MPPs expressing Flt3 at a high level retained granulocytes/monocytes (GM) but not megakaryocyte/erythrocyte (MegE) potential together with lymphoid potential, suggesting the existence of common progenitor for GM and lymphoid lineages within the LSK fraction. Based on this data, the coupled loss of self-renewal activity and MegE potential in the early HSC commitment has been proposed. How can we reconcile the controversy in the early hematopoietic lineage map? By utilizing mice having GATA-1 or PU.1 transcriptional reporters, we here present a high-resolution map containing new lineage-restricted progenitor populations within the MPP population of CD34+ LSK phenotype. Initial upregulation of GATA-1 and PU.1 occurred independently at the MPP stage. The GATA-1+ MPP displayed potent myeloerythroid potential without giving rise to lymphocytes, whereas the PU.1+ MPP showed granulocyte/monocyte/lymphoid-restricted progenitor activity without megakaryocyte/erythroid differentiation. Furthermore, GATA-1+ and PU.1+ MPPs possessed huge expansion potential, and differentiated into the original CMPs and CLPs, respectively. Thus, the reciprocal activation of GATA-1 and PU.1 primarily organizes hematopoietic lineage fate decision to form the earliest hematopoietic branchpoint that comprises new, isolatable myeloerythroid and myelolymphoid progenitor populations.
Thrombopoietin receptor agonist (TPO-RA) is effective for aplastic anemia (AA) and idiopathic thrombocytopenic purpura (ITP). However, the risk of thrombosis during ITP treatment with TPO-RA is ...higher than without TPO-RA. It is unclear whether TPO-RA increases the risk of thrombosis in patients with AA. We report a case of a 66-year-old female with severe AA having paroxysmal nocturnal hemoglobinuria (PNH) clones in the peripheral blood who developed ischemic colitis after three days of starting eltrombopag. Contrast-enhanced computed tomography showed ischemic colitis and contrast enhancement defect in the left atrial appendage, which indicated a thrombus in the heart. Stopping eltrombopag and providing supportive care improved her symptoms, and her blood cell counts gradually increased. Thrombosis should be considered when TPO-RA is administered during the immunosuppressive treatment of AA.
It has been reported that disruption of transcription factors critical for hematopoiesis, such as C/EBPa and AML1, is involved in leukemogenesis. PU.1 is a transcription factor important for both ...myeloid and lymphoid development. We reported that mice in which the levels of PU.1 were 20% of that of wild-type developed acute myeloid leukemia, T cell lymphoma, and a CLL-like disease. These findings strongly suggest that PU.1 has tumor suppressive activity in multiple hematopoietic lineages. Last year, we reported that PU.1 is downregulated in a majority of multiple myeloma cell lines and and freshly isolated CD138 positive myeloma cells from certain number of myeloma patients, and that tet-off inducible exogenous expression of PU.1 in PU.1 negative myeloma cell lines induced cell growth arrest and apoptosis. Based on their PU.1 expression levels, we divided the myeloma patients into two groups, namely PU.1 high and PU.1 low-to-negative, (cutoff index of 25th percentile of the PU.1 expression level distribution among all patients). The PU.1 low-to-negative patients had a significantly poorer prognosis than the PU.1 high patients. To elucidate the mechanisms of downregulation of PU.1, we performed sequence and epigenetic analysis of the promoter region and the -17 kb upstream region that is conserved among mammalians and important for proper expression of PU.1. There are no mutations in these regions of all five myeloma cell lines. In contrast, the -17 kb upstream region was highly methylated in 3 of 4 PU.1 negative myeloma cell lines, while the promoter region was also methylated to various levels in all five myeloma cell lines including one PU.1 positive cell line. These data suggested that the downregulation of PU.1 in myeloma cell lines might be dependent on the methylation of both regulatory regions of PU.1 gene, especially the -17 kb upstream region. We also evaluated the mechanisms of cell growth arrest and apoptosis of myeloma cell lines induced by PU.1. Among apoptosis-related genes, we identified that TRAIL was upregulated after PU.1 induction. To evaluate the effect of upregulation of TRAIL, we stably introduced siRNA for TRAIL into myeloma cell lines expressing PU.1, and we found that apoptosis of these cells was partially suppressed by siRNA for TRAIL, suggesting that apoptosis of myeloma cells induced by PU.1 might be at least partially due to TRAIL upregulation. We are currently performing DNA microarray analysis to compare the expression levels of genes between before and after PU.1 induction, in order to further elucidate the mechanisms of cell growth arrest and apoptosis.
Dendritic cells play a key role in host defense by presenting exogenous antigens to T cells. Two dendritic cell subsets, conventional dendritic cells (cDCs) and plasmacytoid dendritic cells (pDCs), ...express distinct repertoire of Toll-like-receptors and recognize different antigens. We previously reported that murine cDCs and pDCs differentiate via either the myeloid or the lymphoid pathway (Shigematsu et al. Immunity ). It is, however, still unclear whether human cDCs and pDCs develop from myeloid, lymphoid or both lineages. In order to analyze the in vivo differentiation of human dendritic cells, we employed the newly-developed xenotrasplant assay system which utilizes newborn NOD-scid/IL2rgnull mice (Ishikawa et al., Blood, in press). Transplantation of 104 Lin-CD34+CD38- hematopoietic stem cells into sublethally irradiated newborn NOD-scid/IL2rgnull mice resulted in generation of all hematopoietic and lymphoid components for a long-term via physiological intermediates such as common myeloid progenitors (CMP) and common lymphoid progenitors (CLP). We found that in this system, dendritic cell subcomponents such as hCD11c+hIL3Ralow cDCs and hCD11c-hIL3Rahigh pDCs, efficiently developed in recipients' bone marrow, spleen and peripheral blood. To elucidate the origin of human mDCs and pDCs, we purified CMP or CLP from the cord blood, and transplanted these cells into sublethally irradiated newborn NOD-scid/IL2rgnull mice via facial vein. At 4-6 weeks post-transplantation, CMP gave rise only to myeloid cells such as erythroid cells, platelets and granulocytes, while CLP exclusively generated T, B and NK cells. Interestingly, in either mouse group injected with CMP or CLP, cDCs and pDCs were easily detected in the spleen and in the bone marrow. Phenotypic and RT-PCR analyses of purified CMP- or CLP-derived DCs revealed that DCs possessed similar phenotypic characteristics, and transcription profiles in TLR families, BDCA antigens and costimulation molecules, irrespective of their lineage origin. Thus, human cDCs and pDCs develop through both myeloid and lymphoid pathways as in case of mouse hematopoiesis. Further characterization of DCs of different lineage origin is currently performed by microarray analyses in order to find genes specifically expressed in each DC subset.
Primary non-engraftment or early rejection after transplantation of haematopoietic stem cells represent life-threatening complications of allogeneic stem cell transplantation. Management of early ...graft failure has been problematic, as the risk of fatal infectious complications increases with the time of pancytopenia and as a second transplant preceded by a conventional myeloablative conditioning regimen has been associated with high rates of cumulative organ toxicity. For paediatric patients with early graft failure following the transplantation of highly purified major histocompatibility complex (MHC)-disparate haematopoietic stem cells, we have evaluated an immunosuppressive OKT-3/methylprednisolone-based reconditioning regimen with low toxicity in preparation for a secondary transplant of purified haematopoietic stem cells from the same donor. This report presents the results from a 4-year pilot study including six patients with early graft failure. The results demonstrate that this antibody-based regimen can be used effectively to prepare patients for secondary transplantation. Successful engraftment after a second transplant procedure was achieved in five of these six high-risk patients. The median interval between first and second transplant was 27 d (range 22-51 d), and the median time for engraftment was 10 d (range 9-13 d). Chimaerism analysis of microsatellite regions by polymerase chain reaction (PCR) demonstrated complete donor chimaerism in four of these patients within the first month after secondary transplant and revealed mixed chimaerism in one patient who converted to complete chimaerism after T-cell add-back.
Several reports have demonstrated the persistent detection of AML1-MTG8 fusion products, representing minimal residual disease (MRD), in patients with t(8;21) acute myelogenous leukaemia (AML) who ...are in long-term remission. It is probable that immune-mediated mechanisms that are able to suppress the expansion of MRD may result in the continuance of remission. It was previously shown that some t(8;21) AML patients had high anti-MTG8 antibody titres. MTG8 expression in normal adult tissues is limited to the brain or heart in which human leucocyte antigen (HLA) class I cell-surface antigens are either not or are only faintly detectable. We hypothesized that the overexpression of the MTG8 gene in t(8;21) AML cells could act as a possible tumour antigen, which might be able to induce the immune-mediated suppression of the expansion of MRD. We were able to induce HLA-A0201-restricted cytotoxic T-lymphocyte (CTL) lines against an MTG8 peptide (MTG8b amino acids 182-191) using monocyte-derived dendritic cells from a healthy donor. T-cell receptor (TCR)Valpha17, TCRVbeta14 and 15, and TCRJbeta2.1 and 2.3 are predominantly used in these CTL lines. Our data, which suggest that the MTG8 protein could be one of the tumour antigens recognized by CTLs, may be helpful in further investigations of TCR analysis in t(8;21) AML patients with HLA-A0201 who are in long-term remission.
Several reports have demonstrated the persistent detection of AML1–MTG8 fusion products, representing minimal residual disease (MRD), in patients with t(8;21) acute myelogenous leukaemia (AML) who ...are in long‐term remission. It is probable that immune‐mediated mechanisms that are able to suppress the expansion of MRD may result in the continuance of remission. It was previously shown that some t(8;21) AML patients had high anti‐MTG8 antibody titres. MTG8 expression in normal adult tissues is limited to the brain or heart in which human leucocyte antigen (HLA) class I cell‐surface antigens are either not or are only faintly detectable. We hypothesized that the overexpression of the MTG8 gene in t(8;21) AML cells could act as a possible tumour antigen, which might be able to induce the immune‐mediated suppression of the expansion of MRD. We were able to induce HLA‐A0201‐restricted cytotoxic T‐lymphocyte (CTL) lines against an MTG8 peptide (MTG8b amino acids 182–191) using monocyte‐derived dendritic cells from a healthy donor. T‐cell receptor (TCR)Vα17, TCRVβ14 and 15, and TCRJβ2.1 and 2.3 are predominantly used in these CTL lines. Our data, which suggest that the MTG8 protein could be one of the tumour antigens recognized by CTLs, may be helpful in further investigations of TCR analysis in t(8;21) AML patients with HLA‐A0201 who are in long‐term remission.
We vaccinated a refractory essential monoclonal cryoglobulinemia patient with monocyte-derived DCs (Mo-DCs) pulsed with purified cryoglobulin as a tumor antigen. During the vaccinations, his ...acrocyanosis improved and we were able to reduce the number of hot baths used to treat his symptoms, with no sick effects. Furthermore, cryoglobulin-specific proliferative responses were observed after the vaccination. As there wax a recurrence of acrocyanosis after the final vaccination, vaccination with Mo-DCs pulsed with purified cryoglobulin would seem to be a useful treatment for refractory essential monoclonal cryoglobulinemia.
PDF
