Yoshimichi Tachikawa

Pivotal role of Notch signaling in regulation of erythroid maturation and proliferation

Abstract:  Notch signaling plays an important role in cell fate decisions in developmental systems. To clarify its role in committed hematopoietic progenitor cells, we investigated the effects of Notch signaling in erythroid colony forming cells (ECFCs) generated from peripheral blood. ECFCs express Notch receptors, Notch1 and Notch2, and Notch ligands Delta1, Delta4, and Jagged1. When we assayed the effects of Notch ligands on erythroid maturation by flow cytometry, we found that immobilized Delta1 and immobilized Delta4 in particular inhibited maturation, whereas Jagged1 had no effect. In addition, Delta4 inhibited proliferation without reducing cell viability. Increases in expression levels of the Notch target gene hairy enhancer of split (HES) ‐1 were evident by real‐time PCR after stimulation with immobilized Delta4. The effect of soluble Delta4 on expression of HES‐1 was less pronounced than that seen with the immobilized form, indicating that all surface‐bound ligands are important for effective signal transduction. When ECFCs were cultured in the presence of soluble Delta4 at a low cell concentration, erythroid maturation was slightly inhibited, but at a high concentration, maturation was promoted via competition of soluble Delta4 with endogenous ligands. These results indicate a pivotal role of Notch signaling in regulating erythroid maturation and proliferation, and further suggest that cell–cell interactions modulate growth of erythroid progenitor cells via Notch system.

Monitoring minimal residual disease in patients with MLL-AF6 fusion transcript-positive acute myeloid leukemia following allogeneic bone marrow transplantation.

Acute myeloid leukemia (AML) patients with chromosome 11q23 abnormalities or MLL rearrangements have a poor prognosis when treated with conventional chemotherapy. However, the efficacy of allogeneic bone marrow transplantation (BMT) for this type of leukemia is not yet clear.We describe 2MLL-AF6 fusion transcript-positive AML patients treated with allogeneic BMT who were monitored for minimal residual disease (MRD) by reverse transcriptase polymerase chain reaction. Although long survival or cure of this type of AML is rarely reported, 1 patient had durable remissions. Fusion transcripts disappeared in 1 patient but not in the other, even after the graft-versus-host disease effect was increased by the discontinuation of immmunosuppressive therapy. This is the first report of MRD and the probability of graft-versus-leukemia effects following BMT in AML patients who areMLL-AF6 fusion transcript positive.

Vitamin K2 modulates differentiation and apoptosis of both myeloid and erythroid lineages

Vitamin K2 (VK2) can improve cytopenia in some patients with myelodysplastic syndrome (MDS). Although it is well known that VK2 induces differentiation and apoptosis in acute myeloid leukemia (AML) cell lines, little is known about its effect on normal hematopoietic progenitors. The effects of VK2 on primary myeloid and erythroid progenitors were examined. Mobilized CD34‐positive cells from peripheral blood were used for the examination of myeloid lineage cells, and erythroid progenitors purified from peripheral blood were used for erythroid lineage cells. VK2 upregulated the expressions of myeloid markers CD11b and CD14, and increased the mRNA expression levels of CCAAT/enhancer binding protein‐α (C/EBPα) and PU.1 in myeloid progenitors. In erythroid progenitors, VK2 did not show a significant effect on differentiation. However, VK2 exhibited an anti‐apoptotic effect on erythroid progenitors under erythropoietin depletion. This anti‐apoptotic effect was restricted to normal erythroid progenitors and was not shown in erythroleukemic cell line AS‐E2. Steroid and xenobiotic receptor (SXR), which was recently identified as a receptor of VK2, was expressed on myeloid progenitors, and the SXR agonist rifampicin (RIF) also upregulated CD11b and CD14 expressions on myeloid progenitors. These results indicate that SXR is involved in the effect of VK2 on myeloid progenitors. The major effect of VK2 on myeloid progenitors was promoting differentiation, whereas its anti‐apoptotic effect seemed to be dominant in erythroid progenitors. Although the detailed mechanism of VK2’s effect on differentiation or apoptosis of hematopoietic progenitors remains unknown, the effect of VK2 therapy in patients with MDS could be partly explained by these mechanisms.

Spontaneous splenic rupture in a patient with light-chain deposition disease undergoing autologous peripheral blood stem cell transplantation.

Light-chain deposition disease (LCDD) is a rare plasma cell neoplasm that secretes an abnormal immunoglobulin light chain, which is deposited in tissues, leading to organ dysfunction. Spontaneous splenic rupture is a rare and life-threatening complication of treatment with granulocyte colony-stimulating factor (G-CSF). Herein, we describe spontaneous splenic rupture after the administration of lenograstim to a patient with LCDD undergoing autologous stem cell transplantation (ASCT). The patient was successfully treated by transcatheter embolization of the splenic artery, and long-term stringent complete remission was attained. Plasma cell neoplasms, including multiple myeloma with amyloidosis, are among the most commonly reported conditions associated with spontaneous splenic rupture in patients undergoing ASCT. This finding suggests that, in addition to the effect of G-CSF on the spleen, a combination of factors, including tissue vulnerability induced by the infiltration of abnormal immunoglobulins, may be involved in the pathogenesis of spontaneous splenic rupture. Notably, splenomegaly is not always evident in these patients. Surgical treatment may not be an option, because of severe myelosuppression, and thus less invasive treatment using transcatheter embolization may be feasible.

Composite gastrointestinal lymphoma consisting of diffuse large B-cell lymphoma and peripheral T-cell lymphoma

Composite lymphomas are defined as two different types of lymphomas presenting in the same anatomic site [1]. A rare case of a composite gastrointestinal lymphoma consisting of diffuse large B-cell lymphoma (DLBCL) and peripheral T-cell lymphoma (PTCL) is presented. A 65-year-old woman was diagnosed with mucosaassociated lymphoid tissue lymphoma of the duodenum in 2001. Eradication therapy for Helicobacter pylori resulted in complete remission of the lymphoma. After 4 years, she was admitted to our hospital due to hematemesis in December 2005. The levels of hemoglobin and soluble interleukin-2 receptor were 10.4 g/dL and 938.1 U/mL, respectively. Endoscopic examination revealed multiple ulcers in the stomach and ileum. On microscopy, both gastric and ileal ulcers showed diffuse proliferation of large lymphoid cells, which were positive for CD20, CD79a, and Epstein–Barr virus (EBV) encoded RNA-1 (EBER-1) in situ hybridization (ISH) and negative for CD3 and CD45RO (Fig. 1a–d). These findings were compatible with EBV-positive DLBCL of the elderly, according to the new WHO classification [2]. After 3 courses of combination chemotherapy (pirarubicin, vincristine, cyclophosphamide and prednisolone; THP-COP) with rituximab, the ileal ulcers disappeared, but the area of the gastric lymphoma enlarged. A partial gastrectomy was performed with a diagnosis of perforation of the stomach in April 2006. Unexpectedly, pathological examination of the resected specimen demonstrated diffuse proliferation of smallto large-sized lymphocytes with T-cell markers (positive for CD3, CD4, CD45RO, CD56 and TIA-1, and negative for CD8, CD20, CD79a and EBER-ISH, Fig. 1e–h). The diagnosis of PTCL was made, and the distribution of the disease and strong positivity of TIA-1 suggested enteropathyassociated T-cell lymphoma. Since the size of the lymphoma cells was mainly small to medium and they were positive for CD56, we speculated that the lymphoma could be classified into enteropathy-associated T-cell lymphoma type 2 [3, 4]. However, the mucosa of the specimen was almost destroyed and the distribution pattern was not clear. Retrospectively, we performed PCR analysis of T-cell receptor (TCR) gamma chain gene in the gastric specimen at the DLBCL stage in 2005 and PTCL stage in 2006 (Fig. 2). Although scattered T cells were present in the specimen, rearrangement of TCR was not detected. On the other hand, strong rearranged band was detected at the PTCL stage. Since PTCL was diagnosed during the course of chemotherapy against DLBCL and residual B-cell disease could not be denied after gastrectomy, the patient was given 2 courses of consolidation chemotherapy (etoposide, methylpredonisolone, cytarabine and cisplatin; ESHAP) with rituximab. Achievement of complete remission was confirmed by 18[F]fluorodeoxyglucose (FDG)-positron emission tomography (PET) scan in June 2006. However, Y. Tachikawa M. Shiratsuchi E. Sada K. Idutsu J. Kiyasu R. Takayanagi Y. Abe (&) Department of Medicine and Bioregulatory Science, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan e-mail: abey@intmed3.med.kyushu-u.ac.jp

Epithelioid hemangioendothelioma presenting with severe myelofibrosis and a high serum hyaluronan level

Epithelioid hemangioendothelioma (EHE) is a rare tumor originating from the vascular endothelium; it has an intermediate malignant potential. EHEs affect all age groups and mostly originate from the soft tissues of the extremities, lungs, and liver. Spinal EHEs, especially those occurring in the bone marrow region, are extremely rare. We report a case of EHE with massive involvement of the liver, vertebrae, and cranial bones that caused severe myelofibrosis (MF) in a 67‐yr‐old‐male patient. Hyaluronan deposits were diffusely observed in the tumor tissue biopsies obtained from both the liver and bone marrow. Furthermore, the serum hyaluronan level increased markedly along with rapid progression of the disease. To the best of our knowledge, this is the first report of MF occurring in an EHE; hyaluronan may have played an important role in the pathogenesis of fibrosis in this case.

Successful Treatment with Nonmyeloablative Allogeneic Hematopoietic Stem Cell Transplantation in a Patient with Acute Myeloid Leukemia Complicated with Pulmonary Infection

We describe the case of a 48-year-old man with acute myeloid leukemia complicated with pulmonary infection that was successfully treated by nonmyeloablative allogeneic peripheral blood stem cell transplantation with conditioning by low-dose total body irradiation and fludarabine. The disease was diagnosed immunophenotypically as myeloid/natural killer cell precursor acute leukemia. After two courses of induction therapy, complete remission was achieved. However, the patient developed pneumonia from prolonged severe neutropenia. Nonmyeloablative allogeneic transplantation was performed because of the active pulmonary infection and the patients poor performance status. Myelosuppression after transplantation was mild, and the pulmonary infiltration was well controlled during the course of treatment. At the time of this report the patient was an outpatient in our clinic, and on day 500, his disease was in remission with well-controlled chronic graft-versus-host disease. Nonmyeloablative transplantation may provide a new therapeutic strategy for treating patients with active infection who cannot tolerate conventional transplantation with high-dose chemoradiotherapy.

Methotrexate-associated lymphoproliferative disorders with angioimmunoblastic T-cell lymphoma-like features accompanied by gamma-heavy chain disease in a patient with rheumatoid arthritis: AITL-like MTX-LPDs accompanied by γ-HCD

Although gamma heavy chain disease (γ‐HCD) lesions occasionally morphologically resemble angioimmunoblastic T‐cell lymphoma (AITL), no association has been described in detail due to the rarity of the disease. In this report, we present a rare manifestation of methotrexate (MTX)‐associated lymphoproliferative disorders (LPDs) with AITL‐like features accompanied by γ‐HCD in a 75‐year‐old man with rheumatoid arthritis (RA). A biopsy specimen was evaluated using immunohistochemistry, clonal analyses of immunoglobulin VH and T‐cell receptor γ gene rearrangements by polymerase chain reaction, and Sanger sequencing for confirmation of the structure of deleted γ‐HCD clones. The histological features characterized by proliferation of CD4‐ and PD‐1‐positive medium‐sized T cells and arborizing high endothelial venules together with numbers of small lymphocytes, eosinophils, plasma cells, and histiocytes in the background mimicked those of AITL, but did not completely fulfill the diagnostic criteria. Clonal analysis demonstrated that the specimen contained multiple LPDs of both B‐cell and T‐cell lineages. Sequence analysis confirmed the co‐existence of a clone responsible for production of the abnormal heavy chain. This report provides new insights into the pathology of γ‐HCD. Multiple host‐derived factors (e.g., RA and/or use of MTX) may be responsible for the occurrence of LPDs of multiple lineages within a single lymph node.