Somatic mutation of RUNX1 is implicated in various hematological malignancies, including myelodysplastic syndrome and acute myeloid leukemia (AML), and previous studies using mouse models disclosed its critical roles in hematopoiesis. However, the role of RUNX1 in human hematopoiesis has never been tested in experimental settings. Familial platelet disorder (FPD)/AML is an autosomal dominant disorder caused by germline mutation of RUNX1, marked by thrombocytopenia and propensity to acute leukemia. To investigate the physiological function of RUNX1 in human hematopoiesis and pathophysiology of FPD/AML, we derived induced pluripotent stem cells (iPSCs) from three distinct FPD/AML pedigrees (FPD-iPSCs) and examined their defects in hematopoietic differentiation. By in vitro differentiation assays, FPD-iPSCs were clearly defective in the emergence of hematopoietic progenitors and differentiation of megakaryocytes, and overexpression of wild-type (WT)-RUNX1 reversed most of these phenotypes. We further demonstrated that overexpression of mutant-RUNX1 in WT-iPSCs did not recapitulate the phenotype of FPD-iPSCs, showing that the mutations were of loss-of-function type. Taken together, this study demonstrated that haploinsufficient RUNX1 allele imposed cell-intrinsic defects on hematopoietic differentiation in human experimental settings and revealed differential impacts of RUNX1 dosage on human and murine megakaryopoiesis. FPD-iPSCs will be a useful tool to investigate mutant RUNX1-mediated molecular processes in hematopoiesis and leukemogenesis.

Pregnancy with paroxysmal nocturnal hemoglobinuria (PNH) is associated with significant risk of complications, such as life-threatening thrombosis. Recently, eculizumab has come into clinical use and revolutionized the treatment of PNH. However, clinical information regarding eculizumab use for PNH during pregnancy is limited. The present report describes pregnancies with PNH treated with eculizumab that were registered with the Japan PNH study group and reviews the literature. In case 1, the patient received eculizumab throughout pregnancy and delivered a healthy neonate at term, although breakthrough hemolysis occurred at 20 weeks of gestation. In case 2, the patient discontinued eculizumab before pregnancy and developed preeclampsia at 27 weeks of gestation. She received eculizumab and delivered a preterm, but healthy, neonate by cesarean section. In case 3, the patient received eculizumab from 18 weeks of gestation and delivered a healthy neonate at term without any complications. Reports of 11 pregnant women treated with eculizumab were identified in the literature. Of 14 pregnancies, including our own cases, breakthrough hemolysis and preeclampsia occurred in five and two cases, respectively. There were no thrombotic complications, maternal or neonatal deaths, or fetal structural abnormalities. Thus, eculizumab appears to be safe and effective for managing PNH during pregnancy.

We describe a patient with Philadelphia chromosome (Ph)-positive chronic myelogenous leukemia (CML) who developed an extramedullary blast crisis in the central nervous system (CNS) and then a subcutaneous tumor of the neck during treatment with imatinib mesylate. Administered 400 mg of imatinib mesylate after the diagnosis of chronic-phase CML, the patient achieved a complete cytogenetic remission 4 months later. However, he developed a mixed myeloid/B-cell blast crisis with additional karyotype abnormalities only in the CNS during a complete cytogenetic remission in the bone marrow. Several doses of intrathecal chemotherapy and whole-brain irradiation were effective in treating the blast crisis in the CNS. After 7 months of complete cytogenetic remission, the patient experienced a subcutaneous tumor in the right neck. A biopsy of the tumor revealed a mixed myeloid/T-cell blast crisis. The cytogenetic analysis showed that the blast crisis clone in the neck tumor was different from that of the CNS. An increased dose of imatinib mesylate was ineffective in treating the neck tumor. Irradiation to the right neck was therefore undertaken. This case suggests that the development of a clone resistant to imatinib mesylate is not always detected in the bone marrow and that multiple Ph-positive clones have the potential to become transformed into a blast crisis.

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A study to evaluate WT1 mRNA expression levels in peripheral blood (PB) and bone marrow aspirate (BM) was conducted in 172 patients, including 115 with myelodysplastic syndromes (MDS), in Japan. The level of WT1 mRNA expression was evaluated according to the French-American-British (FAB) and World Health Organization (WHO) classifications (2001, 2008) and using the International Prognostic Scoring System and the WHO Prognostic Scoring System scales. WT1 mRNA expression levels in PB and BM were well correlated (r = 0.85), and they tended to increase with disease stage progression and in those at higher risk of leukemic transformation. WT1 mRNA expression can be a useful marker for the diagnosis and risk evaluation of MDS.

Iron overload is the accumulation of excess iron in the body that may occur as a result of various genetic disorders or as a consequence of repeated blood transfusions. The surplus iron is then stored in the liver, pancreas, heart and other organs, which may lead to chronic liver disease or cirrhosis, diabetes and heart disease, respectively. In addition, excessive iron may impair hematopoiesis, although the mechanisms of this deleterious effect is not entirely known. In this study, we found that ferrous ammonium sulfate (FeAS), induced growth arrest and apoptosis in immature hematopoietic cells, which was mediated via reactive oxygen species (ROS) activation of p38MAPK and JNK pathways. In in vitro hematopoiesis derived from embryonic stem cells (ES cells), FeAS enhanced the development of dysplastic erythroblasts but inhibited their terminal differentiation; in contrast, it had little effect on the development of granulocytes, megakaryocytes, and B lymphocytes. In addition to its directs effects on hematopoietic cells, iron overload altered the expression of several adhesion molecules on stromal cells and impaired the cytokine production profile of these cells. Therefore, excessive iron would affect whole hematopoiesis by inflicting vicious effects on both immature hematopoietic cells and stromal cells.

The involvement of adult T-cell leukemia (ATL) cells in organs such as the skin and lymph nodes is observed in about 50% of cases of ATL. Epstein-Barr virus (EBV) infection has often been observed in the clinical course of ATL. In this study, we established two B-cell lines from peripheral blood of patients with ATL. EBV DNA, proviral DNA for HTLV-1 and Tax mRNA were detected in both lines. As part of the characterization of these cells, an enhanced expression of intercellular adhesion molecule-1 (ICAM-1) (CD54) or ICAM-3 (ICAM-3) (CD50), lymphocyte function-1 (LFA-1) (CD11a/CD18), and Mac-1 (CD11b/CD18) was observed. To investigate the role of the interaction of these viruses, we transfected EBV and/or HTLV-1 into a healthy donor's lymphocytes, an EBV-infected B cell line, Raji, and a HTLV-1 negative T-cell line, Jurkat. Enhanced expression of adhesion molecules was also observed in double transfectants (EBV and HTLV-1). In the clinical course of ATL, LMP-1, EBNA-2, CD50 and CD54 were detected in lymph nodes and skin specimens by immunohistochemical staining. Furthermore, high levels of interleukin-4 (IL-4) were detected in these cell lines and transfectants. The results indicated that coinfection with HTLV-1 and EBV may induce aggressive organ involvement through the enhanced expression of adhesion molecules via IL-4 signaling. A new mechanism of ATL involvement is discussed.