KUMANO KEIKI

<title>Abstract</title>Although the physiological function of the omentum remains elusive, it has been proposed that it plays an important role in fat storage, immune regulation, and regeneration of injured tissues and organs. Although the omentum undergoes expansion upon activation, reports on the accurate assessment of increased cell types and the origin of the increased cells remain limited. To investigate this aspect, the omenta of parabiotic mice were subjected to activation using distinct fluorescent markers and single-cell RNA sequencing (scRNA-seq) was performed to identify circulation-derived omental cells. We found that a considerable number of circulating cells contributed to the activation of the omentum. The omental cells derived from circulating cells exhibited morphological features similar to those of fibroblasts. scRNA-seq revealed the existence of a novel cell population that co-expressed macrophage and fibroblast markers in the activated omentum, suggesting that it corresponded to circulating macrophage-derived fibroblast-like cells. Lineage tracing experiments revealed that most fibroblasts in the activated omentum were not derived from WT1-positive mesenchymal progenitors. The cell cluster also expressed various chemokine genes, indicating its role in the activation and recruitment of immune cells. These results provide important information regarding the activation of the omentum.

<title>Abstract</title> Accumulated experience supports the efficacy of allogenic haematopoietic stem cell transplantation in arresting the progression of childhood-onset cerebral form of adrenoleukodystrophy in early stages. For adulthood-onset cerebral form of adrenoleukodystrophy, however, there have been only a few reports on haematopoietic stem cell transplantation and the clinical efficacy and safety of that for adulthood-onset cerebral form of adrenoleukodystrophy remain to be established. To evaluate the clinical efficacy and safety of haematopoietic stem cell transplantation, we conducted haematopoietic stem cell transplantation on 12 patients with adolescent-/adult-onset cerebral form/cerebello-brainstem form of adrenoleukodystrophy in a single-institution-based prospective study. Through careful prospective follow-up of 45 male adrenoleukodystrophy patients, we aimed to enrol patients with adolescent-/adult-onset cerebral form/cerebello-brainstem form of adrenoleukodystrophy at early stages. Indications for haematopoietic stem cell transplantation included cerebral form of adrenoleukodystrophy or cerebello-brainstem form of adrenoleukodystrophy with Loes scores up to 13, the presence of progressively enlarging white matter lesions and/or lesions with gadolinium enhancement on brain MRI. Clinical outcomes of haematopoietic stem cell transplantation were evaluated by the survival rate as well as by serial evaluation of clinical rating scale scores and neurological and MRI findings. Clinical courses of eight patients who did not undergo haematopoietic stem cell transplantation were also evaluated for comparison of the survival rate. All the patients who underwent haematopoietic stem cell transplantation survived to date with a median follow-up period of 28.6 months (4.2–125.3 months) without fatality. Neurological findings attributable to cerebral/cerebellar/brainstem lesions became stable or partially improved in all the patients. Gadolinium-enhanced brain lesions disappeared or became obscure within 3.5 months and the white matter lesions of MRI became stable or small. The median Loes scores before haematopoietic stem cell transplantation and at the last follow-up visit were 6.0 and 5.25, respectively. Of the eight patients who did not undergo haematopoietic stem cell transplantation, six patients died 69.1 months (median period; range 16.0–104.1 months) after the onset of the cerebral/cerebellar/brainstem lesions, confirming that the survival probability was significantly higher in patients with haematopoietic stem cell transplantation compared with that in patients without haematopoietic stem cell transplantation (P = 0.0089). The present study showed that haematopoietic stem cell transplantation was conducted safely and arrested the inflammatory demyelination in all the patients with adolescent-/adult-onset cerebral form/cerebello-brainstem form of adrenoleukodystrophy when haematopoietic stem cell transplantation was conducted in the early stages. Further studies are warranted to optimize the procedures of haematopoietic stem cell transplantation for adolescent-/adult-onset cerebral form/cerebello-brainstem form of adrenoleukodystrophy.

Chronic myelomonocytic leukemia (CMML) is an entity of myelodysplastic syndrome/myeloproliferative neoplasm. Although CMML can be cured with allogeneic stem cell transplantation, its prognosis is generally very poor due to the limited efficacy of chemotherapy and to the patient's age, which is usually not eligible for transplantation. Comprehensive analysis of CMML pathophysiology and the development of therapeutic agents have been limited partly due to the lack of cell lines in CMML and the limited developments of mouse models. After successfully establishing patient's derived disease-specific induced pluripotent stem cells (iPSCs) derived from a patient with CMML, we utilized these CMML-iPSCs to achieve hematopoietic re-differentiation in vitro, created a humanized CMML mouse model via teratomas, and developed a drug-testing system. The clinical characteristics of CMML were recapitulated following hematopoietic re-differentiation in vitro and a humanized CMML mouse model in vivo. The drug-testing system using CMML-iPSCs identified a MEK inhibitor, a Ras inhibitor, and liposomal clodronate as potential drugs for treating CMML. Clodronate is a drug commonly used as a bisphosphonate for osteoporosis. In this study, the liposomalization of clodronate enhanced its effectiveness in these assays, suggesting that this variation of clodronate may be adopted as a repositioned drug for CMML therapy.

Properties of cancer stem cells involved in drug resistance and relapse have significant effects on clinical outcome. Although tyrosine kinase inhibitors (TKIs) have dramatically improved survival of patients with chronic myeloid leukemia (CML), TKIs have not fully cured CML due to TKI-resistant CML stem cells. Moreover, relapse after discontinuation of TKIs has not been predicted in CML patients with the best TKI response. In our study, a model of CML stem cells derived from CML induced pluripotent stem cells identified ADAM8 as an antigen of TKI-resistant CML cells. The inhibition of expression or metalloproteinase activity of ADAM8 restored TKI sensitivity in primary samples. In addition, residual CML cells in patients with optimal TKI response were concentrated in the ADAM8+ population. Our study demonstrates that ADAM8 is a marker of residual CML cells even in patients with optimal TKI response and would be a predictor of relapse and a therapeutic target of TKI-resistant CML cells.

The murine intestine, like that of other mammalians, continues to develop after birth until weaning; however, whether this occurs in response to an intrinsic developmental program or food intake remains unclear. Here, we report a novel system for the allotransplantation of small intestine and colon harvested from Lgr5(EGFP-IRES-CreERT2/+); Ros alpha 26(rbw/+) mice immediately after birth into the subrenal capsule of wild-type mice. By histological and immunohistochemical analysis, the developmental process of transplanted small intestine and colon was shown to be comparable with that of the native tissues: mature intestines equipped with all cell types were formed, indicating that these organs do not require food intake for development. The intestinal stem cells in transplanted tissues were shown to self-renew and produce progeny, resulting in the descendants of the stem cells occupying the crypt-villus unit of the small intestine or the whole crypt of the colon. Collectively, these findings indicate that neonatal intestine development follows an intrinsic program even in the absence of food stimuli.

Although the existence of cancer stem cells in intestine tumors has been suggested, direct evidence has not been yet provided. Here, we showed, using the multicolor lineage-tracing method and mouse models of intestinal adenocarcinoma and adenoma that Bmi1-or Lgr5-positive tumorigenic cells clonally expanded in proliferating tumors. At tumor initiation and during tumor propagation in the colon, the descendants of Lgr5-positive cells clonally proliferated to form clusters. Clonal analysis using ubiquitous multicolor lineage tracing revealed that colon tumors derived from Lgr5-positive cells were monoclonal in origin but eventually merged with neighboring tumors, producing polyclonal tumors at the later stage. In contrast, the origin of small intestine tumors was likely polyclonal, and during cancer progression some clones were eliminated, resulting in the formation of monoclonal tumors, which could merge similar to colon tumors. These results suggest that in proliferating intestinal neoplasms, Bmi1-or Lgr5-positive cells represent a population of cancer stem cells, whereas Lgr5-positive cells also function as cells-of-origin for intestinal tumors.

Abstract Since the emergence of tyrosine kinase inhibitors (TKIs), long-term survival of patients with chronic myelogenous leukemia (CML) has been improved. However, those TKIs have not fully succeeded in curing CML, mainly due to TKI-resistant CML stem cells. CML stem cells are often difficult to analyze because they represent an extremely minor population of CML cells. To overcome this obstacle, we established integration-free induced pluripotent stem cells (iPSCs) from bone marrow (BM) cells of two patients with CML in chronic phase (CML-CP) and obtained CML pre-hematopoietic progenitor cells (CML-pre-HPCs), immature hematopoietic cells phenotypically defined by CD34+/CD45-/CD43+ cells. In semisolid and liquid cultures, CML-pre-HPCs recapitulated the principal features of CML stem cells, multi-potency and the resistance against imatinib. Gene expression enrichment analysis for CML-pre-HPCs demonstrated that several gene sets, including those related to the maintenance of hematopoietic stem cells were enriched. In addition, we found that a disintegrin and metalloprotease 8 (ADAM8), also known as CD156, was highly enhanced in CML-pre-HPCs and the expression level of ADAM8 was even increased after the treatment of imatinib in vitro. To address the significance of ADAM8 in CMP-CP patient, we evaluated purified ADAM8+ cells by fluorescence-activated cell sorting (FACS) in primary samples. First, FACS analysis found that ADAM8+ cells were enriched more in BM samples of patient with newly diagnosed CML-CP than normal or other types of leukemias among CD34+ fraction. ADAM8+ cells were enriched in CD34+/CD38- fraction compaered to CD34+/38+ fraction in BM of CML-CP patients, indicating that ADMA8+ cells represent immature hematopietic cells. In cell viability assays, ADAM8+/CD38+ CML cells in newly diagnosed CML-CP patient enhibited imatinib-resistance and imatinib-induced apoptosis in vitro was strongly suppressed in ADAM8+ CML cells compared to ADAM8- cells. Even in CD34+/CD38+ fraction, which was previously known as TKI-sensitive fraction, ADAM8+ cells exhibited TKI-resistance in both cell viability and apoptosis assay, indicating that ADAM8 would be a useful marker of TKI-resistant CML cells. Finally, to evaluate the significance of ADAM8 as a marker of TKI-resistant CML cells in vivo, we measured the frequency of CML cells in BM samples of CML-CP patients who had achieved major or complete molecular response (MMR; n = 2 or CMR; n = 1) after the administration of TKIs by limiting dilution analysis. In CML patients with MMR, CML cells remained in ADAM8+ cells at higher frequency in spite of steep decline of CML cells in ADAM8- cells The frequency of CML cells was as high in CD34+/CD38+/ADAM8+ fraction as in CD34+/38- CML stem cell fraction. Even in a patient with CMR, residual CML cells were detected in ADAM8+ population among CD34+/CD38+ fraction, whereas CML cells were undetectable in ADAM8- population. In conclusion, we have established a powerful platform with CML-iPSCs to investigate the pathophysiology of TKI-resistant CML stem cells. Using this platform, we have identified ADAM8 as a novel marker of TKI-resistant CML cells. CD34+/CD38+/ADAM8+ fraction, as well as CD34+/CD38- fraction, was an important population that defines residual CML cells even in CML-CP patients with deep molecular response after the treatment of TKI. ADAM8 would become an attractive candidate of novel therapeutic targets against TKI-resistant CML cells. Disclosures Kataoka: Yakult: Honoraria; Boehringer Ingelheim: Honoraria; Kyowa Hakko Kirin: Honoraria.

<p>Recent studies have identified markers for germ stem cells (GSCs) in the testis, such as Nanos2, Ngn3, and c-kit. The differentiation-stage specific expression of these markers indicates a hierarchical relationship between GSC populations and their plasticity. However, the exact nature of most primitive fraction of Asingle GSCs is unclear because direct kinetic assay of Asingle GSCs have not been performed. Here we show that Bmi1 is a specific marker for Asingle GSCs. Bmi1-positive GSCs are a part of GFRα1-positive GSCs, furthermore its expression correlates with the seminiferous stages. Bmi1 expression is followed by proliferative stage of Asingle GSCs. Bmi1-positive GSCs maintain spermatogenesis. They are resistant to irradiation-induced injury, and they regenerate. Thus, the present study first indicates that Bmi1 is a novel marker for Asingle GSCs whose cyclic expression suggests a regulatory role in the seminiferous stages.</p>

We recently reported that the polycomb complex protein Bmi1 is a marker for lingual epithelial stem cells (LESCs), which are involved in the long-term maintenance of lingual epithelial tissue in the physiological state. However, the precise role of LESCs in generating tongue tumors and Bmi1-positive cell lineage dynamics in tongue cancers are unclear. Here, using a mouse model of chemically (4-nitroquinoline-1-oxide: 4-NQO) induced tongue cancer and the multicolor lineage tracing method, we found that each unit of the tumor was generated by a single cell and that the assembly of such cells formed a polyclonal tumor. Although many Bmi1-positive cells within the tongue cancer specimens failed to proliferate, some proliferated continuously and supplied tumor cells to the surrounding area. This process eventually led to the formation of areas derived from single cells after 1-3 months, as determined using the multicolor lineage tracing method, indicating that such cells could serve as cancer stem cells. These results indicate that LESCs could serve as the origin for tongue cancer and that cancer stem cells are present in tongue tumors.

Familial platelet disorder with propensity to acute myeloid leukemia (FPD/AML) is an autosomal dominant disease associated with a germline mutation in the RUNX1 gene and is characterized by thrombocytopenia and an increased risk of developing myeloid malignancies. We generated induced pluripotent stem cells (iPSCs) from dermal fibroblasts of a patient with FPD/AML possessing a nonsense mutation R174X in the RUNX1 gene. Consistent with the clinical characteristics of the disease, FPD iPSC-derived hematopoietic progenitor cells were significantly impaired in undergoing megakaryocytic differentiation and subsequent maturation, as determined by colony-forming cell assay and surface marker analysis. Notably, when we corrected the RUNX1 mutation using transcription activator-like effector nucleases in conjunction with a donor plasmid containing normal RUNX1 cDNA sequences, megakaryopoiesis and subsequent maturation were restored in FPD iPSC-derived hematopoietic cells. These findings clearly indicate that the RUNX1 mutation is robustly associated with thrombocytopenia in patients with FPD/AML, and transcription activator-like effector nuclease-mediated gene correction in iPSCs generated from patient-derived cells could provide a promising clinical application for treatment of the disease. Copyright (C) 2015 ISEH - International Society for Experimental Hematology. Published by Elsevier Inc.

The skin is responsible for a variety of physiological functions and is critical for wound healing and repair. Therefore, the regenerative capacity of the skin is important. However, stem cells responsible for maintaining the acral epithelium had not previously been identified. In this study, we identified the specific stem cells in the acral epithelium that participate in the long-term maintenance of sweat glands, ducts, and interadnexal epidermis and that facilitate the regeneration of these structures following injury. Lgr6-positive cells and Bmi1-positive cells were found to function as long-term multipotent stem cells that maintained the entire eccrine unit and the interadnexal epidermis. However, while Lgr6-positive cells were rapidly cycled and constantly supplied differentiated cells, Bmi1-positive cells were slow to cycle and occasionally entered the cell cycle under physiological conditions. Upon irradiation-induced injury, Bmi1-positive cells rapidly proliferated and regenerated injured epithelial tissue. Therefore, Bmi1-positive stem cells served as reservoir stem cells. Lgr5-positive cells were rapidly cycled and maintained only sweat glands; therefore, we concluded that these cells functioned as lineage-restricted progenitors. Taken together, our data demonstrated the identification of stem cells that maintained the entire acral epithelium and supported the different roles of three cellular classes. (C) 2015 The Authors. Published by Elsevier Inc.

In recent years, several molecularly targeted therapies have been developed as part of lung cancer treatment; they have produced dramatically good results. However, among the many oncogenes that have been identified to be involved in the development of lung cancers, a number of oncogenes are not covered by these advanced therapies. For the treatment of lung cancers, which is a group of heterogeneous diseases, persistent effort in developing individual therapies based on the respective causal genes is important. In addition, for the development of a novel therapy, identification of the lung epithelial stem cells and the origin cells of lung cancer, and understanding about candidate cancer stem cells in lung cancer tissues, their intracellular signaling pathways, and the mechanism of dysregulation of the pathways in cancer cells are extremely important. However, the development of drug resistance by cancer cells, despite the use of molecularly targeted drugs for the causal genes, thus obstructing treatment, is a well-known phenomenon. In this article, we discuss major causal genes of lung cancers and intracellular signaling pathways involving those genes, and review studies on origin and stem cells of lung cancers, as well as the possibility of developing molecularly targeted therapies based on these studies.

Induced pluripotent stem cells (iPS) derived from disease cells are expected to provide a new experimental material, especially for diseases from which samples are difficult to obtain. In this study, we generated iPS from samples from patients with primary and secondary myelofibrosis. The primary myelofibrosis cells had chromosome 13q deletions, and the secondary myelofibrosis (SMF) cells had JAK2V617F mutations. The myelofibrosis patient cell-derived iPS (MF-iPS) were confirmed as possessing these parental disease-specific genomic markers. The capacity to form three germ layers was confirmed by teratoma assay. By co-culture with specific feeder cells and cytokines, MF-iPS can re-differentiate into blood progenitor cells and finally into megakaryocytes. We found that mRNA levels of interleukin-8, one of the candidate cytokines related to the pathogenesis of myelofibrosis, was elevated predominantly in megakaryocytes derived from MF-iPS. Because megakaryocytes from myelofibrosis clones are considered to produce critical mediators to proliferate fibroblasts in the bone marrow and iPS can provide differentiated cells abundantly, the disease-specific iPS we established should be a good research tool for this intractable disease. (C) 2014 ISEH - International Society for Experimental Hematology. Published by Elsevier Inc.

A(single) cells in undifferentiated spermatogonia are considered to be the most primitive forms of germ stem cells (GSCs). Although GFR alpha 1 is thought to be a marker of A(single) cells, we found that Bmi1(High) is more specific than GFR alpha 1 for A(single) cells. Bmi1(High) expression in A(single) cells is correlated with seminiferous stages, and its expression was followed by the proliferative stage of A(single) GSCs. In contrast, GFR alpha 1 expression was seminiferous stage-independent. Fate analyses of EdU-positive Bmi1(High)-positive cell-derived A(single) cells revealed that these cells self-renewed or generated transient amplifying A(paired) cells. Bmi1(High)-positive cells were resistant to irradiation-induced injury, after which they regenerated. Elimination of Bmi1(High)-positive cells from seminiferous tubules resulted in the appearance of tubules with seminiferous stage mismatches. Thus, in this study, we found that Bmi1(High) is a seminiferous stage-dependent marker for long-term GSCs and that Bmi1(High)-positive cells play important roles in maintaining GSCs and in regenerating spermatogenic progenitors after injury.

Just as normal stem cells require niche cells for survival, leukemia-initiating cells (LICs) may also require niche cells for their maintenance. Chronic myeloid leukemia (CML) is caused by the activity of BCR-ABL, a constitutively active tyrosine kinase. CML therapy with tyrosine kinase inhibitors is highly effective; however, due to the persistence of residual LICs, it is not curative. Several factors are known to support CML LICs, but purification of LICs and a thorough understanding of their niche signals have not yet been achieved. Using a CML-like mouse model of myeloproliferative disease, we demonstrate that CML LICs can be divided into CD25(+) Fc epsilon RI alpha(-) Lineage marker (Lin)(-) Sca-1(+) c-Kit(+) (F-LSK) cells and CD25(-)F(-)LSK cells. The CD25(+)F(-)LSK cells had multilineage differentiation capacity, with a preference toward cytokine-producing mast cell commitment. Although cells interconverted between CD25(-)F(-)LSK and CD25(+)F(-)LSK status, the CD25(+)F(-)LSK cells exhibited higher LIC capacity. Our findings suggest that interleukin-2 derived from the microenvironment and CD25 expressed on CML LICs constitute a novel signaling axis. The high levels of CD25 expression in the CD34(+)CD38(-) fraction of human CML cells indicate that CD25(+) LICs constitute an "LIC-derived niche" that could be preferentially targeted in therapy for CML.

Acute myeloid leukemia (AML) is a heterogeneous hematologic malignancy that originates from leukemia-initiating cells (LICs). The identification of common mechanisms underlying LIC development will be important in establishing broadly effective therapeutics for AML. Constitutive NF-kappa B pathway activation has been reported in different types of AML; however, the mechanism of NF-kappa B activation and its importance in leukemia progression are poorly understood. Here, we analyzed myeloid leukemia mouse models to assess NF-kappa B activity in AML LICs. We found that LICs, but not normal hematopoietic stem cells or non-LIC fractions within leukemia cells, exhibited constitutive NF-kappa B activity. This activity was maintained through autocrine TNF-alpha secretion, which formed an NF-kappa B/TNF-alpha positive feedback loop. LICs had increased levels of active proteasome machinery, which promoted the degradation of I kappa B alpha and further supported NF-kappa B activity. Pharmacological inhibition of the proteasome complex markedly suppressed leukemia progression in vivo. Conversely, enhanced activation of NF-kappa B signaling expanded LIC frequency within leukemia cell populations. We also demonstrated a strong correlation between NF-kappa B activity and TNF-alpha secretion in human AML samples. Our findings indicate that NF-kappa B/TNF-alpha signaling in LICs contributes to leukemia progression and provide a widely applicable approach for targeting LICs.

Ecotropic viral integration site 1 (Evi1) is one of the master regulators in the development of acute myeloid leukemia (AML) and myelodysplastic syndrome. High expression of Evi1 is found in 10% of patients with AML and indicates a poor outcome. Several recent studies have indicated that Evi1 requires collaborative factors to induce AML. Therefore, the search for candidate factors that collaborate with Evi1 in leukemogenesis is one of the key issues in uncovering the mechanism of Evi1-related leukemia. Previously, we succeeded in making a mouse model of Evi1-related leukemia using a bone marrow transplantation (BMT) system. In the Evi1-induced leukemic cells, we identified frequent retroviral integrations near the CCAAT/enhancer-binding protein beta (C/EBP beta) gene and overexpression of its protein. These findings imply that C/EBP beta is a candidate gene that collaborates with Evi1 in leukemogenesis. Cotransduction of Evi1 and the shortest isoform of C/EBP beta, liver inhibitory protein (LIP), induced AML with short latencies in a mouse BMT model. Overexpression of LIP alone also induced AML with longer latencies. However, excision of all 3 isoforms of C/EBP beta (LAP*/LAP/LIP) did not inhibit the development of Evi1-induced leukemia. Therefore, isoform-specific intervention that targets LIP is required when we consider C/EBP beta as a therapeutic target.

Abstract Abstract 654 Acute myeloid leukemia (AML) is an aggressive hematologic malignancy arising from leukemia initiating cells (LIC), and is comprised of highly heterogeneous groups with different cytogenetic and molecular abnormalities, which makes it difficult to establish a broadly effective therapeutic strategy. Since constitutive NF-kB pathway activation has been reported in different types of AML cells, it is one of the promising candidates which are universally involved in the LIC phenotype. However, the mechanism of activation and its significance in leukemia progression have not been studied well. In this study, we explored NF-kB pathway activity and its role in LICs using various myeloid leukemia mouse models including MLL-ENL, MOZ-TIF2, and BCR-ABL/Nup98-HoxA9 leukemias. A number of NF-kB target genes showed elevated expression in LIC of each model: leukemic granulocyte-monocyte progenitors (L-GMP) in MLL-ENL or MOZ-TIF2 model and lineage- Sca-1+ fraction in BCR-ABL/Nup98-HoxA9 model, compared with normal hematopoietic stem cells (HSC) and GMP. Moreover, in immunofluorescence staining, each type of LIC displayed prominent nuclear translocation of NF-kB subunit p65. On the other hand, p65 was localized mainly in the cytoplasm in normal cells and, interestingly, non-LIC fraction in the bone marrow cells of the leukemia mice. To our surprise, LIC retained NF-kB activity even after serum-free culture, indicating that NF-kB pathway is prevalently activated in LIC in an autonomous fashion. To study the mechanism of activation, we analyzed gene expression profiles of LIC and normal HSC in murine and human AMLs and found that LIC showed distinctly elevated expression of TNF-a, one of the major activators of the NF-kB pathway. Consistent with these results, the culture media conditioned by LIC had higher TNF-a levels than those of normal cells. In all of the three types of leukemia mice, bone marrow extracellular fluid included higher TNF-a than that of control mice. Importantly, TNF-a blockage by the neutralizing antibody significantly attenuated p65 nuclear localization in LIC, and NF-kB inhibition by expression of a super repressor form of IkBa (IkB-SR) suppressed the TNF-a expression in LIC, indicating that LIC maintains its NF-kB activity by autocrine NF-kB/TNF-a positive feedback loop. Disruption of this loop by induction of IkB-SR or shRNA-mediated knockdown of TNF-a significantly reduced colony-forming abilities of leukemia cells and prolonged survival of leukemic mice in all the three models. In contrast, transduction of IkB-SR into normal HSC exerted no influence on their colony-forming ability. These results suggested that the NF-kB/TNF-a positive feedback loop plays a vital role for LIC propagation. We also addressed the mechanism of the difference in NF-kB activity between LIC and non-LIC. Notably, LIC had decreased protein levels of IkBa compared with non-LIC in spite of the same mRNA expression levels between them. In addition, basal 20S proteasome activity and the expression levels of proteasome subunit genes in LIC were higher than those in non-LIC, indicating that enhanced proteasomal degradation of IkBa could lead to selectively high NF-kB activity of LIC. The same propensity was seen in human AML CD34+CD38- cells versus CD34- cells in the analysis of microarray expression data. Proteasome inhibition by bortezomib diminished the differences of IkBa protein level. Moreover, its administration to leukemic mice selectively killed LIC fraction and prolonged survival in the in vivo transplantation model. Finally, forcible maintenance of NF-kB activity in LIC by shRNA-mediated knockdown of IkBa significantly enhanced its self-renewal activity as determined by surface marker profiles after in vitro culture. In the analysis of mice reconstituted with the IkBa-downregulated leukemic cells, bone marrow mononuclear cells had increased colony-forming cell ability and enhanced LIC frequency as determined by in vivo limiting dilution serial transplantation assay. These results indicated that the transition from LIC to non-LIC might be associated with the attenuation of NF-kB activity due to inefficient degradation of IkBa. In summary, these findings elucidate that NF-kB/TNF-a signaling in LIC, under support of the proteasome activity, has a critical role for both maintenance and propagation of LIC and provide a widely applicable approach for targeting LIC in myeloid leukemias. Disclosures: No relevant conflicts of interest to declare.

Induced pluripotent stem cells (iPSCs) can be generated by the expression of defined transcription factors not only from normal tissue, but also from malignant cells. Cancer-derived iPSCs are expected to provide a novel experimental opportunity to establish the disease model. We generated iPSCs from imatinib-sensitive chronic myelogenous leukemia (CML) patient samples. Remarkably, the CML-iPSCs were resistant to imatinib although they consistently expressed BCR-ABL oncoprotein. In CML-iPSCs, the phosphorylation of ERK1/2, AKT, and JNK, which are essential for the maintenance of both BCR-ABL (+) leukemia cells and iPSCs, were unchanged after imatinib treatment, whereas the phosphorylation of signal transducer and activator of transcription (STAT) 5 and CRKL was significantly decreased. These results suggest that the signaling for iPSCs maintenance compensates for the inhibition of BCR-ABL. CML-iPSC-derived hematopoietic cells recovered the sensitivity to imatinib although CD34(+)38(-)90(+)45(+) immature cells were resistant to imatinib, which recapitulated the pathophysiologic feature of the initial CML. CML-iPSCs provide us with a novel platform to investigate CML pathogenesis on the basis of patient-derived samples. (Blood. 2012;119(26):6234-6242)

RUNX1 is essential for definitive hematopoiesis and T-cell differentiation. It has been shown that RUNX1 is phosphorylated at specific serine and threonine residues by several kinase families. However, it remains unclear whether RUNX1 phosphorylation is absolutely required for its biological functions. Here, we evaluated hematopoietic activities of RUNX1 mutants with serine (S)/threonine (T) to alanine (A), aspartic acid (D), or glutamic acid (E) mutations at phosphorylation sites using primary culture systems. Consistent with the results of knockin mice, RUNX1-2A, carrying two phospho-deficient mutations at S276 and S293, retained hematopoietic activity. RUNX1-4A, carrying four mutations at S276, S293, T300, and S303, showed impaired T-cell differentiation activity, but retained the ability to rescue the defective early hematopoiesis of Runx1-deficient cells. Notably, RUNX1-5A, carrying five mutations at S276, S293, T300, S303, and S462, completely lost its hematopoietic activity. In contrast, the phospho-mimic proteins RUNX1-4D/E and RUNX1-5D/E exhibited normal function. Our study identifies multiple phosphorylation sites that are indispensable for RUNX1 activity in hematopoiesis.

We investigated the mechanisms of hematopoietic disorders caused by iron overload and chelation, in particular, the inhibition of erythroblast differentiation. Murine c-kit(+) progenitor cells or human CD34(+) peripheral blood hematopoietic progenitors were differentiated in vitro to the erythroid lineage with free iron and/or an iron chelator. Under iron overload, formation of erythroid burst-forming unit colonies and differentiation to mature erythroblasts were significantly suppressed; these effects were canceled by iron chelation with deferoxamine (DFO). Moreover, excessive iron burden promoted apoptosis in immature erythroblasts by elevating intracellular reactive oxygen species (ROS). Interestingly, both DFO and a potent anti-oxidant agent reduced intracellular ROS levels and suppressed apoptosis, thus restoring differentiation to mature erythroblasts. Accordingly, intracellular ROS may represent a new therapeutic target in the treatment of iron overload.

Functional deregulation of transcription factors has been found in many types of tumors. Transcription factor AML1/RUNX1 is one of the most frequent targets of chromosomal abnormalities in human leukemia and altered function of AML1 is closely associated with malignant transformation of hematopoietic cells. However, the molecular basis and therapeutic targets of AML1-related leukemia are still elusive. Here, we explored immediate tar-get pathways of AML1 by in vitro synchronous inactivation in hematopoietic cells. We found that AML1 inhibits NF-kappa B signaling through interaction with I kappa B kinase complex in the cytoplasm. Remarkably, AML1 mutants found in myeloid tumors lack the ability to inhibit NF-kappa B signaling, and human cases with AML1-related leukemia exhibits distinctly activated NF-kappa B signaling. Furthermore, inhibition of NF-kappa B signaling in leukemic cells with mutated AML1 efficiently blocks their growth and development of leukemia. These findings reveal a novel role for AML1 as a cytoplasmic attenuator of NF-kappa B signaling and indicate that NF-kappa B signaling is one of the promising therapeutic targets of hematologic malignancies with AML1 abnormality. (Blood. 2011;118(25):6626-6637)

Ecotropic viral integration site 1 (Evi1), a transcription factor of the SET/ PR domain protein family, is essential for the maintenance of hematopoietic stem cells (HSCs) in mice and is overexpressed in several myeloid malignancies. Here, we generate reporter mice in which an internal ribosome entry site (IRES)-GFP cassette is knocked-in to the Evi1 locus. Using these mice, we find that Evi1 is predominantly expressed in long-term HSCs (LT-HSCs) in adult bone marrow, and in the hematopoietic stem/ progenitor fraction in the aortagonad- mesonephros, placenta, and fetal liver of embryos. In both fetal and adult hematopoietic systems, Evi1 expression marks cells with long-term multilineage repopulating activity. When combined with conventional HSC surface markers, sorting according to Evi1 expression markedly enhances purification of cells with HSC activity. Evi1 heterozygosity leads to marked impairment of the self-renewal capacity of LT-HSCs, whereas overexpression of Evi1 suppresses differentiation and boosts self-renewal activity. Reintroduction of Evi1, but not Mds1-Evi1, rescues the HSC defects caused by Evi1 heterozygosity. Thus, in addition to documenting a specific relationship between Evi1 expression and HSC selfrenewal activity, these findings highlight the utility of Evi1-IRES-GFP reporter mice for the identification and sorting of functional HSCs.

The choice of conditioning regimen before allogeneic stem cell transplantation (SCT) in patients with acute lymphoblastic leukemia (ALL) is important. We retrospectively compared outcomes of medium-dose VP-16/cyclophosphamide/total body irradiation (VP/CY/TBI) regimen and CY/TBI. Five hundred and twenty-nine patients (VP/CY/TBI: n = 35, CY/TBI: n = 494) who met all of the following criteria were compared: first time for SCT, aged 15-59 years; first or second complete remission at SCT; bone marrow or peripheral blood as stem cell source; and HLA phenotypically matched donor. Median age of the patients was 34 years, and patients who received VP/CY/TBI were younger (28 vs. 34 years, P = 0.02). Cumulative incidences of relapse and non-relapse mortality (NRM) were higher for patients who received CY/TBI (P = 0.01 for relapse, P &lt; 0.01 for NRM). After a median follow-up period of 36.9 months, 5-year overall survival (OS) rates were 82.2% in the VP/CY/TBI group and 55.2% in the CY/TBI group. OS, and disease-free survival (DFS) in the VP/CY/TBI group were shown to be significantly better by multivariate analysis [hazard ratio: 0.21 (95% confidence interval: 0.06-0.49) for DFS, hazard ratio: 0.25 (95% confidence interval: 0.08-0.59) for OS]. VP/CY/TBI was associated with a lower relapse rate and no increase in NRM, resulting in better survival than that in CY/TBI for adult ALL patients.

Dysfunction of AML1/Runx1, a transcription factor, plays a crucial role in the development of many types of leukemia. Additional events are often required for AML1 dysfunction to induce full-blown leukemia; however, a mechanistic basis of their cooperation is still elusive. Here, we investigated the effect of AML1 deficiency on the development of MLL-ENL leukemia in mice. Aml1 excised bone marrow cells lead to MLL-ENL leukemia with shorter duration than Aml1 intact cells in vivo. Although the number of MLL-ENL leukemia-initiating cells is not affected by loss of AML1, the proliferation of leukemic cells is enhanced in Aml1-excised MLL-ENL leukemic mice. We found that the enhanced proliferation is the result of repression of p19(ARF) that is directly regulated by AML1 in MLL-ENL leukemic cells. We also found that downregulation of p19(ARF) induces the accelerated onset of MLL-ENL leukemia, suggesting that p19(ARF) is a major target of AML1 in MLL-ENL leukemia. These results provide a new insight into a role for AML1 in the progression of leukemia. (Blood.2011;118(9):2541-2550)

Notch receptor-mediated signaling is involved in the developmental process and functional modulation of lymphocytes, as well as in mast cell differentiation. Here, we investigated whether Notch signaling is required for antipathogen host defense regulated by mast cells. Mast cells were rarely found in the small intestine of wildtype C57BL/6 mice but accumulated abnormally in the lamina propria of the small-intestinal mucosa of the Notch2-conditional knockout mice in naive status. When transplanted into mast cell-deficient W(sh)/W(sh) mice, Notch2-null bone marrow-derived mast cells were rarely found within the epithelial layer but abnormally localized to the lamina propria, whereas control bone marrow-derived mast cells were mainly found within the epithelial layer. After the infection of Notch2 knockout and control mice with L3 larvae of Strongyloides venezuelensis, the abundant number of mast cells was rapidly mobilized to the epithelial layer in the control mice. In contrast, mast cells were massively accumulated in the lamina propria of the small intestinal mucosa in Notch2-conditional knockout mice, accompanied by impaired eradication of Strongyloides venezuelensis. These findings indicate that cell-autonomous Notch2 signaling in mast cells is required for proper localization of intestinal mast cells and further imply a critical role of Notch signaling in the host-pathogen interface in the small intestine. (Blood. 2011;117(1):128-134)

Late-onset noninfectious pulmonary complications (LONIPCs) are life threatening for allogeneic hematopoietic SCT (allo-HSCT) recipients. However, the impact of LONIPCs on survival has not been properly evaluated and little is known about treatment efficacy. We retrospectively investigated 290 allo-HSCT recipients in our institute and reviewed the clinical aspects of 44 patients who had been diagnosed with LONIPCs. LONIPCs were significantly associated with higher rates of chronic GVHD (P&lt;0001) and nonrelapse mortality (P = 0.013), and lower rates of relapse (P = 0.009). As a result of these effects, OS was significantly worse in those with LONIPCs (P = 0.003). This result differs from a previous report. We then assessed short-term treatment response and final outcome. These results were defined by radiological findings, subjective symptoms, oxygen requirement and survival. Use of inhaled and systemic steroids did not affect either short-term response or final outcomes. However, administration of systemic corticosteroids earlier than at 21 days (median interval of time from onset of symptoms to systemic corticosteroids administration) was associated with a better outcome (P = 0.054 for short-term response, and 0.016 for final outcome). Our study indicates that LONIPCs reduce OS, and early intervention with systemic corticosteroids may be effective. Bone Marrow Transplantation (2010) 45, 1719-1727; doi:10.1038/bmt.2010.48; published online 8 March 2010

Fluid retention is characteristic of veno-occlusive disease (VOD). We hypothesized that plasma brain natriuretic peptide (BNP), a neurohormone secreted in response to volume expansion, may be associated with VOD after hematopoietic stem cell transplantation (HSCT). BNP was measured before and weekly after HSCT in 46 recipients. Sixteen patients developed VOD. BNP concentrations were similar before and on day 0 in patients with and without VOD, but were significantly higher on day 7 and later in those with VOD. Patients with VOD had significantly higher peak BNP concentrations before engraftment than those without VOD (median, 634.4 versus 80.9 pg ml(-1); P = 0.01). Multivariate analysis showed that VOD was independently associated with BNP elevation (odds ratio, 50.1; 95% CI: 5.2-478.4; P &lt; 0.01). Landmark analysis at day 7 showed that patients with peak BNP concentration of &gt;= 180 pg ml(-1) had significantly worse 100-day survival than patients with peak BNP &lt;180 pg ml(-1) (54 versus 91%; P &lt; 0.01). In multivariate analysis, BNP elevation before day 7 significantly predicted 100-day survival (hazard ratio 5.3; 95% CI: 1.1-24.3; P = 0.03). These findings suggest that plasma BNP may serve as a diagnostic and prognostic marker of VOD. Bone Marrow Transplantation (2010) 45, 1631-1637; doi:10.1038/bmt.2010.26; published online 22 February 2010

Hairy enhancer of split 1 (Hes1) is a basic helix-loop-helix transcriptional repressor that affects differentiation and often helps maintain cells in an immature state in various tissues. Here we show that retroviral expression of Hes1 immortalizes common myeloid progenitors (CMPs) and granulocyte-macrophage progenitors (GMPs) in the presence of interleukin-3, conferring permanent replating capability on these cells. Whereas these cells did not develop myeloproliferative neoplasms when intravenously administered to irradiated mice, the combination of Hes1 and BCR-ABL in CMPs and GMPs caused acute leukemia resembling blast crisis of chronic myelogenous leukemia (CML), resulting in rapid death of the recipient mice. On the other hand, BCR-ABL alone caused CML-like disease when expressed in c-Kit-positive, Sca-1-positive, and lineage-negative hematopoietic stem cells (KSLs), but not committed progenitors CMPs or GMPs, as previously reported. Leukemic cells derived from Hes1 and BCR-ABL-expressing CMPs and GMPs were more immature than those derived from BCR-ABL-expressing KSLs. Intriguingly, Hes1 was highly expressed in 8 of 20 patients with CML in blast crisis, but not in the chronic phase, and dominant negative Hes1 retarded the growth of some CML cell lines expressing Hes1. These results suggest that Hes1 is a key molecule in blast crisis transition in CML. (Blood. 2010; 115(14): 2872-2881)

This retrospective study examined the differences in the prognostic impact of the haematopoietic cell transplantation- specific comorbidity index (HCT-CI) on transplant outcomes by disease status and time from transplant in allogeneic haematopoietic stem cell transplantation (HSCT) recipients at a Japanese transplant centre. Of 187 patients, nonrelapse mortality (NRM) at 3 years was 9.6, 21.2 and 27.8% in the low-risk (score 0), intermediate-risk (score 1-2) and high-risk (score &gt;= 3) HCT-CI groups, respectively (P=0.03). The corresponding overall survival (OS) at 3 years was 70.1, 60.5 and 38.9%, respectively (P&lt;0.01). In multivariate analyses, high-risk HCT-CI significantly predicted higher NRM (relative risk, (RR) 2.44 (95% confidence interval, (CI) 1.02-5.85); P=0.04) and worse OS (RR 2.02 (95% CI 1.15-3.54); P=0.01). In the subgroup analysis according to disease status, the HCT-CI was associated with OS (P&lt;0.01) and NRM (P-0.07) in patients with low-risk diseases, but not in those with high-risk diseases. Within patients who survived without relapse &gt;1 year after HSCT, the HCT-CI did not predict OS (P=0.59) or NRM (P-0.31). These findings can be useful to determine the role of pretransplant comorbidity in allogeneic HSCT.

Constitutive activation of Notch signaling is required for the proliferation of a subgroup of human T-cell acute lymphoblastic leukemias (T-ALL). Previous in vitro studies have demonstrated the therapeutic potential of Notch signaling inhibitors for treating T-ALL. To further examine this possibility, we applied a gamma-secretase inhibitor (GSI) to T-ALL xenograft models. Treatment of established subcutaneous tumors with GSI resulted in partial or complete regression of tumors arising from four T-ALL cell lines that were also sensitive to GSI in vitro. To elucidate the mechanism of action, we transduced DND-41 cells with the active form of Notch1 (aN1), which conferred resistance to in vitro GSI treatment. Nevertheless, in vivo treatment with GSI induced a partial but significant regression of subcutaneous tumors that developed from aN1-transduced DND-41 cells, whereas it induced complete regression of tumors that developed from mock-transduced DND-41 cells. These findings indicate that the remarkable efficacy of GSI might be attributable to dual mechanisms, directly via apoptosis of DND-41 cells through the inhibition of cell-autonomous Notch signaling, and indirectly via disturbance of tumor angiogenesis through the inhibition of non-cell-autonomous Notch signaling. (Cancer Sci 2009; 100: 2444-2450).

Acquired uniparental disomy(aUPD) is a common feature of cancer genomes, leading to loss of heterozygosity. aUPD is associated not only with loss-of-function mutations of tumour suppressor genes(1), but also with gain-of-function mutations of proto-oncogenes(2). Here we show unique gain-of-function mutations of the C-CBL (also known as CBL) tumour suppressor that are tightly associated with aUPD of the 11q arm in myeloid neoplasms showing myeloproliferative features. The C-CBL proto-oncogene, a cellular homologue of v-Cbl, encodes an E3 ubiquitin ligase and negatively regulates signal transduction of tyrosine kinases(3-6). Homozygous C-CBL mutations were found in most 11q-aUPD-positive myeloid malignancies. Although the C-CBL mutations were oncogenic in NIH3T3 cells, c-Cbl was shown to functionally and genetically act as a tumour suppressor. C-CBL mutants did not have E3 ubiquitin ligase activity, but inhibited that of wild-type C-CBL and CBL-B (also known as CBLB), leading to prolonged activation of tyrosine kinases after cytokine stimulation. c-Cbl(-/-) haematopoietic stem/progenitor cells (HSPCs) showed enhanced sensitivity to a variety of cytokines compared to c-Cbl(+/+) HSPCs, and transduction of C-CBL mutants into c-Cbl(-/-) HSPCs further augmented their sensitivities to a broader spectrum of cytokines, including stem-cell factor (SCF, also known as KITLG), thrombopoietin (TPO, also known as THPO), IL3 and FLT3 ligand (FLT3LG), indicating the presence of a gain-of-function that could not be attributed to a simple loss-of-function. The gain-of-function effects of C-CBL mutants on cytokine sensitivity of HSPCs largely disappeared in a c-Cbl(-/-) background or by co-transduction of wild-type C-CBL, which suggests the pathogenic importance of loss of wild-type C-CBL alleles found in most cases of C-CBL-mutated myeloid neoplasms. Our findings provide a new insight into a role of gain-of-function mutations of a tumour suppressor associated with aUPD in the pathogenesis of some myeloid cancer subsets.

We investigated the role of therapeutic dose monitoring (TDM) in the treatment of fungal infections with voriconazole through 49 analyses of 34 patients who received treatment for hematologic diseases. Voriconazole concentration was highly variable among patients regardless of renal, liver functions, or age, and the effect of dose enhancement was not constant. This indicates the difficulty of predicting voriconazole concentration without TDM. We evaluated the outcome with the composite assessment system where patients were assumed non-responders when they failed to show improvement in at least 2 of the following 3 criteria: clinical, radiologic, and mycologic. We showed that concentration-response relationship depended on the status of underlying hematologic diseases; this relationship was observed only in cases without refractory hematologic diseases, but not in those with refractory diseases. In the former group, cases with &gt; 2 mg/L of concentration were associated with good response to voriconazole. On the other hand, elevation of hepatic enzyme was frequently observed when voriconazole concentration was &gt; 6 mg/L. From these results, we concluded that TDM should be executed and targeted to 2-6 mg/L to improve efficacy and to avoid side effects.