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Refractoriness to platelet transfusion is a major problem in a small group of patients, and large-scale manufacturing of clinical grade functional platelets ex vivo has remained an elusive goal. Sugimoto et al report on the results of the first clinical trial of an autologous transfusion of induced pluripotent stem cell (iPSC)-derived platelets in a patient who had severe aplastic anemia but no compatible platelet donor. Using methodology described in a complementary article in Blood Advances, the results provide proof-of-principle and illustrate the challenges to be faced in taking this approach further.

The mononuclear phagocyte system (MPS), composed of monocytes/macrophages and dendritic cells (DCs), plays a critical role at the interface of the innate and adaptive immune systems. However, the simplicity of MPS has been challenged recently by discoveries of novel cellular components. In the current study, we identified the CD135+ subset of monocytes as a novel class of APCs in mice. CD135+ monocytes were readily found in the bone marrow, spleen, and peripheral blood at steady state, and they expressed markers specific to DCs, including MHC class II and CD209a, along with markers for monocytes/macrophages. In addition, this subset phagocytosed bacteria and activated naive T lymphocytes, fulfilling the criteria for APCs. CD135+ monocytes were derived directly from macrophage DC progenitors, not from common monocyte progenitors or other monocytes, suggesting that these are distinct from conventional monocytes. These findings facilitate our understanding of the MPS network that regulates immune responses for host defense.

List of antibodies used for Flow cytometry

Simultaneous immunofluorescence staining for CCR1 (red) and CD3 (A), CD8 (B), CD68 (C), α-SMA (D), CD14 (E), or CXCR2 (F) (green).

CCR3+ cells accumulation in primary CRC.

Purpose:SMAD4 is a key transcriptional factor of TGFβ signaling and acts as a tumor suppressor in colorectal cancer. In the present study, we explored the immunologic effect of SMAD4 on the tumor microenvironment.Experimental Design:Using 99 clinical specimens and human colorectal cancer cell lines, we investigate the relationship between SMAD4 expression and neutrophil accumulation. We immunohistochemically analyzed expression of SMAD4, CXCL1, CXCL8, CXCR2, and other proteins with clinical specimens. Finally, we determined the serum levels of CXCL1 and CXCL8 in 125 patients with colorectal cancer.Results:SMAD4 knockdown from human colorectal cancer cells upregulated the expression of CXCL1 and CXCL8, which recruited neutrophils to colorectal cancer tumor via CXCR2. In turn, when neutrophils were exposed to the supernatant of SMAD4-negative colorectal cancer cells, they produced a large amount of CXCL1 and CXCL8 by themselves in vitro. In human clinical specimens, we found that neutrophil infiltration into the peritumoral stroma was more marked in SMAD4-negative colorectal cancer compared with that in SMAD4-positive colorectal cancer, and that both CXCL1 and CXCL8 were abundantly expressed in the tumor-infiltrating neutrophils. Neutrophils isolated from primary colorectal cancer expressed significantly higher levels of CXCL1 and CXCL8 than did those isolated from peripheral blood. Furthermore, tumor-infiltrating neutrophils expressed MMP2 and MMP9 in addition to ARG1 and IDO. Serum CXCL8 level was significantly higher in colorectal cancer patients, especially those at stage II/III, and statistical analysis indicated a high CXCL8 level was associated with a shorter overall survival and relapse-free survival.Conclusions:Blockade of the CXCL1/8–CXCR2 axis could be a novel therapeutic approach against SMAD4-negative colorectal cancer.

A) Kaplan-Meier curves of OS in CRC patients after pulmonary resection. B) Effects of CCL15 expression on OS in CRC patients after pulmonary resection with lung metastases.

Supplementary Figure 1. A, Chemokine array using the SW837 cells engineered with stable SMAD4-knockdown (SW837-shSMAD4 #2) and scramble control

Purpose: We have reported loss of SMAD4 promotes expression of CCL15 from colorectal cancer to recruit CCR1+ myeloid cells through the CCL15-CCR1 axis, which contributes to invasion and liver metastasis. However, the molecular mechanism of lung metastasis is yet to be elucidated. Our purpose is to determine whether similar mechanism is involved in the lung metastasis of colorectal cancer.Experimental Design: In a mouse model, we examined whether SMAD4 could affect the metastatic activity of colorectal cancer cells to the lung through the CCL15-CCR1 axis. We immunohistochemically analyzed expression of SMAD4, CCL15, and CCR1 with 107 clinical specimens of colorectal cancer lung metastases. We also characterized the CCR1+ myeloid cells using several cell-type–specific markers.Results: In a mouse model, CCL15 secreted from SMAD4-deficient colorectal cancer cells recruited CCR1+ cells, promoting their metastatic activities to the lung. Immunohistochemical analysis of lung metastases from colorectal cancer patients revealed that CCL15 expression was significantly correlated with loss of SMAD4, and that CCL15-positive metastases recruited approximately 1.9 times more numbers of CCR1+ cells than CCL15-negative metastases. Importantly, patients with CCL15-positive metastases showed a significantly shorter relapse-free survival (RFS) than those with CCL15-negative metastases, and multivariate analysis indicated that CCL15 expression was an independent predictor of shorter RFS. Immunofluorescent staining showed that most CCR1+ cells around lung metastases were tumor-associated neutrophil, although a minor fraction was granulocytic myeloid-derived suppressor cell.Conclusions: CCL15-CCR1 axis may be a therapeutic target to prevent colorectal cancer lung metastasis. CCL15 can be a biomarker indicating poor prognosis of colorectal cancer patients with lung metastases. Clin Cancer Res; 23(3); 833–44. ©2016 AACR.

Purpose: We previously reported that loss of SMAD4 promotes chemokine CCL15 expression to recruit CCR1+ myeloid cells via the CCL15–CCR1 axis, which facilitates metastasis of colorectal cancer to the liver. The purposes of this study were to investigate whether essentially the same mechanism works in tumor invasion of the primary colorectal cancer and to evaluate the clinical importance of CCL15 expression and CCR1+ cell accumulation.Experimental Design: Using human colorectal cancer cell lines with reduced expression of SMAD4 or CCL15, we investigated tumor growth activities in vivo. We used immunohistochemistry (IHC) to investigate expression of SMAD4, CCL15, and CCR1 with 333 clinical specimens of primary colorectal cancer. We next characterized the CCR1+ cells using double immunofluorescence staining with several specific cell-type markers. Finally, we determined the serum CCL15 levels in 132 colorectal cancer patients.Results: In an orthotopic xenograft model, CCL15 secreted from SMAD4-deficient colorectal cancer cells recruited CCR1+ cells, resulting in aggressive tumor growth. IHC indicated that loss of SMAD4 was significantly associated with CCL15 expression, and that CCL15-positive primary colorectal cancers recruited approximately 2.2 times more numbers of CCR1+ cells at their invasion front than CCL15-negative colorectal cancers. Importantly, these CCR1+ cells were of the myeloid-derived suppressor cell (MDSC) phenotype (CD11b+, CD33+, and HLA-DR−). Most CCR1+ cells showed the granulocytic-MDSC phenotype (CD15+), whereas some showed the monocytic-MDSC phenotype (CD14+). Serum CCL15 levels in colorectal cancer patients were significantly higher than in controls.Conclusions: Blocking the recruitment of CCR1+ MDSCs may represent a novel molecular-targeted therapy, and serum CCL15 concentration can be a novel biomarker for colorectal cancer. Clin Cancer Res; 22(2); 492–501. ©2015 AACR.

Supplemental Table 1, 2 and 3. Supplemental Table 1: List of antibodies. Table 2: CCL15 expression according to Stage- and T factor-based classifications. Table 3: Tumor characteristics of another cohort of 132 patients.

Kaplan-Meier curves of overall survival (OS) and relapse-free survival (RFS) in CRC patients.

A) Western blot of SMAD4. B) Quantitative RT-PCR of CCL15. C) Western blot of SMAD proteins. D) Quantitative RT-PCR of CCL15. E)Immunohistochemistry of metastatic foci. F) Cell proliferation. G) Experimental schedule. H) Relative quantification of the lung metastatic.

A) Kaplan-Meier curves of RFS in CRC patients after curative pulmonary resection. B) Effect of T factor of primary CRC on RFS after curative pulmonary resection. C) Effect of N factor of primary CRC on RFS after curative pulmonary resection. D) Effect of preoperative CEA level on RFS after curative pulmonary resection.

A. CCL15 concentration in Colo205 cells. B. Cell proliferation rates of HT29 and Colo205 cells.

Supplementary Figure legend

Double immunofluorescence staining with several cell markers in order to characterize CCR1+ cells.

Figure legends of supplemental Figure S1, S2, S3 and S4.

Simultaneous immunofluorescence staining for CCR1 (red) and CD11b (A), CD33 (B), HLA-DR (C), or CD15 (D) (green).

Supplementary information contains figure legends of all supplementary figures (1-6).

Supplementary material and methods. In vivo xenograft studies, lentiviral transduction, cell viability assay and ELISA.

Supplementary Figure 2. A, Screening with a series of kinase inhibitors treated for 24 hours. qRT-PCR analysis for CXCL1 (top) and CXCL8 (bottom). B, Chemotactic responses of neutrophils toward the human recombinant CXCL1 and CXCL8. Mean; bars, {plus minus} SD. *P < 0.05 by Student's t-test. C, Neutrophils were isolated from peripheral blood and from CRC specimens of the same patients (n = 6) by FACS with CD45, CD66b, CD14, CD15, and CD16.

ABL1 tyrosine kinase inhibitors (TKIs) dramatically improve the prognosis of chronic myeloid leukemia (CML), but 10-20% of patients achieve suboptimal responses with low TKIs sensitivity. Furthermore, residual leukemic stem cells (LSCs) are involved in the molecular relapse after TKIs discontinuation. Aberrant DNA hypermethylation contributes to low TKIs sensitivity and the persistence of LSCs in CML. DNMT1 is a key regulator of hematopoietic stem cells, suggesting that aberrant DNA hypermethylation targeting DNMT1 represents a potential therapeutic target for CML. We investigated the efficacy of OR-2100 (OR21), the first orally available single-compound prodrug of decitabine. OR21 exhibited anti-tumor effects as a monotherapy, and in combination therapy it increased TKI-induced apoptosis and induction of tumor suppressor genes including PTPN6 encoding SHP-1 in CML cells. OR21 in combination with imatinib significantly suppressed tumor growth in a xenotransplant model. OR21 and combination therapy decreased the abundance of LSCs and inhibited engraftment in a BCR-ABL1-transduced mouse model. These results demonstrate that targeting DNMT1 using OR21 exerts anti-tumor effects and impairs LSCs in CML. Therefore, combination treatment of TKIs and OR21 represents a promising treatment strategy in CML.

The emergence of tyrosine kinase inhibitors as part of a front-line treatment has greatly improved the clinical outcome of the patients with Ph⁺ acute lymphoblastic leukemia (ALL). However, a portion of them still become refractory to the therapy mainly through acquiring mutations in the BCR-ABL1 gene, necessitating a novel strategy to treat tyrosine kinase inhibitor (TKI)-resistant Ph⁺ ALL cases. In this report, we show evidence that RUNX1 transcription factor stringently controls the expression of BCR-ABL1, which can strategically be targeted by our novel RUNX inhibitor, Chb-M'. Through a series of in vitro experiments, we identified that RUNX1 binds to the promoter of BCR and directly transactivates BCR-ABL1 expression in Ph⁺ ALL cell lines. These cells showed significantly reduced expression of BCR-ABL1 with suppressed proliferation upon RUNX1 knockdown. Moreover, treatment with Chb-M' consistently downregulated the expression of BCR-ABL1 in these cells and this drug was highly effective even in an imatinib-resistant Ph⁺ ALL cell line. In good agreement with these findings, forced expression of BCR-ABL1 in these cells conferred relative resistance to Chb-M'. In addition, in vivo experiments with the Ph⁺ ALL patient-derived xenograft cells showed similar results. In summary, targeting RUNX1 therapeutically in Ph⁺ ALL cells may lead to overcoming TKI resistance through the transcriptional regulation of BCR-ABL1. Chb-M' could be a novel drug for patients with TKI-resistant refractory Ph⁺ ALL.

Cancer cachexia is a multifactorial disease that causes continuous skeletal muscle wasting. Thereby, it seems to be a key determinant of cancer-related death. Although anamorelin, a ghrelin receptor agonist, has been approved in Japan for the treatment of cachexia, few medical treatments for cancer cachexia are currently available. Myostatin (MSTN)/growth differentiation factor 8, which belongs to the transforming growth factor-β family, is a negative regulator of skeletal muscle mass, and inhibition of MSTN signaling is expected to be a therapeutic target for muscle-wasting diseases. Indeed, we have reported that peptide-2, an MSTN-inhibiting peptide from the MSTN prodomain, alleviates muscle wasting due to cancer cachexia. Herein, we evaluated the therapeutic benefit of myostatin inhibitory D-peptide-35 (MID-35), whose stability and activity were more improved than those of peptide-2 in cancer cachexia model mice. The biologic effects of MID-35 were better than those of peptide-2. Intramuscular administration of MID-35 effectively alleviated skeletal muscle atrophy in cachexia model mice, and the combination therapy of MID-35 with anamorelin increased food intake and maximized grip strength, resulting in longer survival. Our results suggest that this combination might be a novel therapeutic tool to suppress muscle wasting in cancer cachexia.

Tumor-stromal interaction is implicated in tumor progression. Although CCR1 expression in myeloid cells could be associated with pro-tumor activity, it remains elusive whether disruption of CCR1-mediated myeloid cell accumulation can suppress tumor progression. Here, we investigated the role of CCR1 depletion in myeloid cells in two syngeneic colorectal cancer mouse models: MC38, a transplanted tumor model and CMT93, a liver metastasis model. Both cells induced tumor accumulation of CCR1+ myeloid cells that express MMP2, MMP9, iNOS, and VEGF. Lack of the Ccr1 gene in host mice dramatically reduced MC38 tumor growth as well as CMT93 liver metastasis. To delineate the contribution of CCR1+ myeloid cells, we performed bone marrow (BM) transfer experiments in which sub-lethally irradiated wild-type mice were reconstituted with BM from either wild-type or Ccr1-/- mice. Mice reconstituted with Ccr1-/- BM exhibited marked suppression of MC38 tumor growth and CMT93 liver metastasis, compared with control mice. Consistent with these results, administration of a neutralizing anti-CCR1 monoclonal antibody, KM5908, significantly suppressed MC38 tumor growth and CMT93 liver metastases. Our findings highlight the importance of the application of CCR1 blockade as a therapeutic strategy.

Summary The suppressors of cytokine signaling (SOCS) proteins are negative regulators of cytokine signaling required to prevent excessive cellular responses. In particular, SOCS3 is involved in the regulation of metabolic syndromes, such as obesity and diabetes, by suppressing leptin and insulin signals. SOCS3 also suppresses the inflammatory response associated with metabolic stress, but this specific role remains undefined. Wild-type mice on a high-fat diet (HFD) exhibited only fatty liver, whereas systemic deletion of SOCS3 resulted in excessive myeloid hematopoiesis and hepatic inflammation. In addition, depletion of the gut microbiota resulted in considerable improvement in excess granulopoiesis and splenomegaly, halting the progression of systemic inflammation in SOCS3KO mice on the HFD. This result suggests that intestinal dysbiosis is involved in inflammation associated with SOCS3KO. Although contributing to diet-induced obesity and fatty liver, SOCS3 is nevertheless critical to suppress excess myeloid hematopoiesis and severe systemic inflammation associated with intestinal dysbiosis on HFD., Graphical abstract, Highlights • SOCS3 suppresses severe systemic inflammation associated with high-fat diet • SOCS3 deficiency on high-fat diet accelerates excess myeloid hematopoiesis • SOCS3 controls gut dysbiosis on high-fat diet, Immunology; Microbiome

Granulocyte transfusion (GTX) is a therapeutic option for severe bacterial or fungal infection in patients with sustained neutropenia after chemotherapy or stem cell transplantation. However, high molecular weight hydroxyethyl starch (HES), which has been used for selective sedimentation of red blood cells during apheresis, is not easily available in many countries including Japan. In this study, we evaluated the efficiency of granulocyte collection using medium molecular weight HES (130 kDa) in combination with the Spectra Optia apheresis system. Apheresis was performed for 2 consecutive days from seven donors and the mean total neutrophil yield from the first and second apheresis was 5.27 ± 3.10 × 1010 and 2.91 ± 2.92 × 1010, respectively. Infusion of concentrates from the first apheresis resulted in a significant neutrophil count increase and concentrates from the second apheresis were enough for maintenance of the neutrophil counts in all the recipients. Although the number of cases is limited, our results clearly show that sufficient number of granulocytes can be harvested by using medium molecular weight HES and this strategy is a safe and effective clinical practice in countries where high molecular weight HES is not available.

Even in the era of ABL tyrosine kinase inhibitors, eradication of chronic myeloid leukemia (CML) stem cells is necessary for complete cure of the disease. Interferon-α (IFN-α) has long been used for the treatment of chronic-phase CML, but its mechanisms of action against CML stem cells remain unclear. We found that IFN-α upregulated CCAAT/enhancer binding protein β (C/EBPβ) in BCR-ABL–expressing mouse cells by activating STAT1 and STAT5, which were recruited to a newly identified 3′ distal enhancer of Cebpb that contains tandemly aligned IFN-γ–activated site elements. Suppression or deletion of the IFN-γ–activated site elements abrogated IFN-α–dependent upregulation of C/EBPβ. IFN-α induced differentiation and exhaustion of CML stem cells, both in vitro and in vivo, in a C/EBPβ-dependent manner. In addition, IFN-α upregulated C/EBPβ and induced exhaustion of lineage− CD34+ cells from CML patients. Collectively, these results clearly indicate that C/EBPβ is a critical mediator of IFN-α–induced differentiation and exhaustion of CML stem cells.

The mononuclear phagocyte system (MPS), composed of monocytes/macrophages and dendritic cells (DCs), plays a critical role at the interface of the innate and adaptive immune systems. However, the simplicity of MPS has been challenged recently by discoveries of novel cellular components. In the current study, we identified the CD135

The transcription factor CCAAT enhancer-binding protein β (C/EBPβ) is required for stress-induced granulopoiesis at the level of hematopoietic stem/progenitor cells (HSPCs); however, its role and mechanisms of action in HSPCs are unknown. In this study, we assessed the regulation and functions of C/EBPβ in HSPCs, especially under stress conditions. After 5-fluorouracil treatment or bone marrow transplantation, Cebpb−/− HSPCs exhibited impaired cell-cycle activation and myeloid differentiation at the early and late phases of regeneration, respectively, whereas at steady state, Cebpb deficiency did not affect HSPCs. C/EBPβ was upregulated in response to hematopoietic stress, especially in CD150high long term-hematopoietic stem cells (LT-HSCs). Intracellular flow cytometric analysis that detected distinct domains of C/EBPβ revealed that, among the 3 isoforms of C/EBPβ, liver-enriched inhibitory protein (LIP) was upregulated in LT-HSCs prior to liver-enriched activating protein (LAP)/LAP* during regeneration. Early upregulation of LIP promoted cell-cycle entry of LT-HSCs by positively regulating Myc and expanded the HSPCs pool. Subsequent myeloid differentiation of amplified HSPCs was mediated by LAP/LAP*, which were upregulated at a later phase of regeneration. Collectively, our findings show that stress-induced sequential upregulation of C/EBPβ isoforms is critical for fine-tuning the proliferation and differentiation of regenerating HSPCs.

Introduction: Platelet transfusion have saved lives of patients with thrombocytopenia through preventing or treating bleeding complications. Currently, platelet products are provided from blood banks which collect blood from healthy donors. However, our ageing society bears the risk of supply in the future. Furthermore, although the rate is decreasing, alloimmune platelet transfusion refractoriness (allo-PTR) is still found in 5% of platelet transfusion patients. Gestation and previous platelet transfusion cause sensitization to produce alloantibodies mostly against class I human leukocyte antigens (HLA-I) and less frequently against human platelet antigens (HPA), resulting in allo-PTR. In these cases, platelets from compatible donors are transfused, but for patients with rare HLA or HPA, donors are difficult to find. As a possible solution, we proposed the application of platelets from induced pluripotent stem cells (iPSC-platelets), which we have succeeded in the ex vivo production at clinical scale. iPSC-platelets are produced from expandable megakaryocyte cell lines (imMKCLs) as master cells and using a "turbulent flow" bioreactor and various new drugs. imMKCLs are established from iPSCs during megakaryocytic differentiation by overexpression of c-MYC, BMI1 and BCL-XL under the doxycycline control promoter. Switching off these transgenes leads to the maturation of imMKCLs. Turbulent flow was found to be a crucial factor in efficient ex vivo production of healthy iPSC-platelets from imMKCLs. We also developed TA-316, a thrombopoietin mimetic compound, KP-547, an ADAM17 inhibitor that inhibits CD42b shedding and stores platelet function, and also found the combination of AhR antagonist and ROCK inhibitor enables feeder-free liquid culture in imMKCL maturation. Aim: To evaluate the safety of autologous iPS-platelets administered to an aplastic anemia patient with allo-PTR due to anti-HPA alloantibody, who experienced systemic post-transfusion purpura-like complication and have no compatible donor in Japan. Methods and Results: Preclinical studies showed that iPSC-platelets were competent in in vitro assays and mouse and rabbit models for circulation and hemostasis, and pathogen and tumorigenicity free. The clinical study was approved by the Certified Special Committee for Regenerative Medicine of the Kyoto University and by the Health Sciences Council of the Japan Ministry of Health, Labour and Welfare as meeting the Act on the Safety of Regenerative Medicine. The clinical study started in March 2019. Using imMKCL master cells derived from the patient, iPS-platelets were manufactured at the Facility for iPS Cell Therapy (FiT) in Center for iPS Cell Research and Application (CiRA), Kyoto University according to the GMP standard. Three doses of 1x10^10, 3x10^10 and 1x10^11 were administered in a dose escalation single-center open-label uncontrolled study at Kyoto University Hospital. The primary endpoint was safety as measured by frequency and extent of adverse events, which were evaluated by the Efficacy Safety Assessment Committee for each dose cohort. Three doses of the administration of autologous iPS-platelets have been completed. No significant adverse event was observed during the full observation period of one year after the last dose. Conclusion: The iPLAT1 study completed the administration of iPSC-platelets for the first time and confirmed the safety in an allo-PTR patient who would otherwise have no HPA-compatible platelet product. The insights gained from the current study should further contribute to development of allogeneic iPSC-platelet products that can be readily administered to wide range of patients. (Japan Registry of Clinical Trials number jRCTa050190117) Figure 1 Figure 1. Disclosures Sugimoto: Astellas Pharma Inc.: Honoraria; Ebara Corporation: Honoraria; Kyowa Kirin Co., Ltd.: Honoraria; Megakaryon Co: Consultancy, Honoraria; Novartis Pharma K.K.: Honoraria; Takeda Pharmaceutical Company Limited: Honoraria. Kanda: Sumitomo Dainippon Pharma Co., Ltd.: Honoraria; SymBio Pharmaceuticals, Ltd.: Membership on an entity's Board of Directors or advisory committees; Sanofi K.K.: Honoraria; Otsuka Pharmaceutical Co., Ltd.: Honoraria; Ono Pharma Inc.: Honoraria; Novartis Pharma K.K.: Honoraria; NextGeM Inc: Patents & Royalties; Megakaryon Co: Honoraria, Membership on an entity's Board of Directors or advisory committees; Kyowa Kirin Co., Ltd.: Honoraria; Janssen Pharmaceutical K.K.: Honoraria, Membership on an entity's Board of Directors or advisory committees; Eisai: Research Funding; DAIICHI SANKYO Co., Ltd.: Honoraria, Membership on an entity's Board of Directors or advisory committees; CHUGAI PHARMACEUTICAL Co., Ltd.: Honoraria; Bristol-Myers Squibb Co: Honoraria; Astellas Pharma Inc.: Consultancy, Honoraria; Amgen Astellas BioPharma: Honoraria; Takeda Pharmaceutical Company Limited: Honoraria, Membership on an entity's Board of Directors or advisory committees; TEIJIN PHARMA LIMITED.: Honoraria. Kondo: Asahi Kasei Pharmaceutical: Research Funding; Otsuka Pharmaceutical Co., Ltd.: Honoraria; Chugai Pharma: Honoraria; MSD Pharmaceutical: Honoraria; Sumitomo Dainippon Pharma: Honoraria. Shimizu: Megakaryon co: Consultancy. Hirai: Kyowa Kirin: Patents & Royalties, Research Funding; Bristol-Myers K.K.: Research Funding; CSL Behring: Research Funding; Mitsubishi Tanabe Pharma: Research Funding; Sumitomo Dainippon Pharma: Research Funding; Novartis Pharma: Membership on an entity's Board of Directors or advisory committees, Research Funding. Takaori-Kondo: Bristol-Myers K.K.: Honoraria; ONO PHARMACEUTICAL CO., LTD.: Research Funding; Celgene: Research Funding. Eto: Megakaryon co: Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding; Otsuka Pharmaceutical Co., Ltd.: Research Funding; Kyowa Kirin Co., Ltd.: Honoraria; Takeda Pharmaceutical Co Ltd: Honoraria; Kowa Co Ltd: Honoraria; Sumitomo Dainippon Pharma Co., Ltd.: Honoraria; TEIJIN PHARMA LIMITED.: Honoraria; Kyoto Manufacturing Co., Ltd.: Research Funding.

A substantial proportion of patients with acute graft-versus-host disease (aGVHD) respond to cell therapy with culture-expanded human bone marrow mesenchymal stromal/stem cells (BM-MSCs). However, the mechanisms by which these cells can ameliorate aGVHD-associated complications remain to be clarified. We show here that BM-MSC-derived extracellular vesicles (EVs) recapitulated the therapeutic effects of BM-MSCs against aGVHD. Systemic infusion of human BM-MSC-derived EVs prolonged the survival of mice with aGVHD and reduced the pathologic damage in multiple GVHD-targeted organs. In EV-treated GVHD mice, CD4+ and CD8+ T cells were suppressed. Importantly, the ratio of CD62L-CD44+ to CD62L + CD44- T cells was decreased, suggesting that BM-MSC-derived EVs suppressed the functional differentiation of T cells from a naive to an effector phenotype. BM-MSC-derived EVs also preserved CD4 + CD25 + Foxp3+ regulatory T cell populations. In a culture of CD3/CD28-stimulated human peripheral blood mononuclear cells with BM-MSC-derived EVs, CD3+ T cell activation was suppressed. However, these cells were not suppressed in cultures with EVs derived from normal human dermal fibroblasts (NHDFs). NHDF-derived EVs did not ameliorate the clinical or pathological characteristics of aGVHD in mice, suggesting an immunoregulatory function unique to BM-MSC-derived EVs. Microarray analysis of microRNAs in BM-MSC-derived EVs versus NHDF-derived EVs showed upregulation of miR-125a-3p and downregulation of cell proliferative processes, as identified by Gene Ontology enrichment analysis. Collectively, our findings provide the first evidence that amelioration of aGVHD by therapeutic infusion of BM-MSC-derived EVs is associated with the preservation of circulating naive T cells, possibly due to the unique microRNA profiles of BM-MSC-derived EVs.

The transcription factor CCAAT/enhancer-binding protein β (C/EBPβ) is highly expressed in monocytes/macrophages. However, its roles in monopoiesis are largely unknown. Here, we investigated the roles of C/EBPβ in monopoiesis. Further subdivision of monocytes revealed that Cebpb messenger RNA was highly upregulated in Ly6C- monocytes in bone marrow. Accordingly, the number of Ly6C- monocytes was significantly reduced in Cebpb-/- mice. Bone marrow chimera experiments and Mx1-Cre-mediated deletion of Cebpb revealed a cell-intrinsic and monocyte-specific requirement for C/EBPβ in monopoiesis. In Cebpb-/- mice, turnover of Ly6C- monocytes was highly accelerated and apoptosis of Ly6C- monocytes was increased. Expression of Csf1r, which encodes a receptor for macrophage colony-stimulating factor, was significantly reduced in Ly6C- monocytes of Cebpb-/- mice. C/EBPβ bound to positive regulatory elements of Csf1r and promoted its transcription. Collectively, these results indicate that C/EBPβ is a critical factor for Ly6C- monocyte survival, at least in part through upregulation of Csf1r.

Background In recent years, increasing attention has been paid to the effects of low-dose irradiation on human health. We examined whether low-dose irradiation affected the functions of mesenchymal stromal/stem cells (MSCs), which are tissue/organ-supportive stem cells, derived from bone marrow (BM). Methods Normal human BM-MSCs from five healthy individuals were used in this study. Culture-expanded BM-MSCs were exposed to 0.1 gray (Gy) of γ-radiation (Cesium-137) at a rate of 0.8 Gy/min (Ir-MSCs), and their expansion, multi-differentiation, and hematopoiesis-supportive capabilities were investigated. Results The expansion of BM-MSCs was transiently delayed after low-dose γ-irradiation compared with that of non-irradiated BM-MSCs (non-Ir-MSCs) in two out of five lots. Adipogenic and osteogenic differentiation capabilities were not significantly affected by low-dose irradiation, although one lot of BM-MSCs tended to have transiently reduced differentiation. When human BM hematopoietic stem/progenitor cells (HPCs) were co-cultured with Ir-MSCs, the generation of CD34+CD38+ cells from HPCs was enhanced compared with that in co-cultures with non-Ir-MSCs in two out of five lots. The mRNA expression level of interleukin (IL)-6 was increased and those of stem cell factor (SCF) and fms-related tyrosine kinase 3 ligand (Flt3L) were decreased in the affected lots of Ir-MSCs. In the other three lots of BM-MSCs, a cell growth delay, enhanced generation of CD34+CD38+ cells from HPCs in co-culture, and a combination of increased expression of IL-6 and decreased expression of SCF and Flt3L were not observed. Of note, the characteristics of these affected Ir-MSCs recovered to a similar level as those of non-Ir-MSCs following culture for 3 weeks. Conclusions Our results suggest that acute exposure to low-dose (0.1 Gy) radiation can transiently affect the functional characteristics of human BM-MSCs.

The poor prognosis of adults with B cell precursor acute lymphoblastic leukemia (BCP-ALL) is attributed to leukemia cells that are protected by the bone marrow (BM) microenvironment. In the present study, we explored the pharmacological targeting of mesenchymal stromal/stem cells in BM (BM-MSCs) to eliminate chemoresistant BCP-ALL cells. Human BCP-ALL cells (NALM-6 cells) that adhered to human BM-MSCs (NALM-6/Ad) were highly resistant to multiple anti-cancer drugs, and exhibited pro-survival characteristics, such as an enhanced Akt/Bcl-2 pathway and increased populations in the G0 and G2/S/M cell cycle stages. Bortezomib, a proteasome inhibitor, interfered with adhesion between BM-MSCs and NALM-6 cells and up-regulated the matricellular protein SPARC (secreted protein acidic and rich in cysteine) in BM-MSCs, thereby reducing the NALM-6/Ad population. Inhibition of SPARC expression in BM-MSCs using a small interfering RNA enhanced adhesion of NALM-6 cells. Conversely, recombinant SPARC protein interfered with adhesion of NALM-6 cells. These results suggest that SPARC disrupts adhesion between BM-MSCs and NALM-6 cells. Co-treatment with bortezomib and doxorubicin prolonged the survival of BCP-ALL xenograft mice, with a significant reduction of leukemia cells in BM. Our findings demonstrate that bortezomib contributes to the elimination of BCP-ALL cells through disruption of their adhesion to BM-MSCs, and offer a novel therapeutic strategy for BCP-ALL through targeting of BM-MSCs.

Autoimmune neutropenia (AIN) is a rare disorder that may cause life-threatening infections. In adults, most cases are secondary to other pathological conditions, and primary AIN is extremely rare. We herein report a case involving a 57-year-old woman diagnosed with AIN. A granulocyte immunofluorescence test detected autoantibodies against human neutrophil antigens in her serum, while various examinations revealed no other causes of neutropenia, suggesting her AIN was primary. She was refractory to granulocyte-colony-stimulating factor but responded to prednisolone. Her neutrophil count remained normal after gradual discontinuation of prednisolone. Diagnostic procedures and optimal treatments for this disorder need to be established.

Introduction: Suppressors of cytokine signaling (SOCS) are negative regulators of cytokine signaling; SOCS3 controls myeloid hematopoiesis by suppressing G-CSF. SOCS3 haploinsufficiency attenuates diet-induced obesity by enhanced leptin sensitivity while improving insulin resistance. We established SOCS3 conditional knock-out (KO) mice to elucidate how high fat diets (HFD) affect inflammation and obesity in complete SOCS3 deficiency. Methods: Embryonic lethality of complete SOCS3 deficiency was overcome using a conditional Socs3 allele inactivated by tamoxifen (TAM)-inducible cre-recombinase with SOCS3fl/flRosa26-CreERT2T/+ mice. They were fed HFD (60 kcal% fat) or control chaw (10 kcal% fat) starting at 4 weeks of age and TAM or vehicle administration was done at 8 weeks. Results: Although insulin resistance improved and obesity and fatty liver were not confirmed in SOCS3-KO with HFD (S3HFD), the S3HFD group looked moribund around day 30 post-TAM by systemic inflammation; their mean survival was 62.5 days after TAM. Other groups did not look moribund. Significant granulopoiesis was also observed in S3HFD (peripheral blood neutrophil counts 29301 ± 20581/mm3). This myeloid hematopoiesis occurred in the spleen and not the bone marrow. S3HFD exhibited the progression of various granulocytes from progenitor cells (c-kitint∼highLy6G-) to mature granulocytes (c-kit-Ly6G+).Hematopoietic infiltration was confirmed in the liver in S3HFD with granulocytes, monocytes, and macrophages. Inflammasome-associated genes (IL-1β and Caspase1) were elevated in the liver at day 65 post-TAM in S3HFD. Conclusion: SOCS3 deficiency showed myeloid proliferation under HFD without obesity and adiposity. SOCS3-KO may help in the clarification of the specific mechanism of myeloid proliferation and invasion in HFD-induced inflammation. Disclosure K. Cho: None. T. Ushiki: None. H. Ishiguro: None. T. Katagiri: None. T. Suwabe: None. H. Hirai: None. Y. Nakagawa: None. M. Masuko: None. W. Alexander: None. H. Shimano: None. H. Sone: Research Support; Self; Astellas Pharma Inc., Boehringer Ingelheim Pharmaceuticals, Inc., Daiichi Sankyo Company, Limited, Kowa Pharmaceutical Europe Co. Ltd., Kyowa Hakko Kirin Co., Ltd., Novo Nordisk Inc., Ono Pharmaceutical Co., Ltd., Taisho Pharmaceutical Co., Ltd., Takeda Pharmaceutical Company Limited, Teijin Pharma Limited.

Purpose: SMAD4 is a key transcriptional factor of TGFβ signaling and acts as a tumor suppressor in colorectal cancer. In the present study, we explored the immunologic effect of SMAD4 on the tumor microenvironment. Experimental Design: Using 99 clinical specimens and human colorectal cancer cell lines, we investigate the relationship between SMAD4 expression and neutrophil accumulation. We immunohistochemically analyzed expression of SMAD4, CXCL1, CXCL8, CXCR2, and other proteins with clinical specimens. Finally, we determined the serum levels of CXCL1 and CXCL8 in 125 patients with colorectal cancer. Results: SMAD4 knockdown from human colorectal cancer cells upregulated the expression of CXCL1 and CXCL8, which recruited neutrophils to colorectal cancer tumor via CXCR2. In turn, when neutrophils were exposed to the supernatant of SMAD4-negative colorectal cancer cells, they produced a large amount of CXCL1 and CXCL8 by themselves in vitro. In human clinical specimens, we found that neutrophil infiltration into the peritumoral stroma was more marked in SMAD4-negative colorectal cancer compared with that in SMAD4-positive colorectal cancer, and that both CXCL1 and CXCL8 were abundantly expressed in the tumor-infiltrating neutrophils. Neutrophils isolated from primary colorectal cancer expressed significantly higher levels of CXCL1 and CXCL8 than did those isolated from peripheral blood. Furthermore, tumor-infiltrating neutrophils expressed MMP2 and MMP9 in addition to ARG1 and IDO. Serum CXCL8 level was significantly higher in colorectal cancer patients, especially those at stage II/III, and statistical analysis indicated a high CXCL8 level was associated with a shorter overall survival and relapse-free survival. Conclusions: Blockade of the CXCL1/8–CXCR2 axis could be a novel therapeutic approach against SMAD4-negative colorectal cancer.

Purpose: We previously reported that loss of SMAD4 promotes chemokine CCL15 expression to recruit CCR1+ myeloid cells via the CCL15–CCR1 axis, which facilitates metastasis of colorectal cancer to the liver. The purposes of this study were to investigate whether essentially the same mechanism works in tumor invasion of the primary colorectal cancer and to evaluate the clinical importance of CCL15 expression and CCR1+ cell accumulation. Experimental Design: Using human colorectal cancer cell lines with reduced expression of SMAD4 or CCL15, we investigated tumor growth activities in vivo. We used immunohistochemistry (IHC) to investigate expression of SMAD4, CCL15, and CCR1 with 333 clinical specimens of primary colorectal cancer. We next characterized the CCR1+ cells using double immunofluorescence staining with several specific cell-type markers. Finally, we determined the serum CCL15 levels in 132 colorectal cancer patients. Results: In an orthotopic xenograft model, CCL15 secreted from SMAD4-deficient colorectal cancer cells recruited CCR1+ cells, resulting in aggressive tumor growth. IHC indicated that loss of SMAD4 was significantly associated with CCL15 expression, and that CCL15-positive primary colorectal cancers recruited approximately 2.2 times more numbers of CCR1+ cells at their invasion front than CCL15-negative colorectal cancers. Importantly, these CCR1+ cells were of the myeloid-derived suppressor cell (MDSC) phenotype (CD11b+, CD33+, and HLA-DR−). Most CCR1+ cells showed the granulocytic-MDSC phenotype (CD15+), whereas some showed the monocytic-MDSC phenotype (CD14+). Serum CCL15 levels in colorectal cancer patients were significantly higher than in controls. Conclusions: Blocking the recruitment of CCR1+ MDSCs may represent a novel molecular-targeted therapy, and serum CCL15 concentration can be a novel biomarker for colorectal cancer. Clin Cancer Res; 22(2); 492–501. ©2015 AACR.

Under stress or regenerative conditions, HSCs rapidly enter into cell cycle and are reprogrammed toward myeloid-biased hematopoiesis to meet the increasing demand of myeloid cells. We have previously shown that the transcription factor C/EBPβ plays critical roles at the level of HSPCs under stress conditions (Nat Immunol 2006, J Immunol 2012, Leukemia 2013 and Blood Adv 2019). However, underlying molecular mechanisms of action remain largely unknown. In this study, we have investigated the detailed function of C/EBPβ in regulation of HSPCs. We first evaluated the impact of C/EBPβ on the cell cycle status of LT-HSCs. To exclude the cell-extrinsic contribution of C/EBPβ, CD45.2+ BM cells from WT or Cebpb-/- mice were transplanted into lethally irradiated CD45.1+ WT mice, and these "BM-replaced" recipients were subjected to the following experiments. At steady state, the cell cycle statuses and the numbers of HSPCs did not significantly differ between the recipients of WT cells and those of Cebpb-/- cells. Immediately after 5-FU treatment, WT LT-HSCs entered the cell cycle, as revealed by the decreased percentage of cells in G0 phase and the increased percentage of cells in S/G2M phase. All these parameters of cell cycle acceleration were observed prior to the nadir of LT-HSCs induced by 5-FU and were significantly attenuated in Cebpb-/- LT-HSCs. Next, we assessed the numbers of LT-HSCs, KSL cells, and KL cells after 5-FU treatment. Following the nadir, the recovery of LT-HSCs preceded that of KSL and KL cells, suggesting the differentiation of LT-HSCs to KSL and KL cells. In the recipients of Cebpb-/- cells, the recovery of KSL and KL cells was delayed significantly. Collectively, cell cycle acceleration and subsequent differentiation of LT-HSCs under stress conditions were impaired in the absence of Cebpb. The Cebpb is a single exon gene, and three isoforms, namely, LAP*, LAP and LIP which lacks N-terminus, are translated from its unique mRNA. Due to their structural difference, they should have distinct functions. Here, we focused on expression and functions of these isoforms in regenerating HSPCs. To monitor expression of these isoforms in small numbers of HSCs, we devised a novel intracellular double staining method for flow cytometric analysis using two distinct anti-C/EBPβ antibodies. An antibody against the C-terminus of C/EBPβ recognized all three isoforms, while an antibody against the N-terminus of C/EBPβ only recognized LAP* and LAP. Thus, simultaneous staining with both antibodies should enable us to distinguish cells that dominantly expressed LIP (C-term+ N-term-) from those that expressed all three isoforms (C-term+ N-term+). Using this method, we monitored the expression patterns of these isoforms in LT-HSCs after 5-FU treatment. LT-HSCs initially became C-term single positive in response to 5-FU and subsequently changed to C- and N-term double positive, suggesting that LIP was upregulated prior to LAP/LAP* under stress conditions. These results suggest that phase-specific upregulation of LIP and LAP/LAP* is strongly associated with phase-specific functions of C/EBPβ in cell cycle activation and differentiation, respectively. Indeed, when EML cells, a mouse HSC line, were retrovirally transduced with LIP, the transduced cells were more proliferative and actively cycling than those transduced with the control vector, whereas proliferation and cell cycle were markedly suppressed in LAP*- and LAP-expressing EML cells. LIP-expressing cells remained undifferentiated, while LAP*- and LAP-expressing cells rapidly differentiated into CD11b+ myeloid cells and eventually stopped proliferating. In summary, our findings clearly suggest that sequential upregulation of C/EBPβ isoforms is critical for the regulation of HSCs under stress conditions. LIP amplifies the "reservoir" of HSPCs by accelerating the proliferation of HSCs during the early phase of regeneration, while LAP*/LAP induce their myeloid differentiation at a later phase. These findings should facilitate our understanding of the pathophysiology of infection, inflammation, and regenerating hematopoiesis in response to myeloablative chemotherapies or hematopoietic stem cell transplantation, all of which increase the hematopoietic demands. Disclosures Hirai: Kyowa Kirin: Research Funding.

Under stress conditions such as infection, inflammation, and hematopoietic recovery following chemotherapy or transplantation, the hematopoietic system is required to meet the increasing demands, especially from myeloid cells. Therefore, an understanding of the molecular mechanism underlying stress hematopoiesis is clinically imperative. We previously showed that C/EBPβ, which is a transcription factor required for emergency granulopoiesis, plays a pivotal role at the level of hematopoietic stem/progenitor cells under stress conditions. Upon exposure to stress, the C/EBPβ protein is upregulated in the hematopoietic stem cells. A close examination of C/EBPβ knockout mice revealed that C/EBPβ regulates the proliferation and differentiation of hematopoietic stem cells at the cost of the self-renewing activity. Further elucidation of the functions and regulation of C/EBPβ in hematopoietic stem cells will facilitate an understanding of stress hematopoiesis.

The emergence of new molecular targeting agents has improved the prognosis of patients with multiple myeloma (MM). However, MM remains incurable because MM stem cells are likely resistant to these agents. Thus, it is important to further investigate the biology of MM stem cells, which reside in the hypoxic bone marrow niche. In this study, we established and investigated the characteristics of hypoxia-adapted MM (HA-MM) cells, which could proliferate for more than six months under hypoxic conditions (1% O2). The G0 fraction of HA-MM cells was larger than that of parental MM cells under normoxic conditions (20% O2). HA-MM cells possess enhanced tumorigenicity in primary and secondary transplantation studies. HA-MM cells also exhibited increased mRNA levels of stem cell markers and an enhanced self-renewal ability, and thus demonstrated characteristics of MM stem cells. These cells overexpressed phosphorylated Smad2, and treatment with a transforming growth factor (TGF)-β/Smad signaling inhibitor decreased their clonogenicity in a replating assay. In conclusion, MM cells adapted to long-exposure of hypoxia exhibit stem cell characters with TGF-β/Smad pathway activation.