Various derivatives of thalidomide, a drug that is well-known for its teratogenicity, have recently been developed; among them, lenalidomide and pomalidomide, known as immunomodulatory drugs (IMiDs), have potent anticancer activity. These drugs have been approved by Food and Drug Administration for the treatment of several diseases, including multiple myeloma, under strict control. The primary direct target protein of thalidomide and IMiDs is cereblon (CRBN), a substrate receptor of Cullin-RING ligase 4 (CRL4). CRL4^CRBN is a unique E3 ubiquitin ligase because its substrate selectivity is altered by ligands such as IMiDs. Each IMiD induces degradation of neosubstrates, such as Ikaros or CK1a. Because the activity of new CRBN-binding compounds is not limited to immunomodulation, the designation of “cereblon modulators” has been proposed for these small CRBN-binding compounds. Currently, researchers are investigating CC-122 (avadomide) and CC-220 (iberdomide) for the treatment of diffuse large B-cell lymphoma and systemic lupus erythematosus, respectively. Other recent studies have been investigating heterobifunctional molecules called proteolysis-targeting chimeras (PROTACs) for protein of interest degradation. Moreover, several proteins, such as BRD4, CDK9, or Tau, have already been successfully degraded by CRBN-based PROTACs. In this review, recent advances in CRBN and its binding compounds have been discussed.

Fifty years after its discovery, the enigma of monosomy 7 (−7) is eventually unraveling. The key to understanding −7 is “haploinsufficiency” mechanism, through which the function of myeloid tumor-suppressor genes is lost via the deletion/mutation of one allele. In this century, powerful tools such as microarray-CGH and next generation sequencing have enabled the search for tumor-suppressor genes on chromosome 7. Five genes (Samd9, Samd9-like (Samd9L), Ezh2, MLL3, and CUX1) have been identified and their myeloid tumor suppression potential has been verified using mouse models. Mice lacking one Samd9L gene developed MDS at an advanced age, whereas mice children harboring a gain-of-function mutation of Samd9 or Samd9L gene suffer from bone marrow failure, which is frequently followed by childhood MDS with −7, suggesting that these tumor-suppressor genes are the key to understanding not only MDS with −7 but also MDS in general. However, lack of Ezh2 and MLL3, which encode epigenetic regulators, contribute to the promotion of the progression of myeloid tumor cells that harbor abnormalities in the p53 or Ras pathways.

Cellular senescence is a state of durable cell cycle arrest after a defined number of cell divisions. The number of population doublings of normal cells in culture depends on the species but not on the types of cells used to establish the culture, showing a positive correlation with the life span of the animals. Therefore, the results suggest a physiological link between a limited proliferative capacity in cell culture and the processes observed in organismal aging. The pivotal role of senescence in organismal aging and the onset of age-related disorders, such as atherosclerosis, type II diabetes, and Alzheimer's disease, is supported by the observation that the clearance of p16-positive senescent cells delays various age-associated disorders and extends healthy lifespan. In this review, I provide an overview of recent advances in understanding the mechanisms underlying the induction of senescence and maintenance of the specific phenotypes, such as senescence associated secretory phenotypes (SASP).

As genome editing techniques are developed, they have been applied to somatic cells in clinical use. Regarding the adaptation of these techniques in human zygotes, advances in single-cell analysis technology are expected to enhance knowledge at the molecular level, even in human preimplantation embryo development, and the application of genome editing technology for molecular functional analysis is expected. However, the use of genetic modification techniques on germlines, including zygotes, spreads to all cells of an individual and is subsequently passed down through generations. Here we explore the possibilities and challenges of applying genome editing techniques to better understand the scientific aspects of the human germline.

Human iPS cells are somatic cells reprogrammed to the pluripotent state. Because of their pluripotent nature, iPS cells are now commonly used to model several developmental processes including hematopoiesis in vitro. The in vitro models can be used to study the mechanisms regulating not only normal hematopoiesis but also hematological diseases ranging from monogenic congenital disorders to genetically multifactorial malignancies. Those disease models can also be used to investigate novel treatments through procedures including high throughput drug screening. The possible clinical applications of iPS cell-derived hematopoietic cells include immunotherapy with T lymphocytes, NK cells and macrophages, and transfusion therapy with platelets and red blood cells. Platelets have now been produced from iPS cells in quantities sufficient for clinical use. By developing expandable immortalized megakaryocyte cell lines (imMKCLs), several novel drugs and turbulence-incorporated bioreactors, efficient and scalable generation of platelets was achieved. This review summarizes the current status of iPS cell research in hematopoiesis with details on iPS cell-derived platelets.

The hematopoietic stem cells, defined as blood stem cells with self-replication ability and multipotency, are key to successful hematopoietic stem cell transplantation. With the history of transplantation in the past 60 years and advances in stem cell technologies, our understanding of the hematopoietic system has deepened. However, the molecular mechanisms of self-renewal and pluripotency, which are the essence of the hematopoietic stem cells, remain poorly understood. One reason is that the identification/purification methods of the hematopoietic stem cells, particularly the long-term hematopoietic stem cells capable of lifelong self-renewal, is technically difficult owing to their scarcity in the bone marrow and has not been established to this date. Considering that a long-lasting blood production after hematopoietic stem cell transplantation is crucial, it is essential to understand the biology of the long-term hematopoietic stem cells not only scientifically but also clinically. This review describes the scientific and clinical significance of the long-term hematopoietic stem cells by showing the results of the latest researches in the introduction of hematopoietic stem cell identification/purification history.

In modern hematology, research on hematopoiesis and blood cells in vertebrates, such as birds, reptiles, amphibians, and fish, is lagging. This is because there are many experimental constraints when selecting subjects other than humans and mice as research subjects. Currently, the availability of flow cytometry to count classified nucleated blood cells and utilization of whole genome information have led to novel findings. For example, in case of amphibian hematopoiesis studies, megakaryocytes have been found to be present in African clawed frogs (Xenopus laevis), which do not have platelets but have circulating nucleated thrombocytes. Moreover, we shed light on several mysteries, such as the C-terminal region in human TPO molecules not being found in birds, amphibians, and fish TPO molecules and the functional universalities of mutant CALR-MPL binding and EPO-EphB4 binding, in conjunction with comparative hematology.

The secretion of extracellular vesicles (EVs) from cells has been observed. Recently, because EVs were found to contain functional molecules such as micro RNAs (miRNAs) and possess the ability to transfer them to other cells, its functions were expanded as an “intracellular communicator.” The exosome is one such EV that has been extensively investigated, particularly in cancer research because cancer cells abundantly secrete exosomes, suggesting their potential as promising diagnostic markers. Research on exosomes in the hematopoietic system has just begun. We recently reported that the exosome secreted from the EBV-infected lymphoma cells has critical functions in lymphomagenesis and maintenance. Moreover, EVs in HBV infection are now being investigated to generalize their functions.

The mechanism underlying production of various types of blood cells from hematopoietic stem and progenitor cells has been a central theme in hematology. Conventionally, hematopoietic cell populations are analyzed by cell surface markers to judge cell types and differentiation stages, and by transplantation assays to assess differentiation potential. Recently, however, next-generation sequencing technology has enabled single-cell transcriptome and epigenome analyses and cell barcoding-based lineage tracing during unperturbed hematopoiesis. These innovative assays revealed that each cell population is extensively heterogenous. Many cells within hematopoietic stem cell populations may not be multipotent, and conversely, hematopoietic progenitor cells often display self-renewal capacity. Moreover, cells tend to make their lineage choice much earlier than previously thought. Altogether, these results challenge the current hierarchical differentiation models and propose new continuous models. Single-cell analyses are expected to greatly contribute to our understanding of normal and abnormal hematopoiesis and to the development of new therapies for blood disorders.

The blood supply system for transfusions in Japan functions well. However, in cases of sudden hemorrhagic shock, the swift supply of red blood cell (RBC) product might be difficult, particularly when medical care is required in remote regions and in obstetric medicine, where there is always a risk of hemorrhage. Blood pressure maintenance by infusion of volume expanders, such as crystalloids or colloids, may be insufficient to preserve the function of vital organs because they do not contain any oxygen-carrying molecules. If artificial RBCs were at hand, they could be used as a blood substitute until blood products are received from blood banks. This would save patients without degrading their quality of life. In the 1990s, we developed an artificial RBC in the form of a hemoglobin vesicle (Hb-V). Hb-V is a liposomal microparticle that encloses oxygen-carrying human Hb molecules. Different from RBCs, it has no blood type and is stable at room temperature, ensuring a long shelf-life. Its excellent biocompatibility and oxygen-carrying capacity have been proven in a number of animal experiments, and its production technique has also been established. Therefore, translational research is being designed with the aid of the Japan Agency of Medical Research and Development.

Previous randomized controlled trials (RCTs) have shown beneficial effects of iron supplementation other than anemia improvement including treatment of restless leg syndrome and general fatigue, even in non-anemic subjects with iron deficiency. Recently, some RCTs in congestive heart failure (CHF) demonstrated that intravenous administration of ferric carboxymaltose improves patient symptoms and reduces incidence of hospitalization for worsening heart failure. Consequently, the European Society of Cardiology recommends that iron deficient patients with CHF are administered ferric carboxymaltose (evidence level A). Moreover, the PIVOTAL study for hemodialysis patients proved that proactive administration of iron sucrose decreases the dose of erythropoiesis-stimulating agents and frequency of transfusion compared with its sole administration in reaction to iron deficiency. Notably, this proactive treatment is superior to a low-dose regimen in preventing the primary composite endpoints of nonfatal myocardial infarction, stroke, hospitalization for CHF, and death. These clinical findings are supported by basic research on cardiomyocyte-specific transferrin receptor knock-out mice showing heart failure with impaired mitochondrial respiratory function. In this model, cardiac iron deficiency impairs the mitochondrial electron transport chain, thus leading to low adenosine triphosphate production, and it subsequently prevents mitophagy resulting in damaged mitochondrial accumulation in the heart.

In 2017, The British Society of Haematology published new guidelines for the diagnosis and management of autoimmune hemolytic anemia (AIHA). Usually this is diagnosed using a combination of clinical and laboratory findings of hemolysis using the direct antiglobulin test (DAT). The revised guidelines propose several steps to evaluate and diagnose patients with unexplained hemolysis and a negative DAT, and they recommend screening for cold agglutinin disease (CAD) using a direct agglutination test (DAggT) before evaluating the cold agglutinin titer. Rituximab is becoming the preferred second-line choice for steroid-refractory warm AIHA and the first-line choice for primary CAD. Rituximab is an off-label drug for use in AIHA treatment in Japan, but in future will be used as standard therapy. Anti-C1s antibody is a new drug for CAD that has entered phase 3 trials.

Conventional chemotherapy with cytarabine and anthracycline (often referred to as “7+3”) has been used for many years in the treatment of acute myeloid leukemia (AML). Despite meaningful advances in areas of supportive care and transplantation, little progress has been made in developing new chemotherapy options. In 2018, The Food and Drug Administration (FDA) of the US approved several novel agents for AML treatment as follows: ivosidenib, an inhibitor of isocitrate dehydrogenase-1; venetoclax, a potent inhibitor of bcl2; and glasdegib, an inhibitor of hedgehog signaling pathway. Moreover, clinical trials of alvocidib (flavopiridol), an inhibitor of the CDK9, pevonedistat, an inhibitor of NEDD8, and APR-246, a reactivator of mutant p53, are in progress. These agents will either be incorporated into the conventional 7+3 regimen or combined with hypomethylating agents to improve the outcome of AML therapy, and the results will guide the next stage of precision medicine in the treatment of AML.

Acute myeloid leukemia is a disease that mainly affects older populations, with a median age at diagnosis of 67 years, and outcomes for these patients are poor. Reduced-intensity regimen improves survival after allogeneic hematopoietic cell transplantation (HCT), but this has not been well studied. To reduce non-relapse mortality (NRM) among the elderly, geriatric assessment, HCT-Comorbidity index, and disease risk must be studied before HCT.

The two main treatment options for patients with higher risk of myelodysplastic syndromes (MDS) are allogeneic hematopoietic stem cell transplantation and azacitidine therapy. Of these, only allogeneic hematopoietic stem cell transplantation is curative, and azacitidine treatment is selected for patients not suitable for transplantation. Compared to conventional treatment with supportive treatment alone or with low dose cytarabine, azacitidine treatment improves survival in MDS patients, even in patients over the age of 75. Because azacitidine treatment takes 4-6 cycles until an initial response, several response-predicting scoring systems have been developed. Novel therapeutic agents and combination therapies of azacitidine with a variety of drugs are currently under study.

Imatinib, nilotinib, dasatinib, bosutinib, and ponatinib are tyrosine kinase inhibitors used to treat chronic myeloid leukemia (CML). Therapeutic drug monitoring (TDM) and target concentration intervention (TCI) are novel strategies that use concentration-controlled dosing (CCD) to attain a faster and more profound clinical response in patients with CML. The target plasma trough concentration (C₀) of imatinib is 1,000 ng/ml to obtain a higher major molecular response (MMR) rate. Target nilotinib and bosutinib C₀ of 900 and 62 ng/ml, respectively, are recommended to attain a better response, whereas a target ponatinib C₀ of 21.3 ng/ml has been proposed to obtain a better response and decrease the risk of adverse events, such as vascular toxicity. Approaches for these four TKIs involve the use of TCI with specific target concentrations rather than TDM with a therapeutic range. Conversely, for dasatinib, a lower C₀ of <4.33 ng/ml is the maximum toxic concentration recommended to avoid pleural effusion. Therefore, precision dosing using CCD of TKIs for CML could maximize the clinical benefit and minimize toxicity.

The median survival time in myelofibrosis is about 5 years, and allogeneic hematopoietic stem cell transplantation is the only curative treatment. Because the clinical course and prognosis of myelofibrosis is not uniform, transplantation-related death or long-term prognosis should be evaluated by varied prognostic prediction systems. This includes assessing gene mutation information in each patient, and the indication and timing of transplantation should be decided based on this information. Previous reports have shown that transplanted hematopoietic stem cells can be engrafted despite marked fibrosis in the bone marrow, and allogeneic hematopoietic stem cell transplantation is a curative treatment for myelofibrosis. However, the transplant-related mortality rate is 30-50%, and the overall survival rate is only around 50%. Future work should focus on methods to decrease transplant-related mortality, including the selection of stem cell source, the development of optimal pre-transplant treatment, and how to best incorporate JAK2 inhibitors before transplantation.

The 8p11 myeloproliferative syndrome (EMS) is a relatively rare hematological malignancy defined by the presence of chromosomal abnormalities associated with fibroblast growth factor-1 gene, located in the 8p11-12.1 chromosomal locus. To date, only around a hundred cases have been reported in the literature. Patients with EMS present with various forms of myeloid/lymphoid malignancies, such as myeloproliferative neoplasms, acute myeloid leukemia, and T- or B-linage lymphoblastic lymphoma, which are frequently associated with eosinophilia. Prognosis of EMS is poor and a standard treatment strategy has not yet been established. In contrast to myeloid/lymphoid neoplasms associated with PDGFR-A or PDGFR-B rearrangement, the tyrosine kinase inhibitor (TKI) imatinib is not an effective therapeutic option for EMS patients. Other types of TKI, i.e., PKC412, sorafenib, ponatinib, dasatinib, and dovitinib, show growth-inhibitory effects against the cells harboring several types of FGFR-1 fusion genes in in vitro studies; however, the usefulness of either drug has not been confirmed by clinical trials. Therefore, at present, allo-hematopoietic stem cell transplantation is the only curative methods for EMS. Very recently, a phase-2 study with pemigatinib, an inhibitor for FGFR1, showed clinical benefits for EMS patients, including major cytogenetic response, suggesting a new therapeutic option for EMS.

The classical myeloproliferative neoplasms (MPN), polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF), are characterized by clonal myeloproliferation without features of myelodysplasia. The diagnostic approach proposed by the World Health Organization (WHO) uses clinical features, peripheral blood counts and smear analysis, bone marrow (BM) morphology, karyotype and molecular genetic tests to classify MPN subtypes. The detection of characteristic driver mutations like JAK2V617F, JAK2 exon 12, MPL, and calrecticulin (CALR) is a major diagnostic feature. JAK2 mutations are detected in more than 90% of patients with PV and are therefore used as highly sensitive clonal marker in this subtype. However, JAK2 mutations may also occur in ET and PMF, while CALR is virtually not seen in PV. Therefore, BM remains the central diagnostic platform and is essential for distinguishing ET from pre-fibrotic PMF and diagnosing cases which do not express JAK2, MPL or CALR (‘wild-type’ or ‘triple-negative’ MPN). The standardization of relevant BM features is mandatory to recognize characteristic and easy to assess patterns that enable an accurate discrimination between the MPN subtypes. Key parameters include cellularity, erythropoiesis and neutrophil granulopoiesis in context with specific features of megakaryocytes as well as the BM fiber content, especially in early stage MPN that present with thrombocytosis and clinically mimic essential thrombocythemia.

Although the Janus kinase (JAK) inhibitor ruxolitinib has long been the only drug licensed for treatment of the classic Philadelphia chromosome negative (Ph⁻) myeloproliferative neoplasms, years of drug development efforts have begun to bear fruit with the recent approval of a novel monopegylated interferon alfa-2b, ropeginterferon alfa, for patients with polycythemia vera without symptomatic splenomegaly in Europe. Several newer JAK inhibitors (fedratinib, pacritinib, momelotinib) have shown activity in phase 3 trials in patients with myelofibrosis but have, for various reasons, not yet received regulatory approval; all these agents, however, remain in active clinical development. Many other agents with diverse mechanisms of action are being explored in clinical trials in patients with myelofibrosis, both as single agents and in combination with ruxolitinib. Besides splenomegaly and symptoms, improvement of anemia has become a new focus of drug development in myelofibrosis. Ruxolitinib appears promising also in chronic neutrophilic leukemia, where mutations in CSF3R are common. Pemigatinib, a potent and selective inhibitor of fibroblast growth factor receptor (FGFR), has shown impressive efficacy in a small registration-directed trial in patients with FGFR1-rearranged myeloid/lymphoid neoplasms. Finally, avapritinib, a highly potent and selective inhibitor of KIT^D816V, has demonstrated unprecedented response rates in patients with advanced systemic mastocytosis.

Hematopoietic tumors represent a range of clinically and biologically diverse diseases, and within this, the lymphoid malignancies, especially B-cell lymphomas, are classified into many entities in the WHO classification system. It is thought that various molecular genetic abnormalities are involved in the tumorigenesis of diffuse large B-cell lymphoma (DLBCL). Due to recent developments in genetic analysis technology, novel and recurrent genetic abnormalities have been discovered. This is important knowledge for the development of new therapeutic drugs and may support indications for clinical trials, ultimately leading to the availability of more targeted therapies and precision medicine in the DLBCL arena. Here the possibility of patient stratification, based on genetic abnormality, has been described.

In 2018 the practical guidelines for hematological malignancies, edited by Japanese Society of Hematology, underwent major revision for the first time in five years. R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone) remains the standard treatment for diffuse large B-cell lymphoma (DLBCL) in line with the prior 2013 guidelines. R-CHOP has been considered as the standard treatment for DLBCL since early 2000s, when a 20% improvement in survival was observed when adding rituximab to CHOP. Following this, several clinical trials were conducted, but most attempts to exceed R-CHOP have failed. Moreover, this evidence has raised further research questions. In this report, the current evidence and the problems associated with DLBCL treatments have been reviewed.

The treatment of follicular lymphoma (FL) continues to evolve. Those patients who present with minimal symptoms often are observed without therapy until significant progression occurs. When treatment is needed, initial options include single agent rituximab (R, anti-CD20), or various forms of chemoimmunotherapy including either R or the newer anti-CD20 monoclonal antibody obinutuzumab (O), with or without maintenance administration. Recent data suggest that the immunomodulatory agent lenalidomide can also be effective in combination with rituximab in both the upfront and relapsed setting. Patients with recurrent disease are frequently treated with chemoimmunotherapy or phosphoinositol-3-kinase (PI3K) inhibitors. Current information suggests that the most important prognostic feature of FL is the presence or absence of early progression (within 2 years of initial treatment/diagnosis). Ongoing efforts are focused on biomarkers to optimally match treatment to patient populations and further improve clinical outcomes.

Multicentric Castleman disease (MCD) is a rare polyclonal lymphoproliferative disease that causes systemic inflammation. In Western countries, human herpesvirus 8 (HHV-8) is frequently associated with MCD pathogenesis, especially in human immunodeficiency virus (HIV)-positive cases, whereas HHV-8 is seldom related to MCD cases in Japan and is referred to as idiopathic MCD (iMCD). iMCD can present as a variety of systemic symptoms and characteristic laboratory abnormalities due to IL-6 overproduction, occasionally causing organ failure. Although there have been no recent studies other than pathologic studies of iMCD, its association with TAFRO (thrombocytopenia, anasarca, reticulin fibrosis of the bone marrow, renal dysfunction, and organomegaly) syndrome has recently attracted attention in Japan as well as internationally. In 2015, a research team for iMCD published a medical reference guide and organized regional core hospitals in Japan for the diagnosis and treatment of iMCD. As a result, iMCD was designated the 331st intractable disease by the Japanese Ministry of Health, Labor and Welfare. iMCD can be expected to have a good prognosis if properly diagnosed and treated. We are optimistic that iMCD research will aid the development of medical treatment for this disease.

It is well known that acute lymphoblastic leukemia (ALL) cells can invade the central nervous system (CNS), but the underlying mechanism of such invasion is still unclear. We discovered the direct routes taken by ALL cells when migrating into CNS in ALL model mice. We observed that ALL cells migrate along the external surface of vessels that pass directly between the vertebral or calvarial bone marrow and the subarachnoid space. The basement membrane of these bridging vessels is enriched in laminin. The laminin is recognized by integrin α6, which is expressed by ALL cells. The interaction between integrin α6 and laminin mediated the invasion of ALL cells. Furthermore, the expression of integrin α6 depends on PI3Kδ activity. Mice with ALL xenografts were treated with a PI3Kδ inhibitor, which decreased integrin α6 expression on ALL cells. This resulted in significant reductions in blast counts in the cerebrospinal fluid and in CNS disease symptoms. Our data suggest that the PI3Kδ inhibitor has potential to prevent CNS involvement in ALL.

Gene and protein expression profiling has clarified that tumor cells in angioimmunoblastic T-cell lymphoma (AITL) have T follicular helper (TFH) cell characteristics. In AITL, typical genomic abnormalities have been reported that combine G17V RHOA mutations, gene mutations involved in epigenetic pathways, and those involved in T-cell receptor signal pathways. Besides AITL, some lymphomas display a TFH phenotype, prompting the proposal of a new disease classification encompassing those. Interestingly, lymphomas with TFH phenotype characteristics also share most genomic abnormalities with AITL. Furthermore, because AITL genomic abnormalities are highly disease specific, they can be used for diagnosis. Although AITL is a refractory disease, several new drugs have been approved for relapsed and refractory cases. Precision medicine targeting genomic aberrations characteristic of AITL is being investigated.

Recent advances in immunotherapy have highlighted the importance of the tumor microenvironment. Lymphomas are a heterogeneous group of malignancies that arise from lymphocytes and typically develop in lymphoid tissues. It has been recognized that the elements of the lymphoma microenvironment are not mere bystanders to a host antitumor inflammatory response but are important components of the tumor that support proliferation, survival, and chemoresistance of lymphoma cells. Lymphoma cells have individual expression patterns of chemokine receptors and adhesion molecules, according to their histological subtypes, and the patterns of surface molecules determine the sites of tumor involvement. Lymphoma cells often depend on the signals provided by non-tumor cells, such as stromal cells and macrophages, through direct cell contact and paracrine factors. On the other hand, there are genetic and non-genetic mechanisms allowing lymphoma cells to escape from anti-tumor immunity, such as downregulation of HLA molecules, B2M, CD58, CD70, and/or upregulation of PD-L1 and PD-L2. Further understanding of the interactions of lymphoma cells and the tumor microenvironment gives an insight into the pathogenesis of lymphomas and supports new approaches to their treatment.

Recent technology advances in genomic analysis have unraveled the genomic complexity and evolutionary process of multiple myeloma (MM). Hyperdiploidy or IgH translocations t (4;14), t (11;14), t (6;14), t (14;16), and t (14;20), leading to ectopic overexpression of MMSET/FGFR3, CCND1, CCND3, MAF, and MAFB, respectively, are initiating events. Subsequent secondary events, such as gene copy number alterations, and gene somatic mutations, participate in tumor progression in a branching pattern consistent with Darwin's evolutionary model. Copy number alterations, such as 1q21 amplification and del (17p), have been associated with adverse outcomes. N/KRAS mutations are most commonly found in around 20% of patients, but numerous gene mutations are infrequent. Pathological and clinical relevance of gene mutations combined with cytogenetic abnormalities are currently under investigation. Additionally, detailed genomic analysis of individual patients using targeted-sequencing panels has been facilitated, and efforts toward personalized therapy based on molecular features have begun. This paper outlines MM molecular pathology and its clinical application in Japanese patients.

Multiple myeloma is a malignant plasma cell neoplasm that is incurable despite significant progress in treatment over the past several decades. The incorporation of novel agents and combinations into the MM treatment paradigm has resulted in improved survival and tolerability, as well as deeper responses including achieving a minimal residual disease negative state. The addition of new treatment options and combinations has added complexity in treatment selection for myeloma patients. The current strategy for newly diagnosed myeloma involves induction, consolidation, and maintenance therapy. However, nearly all myeloma patients will develop refractory disease. This highlights the need for more effective therapies targeting the myeloma cells and their microenvironment. In this article, we summarize current management of transplant eligible and ineligible newly diagnosed patients in both the upfront and relapsed refractory setting, highlighting risk adapted strategies. We also summarize emerging therapies, such as immune and targeted approaches, as well as drugs with novel mechanisms of action. Emerging strategies offer individualized treatment options and may ultimately offer the possibility of a cure for myeloma patients.

The introduction of proteasome inhibitors (PIs), such as bortezomib (BTZ), and immunomodulatory drugs (IMiDs), including thalidomide (THAL) and lenalidomide (LEN), as first-line therapies in multiple myeloma (MM) has markedly improved the clinical outcomes of patients. However, MM remains incurable, and most patients eventually relapse. Moreover, prognosis is poor in patients who exhibit resistance to BTZ or LEN, and novel therapeutic approaches for such patients are urgently needed. Currently, the following six drugs are available for use in relapsed patients: second generation PIs (carfilzomib and ixazomib), an IMiD (pomalidomide), a histone deacetylase (HDAC) inhibitor (panobinostat), and two monoclonal antibodies (elotuzumab and daratumumab). The choice of treatment should be individualized based on certain factors, such as age, presence of comorbidities, frailty, cytogenetic risk, efficacy and toxicity of prior treatments, and the duration of the previous response. A course of triplet therapy containing two novel agents along with DEX is recommended, on first relapse, in fit and healthy patients, whereas doublet therapy is preferred for unfit or frail patients. Retreatment of relapsed/refractory MM (RRMM) with monoclonal antibodies and IMiDs is promising because these drugs have immunostimulatory effects. In addition, novel agents, including an anti-BCMA antibody-drug conjugate, are being studied. Clinical trials are needed to define the optimal treatment strategy for RRMM.

Multiple myeloma (MM), which is derived from immunoglobulin-producing plasma cells, is treated using novel agents, such as proteasome inhibitors, immunomodulatory drugs (IMiDs), and anti-MM monoclonal antibodies, which have been developed based on preclinical findings. Although these treatments have improved MM prognosis, it still remains an incurable disease. Therefore, development of novel treatment strategies is warranted. Histone deacetylases (HDACs) are a group of deacetylating enzymes that catalyze the deacetylation of histone and non-histone proteins, leading to changes in gene expression and protein function and stability. Panobinostat, a pan-HDAC inhibitor, is now clinically available in combination with bortezomib and dexamethasone for the treatment of MM. To further improve treatment strategies for MM, HDACs are thought to have potential as next-generation therapeutics because HDAC isoform-selective inhibition, but not broad HDAC inhibition, is effective in MM cells. The roles of each HDAC isoform in MM are not yet precisely defined. To maintain or augment anti-MM effects without severe adverse reactions, preclinical and clinical studies are being undertaken to elucidate the impact of each HDAC isoform on MM and develop class- or isoform-selective HDAC inhibitors in combination with other therapeutics.

Hemophilia is a congenital bleeding disorder that occurs due to quantitative and functional abnormalities of FVIII or FIX. It has a long history, dating as far back as the Babylonian era, with many high profile reports, including the British royal family and the last prince of the Romanov dynasty. The treatment used to be blood transfusion, consisting of plasma derived products from the 1970s onwards and recombinant products introduced later in the 1990s. In the 2000s, due to various modifications of factor protein, extended half-life (EHL) products have appeared and replaced conventional products. In EHL research, new products are also being developed that further the extension of the half-life and are more convenient. In 2018, an antibody-based medicine arrived, exhibiting a mechanism different from factor replacement therapy. Some other therapeutic agents used to suppress bleeding, called nonfactor agents, are currently under development. Recently, gene therapy has finally come into the clinical trial space in Japan and can be expected to be a treatment which aims at “cure,” as it can be used with no exposure to bleedings for several years with one injection. This article outlines the future of hemophilia treatment.

It is well known that platelets play a crucial role in hemostasis, but it has recently been revealed that platelets are also necessary for organ development. The platelet activation receptor CLEC-2 activates platelets by binding to the membrane protein, podoplanin, on the surface of lymphatic endothelial cells. This results in the release of TGF-β family from activated platelets to facilitate blood/lymphatic vessel separation. TGF-β also acts on lung mesothelial cells, which leads to their differentiation into alveolar duct myofibroblasts (adMYFs) and their migration into the inside of the lung. adMYFs generate elastin, which gives elasticity to the lung. Therefore, mice deficient in either CLEC-2 or podoplanin exhibit blood/lymphatic vessel misconnection and die just after birth due to respiratory failure. It had been previously surmised that biologically active substances from cells act on neighboring cells, leading to organ development, and the role of blood cells in organ development had not been elucidated. However, it has recently been demonstrated that blood platelets contain biological active substances in their granules, which are released when and where necessary by specific interactions between platelet receptors and their ligands. Now platelets are recognized as a “biological package” that actively facilitates organ development.

This paper describes diagnosis, treatment, and control of acute venous thromboembolism (VTE) and antithrombotic prophylactic management during pregnancy and puerperium, especially in women with inherited thrombophilia. VTE is currently one of the three main causes of maternal morbidity in Japan. With approximately 0.05%-0.08% incidence rate per total number of births, it is becoming increasingly comparable with other developed countries. Pregnancy is characterized by high blood clotting potential due to increased coagulation factors, decreased anticoagulant activity, and fibrinolysis. Additionally, unique obstetric risk factors exist, such as cesarean section, prolonged bed rest, obesity, preeclampsia, and dehydration due to hyperemesis. Moreover, notable risk factors for VTE in pregnancy and puerperium for patients with inherited thrombophilia (e.g., deficiencies in antithrombin, protein C, and protein S) and acquired thrombophilia (e.g., antiphospholipid antibodies, history of VTE) have been reported; this study describes inherited thrombophilia in details.

Down syndrome (DS) is related to constitutional trisomy 21 and is characterized by typical dysmorphic features and various congenital abnormalities. DS is also associated with a broad spectrum of hematological findings, such as transient thrombocytopenia in the neonatal period and acute leukemia. Of those hematological abnormalities, transient abnormal myelopoiesis (TAM) and acute myeloid leukemia (AML) have common genetic abnormalities, i.e., trisomy 21 and GATA1 mutation, and form a continuous spectrum, referred to as myeloid proliferations related to DS. Recent studies have demonstrated interactions between trisomy 21 and GATA1 mutations. Trisomy 21 promotes the expansion of early hematopoietic progenitors and upregulates short form GATA1, resulting in the accelerated production of aberrantly differentiated cells and development of TAM. Following spontaneous remission of TAM, subsequent AML can evolve from a preexisting residual TAM clone through the acquisition of additional mutations involving multiple cohesion components and epigenetic regulators.

Whether Langerhans cell histiocytosis (LCH) is an inflammatory disorder or a neoplasm is an ongoing debate. On the basis of the identification of the BRAF V600E mutation in 2010, LCH should be defined as an inflammatory myeloid neoplasia. Mutually exclusive BRAF V600E (50-60%) and MAP2K1 (12-25%) mutation renders the ERK activation. BRAF V600E mutations were detected in approximately 50-60% of patients with Erdheim-Chester disease (ECD), and these patients are being treated with vemurafenib, a selective BRAF V600 kinase inhibitor, approved by the US Food and Drug Administration. The Japan Langerhans cell histiocytosis study group-02 protocol study showed five-year overall survival rate of 92% and event-free survival of 46% in risk-organ involvement of positive multi-system LCH. We aimed to improve the quality of life by reducing relapses and development of late complications. It is essential to achieve a close cooperation between hematologists catering to pediatric and adult patients with LCH. Furthermore, novel targeted therapies of MAPK inhibitors are required along with intensified chemotherapy to achieve better outcomes in patients with LCH in Japan.

Acute lymphoblastic leukemia (ALL) in infants under 1 is a rare and dismal disease. It is associated with a unique and specific biology, and 80% of cases harbor a KMT2A (MLL) gene rearrangement (KMT2A-r). In contrast to ALL in older children, with a survival rate of 80% or more, the prognosis of infant ALL is very poor, at 40%. In addition, the unique pharmacodynamics exhibited by infants has historically led to independent therapeutic development either in the U.S., Europe, or Japan. To improve the prognosis of infant ALL, it is necessary to uncover a supplementary novel effective agent to be used in combination with the existing conventional multi-agent chemotherapy. Because of the rarity of the disease, this could be only established by an international study, for which the consensus has already been established through discussions between the U.S., Europe, and Japan. Additionally, severe late effects in survivors are also problematic. Establishing novel treatment strategies to reduce relapse rates, treatment-related toxicities, and critical late effects is strongly encouraged in near future.

Graft-versus-host disease (GVHD) is a major barrier to successful allogeneic stem cell transplantation. Therefore, the identification of an alternative donor with a lower risk of GVHD is important for patients lacking an HLA-identical sibling donor. To date, HLA studies of large cohorts of unrelated hematopoietic stem cell transplantation (UR-HSCT) have provided important and helpful information for donor selection. In UR-HSCT through Japan Marrow Donor Program, patient and donor HLA-A, -B, and -C, and HLA-DRB1 and -DQB1 double mismatches are significant risk factors for severe GVHD and mortality. HLA-DPB1 mismatch does not affect survival; however, it reduces the chances of leukemia relapse. In the analysis of a specific allele effect on transplant outcomes, HLA-C^*14:02 was significantly associated with an increased risk of severe acute GVHD. The development of next-generation sequencing (NGS) has enabled full-length HLA allele typing. Evolutionary analysis of the entire HLA-DPB1 revealed that a highly conserved region from exon 3 to 3′UTR provoked acute GVHD that was different from a T-cell epitope mismatching algorithm, reflecting exon 2 polymorphisms. Furthermore, a recent study demonstrated the importance of full-length NGS HLA typing on UR-HSCT outcomes. The usage of NGS may provide important information on the implications of the HLA genes in allogeneic stem cell transplantation.

Chronic active EBV infection (CAEBV) is one of the EBV-associated T/NK lymphoproliferative diseases. The prognosis of CAEBV is very poor, and without curative therapy, almost half of patients will die within five years of onset. The results of a 3-step treatment regimen consisting of step 1 (immunochemotherapy), step 2 (multi-drug chemotherapy), and step 3 (hematopoietic cell transplantation, HCT) are excellent. HCT is the only cure for CAEBV, and reduced-intensity conditioning (RIC) is superior to myeloablative conditioning (MAC). The overall survival rate is typically more than 90% following bone marrow transplantation and cord blood transplantation.

Various types of infectious complications could develop after allogeneic hematopoietic stem cell transplantation (HSCT) due to the associated intensive immunosuppression. Cellular immunity is also impaired, resulting in a higher incidence of viral infections when compared with standard chemotherapy. Cytomegalovirus (CMV) reactivates in seropositive patients under immunosuppression after allogeneic HSCT, causing complications, such as pneumonitis, gastroenteritis, and retinitis. Because intervention before the onset of disease, rather than after, can improve prognosis, preemptive therapy guided by early detection of CMV reactivation has been extensively used. Recently, the introduction of a less myelotoxic agent, letermovir, has enabled prophylactic therapy to be administered safely and effectively. In addition, prophylactic letermovir is expected to reduce transplant-related mortality. However, the onset of CMV infection/disease as either a breakthrough infection or after the discontinuation of letermovir is still problematic. In this section, the management tips for CMV infection after allogeneic HSCT have been summarized.

It has been eight years since the first immune checkpoint-blocking antibody, ipilimumab, was approved for metastatic malignant melanoma treatment by FDA in 2011. During this period, several other immune checkpoint blockers have been newly developed and approved for certain cancers, including malignant melanoma. However, there have been several concerns with some of these. The overall response rate did not exceed 30% in many cancers; although combination therapy with ipilimumab and nivolumab increased efficacy, immune-related adverse events also increased. This observation facilitated the reverse translational research (rTR) approach, using clinical specimens from treated patients to gradually elucidate the mechanism of resistance and biomarkers to select patients who can potentially benefit from immunotherapy. This has also promoted the development of novel combination therapies. In this review, immunological findings that highlight the resistance mechanisms of cancers against immune checkpoint blockers and the novel attempts to achieve a break-through will be discussed.

The adoptive transfer of chimeric antigen receptor (CAR)-modified autologous T cells targeted at the B-cell antigen CD19 is highly effective in patients with relapsed or refractory B-cell malignancies. In Japan, tisagenlecleucel has been approved in March 2019, whereas axicabtagene ciloleucel, lisocabtagene maraleucel, and TBI-1501 have been tested in clinical trials. In addition, allogeneic CD19 CAR T cells from family or third-party donors have been developed for treating B-cell malignancies. Moreover, CAR T-cell therapies for acute myeloid leukemia (AML), T-cell leukemia, and multiple myeloma are still under development. Our group is currently preparing a phase I study on granulocyte macrophage colony-stimulating factor receptor-targeted CAR T cells in pediatric and adult patients with AML.

The former definition of gene therapy was the infusion of genes or cells transduced with genes into humans for the treatment or prevention of a disease, i.e., gene therapy adds a functional gene into the patients' genome, whereas the mutated gene remains as it is. Because most of the immune immunodeficiency disorders (PID) are caused by single gene mutations, this therapeutic option may provide a clinical effect. However, the treatment has a severe problem of leukemogenesis caused by insertional mutagenesis; therefore, it is not applicable for diseases caused by the gain-of-function of mutated genes. To address this, gene therapy using gene correction techniques will come to the forefront of the mainstream research. Herein, I have focused on the present outline of gene therapy by gene addition and described the future prospects of gene therapy by gene correction for PID.

A conflict of interest (COI) is a conflict between private interests and one's official responsibilities. COI is unavoidable and thus needs to be managed. Debates about COI in medical research area began in the United States in the 1980s. COI clause was added to the Helsinki Declaration in the year of 2000 after the Gelsinger affair. Discussions in Japan subsequently followed, and COI management guidelines have been sequentially presented by different organizations, particularly after the Diovan incident in 2013. Guidelines presented by the Japan Medical Association (JMA) in 2017 are currently regarded as standard. COI disclosure is required at research presentations and medical practice guideline announcements, among others, and should be carefully managed in the latter. In 2018, the Japanese Society of Hematology announced revision of the Japanese Society of Internal Medicine common guidance, presenting it in accordance with the JMA's guidelines. In the “Specific Clinical Research” section defined in the “Clinical Research Method Enforcement Rule”, people who should not take a representative position or who should pay special attention when taking it are defined.

Recent progress in cancer therapy has improved the long-term outcomes of cancer patients, and it has increased the importance of managing cardiovascular complications associated with cancer and cancer therapies. In the field of hematology, there is a serious concern about cardiovascular complications associated with a variety of chemotherapeutic drugs, such as anthracyclines, BCR-ABL tyrosine kinase inhibitors, and proteasome inhibitors. Despite the recent accumulation of epidemiological and clinical data and the fact that these are molecularly targeted drugs, molecular mechanisms underlying the pathogenesis of cardiovascular toxicities associated with individual drugs remain to be precisely defined. Recently emerging “onco-cardiology” will extend the interdisciplinary collaboration between oncology, hematology, and cardiology specialists in clinical practice, research, and education in order to protect cancer patients and survivors from cardiovascular complications.

The frequency of hematological malignancies is quite high in children, adolescents and young adults. Infertility after treatment is an important issue affecting the quality of life of long-term survivorsas the outcome of treatment is improved. Recently, several guidelines for infertility and fertility preservation have been published. Consequently, it has become easier to obtain information on the risk of infertility and fertility preservation therapy for each treatment. However, the information on the optimal timing for fertility preservation and current outcomes of assisted reproductive technology using stored oocytes, embryos, ovarian tissues, or sperm remains limited. Further, whether fertility preservation while using a new drug with unknown risk for infertility should be performed remains an unresolved issue.

Precision medicine is a type of medical care designed to optimize the therapeutic efficiency or benefit for particular groups of patients with the use of genetic profiling. The application of precision medicine in cancer treatment is prospected because cancer is reported to be the leading cause of death in Japan. Consequently, Japanese cancer genome medicine will be launched within this fiscal year. In this study, we focus on precision medicine specifically in the field of hematological malignancies with an overview of its clinical utility. We further discuss how precision medicine should be developed in this field, based on our experience of a feasibility study for clinical sequencing in hematological malignancies.

Recently, an “open-access” publishing model has been widely adopted by many journals, in which authors typically pay for an article processing charge to make their journals freely accessible to readers. However, there are an increasing number of low-quality journals aiming to swindle article processing charges by exploiting this model. These corrupt journals invite scientists, via various methods, to submit their work, and accept promptly submitted papers without appropriate peer-review. This results in the publisher claiming expensive charges from authors, which eventually lowers their value as a scientist. There are lists of corrupt journals (black lists) and trustworthy journals (white lists), but neither reach perfection. The most useful criteria may be reputation, based on recommendations from reliable colleagues in the field. To avoid submitting to such corrupted journals, it is important to know and understand the methods and various trappings they employ.

Viral hepatitis during and after hematological disease treatment is a fatal complication and is mostly caused by HBV reactivation among HBV carriers and their pre-existing infected person. In this study, the authors review the current status of HBV reactivation, HBV pathogenesis, and implications of molecularly targeted drugs as a risk factor in the context of hematological conditions and detail the current HBV reactivation preventive strategy based on referred risk factors. Additionally, the recently clarified significance of HBV antibody titer as a preventive factor of HBV reactivation and the discovery and significance of BTNL2 as a novel host factor inducing high HBV antibody levels have also been described, as well as the applicability of an HBV vaccine in prevention of HBV reactivation. By clarifying research questions that should be addressed as soon as possible, the authors aim to establish an HBV reactivation preventive strategy.