Acquired aplastic anemia (AA) is a hematopoietic dyscrasia characterized by pancytopenia and bone marrow hypoplasia. AA is considered to be caused mainly by T-cell attacks on hematopoietic stem cells, as assumption based on good responses to T-cell specific immunosuppressive therapy (IST). Several markers, such as HLA-DRB1^*1501 and an increase in the percentage of paroxysmal nocturnal hemoglobinuria (PNH) phenotype cells, have been shown to represent the immune pathophysiology of AA. However, little is known about the pathogenesis of AA. This review article focuses on immune mechanisms underlying the development of AA and the roles of the aforementioned markers in the management of bone marrow failure.

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Cord blood transplantation (CBT) has increasingly been used in Japan and the annual number of CBT now exceeds 1,200. The cumulative number of CBT reached 12,853 in 2015, accounting for almost 1/3 of total CBT performed worldwide. It is true that smaller body size and lower costs, as compared to western countries, have been advantages for Japanese people in using CB as graft alternative. In addition, several novel findings regarding serious issues following CBT have been obtained, which further enhanced the use of CB. First, several mechanisms of engraftment failure following CBT other than cell dose have been reported, such as the presence of donor-specific anti-HLA antibodies or the development of hemophagocytic syndrome. Second, unique profiles of infectious complications following CBT have been reported, such as higher incidences of early bacterial infections and HHV-6 encephalitis, as compared to those following bone marrow (BM)/peripheral blood (PB) transplants. Third, the incidence of disease relapse was comparable to those following BM/PB transplants. Novel pre-transplant conditioning regimens using intravenous busulfan have been investigated with promising results being obtained to date. A recent analysis of Japanese transplant registry data revealed similar survival following CBT to HLA-matched unrelated BM/PB transplants.

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Bortezomib (BTZ), a proteasome inhibitor, has been widely used for the treatment of multiple myeloma (MM), including newly diagnosed as well as relapsed and refractory cases, and is considered to be a key drug in the induction therapy for MM. However, the precise mechanism underlying the action of this agent has yet to be fully elucidated. Predicting sensitivity to BTZ treatment by using adequate biomarkers would aid in the development of individual targeted therapies for MM. Herein, by reviewing preclinical studies using MM cell lines and other investigations that have analyzed primary MM samples from patients, we describe in detail the induction of MM cell death by proteasome inhibition and the factors that regulate the sensitivity of the proteasome inhibitor BTZ in MM cells.

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Elucidation of the epigenetic mechanisms underlying drug resistance may greatly contribute to the advancement of cancer therapies. In the present study, we identified trimethylation of histone H3 at lysine-27 (H3K27me3) as a critical histone modification for cell adhesion-mediated drug resistance (CAM-DR), which is the most important form of drug resistance in multiple myeloma. Cell adhesion counteracted drug-induced hypermethylation of H3K27 via inactivating phosphorylation of EZH2, leading to sustained expression of anti-apoptotic genes including IGF1, BCL2 and HIF1A. Inhibition of the IGF-1R/PI3K/Akt pathway reversed CAM-DR by promoting EZH2 dephosphorylation and H3K27 hypermethylation both in vitro and in refractory murine myeloma models. To our knowledge, this is the first demonstration of an epigenetic mechanism underlying CAM-DR and provides a rationale for the inclusion of kinase inhibitors counteracting EZH2 phosphorylation in combination chemotherapy aimed at increasing the therapeutic index.

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Half a century ago, the sedative thalidomide caused a serious drug disaster because of its teratogenicity and was withdrawn from the market. However, thalidomide, which has returned to the market, is now used for the treatment of leprosy and multiple myeloma (MM) under strict control. The mechanism of thalidomide action had been a long-standing question. We developed a new affinity bead technology and identified cereblon (CRBN) as a thalidomide-binding protein. We found that CRBN functions as a substrate receptor of an E3 cullin-Ring ligase complex 4 (CRL4) and is a primary target of thalidomide teratogenicity. Recently, new thalidomide derivatives, called immunomodulatory drugs (IMiDs), have been developed by Celgene. Among them, lenalidomide (Len) and pomalidomide (Pom) were shown to exert strong therapeutic effects against MM. It was found that Len and Pom both bind CRBN-CRL4 and recruit neomorphic substrates (Ikaros and Aiolos). More recently it was reported that casein kinase 1a (Ck1a) was identified as a substrate for CRBN-CRL4 in the presence of Len, but not Pom. Ck1a breakdown explains why Len is specifically effective for myelodysplastic syndrome with 5q deletion. It is now proposed that binding of IMiDs to CRBN appears to alter the substrate specificity of CRBN-CRL4. In this review, we introduce recent findings on IMiDs.

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Multiple myeloma (MM) is a neoplastic plasma-cell disorder characterized by clonal proliferation of malignant plasma cells in the bone marrow microenvironment. Novel treatments such as proteasome inhibitors and immunomodulatory agents significantly prolong both progression free survival and overall survival (OS) in patients with MM. However, recent clinical data have indicated that it is difficult to eradicate all MM clones even with the administration of such novel agents. To overcome drug resistance (DR), further investigation of the mechanism underlying DR is required, and strategies to up-regulate, maintain, and restore drug sensitivity will become increasingly important in the clinical setting. The findings from basic research focusing on the microenvironment, genetic abnormalities, and signal transduction disturbances related to MM pathogenesis are excellent strategies for developing new agents. In addition, based on the improved OS over 10 years and the low continuation rate of standard therapy in frail patients, a stratified strategy has the potential to provide total therapy.

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The optimal treatment strategy for primary mediastinal large B-cell lymphoma (PMBL) remains unknown. We retrospectively analyzed 345 patients with newly diagnosed PMBL to identify prognostic factors and optimal treatments. Focusing on patients treated with cyclophosphamide, doxorubicin, vincristine, prednisolone, and rituximab (R-CHOP) (N=187), a higher International Prognostic Index (IPI) and the presence of pleural or pericardial effusion were identified as adverse prognostic factors for overall survival (OS) in patients treated with R-CHOP without consolidative radiation therapy (RT) [IPI: hazard ratio (HR), 4.23; 95% confidence interval (CI), 1.48-12.13; P=0.007; effusion: HR, 4.93; 95% CI, 1.37-17.69; P=0.015]. Combined with IPI and the presence of pleural or pericardial effusion for the stratification of patients treated with R-CHOP without RT, those with lower IPI and the absence of effusion comprised approximately onehalf of these patients and could be identified as curable [OS and progression free survival (PFS) at 4 years, 95% and 87%, respectively)] Taken together, our simple indicators of IPI and the presence of effusion could stratify patients with PMBL and thereby facilitate treatment selection.

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Elucidating the developmental pathway leading to erythrocytes and being able to isolate their progenitors is crucial to understanding and treating disorders of red cell imbalance such as anemia, myelodysplastic syndrome, and polycythemia vera. Endoglin (CD105) is a key marker for purifying mouse erythroid lineage-committed progenitors (EPs) from bone marrow. Herein, we show that human EPs can also be isolated from adult bone marrow. We identified three subfractions that possessed different expression patterns of CD105 and CD71 within the previously defined human megakaryocyte/erythrocyte progenitor (hMEP; Lineage-CD34⁺CD38⁺IL-3Rα^-CD45RA^-) population. Both CD71^-CD105^- and CD71⁺CD105^- MEPs, at least in vitro, retained bipotency for the megakaryocyte (MegK) and erythrocyte (E) lineages, although the latter sub-population had a differentiation potential skewed toward the E-lineage. Notably, the differentiation output of the CD71⁺CD105⁺ subset of cells within the MEP population was completely restricted to the E-lineage with the loss of MegK potential; thus, we termed CD71⁺CD105^- MEPs and CD71⁺CD105⁺ cells as E-biased MEPs (E-MEPs) and EPs, respectively. These previously unclassified populations may facilitate understanding of the molecular mechanisms governing human erythroid development and serve as potential therapeutic targets in disorders of the erythroid lineage.

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We analyzed 11 patients with multiple myeloma (MM) treated using denosumab in our institute. The median age was 69 years (range, 54-76 years), and 7 patients were male. Seven patients had presented with newly diagnosed MM. Four patients were initially treated with zoledronic acid, which was then later switched to denosumab. The median number of injections was 15 (range, 1-27). No patients developed skeletal-related events (SRE) during denosumab treatment. Hypocalcemia was defined as serum calcium levels below the baseline in all patients. To prevent hypocalcemia, 8 patients were administered oral calcium. The first course of denosumab injections in 9 patients resulted in more marked decreases in serum calcium concentrations than subsequent courses. Two patients discontinued denosumab after osteonecrosis of the jaw (ONJ) was suspected, but squamous cell carcinoma was later identified in one of these cases. Denosumab might be effective and safe for preventing SRE. Cautionary measurement of serum calcium concentrations and prophylactic supplementation with oral calcium are warranted to avoid hypocalcemia after the first denosumab injection. The possibility of ONJ also merits attention. The clinical diagnosis of ONJ should be considered based on performing appropriate histological analyses.

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The patient was a 62-year-old woman with CD5⁺ diffuse large B-cell lymphoma. Treatment with the R-CHOP regimen (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisolone) was started. On the eleventh day of the third cycle, headache and low grade fever developed. Her consciousness gradually deteriorated. Seven days after symptom onset, she was brought to the emergency department of our hospital. Cerebrospinal fluid (CSF) analysis revealed a white blood cell count of 25/μl, and a protein level of 188 mg/dl. Antibacterial and antiviral agents were administered based on a diagnosis of acute meningitis. She showed no improvement. We performed another lumbar puncture and intrathecal chemotherapy, a combination of methotrexate and dexamethasone, was administered because we suspected central nervous system involvement of lymphoma. She showed transient improvement. On day 12, we started the R-MPV regimen (rituximab, methotrexate, procarbazine, and vincristine). However, fever and disturbance of consciousness persisted. On day 20, we empirically started anti-tuberculosis treatment. Four days later, tubercle bacilli were confirmed by CSF culture after a 23-day incubation. We ultimately confirmed a diagnosis of tuberculous meningitis. Impaired cellular immunity in lymphoma patients increases the risk of tuberculosis. It is important to consider tuberculous meningitis in the differential diagnosis of a lymphoma patient presenting with meningitis.

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A 75-year-old woman presented with edema of the left leg in December 2012. On examination, there was a palpable 5-cm tumor in the left lower abdomen, and PET/CT showed lymphadenopathy of the tracheal, para-aortic, left iliac and inguinal regions with increased FDG uptake. We performed histopathological examination of the iliac lymph node and diagnosed diffuse large B-cell lymphoma (DLBCL), stage IIIA. The patient received 8 courses of R-CHOP chemotherapy and achieved a complete response. In April 2014, she noticed seven new painful erythematous vesicles <1 cm in size on the skin of the left lower abdominal region. Herpes zoster was suspected and valacyclovir was administered. However, this medication had no effect, and the vesicles enlarged and became nodular. Histopathological examination of one of the skin lesions revealed the infiltration of DLBCL and the diagnosis of zosteriform cutaneous recurrence of DLBCL was thus made. Skin lesions mimicking herpes zoster have been reported in certain types of hematological malignancies, and histopathological diagnosis should be performed in such cases.

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A 58-year-old female was diagnosed with Philadelphia chromosome positive chronic myeloid leukemia (CML) in blast crisis (BC) in 2004. The patient received imatinib, which quickly induced molecular remission, and subsequently underwent bone marrow transplantation (BMT) from an unrelated human leukocyte antigen (HLA)-identical donor. The post-transplant clinical course was essentially uneventful. In 2014, ten years after the BMT, the patient was admitted to our hospital complaining of lymphadenopathy, and blasts were observed in peripheral blood. The patient was diagnosed as having a CML relapse in myeloid BC, with leukemic infiltration in lymph nodes, and was treated with dasatinib. Subsequently, pleural effusion developed and nilotinib was administered, which induced normal blood counts without blasts and partial cytogenetic remission, one month after administration. Six months after the relapse, this patient underwent a second BMT from an HLA-matched unrelated donor. Recent studies have demonstrated the cumulative incidence of CML relapse more than five years after allogeneic hematopoietic stem cell transplantation (allo-HSCT) to be higher than in acute myeloid leukemia. Although rare, the possibility of late relapse should be considered in patients diagnosed with CML after allo-HSCT.

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A 63-year-old man with Bence Jones-κ multiple myeloma (MM) presented with renal impairment. First, we administered a bortezomib-containing regimen which is considered to be the first choice among therapeutic approaches for MM patients with renal failure. However, his condition was refractory to bortezomib, and the renal dysfunction worsened (creatinine 12.55mg/dl) necessitating the initiation of hemodialysis. Subsequently, we administered an adjusted dose of lenalidomide and dexamethasone. Dialysis could be discontinued after 3 cycles of lenalidomide therapy. After 4 cycles, he achieved a stringent complete response (sCR) with the creatinine level at 1.85mg/dl. This case suggests lenalidomide to be an effective drug for patients with multiple myeloma and renal impairment refractory to treatment with bortezomib.

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A 59-year-old man diagnosed with the chronic phase of chronic myeloid leukemia (CML) in June 2011 was started on dasatinib (100 mg/day). He had no signs of pleural effusion (PE) or right heart failure before treatment, but symptoms of PE and dyspnea (New York Heart Association class III) appeared in January 2013 and May 2014, respectively. Doppler transthoracic echocardiography and right heart catheterization revealed pulmonary arterial hypertension (PAH) with an estimated pulmonary artery systolic pressure (PASP) of 80 mmHg and estimated mean pulmonary artery pressure of 29 mmHg. Rheumatoid factor, antinuclear antibody, dsDNA antibody, and SCL70 were not elevated, and computed tomography confirmed the absence of a pulmonary embolism. Therefore, dasatinib-related PAH was diagnosed and treatment with this agent was discontinued. The PASP had decreased to 51 and 40 mmHg at one month and one year, respectively, after dasatinib discontinuation. This patient developed PAH while receiving dasatinib administration and only discontinuation of this agent improved his symptoms. The possibility that dasatinib can cause PAH must be considered before administering this agent to patients with CML.

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A 23-year-old woman presented with a persistent fever and shortness of breath. Computed tomography showed marked pericardial effusion, hepatosplenomegaly, and cervical and mediastinal lymph node swelling. Epstein-Barr virus (EBV) antibody titers were abnormally elevated, and the copy number of EBV-DNA was increased in peripheral blood. Based on these observations, she was diagnosed with chronic active EBV infection (CAEBV). The EBV-infected cells in her peripheral blood were CD4⁺T lymphocytes. Fever and pericardial effusion improved following treatment with a combination of prednisolone, etoposide, and cyclosporine; however, peripheral blood EBV-DNA levels remained high. The patient underwent allogeneic peripheral blood stem cell transplantation from an EBV-seronegative, HLA-matched sibling donor, with fludarabine and melphalan conditioning. The post-transplantation course was uneventful, except for mild skin acute graft-versus-host disease (grade 2). EBV-DNA became undetectable in peripheral blood 98 days post transplantation. She has since been in good health without disease recurrence. CAEBV is a potentially fatal disease caused by persistent EBV infection of T lymphocytes or natural killer cells, thus requiring prompt treatment and allogeneic transplantation. Pericardial effusion is rarely observed in CAEBV and can impede its diagnosis. Therefore, we should be aware that patients may present with marked pericardial effusion as an initial manifestation of CAEBV.

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A female diagnosed as having immune thrombocytopenic purpura (ITP) was found to be simultaneously suffering from monoclonal gammopathy of undetermined significance (IgGλ). Urine Bence-Jones protein was negative. During the course, plasma cells accounted for 21.6% of the bone marrow. Based on these clinical features in our case, the second disease was diagnosed as multiple myeloma (MM). Both ITP and MM were successfully treated with corticosteroids, bortezomib, lenalidomide with dexamethasone and eltrombopag olamine. MM with ITP may show the following features: 1) the great majority are IgG types, 2) λ chain types show marked light chain predominance when these two diseases appear simultaneously, 3) κ chain types are predominant in the cases with MM followed by ITP, and 4) MM cases with ITP are more often seen in Japan.

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A 59-year-old woman with anaplastic large cell lymphoma (ALCL), ALK-negative, was treated with brentuximab vedotin (BV) against relapse after 6 regimens of systemic chemotherapy and radiation. Despite achieving an initial response, skin lesions worsened after 11 courses. A skin biopsy after the development of resistance to BV confirmed loss of CD30 expression by the tumor cells, suggesting a possible cause of resistance. This case shows that down-regulation of CD30 does occur during BV treatment, resulting in resistance to this drug. Because of this possibility, in the future, expression of CD30 should be carefully monitored with extended use of BV against ALCL.

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Eltrombopag, a thrombopoietin (TPO) receptor agonist, is effective for treating refractory immune thrombocytopenia (ITP). However, the development of bone marrow fibrosis is a concern. A 78-year-old man was diagnosed with ITP in 2004. His platelet count did not increase after eltrombopag treatment initiation in 2014. However, anemia progressed, along with the presence of immature myelocytes, erythroblasts, and tear drop cells. At 8 months after initiating eltrombopag treatment, the patient underwent a bone marrow biopsy that showed grade 2 myelofibrosis. Hence, eltrombopag was discontinued. In our experience with this case indicates that careful observation is required while using TPO receptor agonists.

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