Hematopoietic stem cell transplantation (HSCT) plays an important role in treating younger patients with acute myeloid leukemia (AML). Reduced-intensity conditioning regimens allow increased use of allogeneic HSCT for older patients. Current HSCT decisions in patients with AML are being made according to cytogenetic analysis results. A more comprehensive and detailed understanding of the genetic and epigenetic changes that are related to the pathogenesis of AML is required for better classification of risk and for improving approaches to therapy as they pertain to future HSCT decisions.

Chromosomal translocations at the MLL gene generate chimeric genes of MLL and its partner, thereby causing aggressive acute leukemia. The sequence of the MLL gene was revealed in the early 1990s. Several years later, murine leukemia models using genetic engineering or retroviral gene transfer techniques were established, which spurred basic research on this disease. Since then, a series of technological breakthroughs such as DNA arrays, shRNA library screening, and deep sequencing have provided us with a much deeper understanding of the molecular basis of leukemogenesis caused by MLL mutations. Based on the understanding of these molecular mechanisms, several small molecules that inhibit critical processes of leukemogenesis have been developed as molecularly-targeted drug candidates. I herein review the rapid progress in this research on the molecular mechanisms of MLL-associated leukemia.

In addition to morphological and histocytochemical analyses of acute myeloid leukemia (AML), data on cytogenetic abnormalities and somatic mutations are used for classification of AML. The risk stratification based on these examinations facilitates determining the treatment strategy for AML. Cytogenetic risk category definitions by the Southwest Oncology Group (SWOG), Cancer and Leukemia Group B (CALGB), and The Medical Research Council (MRC) classify AML patients into favorable, intermediate, and adverse groups. Approximately 80% of patients in the intermediate group have a normal karyotype and the importance of molecular genetic analyses in these patients is increasing. Somatic mutations of NPM1, CEBPA, and FLT3 are known to be related to the prognosis of AML patients. The European LeukemiaNet (ELN) introduced risk stratification for AML patients based on cytogenetic abnormalities and NPM1, CEBPA, and FLT3 mutations. This risk stratification can be used to select only chemotherapy or chemotherapy with allogeneic hematopoietic stem cell transplantation as consolidation therapy for individual AML patients. Development of molecular targeted therapies against FLT3 or IDH mutations is in progress and these novel therapies are expected to contribute to improving the prognosis of AML patients.

Leukemic stem cells (LSCs) were originally identified in acute myeloid leukemia (AML) cases by using xenograft models, as a distinct cell population that can initiate leukemia in immunodeficient mice. Since then, many efforts have been made to clarify the identities of LSCs and other cancer stem cells in various cancer types, to both understand their biology and determine the most suitable targets for anti-cancer therapies. LSCs were identified as existing in the immature CD34+CD38- leukemic population in most AML cases, and these cells were found to share some features with normal hematopoietic stem cells. On the other hand, recent studies have shown that in childhood acute lymphoblastic leukemia (ALL), LSCs exist among B-lineage-committed progenitors expressing CD19. In contrast to AML, in which LSCs generate leukemic cells in a hierarchical order with LSCs at the top, leukemia propagation in childhood ALL is better explained by a stochastic model. In B-precursor ALL, LSCs form via acquisition of additional genetic change(s) in CD19+ B-lineage progenitor cells with self-renewing capacity. These LSCs possess a growth advantage and the capacity to produce progeny with the same ability as the LSCs. Identification of genetic and cellular targets in leukemic transformation is necessary to develop improved anti-cancer therapies.

Arsenic metabolism affects the susceptibility of humans to arsenic toxicity; therefore, clarification of the factors associated with individual variations in arsenic metabolism is an important task. Genetic polymorphisms such as single nucleotide polymorphisms (SNPs) in arsenic (+3 oxidation state) methyltransferase (AS3MT), which can methylate arsenic compounds using S-adenosyl-l-methionine (AdoMet), have been reported to modify arsenic methylation. In this review, we summarize studies conducted by us in Vietnam and by others on the association of AS3MT genetic polymorphisms with arsenic metabolism as well as human health effects. Most of the SNPs in AS3MT showed inconsistent results in terms of genotype-dependent differences in arsenic metabolism among the studies. However, AS3MT 12390 (rs3740393) and 14458 (rs11191439) were consistently related to arsenic methylation regardless of the study population: AS3MT 12390 (rs3740393) affected the second step of methylation of arsenic, whereas 14458 (rs11191439) affected the first methylation step.

Naturally occurring inorganic arsenic is known to increase the risk of cancers of the skin and several other organs, including the urinary bladder, lung, and liver. Epidemiological studies have also indicated that gestational arsenic exposure is associated with increased incidences of cancers in several organs, including the bladder and liver, in adulthood. Previous studies have shown that epigenetic changes are involved in arsenic-induced carcinogenesis. Among epigenetic changes, DNA methylation changes that are specific to arsenic-induced tumors would be useful for distinguishing such tumors from tumors induced by other factors and for clarifying arsenic carcinogenesis. It has been reported that gestational arsenic exposure of C3H mice, whose males tend to spontaneously develop liver tumors, increases the incidence of tumors in the male offspring. Using the same experimental protocol, we found a number of regions where the DNA methylation status was altered in the liver tumors compared with the normal liver tissues by the methylated DNA immunoprecipitation (MeDIP)-CpG island microarray method. Among such regions, we demonstrated using real-time methylation-specific PCR and bisulfite sequencing that a gene body region of the oncogene Fosb underwent alteration in DNA methylation following gestational arsenic exposure. We also showed that the Fosb expression level significantly increased following gestational arsenic exposure. These findings suggest that the DNA methylation status of the Fosb region is implicated in tumor augmentation and can also be utilized for characterizing tumors induced by gestational arsenic exposure.

We report a 42-year-old man with hereditary medullary thyroid cancer (multiple endocrine neoplasia, MEN2A/familial medullary thyroid carcinoma, FMTC), which was diagnosed at the time of tumor recurrence. He had a past history of a left thyroidectomy with neck dissection 7 years previously. A RET gene analysis revealed a point mutation (codon 618), and we diagnosed him as having hereditary medullary thyroid cancer. We resected the recurrent tumor in the right thyroid lobe together with performing a right lateral and central neck dissection. A RET gene analysis should be performed for patients with medullary thyroid cancer. When a RET gene mutation is present, a total thyroidectomy must be performed for the medullary thyroid cancer.

A 19-year-old Japanese woman had been diagnosed with diabetes at the age of 9 years. She had a strong family history of diabetes, and genetic screening showed she had maturity-onset diabetes of the young type 3 (MODY3). Ultrasonography of the liver and magnetic resonance imaging showed multiple nodules consistent with hepatocellular adenoma (HA). Biopsy of the liver tumors revealed hepatocyte nuclear factor (HNF) 1α-inactivated HA. HA is known as a MODY3-related disease due to mutations in HNF1α. We present the first report of HA associated with MODY3 in Japan.

Primary effusion lymphoma (PEL) is a large B-cell lymphoma proliferating only in the body cavity effusion. It often occurs in advanced AIDS patients and is associated with human herpesvirus 8 (HHV-8). On the other hand, HHV-8 negative effusion lymphoma, which is different from PEL in many ways, has also been reported and is referred to as HHV8-unrelated PEL-like lymphoma. This lymphoma is very rare and its clinical characteristics have not yet been fully clarified. We therefore report an HIV seronegative elderly patient with HHV8-unrelated PEL-like lymphoma. An 89-year-old woman was admitted to our hospital due to general fatigue and dyspnea. The patient presented with left pleural effusion in the absence of lymphadenopathy and tumor masses. The pathological examination of the pleural effusion showed proliferation of atypical large lymphoid cells, which were positive for CD19, CD20, CD10, CD38, CD7, BCL2 and BCL6 but negative for CD5, CD30, MUM1, surface immunoglobulin, HHV-8 and EBV. Cytogenetic analysis showed a complex karyotype including t(8;14)(q24;q32). The pleural effusion decreased in response to monotherapy with oral low-dose etoposide, but recurrence was detected 7 months later. Rituximab was transiently effective for the recurrent pleural effusion, but the patient died of lymphoma exacerbation 13 months after the diagnosis.

Recent advances in sequencing technologies led us to the discovery of mutations in epigenetic and metabolic regulators in peripheral T-cell lymphoma (PTCL). Frequencies of these mutations were found to be especially high in PTCL with features of follicular helper T cells (TFH). These mutations are also identifiable in myeloid malignancies as well as PTCL, suggesting that abnormalities in epigenetic and metabolic pathways are likely to be the fundamental mechanisms underlying various types of hematologic malignancies. The downstream pathways of these mutations have been extensively analyzed in myeloid malignancies, but have yet to be elucidated in PTCL. We clarified a downstream pathway of TET2 mutations in PTCL by analyzing TET2 knockdown mice.

Mutations in isocitrate dehydrogenase (IDH) 1 and 2 are frequently observed in acute myeloid leukemia (AML), glioma, and many other cancers. While wild-type IDHs mediate exchanges between isocitrate and α-ketoglutarate (α-KG), mutant IDHs convert α-KG to oncometabolite 2-hydroxyglutarate (2-HG), which causes dysregulation of a set of α-KG-dependent dioxygenases such as TET, histone demethylase and others. Because mutant IDH has no necessary functions in normal cells, inhibitors directed against mutant IDH are not expected to have the side effects as anti-cancer agents. To determine whether mutant IDH enzymes are valid targets for cancer therapy, we created a mouse model of mutant IDH2-dependent AML. By using a combination of AML model mice with cre-loxp, we conditionally deleted mutant IDH2 from AML mice, which resulted in the loss of leukemia stem cells and significantly delayed the progression of AML. These results indicate that mutant IDHs are promising targets for anticancer therapy.

Stem cell transplantation in conjunction with therapeutic agents such as proteasome inhibitors and immunomodulatory drugs can dramatically improve response rates and the prognoses of patients with multiple myeloma (MM). However, most patients with MM are considered to be incurable, and relapse owing to minimal residual disease (MRD) is the main cause of death among these patients. We utilized a deep sequencing method, which employs consensus primers and next-generation sequencing (NGS), to amplify and sequence all rearranged immunoglobulin gene segments present in a myeloma clone. This technique has been shown to have 1-2 log greater sensitivity than both allele-specific oligonucleotide-polymerase chain reaction (ASO-PCR) (sensitivity 10(-5)) and multiparameter flow cytometry (MFC) (sensitivity at least 10(-4)). To investigate the value of sensitive detection of MRD in autograft by NGS, we compared progression-free survival (PFS) in 11 MRDNGS(-) cases (Group 1) with that in 12 MRDNGS(+) cases in which MRD was not detected by ASO-PCR (MRDASO(-)) (Group 2). Neither group received any post-ASCT therapy. Group 1 showed a better PFS than Group 2 (P=0.027). MRD-negativity in autografts, as revealed by NGS, is more closely associated with durable remission of MM than that revealed by ASO-PCR.

In recent years, attention has been drawn to aberrant epigenetics as well as coding gene mutations in cancers. DNA methylation, histone acetylation and methylation, and micro RNA (miRNA) are included in the field of epigenetics. miRNAs are small RNAs of only 19-25 bases in length which do not encode protein but do they control gene expression by destroying mRNA or inhibiting translation. In multiple myeloma (MM), several miRNA expressions were markedly decreased, while in contrast their target genes, associated with apoptosis, the cell cycle and DNA methylation, were markedly increased. Negative correlations were found between miRNA and target genes expressions. The miR-34 family in itself was methylated, and expression was epigenetically controlled. miRNA and other epigenetic mechanisms underlie network formation, thought to be associated with MM progression. Thus, examining miRNA of MM is currently an important issue in terms of predicting patient outcomes and developing novel therapies.

Myeloproliferative neoplasm (MPN) variants are defined as relatively uncommon myeloid neoplasms which do not meet the criteria for either classical MPN or myelodysplastic syndrome. Due to the lack of specific markers, it has been challenging to accurately diagnose these malignant diseases. Recent studies have revealed new genetic abnormalities in MPN variants. These research advances are anticipated to open new approaches to not only achieving accurate diagnosis but also novel therapeutic options for these diseases.

Mutations in the JAK2 gene are thought to underlie the development of chronic myeloproliferative neoplasms (cMPN). Indeed, ≥95% of polycythemia vera patients, and half or more of essential thrombocythemia and primary myelofibrosis (PMF) patients, harbor the JAK2V617F mutation. Besides the JAK2V617F mutation, the JAK2 exon 12 deletion, the MPLW515L/K, and CALR mutation have been discovered and shown to be involved in the pathogenesis of these diseases. Based on these advancements in the study of cMPN, the JAK2 inhibitor was developed as a new therapy for PMF. Moreover, recent advancements in our ability to diagnose cMPN have paralleled the development of large clinical trials for patients with cMPN. This article provides explanatory information from these large clinical trials that is useful for the actual clinical practice of caring for patients with cMPN in Japan.

We assessed herein the post-operative lymph node metastasis in head and neck cancer, using the One-step nucleotide amplification (OSNA) method targeting matrix metalloproteinase 7 (MMP-7). Compared with the pathological test, the molecular biological test revealed more lymph node metastasis, resulting in poor prognosis. Six cases, of which the number of lymph node metastasis was the same between pathological and molecular biological test, survived. On the other hand, three of four cases, in which number of lymph node metastasis in the molecular biological test were larger than the pathological test, died from metastasis. We concluded that the pathological test underestimated metastasis, and OSNA with MMP-7 was useful for the prediction of post-operative lymph node metastasis.

A 39-year-old man visited our department complaining of general malaise and appetite loss. He presented with anemia and marked thrombocythemia; his plasma transforming growth factor (TGF)-b concentration was markedly increased and his thrombopoietin (TPO)concentration was decreased. Since the patient's disease had progressed to acute myeloid leukemia (AML) with an increase in the peripheral blast count, he was diagnosed with AML along with t(3;3) (q21;q26.2) through a bone marrow aspiration sample. Remission induction therapy was performed using idarubicin/cytarabine. The patient achieved complete remission. His platelet count returned to the normal range, plasma TGF-b concentration decreased, and serum TPO concentration increased. The patient was treated with azacitidine as post-remission therapy for bone marrow transplantation, following which he underwent allogeneic hematopoietic cell transplantation.