Tadashi Miike

TET2 is essential for survival and hematopoietic stem cell homeostasis.

Ten-Eleven-Translocation 2 (TET2) is an enzyme that catalyzes the conversion of 5-methylcytosine into 5-hydroxymethylcytosine (5-hmC) and thereby alters the epigenetic state of DNA; somatic loss-of-function mutations of TET2 are frequently observed in patients with diverse myeloid malignancies. To study the function of TET2 in vivo, we analyzed Ayu17-449 (TET2trap) mice, in which a gene trap insertion in intron 2 of TET2 reduces TET2 mRNA levels to about 20% of that found in wild-type (WT) mice. TET2trap/trap mice were born at Mendelian frequency but died at a high rate by postnatal day 3, indicating the essential role of TET2 for survival. Loss of TET2 results in an increase in the number of hematopoietic stem cells (HSCs)/progenitors in the fetal liver, and TET2trap/trap HSCs exhibit an increased self-renewal ability in vivo. In competitive transplantation assays, TET2trap/trap HSCs possess a competitive growth advantage over WT HSCs. These data indicate that TET2 has a critical role in survival and HSC homeostasis.

Loss-of-TET2 has dual roles in murine myeloproliferative neoplasms: disease sustainer and disease accelerator

Acquired mutations of JAK2 and TET2 are frequent in myeloproliferative neoplasms (MPNs). We examined the individual and cooperative effects of these mutations on MPN development. Recipients of JAK2V617F cells developed primary myelofibrosis-like features; the addition of loss of TET2 worsened this JAK2V617F-induced disease, causing prolonged leukocytosis, splenomegaly, extramedullary hematopoiesis, and modestly shorter survival. Double-mutant (JAK2V617F plus loss of TET2) myeloid cells were more likely to be in a proliferative state than JAK2V617F single-mutant myeloid cells. In a serial competitive transplantation assay, JAK2V617F cells resulted in decreased chimerism in the second recipients, which did not develop MPNs. In marked contrast, cooperation between JAK2V617F and loss of TET2 developed and maintained MPNs in the second recipients by compensating for impaired hematopoietic stem cell (HSC) functioning. In-vitro sequential colony formation assays also supported the observation that JAK2V617F did not maintain HSC functioning over the long-term, but concurrent loss of TET2 mutation restored it. Transcriptional profiling revealed that loss of TET2 affected the expression of many HSC signature genes. We conclude that loss of TET2 has two different roles in MPNs: disease accelerator and disease initiator and sustainer in combination with JAK2V617F.

Calreticulin mutant mice develop essential thrombocythemia that is ameliorated by the JAK inhibitor ruxolitinib

Mutations of calreticulin (CALR) are detected in 25–30% of patients with essential thrombocythemia (ET) or primary myelofibrosis and cause frameshifts that result in proteins with a novel C-terminal. We demonstrate that CALR mutations activated signal transducer and activator of transcription 5 (STAT5) in 293T cells in the presence of thrombopoietin receptor (MPL). Human megakaryocytic CMK11-5 cells and erythroleukemic F-36P-MPL cells with knocked-in CALR mutations showed increased growth and acquisition of cytokine-independent growth, respectively, accompanied by STAT5 phosphorylation. Transgenic mice expressing a human CALR mutation with a 52 bp deletion (CALRdel52-transgenic mice (TG)) developed ET, with an increase in platelet count, but not hemoglobin level or white blood cell count, in association with an increase in bone marrow (BM) mature megakaryocytes. CALRdel52 BM cells did not drive away wild-type (WT) BM cells in in vivo competitive serial transplantation assays, suggesting that the self-renewal capacity of CALRdel52 hematopoietic stem cells (HSCs) was comparable to that of WT HSCs. Therapy with the Janus kinase (JAK) inhibitor ruxolitinib ameliorated the thrombocytosis in TG mice and attenuated the increase in number of BM megakaryocytes and HSCs. Taken together, our study provides a model showing that the C-terminal of mutant CALR activated JAK-STAT signaling specifically downstream of MPL and may have a central role in CALR-induced myeloproliferative neoplasms.

TET2 mutation in diffuse large B-cell lymphoma

Ten-eleven translocation-2 (TET2) mutation is frequently observed in myeloid malignancies, and loss-of-function of TET2 is essential for the initiation of malignant hematopoiesis. TET2 mutation presents across disease entities and was reported in lymphoid malignancies. We investigated TET2 mutations in 27 diffuse large B-cell lymphoma (DLBCL) patients and found a frameshift mutation in 1 case (3.7%). TET2 mutation occurred in some populations of DLBCL patients and was likely involved in the pathogenesis of their malignancies.

Surrounding Gastric Mucosa Findings Facilitate Diagnosis of Gastric Neoplasm as Gastric Adenoma or Early Gastric Cancer

Background and Aim. It is difficult to master the skill of discriminating gastric adenoma from early gastric cancer by conventional endoscopy or magnifying endoscopy combined with narrow-band imaging, because the colors and morphologies of these neoplasms are occasionally similar. We focused on the surrounding gastric mucosa findings in order to determine how to discriminate between early gastric cancer and gastric adenoma by analyzing the characteristics of the gastric background mucosa. Methods. We retrospectively examined 146 patients who underwent endoscopic submucosal dissection for gastric neoplasm between October 2009 and January 2015. The boundary of atrophic gastritis was classified endoscopically according to the Kimura-Takemoto classification system. Of 146 lesions, 63 early gastric cancers and 21 gastric adenomas were ultimately evaluated and assessed. Results. Almost all gastric adenomas were accompanied by open-type gastritis, whereas 47 and 16 early gastric cancers were accompanied by open-type and closed-type gastritis, respectively (p = 0.037). Conclusions. The evaluation of the boundary of atrophic gastritis associated with gastric neoplasms appears to be useful for discrimination between early gastric cancer and gastric adenoma. When gastric neoplasm is present in the context of surrounding localized gastric atrophy, gastric cancer is probable but not certain.

TET2 Mutation in Adult T-Cell Leukemia/Lymphoma

Loss-of-function of ten-eleven translocation-2 (TET2) is a common event in myeloid malignancies, and plays pleiotropic roles, including augmenting stem cell self-renewal and skewing hematopoietic cells to the myeloid lineage. TET2 mutation has also been reported in lymphoid malignancies; 5.7～12% of diffuse large B-cell lymphomas and 18～83% of angioimmunoblastic T-cell lymphomas had TET2 mutations. We investigated TET2 mutations in 22 adult T-cell leukemia/lymphoma (ATLL) patients and identified a missense mutation in 3 cases (14%). TET2 mutation occurred in a number of ATLL patients and was likely involved in their leukemogenesis.

Gene expression profiling of loss of TET2 and/or JAK2V617F mutant hematopoietic stem cells from mouse models of myeloproliferative neoplasms.

Myeloproliferative neoplasms (MPNs) are clinically characterized by the chronic overproduction of differentiated peripheral blood cells and the gradual expansion of malignant intramedullary/extramedullary hematopoiesis. In MPNs mutations in JAK2 MPL or CALR are detected mutually exclusive in more than 90% of cases [1], [2]. Mutations in them lead to the abnormal activation of JAK/STAT signaling and the autonomous growth of differentiated cells therefore they are considered as “driver” gene mutations. In addition to the above driver gene mutations mutations in epigenetic regulators such as TET2 DNMT3A ASXL1 EZH2 or IDH1/2 are detected in about 5%–30% of cases respectively [3]. Mutations in TET2 DNMT3A EZH2 or IDH1/2 commonly confer the increased self-renewal capacity on normal hematopoietic stem cells (HSCs) but they do not lead to the autonomous growth of differentiated cells and only exhibit subtle clinical phenotypes [[4], [6], [7], [8],5]. It was unclear how mutations in such epigenetic regulators influenced abnormal HSCs with driver gene mutations how they influenced the disease phenotype or whether a single driver gene mutation was sufficient for the initiation of human MPNs. Therefore we focused on JAK2V617F and loss of TET2—the former as a representative of driver gene mutations and the latter as a representative of mutations in epigenetic regulators—and examined the influence of single or double mutations on HSCs (Lineage−Sca-1+c-Kit+ cells (LSKs)) by functional analyses and microarray whole-genome expression analyses [9]. Gene expression profiling showed that the HSC fingerprint genes [10] was statistically equally enriched in TET2-knockdown-LSKs but negatively enriched in JAK2V617F–LSKs compared to that in wild-type-LSKs. Double-mutant-LSKs showed the same tendency as JAK2V617F–LSKs in terms of their HSC fingerprint genes but the expression of individual genes differed between the two groups. Among 245 HSC fingerprint genes 100 were more highly expressed in double-mutant-LSKs than in JAK2V617F–LSKs. These altered gene expressions might partly explain the mechanisms of initiation and progression of MPNs which was observed in the functional analyses [9]. Here we describe gene expression profiles deposited at the Gene Expression Omnibus (GEO) under the accession number GSE62302 including experimental methods and quality control analyses.

Efficacy and safety of sofosbuvir and ledipasvir in Japanese patients aged 75 years or over with hepatitis C genotype 1

AIM To evaluate the efficacy and safety of a regimen containing sofosbuvir (SOF) and ledipasvir (LDV) in Japanese patients aged ≥ 75 years with hepatitis C genotype 1. METHODS This multicenter, retrospective study consisted of 246 Japanese patients with HCV genotype 1 at nine centers in Miyazaki prefecture in Japan. Demographic, clinical, virological, and adverse effects (AE)-related data obtained during and after SOF/LDV therapy were collected from medical records. These patients were divided into two groups, younger (aged < 75 years) and elderly (aged ≥ 75 years). Virological data and AEs were analyzed by age group. RESULTS The sustained virological response (SVR) rates at 12 wk after treatment were 99.2%, 99.4%, and 98.7% in the overall population and in patients aged < 75 and ≥ 75 years, respectively. Common AEs during therapy were headache, pruritus, constipation, and insomnia. These occurred in fewer than 10% of patients, and their incidence was not significantly different between the younger and elderly groups. Two patients discontinued treatment, one due to a skin eruption and the other due to cerebral bleeding. CONCLUSION Compared with younger patients, elderly patients had a similar virological response and tolerance to SOF/LDV therapy.

Differences in Hematological and Clinical Features Between Essential Thrombocythemia Cases With JAK2- or CALR-Mutations

Yoko Kubuki, M.D., Kotaro Shide, M.D., Takuro Kameda, M.D., Takumi Yamaji, M.D., Masaaki Sekine, M.D., Ayako Kamiunten, M.D., Keiichi Akizuki, M.D., Haruko Shimoda, M.D., Yuki Tahira, M.D., Kenichi Nakamura, M.D., Hiroo Abe, M.D., Tadashi Miike, M.D., Hisayoshi Iwakiri, M.D., Yoshihiro Tahara, M.D., Mitsue Sueta, M.D., Kanna Hashimoto, M.D., Shojiro Yamamoto, M.D., Satoru Hasuike, M.D., Tomonori Hidaka, M.D., Kenji Nagata, M.D., Akira Kitanaka, M.D., and Kazuya Shimoda, M.D. Department of Transfusion and Cell Therapy, University of Miyazaki Hospital; Department of Gastroenterology and Hematology, Faculty of Medicine, University of Miyazaki; Oncology Unit, University of Miyazaki Hospital; Liver Disease Center, University of Miyazaki Hospital, Miyazaki, Japan

Prediction of Sustained Virological Response to Telaprevir/Simeprevir-Based Triple Therapy in Patients with Genotype 1 Hepatitis C Virus Using Super-Early Viral Response within 2 Weeks

Objective: Rapid virological response (RVR), defined as undetectable serum hepatitis C virus (HCV) RNA at week 4, is a useful predictor of sustained virological response (SVR) to peginterferon (PEG-IFN) plus ribavirin (RBV) therapy and protease inhibitor (telaprevir (TVR)/simeprevir (SMV)) based triple therapy for patients infected with genotype 1 HCV. The aim of this study was to predict SVR using viral response within 2 weeks of therapy initiation. Methods: Fifty-two HCV genotype 1b patients with high viral loads treated with protease inhibitor (TVR/SMV)- based triple therapy were analysed. Thirty-seven patients were treated with TVR-based triple therapy and 15 with SMV-based triple therapy. HCV RNA levels were measured at the following points: the day of therapy initiation, at days 1 and 3, and at weeks 1 and 2. Results: SVR was achieved in 87% (45/52) of patients. There was no difference in SVR rate between the TVRbased triple therapy group (92%) and the SMV-based triple therapy group (73%) (P=0.1726). Univariate analysis of contributors to SVR showed a significant effect of liver fibrosis, platelet count, aspartate transaminase, α-fetoprotein in terms of pre-treatment factors, and HCV RNA load at week 2, reduction of HCV RNA at day 1 and week 2, RVR, and PEG-IFN adherence in terms of on-treatment factors. By multivariate analysis, platelet count and HCV RNA load at week 2 were independently associated with high SVR rate. Conclusion: HCV RNA level at week 2 was the most useful predictor of SVR after TVR/SMV-based triple therapy in patients with genotype 1 HCV.