Takayasu Kato

Comprehensive analysis of genetic alterations and their prognostic impacts in adult acute myeloid leukemia patients.

To clarify the cooperative roles of recurrently identified mutations and to establish a more precise risk classification system in acute myeloid leukemia (AML), we comprehensively analyzed mutations in 51 genes, as well as cytogenetics and 11 chimeric transcripts, in 197 adult patients with de novo AML who were registered in the Japan Adult Leukemia Study Group AML201 study. We identified a total of 505 mutations in 44 genes, while only five genes, FLT3, NPM1, CEBPA, DNMT3A and KIT, were mutated in more than 10% of the patients. Although several cooperative and exclusive mutation patterns were observed, the accumulated mutation number was higher in cytogenetically normal AML and lower in AML with RUNX1-RUNX1T1 and CBFB-MYH11, indicating a strong potential of these translocations for the initiation of AML. Furthermore, we evaluated the prognostic impacts of each sole mutation and the combinations of mutations and/or cytogenetics, and demonstrated that AML patients could be clearly stratified into five risk groups for overall survival by including the mutation status of DNMT3A, MLL-PTD and TP53 genes in the risk classification system of the European LeukemiaNet. These results indicate that the prognosis of AML could be stratified by the major mutation status in combination with cytogenetics.

Reduced TET2 function leads to T-cell lymphoma with follicular helper T-cell-like features in mice

TET2 (Ten Eleven Translocation 2) is a dioxygenase that converts methylcytosine (mC) to hydroxymethylcytosine (hmC). TET2 loss-of-function mutations are highly frequent in subtypes of T-cell lymphoma that harbor follicular helper T (Tfh)-cell-like features, such as angioimmunoblastic T-cell lymphoma (30–83%) or peripheral T-cell lymphoma, not otherwise specified (10–49%), as well as myeloid malignancies. Here, we show that middle-aged Tet2 knockdown (Tet2gt/gt) mice exhibit Tfh-like cell overproduction in the spleen compared with control mice. The Tet2 knockdown mice eventually develop T-cell lymphoma with Tfh-like features after a long latency (median 67 weeks). Transcriptome analysis revealed that these lymphoma cells had Tfh-like gene expression patterns when compared with splenic CD4-positive cells of wild-type mice. The lymphoma cells showed lower hmC densities around the transcription start site (TSS) and higher mC densities at the regions of the TSS, gene body and CpG islands. These epigenetic changes, seen in Tet2 insufficiency-triggered lymphoma, possibly contributed to predated outgrowth of Tfh-like cells and subsequent lymphomagenesis. The mouse model described here suggests that TET2 mutations play a major role in the development of T-cell lymphoma with Tfh-like features in humans.

Hes1 suppresses acute myeloid leukemia development through FLT3 repression.

In leukemogenesis, Notch signaling can be up and downregulated in a context-dependent manner. The transcription factor hairy and enhancer of split-1 (Hes1) is well-characterized as a downstream target of Notch signaling. Hes1 encodes a basic helix–loop–helix-type protein, and represses target gene expression. Here, we report that deletion of the Hes1 gene in mice promotes acute myeloid leukemia (AML) development induced by the MLL–AF9 fusion protein. We then found that Hes1 directly bound to the promoter region of the FMS-like tyrosine kinase 3 (FLT3) gene and downregulated the promoter activity. FLT3 was consequently upregulated in MLL–AF9-expressing immortalized and leukemia cells with a Hes1- or RBPJ-null background. MLL–AF9-expressing Hes1-null AML cells showed enhanced proliferation and ERK phosphorylation following FLT3 ligand stimulation. FLT3 inhibition efficiently abrogated proliferation of MLL–AF9-induced Hes1-null AML cells. Furthermore, an agonistic anti-Notch2 antibody induced apoptosis of MLL–AF9-induced AML cells in a Hes1-wild type but not a Hes1-null background. We also accessed two independent databases containing messenger RNA (mRNA) expression profiles and found that the expression level of FLT3 mRNA was negatively correlated with those of HES1 in patient AML samples. These observations demonstrate that Hes1 mediates tumor suppressive roles of Notch signaling in AML development, probably by downregulating FLT3 expression.

Detection of the G17V RHOA mutation in angioimmunoblastic T-cell lymphoma and related lymphomas using quantitative allele-specific PCR.

Angioimmunoblastic T-cell lymphoma (AITL) and peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS) are subtypes of T-cell lymphoma. Due to low tumor cell content and substantial reactive cell infiltration, these lymphomas are sometimes mistaken for other types of lymphomas or even non-neoplastic diseases. In addition, a significant proportion of PTCL-NOS cases reportedly exhibit features of AITL (AITL-like PTCL-NOS). Thus disagreement is common in distinguishing between AITL and PTCL-NOS. Using whole-exome and subsequent targeted sequencing, we recently identified G17V RHOA mutations in 60–70% of AITL and AITL-like PTCL-NOS cases but not in other hematologic cancers, including other T-cell malignancies. Here, we establish a sensitive detection method for the G17V RHOA mutation using a quantitative allele-specific polymerase chain reaction (qAS-PCR) assay. Mutated allele frequencies deduced from this approach were highly correlated with those determined by deep sequencing. This method could serve as a novel diagnostic tool for 60–70% of AITL and AITL-like PTCL-NOS.

Clinical significance of disease-specific MYD88 mutations in circulating DNA in primary central nervous system lymphoma

Recent sequencing studies demonstrated the MYD88 L265P mutation in more than 70% of primary central nervous system lymphomas (PCNSL), and the clinical significance of this mutation has been proposed as diagnostic and prognostic markers in PCNSL. In contrast, mutational analyses using cell‐free DNAs have been reported in a variety of systemic lymphomas. To investigate how sensitively the MYD88 L265P mutation can be identified in cell‐free DNA from PCNSL patients, we carried out droplet digital PCR (ddPCR) and targeted deep sequencing (TDS) in 14 consecutive PCNSL patients from whom paired tumor‐derived DNA and cell‐free DNA was available at diagnosis. The MYD88 L265P mutation was found in tumor‐derived DNA from all 14 patients (14/14, 100%). In contrast, among 14 cell‐free DNAs evaluated by ddPCR (14/14) and TDS (13/14), the MYD88 L265P mutation was detected in eight out of 14 (ddPCR) and in 0 out of 13 (TDS) samples, implying dependence on the detection method. After chemotherapy, the MYD88 L265P mutation in cell‐free DNAs was traced in five patients; unexpectedly, the mutations disappeared after chemotherapy was given, and they remained undetectable in all patients. These observations suggest that ddPCR can sensitively detect the MYD88 L265P mutation in cell‐free DNA and could be used as non‐invasive diagnostics, but may not be applicable for monitoring minimal residual diseases in PCNSL.

A phase I|[sol]|II trial of intrabone marrow cord blood transplantation and comparison of the hematological recovery with the Japanese nationwide database

Intrabone marrow cord blood transplantation (IB-CBT) was proposed as a promising treatment modality to improve hematological recovery. However, clinical advantages of IB-CBT over conventional IV CBT have been unclear. We conducted a prospective single-center trial of IB-CBT to evaluate its safety and superiority in terms of hematological recovery. Fifteen adults with hematological malignancies were enrolled. A thawed and unwashed single cord blood unit was injected into the bilateral superior-posterior iliac crests under local anesthesia. Engraftments of neutrophils and platelets were achieved in 13 cases, with medians of 17 and 45 days, respectively. For the control, we extracted data from the Japanese nationwide database and compared the hematological recovery of contemporaneously transplanted 1135 CBT cases. Multivariate analysis revealed that IB-CBT enhanced platelet recovery (hazard ratio, 2.13; P=0.007), but neutrophil recovery did not differ significantly (hazard ratio, 1.70; P=0.19). Better donor chimerism was seen in the bone marrow of the ilium than of the sternum on day 14, suggesting that the local hematopoiesis at the injected site was established earlier than that at the remote bone marrow site. Collectively, IB-CBT was well tolerated and may enhance local engraftment, which promotes prompter platelet recovery than does IV-CBT.

Detection of the circulating tumor DNAs in angioimmunoblastic T- cell lymphoma

Recent genetic studies identified that the disease-specific G17V RHOA mutation, together with mutations in TET2, DNMT3A, and IDH2, is a hallmark of angioimmunoblastic T cell lymphomas (AITL). The diagnostic value of these mutations is now being investigated. Circulating tumor DNAs (ctDNAs) may offer a non-invasive testing for diagnosis and disease monitoring of cancers. To investigate whether these mutations are useful markers for ctDNAs in AITL and its related lymphomas, we performed targeted sequencing for TET2, RHOA, DNMT3A, and IDH2 in paired tumors and cell-free DNAs from 14 patients at diagnosis. Eighty-three percent of mutations detected in tumors were also observed in cell-free DNAs. During the disease course, mutations were detectable in cell-free DNAs in a refractory case, while they disappeared in a chemosensitive case. These data suggest that the disease-specific gene mutations serve as sensitive indicators for ctDNAs and may also be applicable for non-invasive monitoring of minimal residual diseases in AITL.

A nationwide survey of co-occurrence of malignant lymphomas and myelodysplastic syndromes/myeloproliferative neoplasms

Dear Editor, Co-occurrence of multiple hematologic malignancies in distinct lineages has been reported as rare cases. The diseases occur simultaneously in some cases, while they occur sequentially in others. Combinations of diseases are different among the cases: B-linage malignancies and T/NK-lineage malignancies, Bor T/NK-lineage malignancies and myeloid malignancies, and so on. Among them, co-occurrence of mature Band T/NK-lineage malignancies comprises composite lymphomas, which constitute 1–4 % of lymphoma [1]. Co-occurrence of malignant lymphomas and myeloid malignancies has also been experienced [2–4]. However, less information is available. To investigate the actual distribution of patients who developed both malignant lymphomas and myelodysplastic syndrome (MDS), myeloproliferative neoplasms (MPN), or idiopathic cytopenia of undetermined significance (ICUS), we conducted a nationwide survey in Japan. In the primary survey, we sent a short questionnaire about the experience of simultaneous or sequential development of malignant lymphomas and MDS, MPN, or ICUS to the institutions throughout Japan, registered as clinical training centers for hematology and pediatric hematology. The sequential development of lymphoid malignancies followed by myeloid malignancies was excluded, because such cases are defined as therapy-related malignancies. The secondary survey was conducted focusing on the detailed clinical information. This study was approved by the ethics committee in the University of Tsukuba Hospital. Questionnaire was sent to the 491 institutes, of which 241 returned the answer. The secondary questionnaire was sent to the 39 institutes that reported experiences of the applicable patients. In total, 72 cases, having both malignant lymphomas and MDS/MPN/ICUS, were reported. Forty five cases simultaneously developed malignant lymphomas and myeloid malignancies, while 27 sequentially developed myeloid malignancies and then malignant lymphomas. Detailed information was available for 45 cases (simultaneous, 26 cases; sequential, 19 cases) (Table 1, Supplementary Table 1, 2). The median age of the patients was 69 years (simultaneous, 69 years; sequential 69 years) (Table 1). History of chemotherapy and/or radiotherapywas found in three out of 45 cases (simultaneous, 3/26 [11.5 %]; sequential, 0/19 [0 %]) (Table 1). The most frequent combination was diffuse large B cell lymphomas (DLBCL) and any subtypes of MDS, which was found in up to 15 out of 45 cases (33.3 %) (simultaneous, 8/26 [30.8 %]; sequential, 7/19 [36.8 %]) (Table 1, Supplementary Table 1, 2). The combination of follicular lymphoma (FL) and any subtypes of MDS was found in four out of 45 cases (8.9 %), whereas it was confined to the simultaneous cases (simultaneous, 4/26 [15.4 %]; sequential, 0/9 [0 %]) (Table 1, Supplementary Table 1, 2). Electronic supplementary material The online version of this article (doi:10.1007/s00277-016-2612-3) contains supplementary material, which is available to authorized users.

Blastic plasmacytoid dendritic cell neoplasm arising from clonal hematopoiesis

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare subtype of myeloid neoplasm. Clonal evolution in the development of BPDCN remains to be elucidated. In the present study, we examined clonal evolution in a case of BPDCN by analyzing the distribution of gene mutations in tumor cells and non-tumor blood cells. The p.D1129fs and p.K1005fs TET2 mutations, p.P95H SRSF2 mutation, and p.L287fs NPM1 mutation were identified in a skin tumor at diagnosis and peripheral blood mononuclear cells at relapse. Notably, the p.D1129fs TET2 and p.L287fs NPM1 mutations were observed only in tumor cells, while the p.K1005fs TET2 and p.P95H SRSF2 mutations were found in both tumor cells and non-tumor blood cells. Recent genetic studies have suggested that some blood cancers may originate from clonal hematopoiesis, harboring somatic mutations. In the present case, the data suggest that BPDCN originated from clonal hematopoiesis with the p.K1005fs TET2 and p.P95H SRSF2 mutations via acquisition of the additional p.D1129fs TET2 and p.L287fs NPM1 mutations.

A single institutional retrospective evaluation for younger patients with primary central nervous lymphomas on a modified R-MPV regimen followed by radiotherapy and high dose cytarabine

We conducted a retrospective analysis of patients younger than 60 years (N = 10, median age 54.5) with newly diagnosed primary central nervous system lymphoma (PCNSL) at the University of Tsukuba Hospital from January 2008 to November 2016. All the patients were scheduled to receive a single regimen without registration to any clinical trials. This was based on a phase 2 study by Memorial Sloan-Kettering Cancer Center (MSKCC); induction chemotherapy with rituximab, methotrexate, procarbazine, and vincristine (R-MPV) (five to seven cycles), followed by whole-brain radiotherapy (rd-WBRT) (23.4 Gy) and two high-dose cytarabine (HD-AC) cycles as a consolidation. The median age was 54.5 years, and median follow up duration was 33.1 months. The 3-year overall survival (OS) and progression-free survival (PFS) were 69% (95% CI 31-89%) and 56% (95% CI 20-81%). The median OS and PFS were not reached, respectively. Acute and delayed toxicities were manageable. In particular, OS and PFS of seven patients who achieved CR by the R-MPV induction chemotherapy were significantly superb (3-year OS, 100%; 3-year PFS, 80%), implying that a large proportion of patients in CR after the completion of this treatment may achieve durable disease control. On the other hand, all of the three patients who had progressive disease during this treatment died of disease progression within 1 year after diagnosis without achieving CR. Identifying the patients having a risk of failure in the R-MPV induction chemotherapy is important, and may allow us to consider a potentially more effective regimen.