論文

This retrospective study examined the differences in the prognostic impact of the haematopoietic cell transplantation-specific comorbidity index (HCT-CI) on transplant outcomes by disease status and time from transplant in allogeneic haematopoietic stem cell transplantation (HSCT) recipients at a Japanese transplant centre. Of 187 patients, nonrelapse mortality (NRM) at 3 years was 9.6, 21.2 and 27.8% in the low-risk (score 0), intermediate-risk (score 1-2) and high-risk (score > or =3) HCT-CI groups, respectively (P=0.03). The corresponding overall survival (OS) at 3 years was 70.1, 60.5 and 38.9%, respectively (P<0.01). In multivariate analyses, high-risk HCT-CI significantly predicted higher NRM (relative risk, (RR) 2.44 (95% confidence interval, (CI) 1.02-5.85); P=0.04) and worse OS (RR 2.02 (95% CI 1.15-3.54); P=0.01). In the subgroup analysis according to disease status, the HCT-CI was associated with OS (P<0.01) and NRM (P=0.07) in patients with low-risk diseases, but not in those with high-risk diseases. Within patients who survived without relapse >1 year after HSCT, the HCT-CI did not predict OS (P=0.59) or NRM (P=0.31). These findings can be useful to determine the role of pretransplant comorbidity in allogeneic HSCT.

Despite the clinical impact of DNMT3A mutation on acute myeloid leukaemia, the molecular mechanisms regarding how this mutation causes leukaemogenesis in vivo are largely unknown. Here we show that, in murine transplantation experiments, recipients transplanted with DNMT3A mutant-transduced cells exhibit aberrant haematopoietic stem cell (HSC) accumulation. Differentiation-associated genes are downregulated without accompanying changes in methylation status of their promoter-associated CpG islands in DNMT3A mutant-transduced stem/progenitor cells, representing a DNA methylation-independent role of mutated DNMT3A. DNMT3A R882H also promotes monoblastic transformation in vitro in combination with HOXA9. Molecularly, the DNMT3A mutant interacts with polycomb repressive complex 1 (PRC1), causing transcriptional silencing, revealing a DNA methylation-independent role of DNMT3A mutation. Suppression of PRC1 impairs aberrant HSC accumulation and monoblastic transformation. From our data, it is shown that DNMT3A mutants can block the differentiation of HSCs and leukaemic cells via PRC1. This interaction could be targetable in DNMT3A-mutated leukaemias.

It has become evident that acute myeloid leukemia (AML) is organized as a cellular hierarchy initiated and maintained by a subset of self-renewing leukemia stem cells. Recent gene expression profile analysis of human leukemia stem cells and hematopoietic stem cell (HSC) populations identified a key transcriptional program shared by leukemia stem cells and HSC, which is associated with adverse outcomes in AML patients. One molecule that has been established as a pivotal regulator in fine-tuning of stem cell properties as well as a potent oncogenic determinant is ecotropic viral integration site 1 (EVI1). EVI1 is a transcription factor that has stem cell-specific expression pattern and is essential for the regulation of HSC self-renewal. This gene is notorious for its involvement in AML, as its activation confers extremely poor prognosis in patients with AML. Molecular analysis has identified a variety of gene products that are involved in HSC regulation as downstream targets or interacting proteins of EVI1. Thus, exploration of the molecular pathogenesis underlying EVI1-related leukemogenesis provides insight into how shared stemness transcriptional programs contribute to leukemia progression and therapeutic resistance in AML. Here, we review the current knowledge regarding the role of EVI1 in HSC self-renewal and leukemogenesis and highlight the relationship between stem cell self-renewal properties and adverse outcome in myeloid malignancies.

Relapse of chronic myeloid leukemia (CML) is triggered by stem cells with a reconstituting capacity similar to that of hematopoietic stem cells (HSCs) and CML stem cells are a source of resistance in drug therapy with tyrosine kinase inhibitors (TKIs). Ecotropic viral integration site 1 (EVI1), a key transcription factor in HSC regulation, is known to predict poor outcomes in myeloid malignancies, however, incapability of prospective isolation of EVI1-high leukemic cells precludes the functional evaluation of intraindividual EVI1-high cells. Introduction of CML into Evi1-internal ribosomal entry site (IRES)-green fluorescent protein (GFP) knock-in mice, a versatile HSC-reporter strain, enables us to separate Evi1-high CML cells from the individual. Evi1-IRES-GFP allele models of CML in chronic phase (CML-CP), by retroviral overexpression of BCR-ABL and by crossing BCR-ABL transgenic mice, revealed that Evi1 is predominantly enriched in the stem cell fraction and associated with an enhanced proliferative as well as a leukemia-initiating capacity and that Evi1-high CML-CP cells exhibit resistance to TKIs. Overexpressing BCR-ABL and NUP98-HOXA9 in Evi1-IRES-GFP knock-in mice to model CML in blast crisis (CML-BC), in which Evi1-high cells turned to be a major population as opposed to a minor population in CML-CP models, showed that Evi1-high CML-BC cells have a greater potential to recapitulate the disease and appear resistant to TKIs. Furthermore, given that Evi1 heterozygosity ameliorates CML-CP and CML-BC development and that the combination of Evi1 and BCR-ABL causes acute myeloid leukemia resembling CML-BC, Evi1 could regulate CML development as a potent driver. In addition, in human CML-CP cases, we show that EVI1 is highly expressed in stem cell-enriched CD34+CD38-CD90+ fraction at single-cell level. This is the first report to clarify directly that Evi1-high leukemic cells themselves possess the superior potential to Evi1-low cells in oncogenic self-renewal, which highlights the role of Evi1 as a valuable and a functional marker of CML stem cells.

Ecotropic viral integration site 1 (Evi1), a transcription factor of the SET/PR domain protein family, is essential for the maintenance of hematopoietic stem cells (HSCs) in mice and is overexpressed in several myeloid malignancies. Here, we generate reporter mice in which an internal ribosome entry site (IRES)-GFP cassette is knocked-in to the Evi1 locus. Using these mice, we find that Evi1 is predominantly expressed in long-term HSCs (LT-HSCs) in adult bone marrow, and in the hematopoietic stem/progenitor fraction in the aorta-gonad-mesonephros, placenta, and fetal liver of embryos. In both fetal and adult hematopoietic systems, Evi1 expression marks cells with long-term multilineage repopulating activity. When combined with conventional HSC surface markers, sorting according to Evi1 expression markedly enhances purification of cells with HSC activity. Evi1 heterozygosity leads to marked impairment of the self-renewal capacity of LT-HSCs, whereas overexpression of Evi1 suppresses differentiation and boosts self-renewal activity. Reintroduction of Evi1, but not Mds1-Evi1, rescues the HSC defects caused by Evi1 heterozygosity. Thus, in addition to documenting a specific relationship between Evi1 expression and HSC self-renewal activity, these findings highlight the utility of Evi1-IRES-GFP reporter mice for the identification and sorting of functional HSCs.

Chronic inflammation is accompanied by recurring cycles of tissue destruction and repair and is associated with an increased risk of cancer(1-3). However, how such cycles affect the clonal composition of tissues, particularly in terms of cancer development, remains unknown. Here we show that in patients with ulcerative colitis, the inflamed intestine undergoes widespread remodelling by pervasive clones, many of which are positively selected by acquiring mutations that commonly involve the NFKBIZ, TRAF3IP2, ZC3H12A, PIGR and HNRNPF genes and are implicated in the downregulation of IL-17 and other pro-inflammatory signals. Mutational profiles vary substantially between colitis-associated cancer and non-dysplastic tissues in ulcerative colitis, which indicates that there are distinct mechanisms of positive selection in both tissues. In particular, mutations in NFKBIZ are highly prevalent in the epithelium of patients with ulcerative colitis but rarely found in both sporadic and colitis-associated cancer, indicating that NFKBIZ-mutant cells are selected against during colorectal carcinogenesis. In further support of this negative selection, we found that tumour formation was significantly attenuated in Nfkbiz-mutant mice and cell competition was compromised by disruption of NFKBIZ in human colorectal cancer cells. Our results highlight common and discrete mechanisms of clonal selection in inflammatory tissues, which reveal unexpected cancer vulnerabilities that could potentially be exploited for therapeutics in colorectal cancer.

Viral infection induces potent cellular immunity and activated intracellular signaling, which may dictate the driver events involved in immune escape and clonal selection of virus-associated cancers, including Epstein-Barr virus (EBV)-positive lymphomas. Here, we thoroughly interrogated PD-L1/PD-L2-involving somatic aberrations in 384 samples from various lymphoma subtypes using high-throughput sequencing, particularly focusing on virus-associated lymphomas. A high frequency of PD-L1/PD-L2-involving genetic aberrations was observed in EBV-positive lymphomas [33 (22%) of 148 cases], including extranodal NK/T-cell lymphoma (ENKTL, 23%), aggressive NK-cell leukemia (57%), systemic EBV-positive T-cell lymphoproliferative disorder (17%) as well as EBV-positive diffuse large B-cell lymphoma (DLBCL, 19%) and peripheral T-cell lymphoma-not otherwise specified (15%). Predominantly causing a truncation of the 3'-untranslated region, these alterations represented the most prevalent somatic lesions in ENKTL. By contrast, the frequency was much lower in EBV-negative lymphomas regardless of histology type [12 (5%) of 236 cases]. Besides PD-L1/PD-L2 alterations, EBV-positive DLBCL exhibited a genetic profile distinct from EBV-negative one, characterized by frequent TET2 and DNMT3A mutations and the paucity of CD79B, MYD88, CDKN2A, and FAS alterations. Our findings illustrate unique genetic features of EBV-associated lymphomas, also suggesting a potential role of detecting PD-L1/PD-L2-involving lesions for these lymphomas to be effectively targeted by immune checkpoint blockade.

Induced pluripotent stem cells (iPS) derived from disease cells are expected to provide a new experimental material, especially for diseases from which samples are difficult to obtain. In this study, we generated iPS from samples from patients with primary and secondary myelofibrosis. The primary myelofibrosis cells had chromosome 13q deletions, and the secondary myelofibrosis (SMF) cells had JAK2V617F mutations. The myelofibrosis patient cell-derived iPS (MF-iPS) were confirmed as possessing these parental disease-specific genomic markers. The capacity to form three germ layers was confirmed by teratoma assay. By co-culture with specific feeder cells and cytokines, MF-iPS can re-differentiate into blood progenitor cells and finally into megakaryocytes. We found that mRNA levels of interleukin-8, one of the candidate cytokines related to the pathogenesis of myelofibrosis, was elevated predominantly in megakaryocytes derived from MF-iPS. Because megakaryocytes from myelofibrosis clones are considered to produce critical mediators to proliferate fibroblasts in the bone marrow and iPS can provide differentiated cells abundantly, the disease-specific iPS we established should be a good research tool for this intractable disease.

Genetic alterations, including mutations and copy-number alterations, are central to the pathogenesis of myelodysplastic syndromes and related diseases (myelodysplasia), but their roles in allogeneic stem cell transplantation have not fully been studied in a large cohort of patients. We enrolled 797 patients who had been diagnosed with myelodysplasia at initial presentation and received transplantation via the Japan Marrow Donor Program. Targeted-capture sequencing was performed to identify mutations in 69 genes, together with copy-number alterations, whose effects on transplantation outcomes were investigated. We identified 1776 mutations and 927 abnormal copy segments among 617 patients (77.4%). In multivariate modeling using Cox proportional-hazards regression, genetic factors explained 30% of the total hazards for overall survival; clinical characteristics accounted for 70% of risk. TP53 and RAS-pathway mutations, together with complex karyotype (CK) as detected by conventional cytogenetics and/or sequencing-based analysis, negatively affected posttransplant survival independently of clinical factors. Regardless of disease subtype, TP53-mutated patients with CK were characterized by unique genetic features and associated with an extremely poor survival with frequent early relapse, whereas outcomes were substantially better in TP53-mutated patients without CK. By contrast, the effects of RAS-pathway mutations depended on disease subtype and were confined to myelodysplastic/myeloproliferative neoplasms (MDS/MPNs). Our results suggest that TP53 and RAS-pathway mutations predicted a dismal prognosis, when associated with CK and MDS/MPNs, respectively. However, for patients with mutated TP53 or CK alone, long-term survival could be obtained with transplantation. Clinical sequencing provides vital information for accurate prognostication in transplantation.

Adult T-cell leukemia/lymphoma (ATL) is a peripheral T-cell neoplasm with a dismal prognosis. It is caused by human T-cell leukemia virus type-1 (HTLV-1) retrovirus. A long latency period from HTLV-1 infection to ATL onset suggests that not only HTLV-1 proteins, such as Tax and HBZ, but also additional genetic and/or epigenetic events are required for ATL development. Although many studies have demonstrated the biological functions of viral genes, alterations of cellular genes associated with ATL have not been fully investigated. Recently, a large-scale integrated genetic analysis revealed the entire landscape of somatic aberrations in ATL. This neoplasm is characterized by frequent gain-of-function alterations in components of the T-cell receptor/NF-kappaB signaling pathway, including activating mutations in the PLCG1, PRKCB, CARD11 and VAV1 genes, and CTLA4-CD28 and ICOS-CD28 fusions. Importantly, molecules associated with immune surveillance, such as HLA-A/B, CD58 and FAS, are affected recurrently. Among them, one notable lesion occurs as frequent structural variations that truncate the PD-L1 3'-untranslated region, leading to its overexpression. Other genetic targets include transcription factors (IRF4, IKZF2, and GATA3) and chemokine receptors (CCR4, CCR7 and GPR183), which are functionally relevant in normal T cells. A substantial proportion of ATL cases show widespread accumulation of repressive epigenetic changes, such as trimethylation of histone H3 lysine 27 and DNA hypermethylation of CpG islands, which coordinately modulate multiple pathways, including Cys2-His2 zinc finger genes involved in silencing retroelements. Here we review the current understanding of the genetic/epigenetic aberrations in ATL, focusing on their relevance in its molecular pathogenesis.

To provide better insight into the genetic signatures of neuroblastomas, we analyzed 500 neuroblastomas (included specimens from JNBSG) using targeted-deep sequencing for 10 neuroblastoma-related genes and SNP arrays analysis. ALK expression was evaluated using immunohistochemical analysis in 259 samples. Based on genetic alterations, the following 6 subgroups were identified: groups A (ALK abnormalities), B (other gene mutations), C (MYCN amplification), D (11q loss of heterozygosity [LOH]), E (at least 1 copy number variants), and F (no genetic changes). Groups A to D showed advanced disease and poor prognosis, whereas groups E and F showed excellent prognosis. Intriguingly, in group A, MYCN amplification was not a significant prognostic marker, while high ALK expression was a relevant indicator for prognosis (P = 0.033). Notably, the co-existence of MYCN amplification and 1p LOH, and the co-deletion of 3p and 11q were significant predictors of relapse (P = 0.043 and P = 0.040). Additionally, 6q/8p LOH and 17q gain were promising indicators of survival in patients older than 5 years, and 1p, 4p, and 11q LOH potentially contributed to outcome prediction in the intermediate-risk group. Our genetic overview clarifies the clinical impact of genetic signatures and aids in the better understanding of genetic basis of neuroblastoma.