Masakatsu Hishizawa

Integrated molecular analysis of adult T cell leukemia/lymphoma

Adult T cell leukemia/lymphoma (ATL) is a peripheral T cell neoplasm of largely unknown genetic basis, associated with human T cell leukemia virus type-1 (HTLV-1) infection. Here we describe an integrated molecular study in which we performed whole-genome, exome, transcriptome and targeted resequencing, as well as array-based copy number and methylation analyses, in a total of 426 ATL cases. The identified alterations overlap significantly with the HTLV-1 Tax interactome and are highly enriched for T cell receptor–NF-κB signaling, T cell trafficking and other T cell–related pathways as well as immunosurveillance. Other notable features include a predominance of activating mutations (in PLCG1, PRKCB, CARD11, VAV1, IRF4, FYN, CCR4 and CCR7) and gene fusions (CTLA4-CD28 and ICOS-CD28). We also discovered frequent intragenic deletions involving IKZF2, CARD11 and TP73 and mutations in GATA3, HNRNPA2B1, GPR183, CSNK2A1, CSNK2B and CSNK1A1. Our findings not only provide unique insights into key molecules in T cell signaling but will also guide the development of new diagnostics and therapeutics in this intractable tumor.

Transplantation of allogeneic hematopoietic stem cells for adult T-cell leukemia: A nationwide retrospective study

Allogeneic hematopoietic stem cell transplantation (HSCT) is increasingly used as a curative option for adult T-cell leukemia (ATL), an intractable mature T-cell neoplasm causally linked with human T-cell leukemia virus type I (HTLV-I). We compared outcomes of 386 patients with ATL who underwent allogeneic HSCT using different graft sources: 154 received human leukocyte antigen (HLA)-matched related marrow or peripheral blood; 43 received HLA-mismatched related marrow or peripheral blood; 99 received unrelated marrow; 90 received single unit unrelated cord blood. After a median follow-up of 41 months (range, 1.5-102), 3-year overall survival for entire cohort was 33% (95% confidence interval, 28%-38%). Multivariable analysis revealed 4 recipient factors significantly associated with lower survival rates: older age (> 50 years), male sex, status other than complete remission, and use of unrelated cord blood compared with use of HLA-matched related grafts. Treatment-related mortality rate was higher among patients given cord blood transplants; disease-associated mortality was higher among male recipients or those given transplants not in remission. Among patients who received related transplants, donor HTLV-I seropositivity adversely affected disease-associated mortality. In conclusion, allogeneic HSCT using currently available graft source is an effective treatment in selected patients with ATL, although greater effort is warranted to reduce treatment-related mortality.

MicroRNA-33 Deficiency Reduces the Progression of Atherosclerotic Plaque in ApoE−/− Mice

Background Cholesterol efflux from cells to apolipoprotein A-I (apoA-I) acceptors via the ATP-binding cassette transporters ABCA1 and ABCG1 is thought to be central in the antiatherogenic mechanism. MicroRNA (miR)-33 is known to target ABCA1 and ABCG1 in vivo. Methods and Results We assessed the impact of the genetic loss of miR-33 in a mouse model of atherosclerosis. MiR-33 and apoE double-knockout mice (miR-33−/−Apoe−/−) showed an increase in circulating HDL-C levels with enhanced cholesterol efflux capacity compared with miR-33+/+Apoe−/− mice. Peritoneal macrophages from miR-33−/−Apoe−/− mice showed enhanced cholesterol efflux to apoA-I and HDL-C compared with miR-33+/+Apoe−/− macrophages. Consistent with these results, miR-33−/−Apoe−/− mice showed reductions in plaque size and lipid content. To elucidate the roles of miR-33 in blood cells, bone marrow transplantation was performed in these mice. Mice transplanted with miR-33−/−Apoe−/− bone marrow showed a significant reduction in lipid content in atherosclerotic plaque compared with mice transplanted with miR-33+/+Apoe−/− bone marrow, without an elevation of HDL-C. Some of the validated targets of miR-33 such as RIP140 (NRIP1) and CROT were upregulated in miR-33−/−Apoe−/− mice compared with miR-33+/+Apoe−/− mice, whereas CPT1a and AMPKα were not. Conclusions These data demonstrate that miR-33 deficiency serves to raise HDL-C, increase cholesterol efflux from macrophages via ABCA1 and ABCG1, and prevent the progression of atherosclerosis. Many genes are altered in miR-33-deficient mice, and detailed experiments are required to establish miR-33 targeting therapy in humans.

APOBEC3G targets human T-cell leukemia virus type 1

BackgroundApolipoprotein B mRNA-editing enzyme-catalytic polypeptide-like 3G (APOBEC3G) is a host cellular protein with a broad antiviral activity. It inhibits infectivitiy of a wide variety of retroviruses by deaminating deoxycytidine (dC) into deoxyuridine (dU) in newly synthesized minus strand DNA, resulting in G-to-A hypermutation of the viral plus strand DNA. To clarify the mechanism of its function, we have examined the antiviral activity of APOBEC3G on human T-cell leukemia virus type 1 (HTLV-1), the first identified human retrovirus.ResultsIn this study, we have demonstrated that overexpressed as well as endogenous APOBEC3G were incorporated into HTLV-1 virions and that APOBEC3G inhibited the infection of HTLV-1. Interestingly, several inactive mutants of APOBEC3G also inhibited HTLV-1 and no G-to-A hypermutation was induced by APOBEC3G in HTLV-1 genome. Furthermore, we introduced the human immunodeficiency virus type 1 (HIV-1) vif gene into HTLV-1 producing cell line, MT-2, to antagonize APOBEC3G by reducing its intracellular expression and virion incorporation, which resulted in upregulation of the infectivity of produced viruses.ConclusionAPOBEC3G is incorporated into HTLV-1 virions and inhibits the infection of HTLV-1 without exerting its cytidine deaminase activity. These results suggest that APOBEC3G might act on HTLV-1 through different mechanisms from that on HIV-1 and contribute to the unique features of HTLV-1 infection and transmission.

Allogeneic hematopoietic stem cell transplantation for adult T-cell leukemia-lymphoma with special emphasis on preconditioning regimen: a nationwide retrospective study.

Adult T-cell leukemia-lymphoma (ATL) is an intractable mature T-cell neoplasm. We performed a nationwide retrospective study of allogeneic hematopoietic stem cell transplantation (HSCT) for ATL in Japan, with special emphasis on the effects of the preconditioning regimen. This is the largest study of ATL patients receiving HSCT. Median overall survival (OS) and 3-year OS of bone marrow or peripheral blood transplantation recipients (n = 586) was 9.9 months (95% confidence interval, 7.4-13.2 months) and 36% (32%-41%), respectively. These values for recipients of myeloablative conditioning (MAC; n = 280) and reduced intensity conditioning (RIC; n = 306) were 9.5 months (6.7-18.0 months) and 39% (33%-45%) and 10.0 months (7.2-14.0 months) and 34% (29%-40%), respectively. Multivariate analysis demonstrated 5 significant variables contributing to poorer OS, namely, older age, male sex, not in complete remission, poor performance status, and transplantation from unrelated donors. Although no significant difference in OS between MAC and RIC was observed, there was a trend indicating that RIC contributed to better OS in older patients. Regarding mortality, RIC was significantly associated with ATL-related mortality compared with MAC. In conclusion, allogeneic HSCT not only with MAC but also with RIC is an effective treatment resulting in long-term survival in selected patients with ATL.

Depletion and impaired interferon-alpha-producing capacity of blood plasmacytoid dendritic cells in human T-cell leukaemia virus type I-infected individuals.

Dendritic cells (DCs) play an important role in innate and adaptive immunity. There are two major populations of blood DCs, myeloid DCs (myDCs) and plasmacytoid DCs (pcDCs). pcDCs are particularly important in antiviral as well as in general host defence, as they are the principal producers of type I interferons (IFNs). In this study, we analysed myDCs and pcDCs in healthy controls, human T‐cell leukaemia virus type I (HTLV‐I)‐infected asymptomatic carriers (ACs), and patients with adult T‐cell leukaemia (ATL). ATL patients had significantly decreased number of pcDCs and myDCs compared with controls. IFN‐α production by peripheral blood mononuclear cells (PBMCs) was markedly reduced in ATL patients. Purified pcDCs from ACs were found to have impaired IFN‐α‐producing capacity, suggesting a functional defect in pcDCs in HTLV‐I‐infected individuals. Interestingly, pcDCs were shown to be susceptible to HTLV‐I infection. Thus, impaired IFN‐α production by pcDCs may contribute to the immunodeficiency observed in ATL. Furthermore, IFN‐α‐producing capacity was inversely correlated with HTLV‐I proviral load in PBMCs from ACs, suggesting a role for pcDCs in maintaining the carrier state. Taken together, we hypothesize that the depletion and impaired IFN‐α‐producing capacity of blood DCs may contribute to the immunodeficiency in ATL and/or the development of ATL.

Impact of graft-versus-host disease on outcomes after allogeneic hematopoietic cell transplantation for adult T-cell leukemia: a retrospective cohort study

Allogeneic hematopoietic cell transplantation (HCT) is an effective treatment for adult T-cell leukemia (ATL), raising the question about the role of graft-versus-leukemia effect against ATL. In this study, we retrospectively analyzed the effects of acute and chronic graft-versus-host disease (GVHD) on overall survival, disease-associated mortality, and treatment-related mortality among 294 ATL patients who received allogeneic HCT and survived at least 30 days posttransplant with sustained engraftment. Multivariate analyses treating the occurrence of GVHD as a time-varying covariate demonstrated that the development of grade 1-2 acute GVHD was significantly associated with higher overall survival (hazard ratio [HR] for death, 0.65; P = .018) compared with the absence of acute GVHD. Occurrence of either grade 1-2 or grade 3-4 acute GVHD was associated with lower disease-associated mortality compared with the absence of acute GVHD, whereas grade 3-4 acute GVHD was associated with a higher risk for treatment-related mortality (HR, 3.50; P < .001). The development of extensive chronic GVHD was associated with higher treatment-related mortality (HR, 2.75; P = .006) compared with the absence of chronic GVHD. Collectively, these results indicate that the development of mild-to-moderate acute GVHD confers a lower risk of disease progression and a beneficial influence on survival of allografted patients with ATL.

Expression of functional interleukin-21 receptor on adult T-cell leukaemia cells

Adult T‐cell leukaemia (ATL) is caused by human T‐cell leukaemia virus type I (HTLV‐I). It has been suggested that cytokines play a role in the development and in the neoplastic cell growth of ATL. However, the precise mechanism involved in this process still remains unclear. Interleukin‐21 (IL‐21) and its receptor (IL‐21R) have been recently described. In this study, we examined the expression of IL‐21R and the effect of IL‐21 on ATL cells. Real‐time reverse transcription polymerase chain reaction showed that HTLV‐I‐infected cell lines and primary ATL cells expressed IL‐21R mRNA. Cell surface expression of IL‐21R on these cells was confirmed by flow cytometric analysis using a newly developed monoclonal antibody against human IL‐21R. In contrast to the expression of IL‐21R, IL‐21 mRNA was scarcely detectable in these cells. Notably, IL‐21 induced the proliferation of ATL‐43T and ED‐40515(+) cells, both of which were derived from leukaemic cell clones of ATL. Concerning the intracellular signalling pathways, IL‐21 activated the phosphorylation of the signal transducers and activators of transcription (STAT)3 and STAT5. Taken together, these findings provide the first evidence that ATL cells express functional IL‐21R, suggesting that it may contribute to the pathophysiology of ATL. In addition, the IL‐21/IL‐21R system may represent a new target for the treatment of ATL.

Impact of graft-versus-host disease on allogeneic hematopoietic cell transplantation for adult T cell leukemia-lymphoma focusing on preconditioning regimens: nationwide retrospective study.

Allogeneic hematopoietic cell transplantation (HCT), but not autologous HCT, can provide long-term remission in some patients with adult T cell leukemia-lymphoma (ATL). We retrospectively analyzed the effects of acute graft-versus-host disease (GVHD) among the 616 patients with ATL who survived at least 30 days after allogeneic HCT with other than cord blood grafts. Multivariate analyses treating the occurrence of GVHD as a time-varying covariate demonstrated an association between grade I-II acute GVHD and favorable overall survival (OS) (hazard ratio [HR], 0.634; 95% confidence interval [CI], 0.477 to 0.843), whereas grade III-IV acute GVHD showed a trend toward unfavorable OS (HR, 1.380; 95% CI, 0.988 to 1.927) compared with nonacute GVHD. In subsequent multivariate analyses of patients who survived at least 100 days after HCT (n = 431), the presence of limited chronic GVHD showed a trend toward favorable OS (HR, 0.597; 95% CI, 0.354 to 1.007), and extensive chronic GVHD had a significant effect on OS (HR, 0.585; 95% CI, 0.389 to 0.880). There were no significant interactions between myeloablative conditioning or reduced-intensity conditioning with OS even when acute GVHD was absent or present at grade I-II or grade III-IV or when chronic GVHD was absent, limited, or extensive. This study demonstrates the actual existence of graft-versus-ATL effects in patients with ATL regardless of whether myeloablative conditioning or reduced-intensity conditioning is used.

T memory stem cells are the hierarchical apex of adult T-cell leukemia.

Adult T-cell leukemia (ATL) is a peripheral CD4(+) T-cell neoplasm caused by human T-cell leukemia virus type 1 (HTLV-1). Despite several investigations using human specimens and mice models, the exact origin of ATL cells remains unclear. Here we provide a new insight into the hierarchical architecture of ATL cells. HTLV-1-infected cells and dominant ATL clones are successfully traced back to CD45RA(+) T memory stem (TSCM) cells, which were recently identified as a unique population with stemlike properties, despite the fact that the majority of ATL cells are CD45RA(-)CD45RO(+) conventional memory T cells. TSCM cells from ATL patients are capable of both sustaining themselves in less proliferative mode and differentiating into other memory T-cell populations in the rapidly propagating phase. In a xenograft model, a low number of TSCM cells efficiently repopulate identical ATL clones and replenish downstream CD45RO(+) memory T cells, whereas other populations have no such capacities. Taken together, these findings demonstrate the phenotypic and functional heterogeneity and the hierarchy of ATL cells. TSCM cells are identified as the hierarchical apex capable of reconstituting identical ATL clones. Thus, this is the first report to demonstrate the association of a T-cell malignancy with TSCM cells.