Chiaki Nakaseko

Tyrosine Phosphorylation Controls Internalization of CTLA-4 by Regulating Its Interaction with Clathrin-Associated Adaptor Complex AP-2

CTLA-4 is a costimulation receptor that binds to the same ligands, CD80 and CD86, as CD28 with high affinity and is transiently expressed on the cell surface of activated T cells. CTLA-4 delivers an inhibitory signal through association of a phosphotyrosine-containing motif in the cytoplasmic domain with Syp tyrosine phosphatase. We now demonstrate that CTLA-4 interacts with the mu2 subunit of the plasma membrane-associated adaptor complex, AP-2, through the same motif involved in the interaction with Syp, except that the interaction with mu2 requires unphosphorylated tyrosine. The interaction with mu2 likely induces rapid internalization of CTLA-4 from the cell surface. Our results suggest that the phosphorylation state of a single tyrosine residue determines whether CTLA-4 delivers a negative signal or is internalized.

Early molecular response predicts outcomes in patients with chronic myeloid leukemia in chronic phase treated with frontline nilotinib or imatinib

We explored the impact of early molecular response (EMR; BCR-ABL ≤10% on the international scale [BCR-ABL(IS)] at 3 or 6 months) on outcomes in patients with newly diagnosed chronic myeloid leukemia in chronic phase treated with nilotinib or imatinib based on 4 years of follow up in Evaluating Nilotinib Efficacy and Safety in Clinical Trials-Newly Diagnosed Patients. Patients (n = 846) received nilotinib 300 mg twice daily, nilotinib 400 mg twice daily, or imatinib 400 mg once daily. At 3 months, more patients had EMR failure (ie, BCR-ABL(IS) >10%) on imatinib (33%) than on nilotinib (9%-11%); similarly at 6 months, 16% of patients in the imatinib arm vs 3% and 7% in the nilotinib arms had EMR failure. In all arms, EMR failure was associated with lower rates of molecular response, an increased risk of progression, and lower overall survival compared with EMR achievement. We also analyzed patient and treatment characteristics associated with EMR and found distinct patterns in the nilotinib arms vs the imatinib arm. High Sokal risk score was associated with a high rate of EMR failure on imatinib, but not on nilotinib. In contrast, reduced dose intensity and dose interruptions were strongly associated with EMR failure in nilotinib-treated, but not imatinib-treated, patients. This study is registered at www.clinicaltrials.gov as #NCT00471497.

Randomized study of induction therapy comparing standard-dose idarubicin with high-dose daunorubicin in adult patients with previously untreated acute myeloid leukemia: the JALSG AML201 Study

We conducted a multi-institutional randomized study to determine whether high-dose daunorubicin would be as effective as standard-dose idarubicin in remission-induction therapy for newly diagnosed adult patients younger than 65 years of age with acute myeloid leukemia. Of 1064 patients registered, 1057 were evaluable. They were randomly assigned to receive either daunorubicin (50 mg/m(2) daily for 5 days) or idarubicin (12 mg/m(2) daily for 3 days) in combination with 100 mg/m(2) of cytarabine by continuous infusion daily for 7 days as induction therapy. Complete remission was achieved in 407 (77.5%) of 525 patients in the daunorubicin group and 416 (78.2%) of 532 in the idarubicin group (P = .79). Patients achieving complete remission received intensive postremission therapy that consisted of either 3 courses of high-dose cytarabine or 4 courses of standard-dose therapy. Overall survival rates at 5 years were 48% for the daunorubicin group and 48% for the idarubicin group (P = .54), and relapse-free survival rates at 5 years were 41% and 41% (P = .97), respectively. Thus, high-dose daunorubicin and standard-dose idarubicin were equally effective for the treatment of adult acute myeloid leukemia, achieving a high rate of complete remission and good long-term efficacy. This study is registered at http://www.umin.ac.jp/ctrj/ as C000000157.

Ezh2 augments leukemogenicity by reinforcing differentiation blockage in acute myeloid leukemia

EZH2, a catalytic component of the polycomb repressive complex 2, trimethylates histone H3 at lysine 27 (H3K27) to repress the transcription of target genes. Although EZH2 is overexpressed in various cancers, including some hematologic malignancies, the role of EZH2 in acute myeloid leukemia (AML) has yet to be examined in vivo. In the present study, we transformed granulocyte macrophage progenitors from Cre-ERT;Ezh2(flox/flox) mice with the MLL-AF9 leukemic fusion gene to analyze the function of Ezh2 in AML. Deletion of Ezh2 in transformed granulocyte macrophage progenitors compromised growth severely in vitro and attenuated the progression of AML significantly in vivo. Ezh2-deficient leukemic cells developed into a chronic myelomonocytic leukemia-like disease with a lower frequency of leukemia-initiating cells compared with the control. Chromatin immunoprecipitation followed by sequencing revealed a significant reduction in the levels of trimethylation at H3K27 in Ezh2-deficient leukemic cells, not only at Cdkn2a, a known major target of Ezh2, but also at a cohort of genes relevant to the developmental and differentiation processes. Overexpression of Egr1, one of the derepressed genes in Ezh2-deficient leukemic cells, promoted the differentiation of AML cells profoundly. Our findings suggest that Ezh2 inhibits differentiation programs in leukemic stem cells, thereby augmenting their leukemogenic activity.

Late-onset noninfectious pulmonary complications after allogeneic stem cell transplantation are significantly associated with chronic graft-versus-host disease and with the graft-versus-leukemia effect

Late-onset noninfectious pulmonary complications (LONIPCs) occurring beyond 3 months after allogeneic stem cell transplantation (allo-SCT) have become recognized as life-threatening complications, and they reduce the recipients quality of life. However, the pathogenesis and optimal treatment for LONIPCs are still unclear. In this study, we retrospectively analyzed the incidence and outcome of LONIPCs among allo-SCT recipients. Between October 1993 and September 2001, 96 patients underwent allo-SCT and 76 patients who survived and were free of disease for more than 3 months after SCT were enrolled. Among the 76 patients, 18 patients (23.7%) developed LONIPCs at a median interval of 227 days after allo-SCT (range, 91-1105 days). The patients with LONIPCs were subclassified into those with bronchiolitis obliterans (BO) (6 patients), with interstitial pneumonia (IP) (11 patients), or with both BO and IP (1 patient). The presence of extensive chronic graft-versus-host disease (GVHD) was significantly associated with the development of LONIPCs (P =.0008). Liver or skin involvement in chronic GVHD was not associated, but sicca syndrome was significantly associated with the development of LONIPCs (P <.0001). Most of the IP patients (58.3%) responded well to immunosuppressive treatment, while BO patients did not respond to the therapy. Eight of the 18 patients with LONIPCs died. The major cause of death was respiratory failure (62.5%). The relapse rate of primary malignant disease in the LONIPC patients was significantly lower than that of non-LONIPC patients (1 of 17 [5.9%] versus 16 of 52 [30.8%]; P =.0387). These results indicate that the development of LONIPCs was strongly associated with chronic GVHD and especially with sicca syndrome and the graft-versus-leukemia (GVL) effect.

Concurrent loss of Ezh2 and Tet2 cooperates in the pathogenesis of myelodysplastic disorders

Deletion of Ezh2 results in transcriptional repression of developmental regulator genes, derepression of oncogenic polycomb targets, and induction of MDS/MPN-like disease in mice that is exacerbated by concurrent deletion of Tet2.

Regulation of Cell Surface Expression of CTLA-4 by Secretion of CTLA-4-Containing Lysosomes Upon Activation of CD4+ T Cells

CTLA-4 is expressed on the surface of activated T cells and negatively regulates T cell activation. Because a low-level expression of CTLA-4 on the cell surface is sufficient to induce negative signals in T cells, the surface expression of CTLA-4 is strictly regulated. We previously demonstrated that the association of CTLA-4 with the clathrin-associated adaptor complex AP-2 induces internalization of CTLA-4 and keeps the surface expression low. However, the mechanism to induce high expression on the cell surface upon stimulation has not yet been clarified. To address this, we investigated the intracellular dynamics of CTLA-4 by analyzing its localization and trafficking in wild-type and mutant CTLA-4-transfected Th1 clones. CTLA-4 is accumulated in intracellular granules, which we identified as lysosomes. CTLA-4 is degraded in lysosomes in a short period, and the degradation process may serve as one of the mechanisms to regulate CTLA-4 expression. Upon TCR stimulation, CTLA-4-containing lysosomes are secreted as proven by the secretion of cathepsin D and β-hexosaminidase in parallel with the increase of surface expression of CTLA-4 and lysosomal glycoprotein 85, a lysosomal marker. These results suggest that the cell surface expression of CTLA-4 is up-regulated upon stimulation by utilizing a mechanism of secretory lysosomes in CD4+T cells.

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.

Autologous peripheral blood stem cell transplantation for POEMS syndrome

Polyneuropathy, organomegaly, endocrinopathy, M-protein, and skin changes syndrome is a rare multisystem disorder. Overproduction of vascular endothelial growth factor (VEGF) by plasmocytoma could be responsible for the symptoms. The authors treated four patients with high-dose chemotherapy and autologous peripheral blood stem cell transplantation. Within 6 months, symptoms associated with rapid normalization of serum VEGF levels improved.

A randomized comparison of 4 courses of standard-dose multiagent chemotherapy versus 3 courses of high-dose cytarabine alone in postremission therapy for acute myeloid leukemia in adults: the JALSG AML201 Study

We conducted a prospective randomized study to assess the optimal postremission therapy for adult acute myeloid leukemia in patients younger than 65 years in the first complete remission. A total of 781 patients in complete remission were randomly assigned to receive consolidation chemotherapy of either 3 courses of high-dose cytarabine (HiDAC, 2 g/m(2) twice daily for 5 days) alone or 4 courses of conventional standard-dose multiagent chemotherapy (CT) established in the previous JALSG AML97 study. Five-year disease-free survival was 43% for the HiDAC group and 39% for the multiagent CT group (P = .724), and 5-year overall survival was 58% and 56%, respectively (P = .954). Among the favorable cytogenetic risk group (n = 218), 5-year disease-free survival was 57% for HiDAC and 39% for multiagent CT (P = .050), and 5-year overall survival was 75% and 66%, respectively (P = .174). In the HiDAC group, the nadir of leukocyte counts was lower, and the duration of leukocyte less than 1.0 × 10(9)/L longer, and the frequency of documented infections higher. The present study demonstrated that the multiagent CT regimen is as effective as our HiDAC regimen for consolidation. Our HiDAC regimen resulted in a beneficial effect on disease-free survival only in the favorable cytogenetic leukemia group. This trial was registered at www.umin.ac.jp/ctr/ as #C000000157.