ALBERT

Description: Abstract 1977 Poster Board I-1000 Anemia is a common complication of chronic kidney disease (CKD), mainly due to the inability of the kidneys to secrete enough erythropoietin to adequately stimulate hematopoiesis. Further, given that the lifespan of red blood cells (RBCs) has been reported to be reduced in CKD patients, this reduction in RBC lifespan is believed to be a part of the etiology of renal anemia. In the present study, we focused on RBC survival and measured the lifespan of RBCs in rats with nephrogenic anemia. We also examined the effects of erythropoietin on RBC lifespan in this anemia model. Nephrogenic anemia was induced by oral administration of adenine (600 mg/kg/day for 10 days) to male Wistar rats. Progressive, serious anemia associated with increased levels of plasma creatinine was observed in the rats. On Day 40, the number of RBCs and hemoglobin (HGB) levels were lower in the adenine-treated rats than in normal, control rats (normal: 930×104/μL, anemic: 677×104/μL for RBC and normal: 17.2 g/dL, anemic: 13.4 g/dL for HGB). However, the number of reticulocytes did not change in the anemic rats (normal: 299×103/μL, anemic: 329×103/μL, P = 0.102). The percentage of annexin V-binding erythrocytes was increased in anemic rats (normal: 0.77%, anemic 1.76%) and inversely correlated with RBC count and HGB levels, suggesting that apoptosis of RBCs increased as anemia progressed. Taking these findings into account, we measured the lifespan of RBCs in rats with nephrogenic anemia. We transfused 5-chloromethylfluorescein diacetate (CMFDA)-labeled RBCs from normal donor rats into either normal or anemic recipients and determined the number of labeled RBCs present in the peripheral blood at various time points thereafter. The time course of the reduction in the percentage of labeled RBCs in peripheral blood revealed that the half-life (t1/2) of RBCs in anemic rats was shorter than in normal rats (normal: 22.5 d, anemic: 13.3 d). This reduction in RBC lifespan was also observed in a rat model of cisplatin-induced renal anemia. Injection of anemic rats with recombinant human erythropoietin (rhEPO) restored the number of RBCs and HGB concentration to normal levels. However, the t1/2of RBCs in these rats was not changed. The clearance of RBCs in anemic rats does not appear to be influenced by rhEPO injection. In conclusion, the survival of RBCs was reduced in rats with nephrogenic anemia, an observation consistent with the shortened survival time of RBCs in renal failure patients. This finding suggests that this model is suitable for investigating drugs which may be used in the treatment of renal anemia. Further, because EPO therapy did not affect the lifespan of RBCs, agents which improve the shortened RBC survival inherent in CKD patients may be useful in treating renal anemia. Disclosures: Iwatsuki: Astellas Pharma Inc.: Employment. Kitamura:Astellas Research Institute of America LLC: Employment. Suzuki:Astellas Pharma Inc.: Employment.

Description: Chronic graft-versus-host disease (cGVHD) is a limiting factor in allogeneic hematopoietic stem cell transplantation (alloHSCT) for the treatment of leukemia and other malignancies. Relative to the process that initiates and promotes cGVHD, the regulation is poorly understood. In this study, we examined the role of naturally occurring regulatory dendritic cells (DCregs) in murine major histocompatibility complex (MHC)-compatible and multiple minor histocompatibility antigen (miHAg)–incompatible model of cGVHD in alloHSCT. DCregs generated from bone marrow in vitro (BM-DCregs) exclusively expressed CD200 receptor 3 (CD200R3), which exerted a suppressive function in the Ag-specific CD4+ T-cell response. CD49+CD200R3+ cells showed similarities in phenotype and function to BM-DCregs, which formally distinguishes them from other leukocytes, suggesting that they are the natural counterpart of BM-DCregs. Treatment of the recipient mice after alloHSCT with the recipient-type CD49+CD200R3+ cells as well as BM-DCregs protected against cGVHD, and the protection was associated with the generation of Ag-specific anergic CD4+ T cells as well as CD4+CD25+Foxp3+ regulatory T cells (Tregs) from donor-derived alloreactive CD4+CD25−Foxp3− T cells. In addition, the depletion of CD49+CD200R3+ cells before alloHSCT enhanced the progression of cGVHD. In conclusion, CD49+CD200R3+ cells act as naturally occurring DCregs to regulate the pathogenesis of cGVHD in alloHSCT mediated through the control of the transplanted alloreactive CD4+ T cells.

Description: Pre–B-cell leukemia spontaneously develops in BLNK-deficient mice, and pre–B-cell acute lymphoblastic leukemia cells in children often lack BLNK protein expression, demonstrating that BLNK functions as a tumor suppressor. However, the mechanism by which BLNK suppresses pre–B-cell leukemia, as well as the identification of other genetic alterations that collaborate with BLNK deficiency to cause leukemogenesis, are still unknown. Here, we demonstrate that the JAK3/STAT5 signaling pathway is constitutively activated in pre-B leukemia cells derived from BLNK−/− mice, mostly due to autocrine production of IL-7. Inhibition of IL-7R signaling or JAK3/STAT5 activity resulted in the induction of p27kip1 expression and cell-cycle arrest, accompanied by apoptosis in the leukemia cells. Transgene-derived constitutively active STAT5 (STAT5b-CA) strongly synergized with the loss of BLNK to initiate leukemia in vivo. In the leukemia cells, exogenously expressed BLNK inhibited autocrine JAK3/STAT5 signaling, resulting in p27kip1 induction, cell-cycle arrest, and apoptosis. BLNK-inhibition of JAK3 was dependent on the binding of BLNK to JAK3. These data indicate that BLNK normally regulates IL-7–dependent proliferation and survival of pre–B cells through direct inhibition of JAK3. Thus, somatic loss of BLNK and concomitant mutations leading to constitutive activation of Jak/STAT5 pathway result in the generation of pre–B-cell leukemia.

Description: Abstract 1958 Poster Board I-981 Background: Evi1 gene is located on chromosome 3q26 and aberrantly expressed in acute myeloid leukemia (AML) patients with or without 3q26 abnormalities, and inappropriate expression of Evi1 associates with poor prognosis. Evi-1 is originally identified in a common integration site of murine leukemia retrovirus and enhanced expression of Evi1 by retrovirus integration is thought to be responsible for leukemogenesis in mouse models. However, retroviral expression of marker genes such as GFP has not induced leukemia even if some clones possessing integration at Evi1 site have been identified. These data indicate that Evi1 requires cooperative factors to induce progressive leukemia, whereas overexpression of Evi1 is enough to lead to clonal expansion of hematopoietic cells. Therefore, identifying genes collaborating with Evi1 is one of the key issues of understanding Evi1-related leukemogenesis. Recently, we demonstrated that a point mutation of the transcription factor AML1 (AML1-D171N) can induce myelodysplastic syndrome (MDS) that progresses to AML in association with overexpression of Evi1 through a mouse bone marrow transplantation model. In that work, we analyzed mice transplanted with BM cells transduced Evi1 alone as control and surprisingly confirmed that all of the mice developed leukemia within 6-11 months after the transplant. In this report, we will describe interesting findings in the novel mouse model of Evi1-induced leukemia. Result: C57BL6/Ly-5.1 murine BM cells infected with retroviruses harboring Evi1 were transplanted into irradiated syngeneic Ly-5.2 mice. The mice looked fine until 5 months, but GFP-positive-Evi1 expressing cells were gradually increased in the peripheral blood (PB), and then the mice died at 6-11 months after the transplantation. The mice showed dysplastic features in myeloid and erythroid cells, increase of blasts in the PB and the BM, hepatosplenomegaly, slight anemia, and some of the mice showed severe leukocytosis. The mice were thought to die of multiple organ failure due to invasion of leukemic cells not due to anemia. The phenotype is different from that of the mouse BMT model expressing Evi1 by retrovirus reported by another group, in which the mice died about 10 months with severe peripheral cytopenia and finally the disease did not progress to AML. Therefore, we considered that Evi1 might have collaborated with unknown genes near retrovirus integration sites in our case and analyzed integration sites by the bubble PCR method. Interestingly, frequent integration at 3' side of C/EBPb gene was found in six mice out of eight mice transplanted with Evi1-transduced BM cells. The integrations were located at 62.5-86.7kb downstream of C/EBPb gene. Next, we examined the expression level of C/EBPb, Tmem189, and Ptpn1, all of which are located near the integration site, and confirmed that C/EBPb showed elevated expression although neither Tmem189 nor Ptpn1 did. We also identified Bcas1, Rps6ka1, and Rapgef4 genes at the retroviral integration site in the other two mice without integration near C/EBPb. Discussion: C/EBPb, also known as NF-IL6, is a transcription factor that specifically binds to an IL1-responsive element in the IL-6 gene and has a role in regulation not only for the IL-6 gene but also for several cytokine genes such as TNF, IL-8, and G-CSF. The hematopoietic progenitor cells of C/EBPb-deficient mice have been reported to respond imperfectly to GM-CSF and G-CSF. Furthermore, C/EBPb is a downstream target of the Ras-Raf pathway. The locus of C/EBPb gene has been reported as a common integration site in the Retrovirus Tagged Cancer Gene Database (RTCGD), which is a database of retroviral insertional mutagenesis in mouse tumors. AKxD mice, Cdkn2a-KO mice, NUP98/HOXD13 transgenic mice, and MYC/Runx2 transgenic mice were reported to develop myeloid or lymphoid leukemia by retroviral insertion into 3' side of C/EBPb gene. In this study, we identified frequent integration at 3' side of C/EBPb gene in Evi1-transduced leukemic cells, whereas we have not identified this locus in AML1-mutants-transduced leukemic cells. Based on these findings and our results, C/EBPb is supposed to be a candidate gene to collaborate with Evi1 in leukemogenesis. Conclusion: We identified involvement of C/EBPb in Evi1-induced leukemogenesis. The novel mouse model that we generated in this study could help understanding the molecular basis of Evi1-related leukemia. Disclosures: No relevant conflicts of interest to declare.

Description: Abstract 4266 Introduction Imatinib, which is the most successful molecularly targeting drug, is the first-line agent for the treatment of chronic myeloid leukemia patients (CML) in chronic phase (CP). However, some patients show poor response against imatinib therapy, resulting in the progression to blastic phase. To date, several reports showed that imatinib trough plasma concentration (Cmin) was associated with the clinical response in CML patients, while it remains unclear whether Cmin reflects the actual inhibitory effect on the BCR-ABL kinase activity. In human plasma, imatinib binds to several plasma proteins, such as albumin (ALB) and alpha1-acid glycoprotein (AGP), and the protein-binding-imatinib lacks the kinase inhibitory activity. Especially, AGP is a major imatinib-binding protein, and the high plasma AGP concentration reportedly reduces the clinical efficacy of imatinib. These results indicate that the free-imatinib concentration is a more reliable surrogate marker for predicting the clinical efficacy than the total imatinib concentration. However, since routine measurements of the free-imatinib concentration is difficult, the inhibitory activity of the patient's plasma (PIA) against the BCR-ABL kinase is proposed to be a direct marker reflecting the actual inhibitory effects of the free-imatinib. In this study, we analyzed the association between Cmin of total imatinib and the clinical response in CML-CP patients in considering the AGP concentration. Furthermore, we evaluate the usefulness of PIA for predicting the clinical response in the CML patients treated with imatinib. Methods We measured Cmin of the total imatinib and AGP and ALB concentrations at the different two points in CML-CP patients who were treated with imatinib alone. The PIA was quantified by determining the de-phosphorylation levels of BCR-ABL and STAT5 in BCR-ABL-expressing Ba/F3 cells after the treatment with patients' plasma. We evaluated the association of these parameters with clinical response. Informed consent was obtained from all patients to use their samples for this study. This study was approved by the ethical committee of Nagoya university school of medicine. Results The study population included 65 CML-CP patients. The mean Cmin of imatinib was 1070 ± 362 ng/ml. Clinical response was evaluated by the achievement of the complete cytogenetic response (CCR) and major molecular response (MMR) at 12 months after the start of imatinib therapy. The CCR and MMR were achieved in 63 (96.9%) and 40 (61.5%) patients, respectively. The mean Cmin of the patients who achieved MMR was significantly higher than that of those who did not (1167 ± 386 ng/ml vs. 913 ± 257ng/ml, P=0.012). The differences of Cmin between the two different points (median interval 28 ± 20 days) in the same patient were not so little (median 123 ± 198 ng/ml, range 12 to 923 ng/ml), but were not associated with clinical outcomes. The PIA was statistically correlated with the Cmin (P=0.018). Although serum AGP level was within normal range (72.8 ± 13.9 mg/dl, range 44 to 106 mg/dl) in most patients, it was notable that the serum AGP level correlated with Cmin of imatinib and clinical outcomes. The Cmin of patients with high AGP level was significantly higher than that of low AGP level (1237 ± 379ng/ml vs. 907 ± 260ng/ml, P=0.0003) and the MMR rate was significantly higher in patients with high AGP level (78%) than in those with low AGP level (45%, P=0.007). Conclusions We demonstrate that the Cmin of imatinib predicts clinical response and reflects the actual kinase inhibitory effects in CML patients treated with imatinib. However, the Cmin is not necessarily stable during the treatment in a part of patients, suggesting that it is recommended to examine Cmin at more than two different points for evaluating its suitability. The serum AGP and ALB levels did not affect the relationship between Cmin and PIA. However, since the serum AGP level was correlated with Cmin and clinical response, the AGP level might influence the kinase inhibitory activity in the patients whose Cmin of imatinib were low. Disclosures: Kiyoi: Novartis Pharma : Research Funding; Kyowa Hakko Kirin Co., Ltd. : Consultancy. Naoe:Kyowa Hakko Kirin Co., Ltd. : Research Funding; Chugai Pharmaceutical Co.,Ltd.: Research Funding; Wyeth K.K.: Research Funding.

Description: STAT5 is a critical mediator of a variety of cytokine signaling whose transcriptional activity is regulated by associating with various proteins. During a search for STAT5-interacting proteins, we identified SHD1, a mammalian homologue of yeast gene Sac3, as a potential interacter. SHD1 was localized in the nucleus, and induced by cytokines that activate STAT5, such as erythropoietin, interleukin-2 (IL-2), or IL-3. SHD1 interacted specifically with STAT5A and STAT5B, and interestingly, it specifically repressed STAT5-dependent transcription in vitro without affecting the stability or phosphorylation of STAT5 protein. Gene disruption study revealed that T, B, or bone marrow cells from mice lacking SHD1 were hyperresponsive to T-cell–receptor engagement, or stimulation with various STAT5-activating cytokines. These results suggest that SHD1 is a novel cytokine-inducible negative feedback regulator of STAT5.

Description: Chronic myelogenous leukemia (CML) is a hematopoietic disorder originating from p210BCR/ABL-transformed stem cells, which begins as indolent chronic phase (CP) but progresses into fatal blast crisis (BC). To investigate molecular mechanism(s) underlying disease evolution, CML-exhibiting p210BCR/ABL transgenic mice were crossed with BXH2 mice that transmit a replication-competent retrovirus. Whereas nontransgenic mice in the BXH2 background exclusively developed acute myeloid leukemia, p210BCR/ABL transgenic littermates developed nonmyeloid leukemias, in which inverse polymerase chain reaction detected 2 common viral integration sites (CISs). Interestingly, one CIS was transgene's own promoter, which up-regulated p210BCR/ABL expression. The other was the 5′ noncoding region of a transcription factor, Zfp423, which induced aberrant Zfp423 expression. The cooperative activities of Zfp423 and p210BCR/ABL were demonstrated as follows: (1) introduction of Zfp423 in p210BCR/ABL transgenic bone marrow (BM) cells increased colony-forming ability, (2) suppression of ZNF423 (human homologue of Zfp423) in ZNF423-expressing, p210BCR/ABL-positive hematopoietic cells retarded cell growth, (3) mice that received a transplant of BM cells transduced with Zfp423 and p210BCR/ABL developed acute leukemia, and (4) expression of ZNF423 was found in human BCR/ABL-positive cell lines and CML BC samples. These results demonstrate that enhanced expression of p210BCR/ABL and deregulated expression of Zfp423/ZNF423 contribute to CML BC.