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p97/VCP is an endoplasmic reticulum (ER)‐associated protein that belongs to the AAA (ATPases associated with diverse cellular activities) ATPase family. It has a variety of cellular functions including ER‐associated protein degradation, autophagy, and aggresome formation. Recent studies have shown emerging roles of p97/VCP and its potential as a therapeutic target in several cancer subtypes including multiple myeloma (MM). We conducted a cell‐based compound screen to exploit novel small compounds that have cytotoxic activity in myeloma cells. Among approximately 2000 compounds, OSSL_325096 showed relatively strong antiproliferative activity in MM cell lines (IC 50, 100‐500 nmol/L). OSSL_325096 induced apoptosis in myeloma cell lines, including a bortezomib‐resistant cell line and primary myeloma cells purified from patients. Accumulation of poly‐ubiquitinated proteins, PERK, CHOP, and IREα, was observed in MM cell lines treated with OSSL_325096, suggesting that it induces ER stress in MM cells. OSSL_325096 has a similar chemical structure to DBeQ, a known p97/VCP inhibitor. Knockdown of the gene encoding p97/VCP induced apoptosis in myeloma cells, accompanied by accumulation of poly‐ubiquitinated protein. IC 50 of OSSL_325096 to myeloma cell lines were found to be lower (0.1‐0.8 μmol/L) than those of DBeQ (2‐5 μmol/L). In silico protein–drug‐binding simulation suggested possible binding of OSSL_325096 to the ATP binding site in the D2 domain of p97/VCP. In cell‐free ATPase assays, OSSL_325096 showed dose‐dependent inhibition of p97/VCP ATPase activity. Finally, OSSL_325096 inhibited the growth of subcutaneous myeloma cell tumors in vivo. The present data suggest that OSSL_325096 exerts anti‐myeloma activity, at least in part through p97/VCP inhibition.

The sialic glycoprotein, MUC1, is known to be involved in the pathogenesis of various types of cancers. KL-6 is one of the surface antigens of MUC1 and also a marker of interstitial pneumonitis. A fraction of patients with myeloma (3.9%) have elevated serum KL-6 levels without any evidence of interstitial pneumonitis and their myeloma cells have high MUC1 expression. We established a myeloma cell line designated EMM1 from a patient with multiple myeloma accompanied with elevated serum KL-6. EMM1 cells expressed high levels of MUC1 compared with other myeloma cell lines. Knockdown of MUC1 in EMM1 cells induced cell cycle arrest during S phase and apoptosis, suggesting that the MUC1 expression is involved in accelerated growth of EMM1 cells. RNA-seq analysis suggests that MUC1 expression activates k-ras and TNFα-induced NFκB pathways in EMM1 cells. We injected EMM1 cells subcutaneously into Rag2-/-Jak3-/- Balb/c mice to establish a mouse xenograft model. These mice had aggressive tumor growth that was accompanied by high serum KL-6 levels. In addition, MUC1 knockdown in EMM1 cells led to inhibited tumor growth. These findings demonstrate that MUC1 serves as a potential target for developing drugs for treatment of patients with KL-6+ myeloma, and EMM1 cells and EMM1-engrafted mice are useful tools for the development of such novel agents.

Immunomodulatory drugs (IMiDs) such as thalidomide, lenalidomide, and pomalidomide are efficacious in the treatment of multiple myeloma and significantly prolong their survival. However, the mechanisms of such effects of IMiDs have not been fully elucidated. Recently, cereblon has been identified as a target binding protein of thalidomide. Lenalidomide-resistant myeloma cell lines often lose the expression of cereblon, suggesting that IMiDs act as an anti-myeloma agent through interacting with cereblon. Cereblon binds to damaged DNA-binding protein and functions as a ubiquitin ligase, inducing degradation of IKZF1 and IKZF3 that are essential transcription factors for B and T cell development. Degradation of both IKZF1 and IKZF3 reportedly suppresses myeloma cell growth. Here, we found that IMiDs act as inhibitors of DNA methyltransferases (DMNTs). We previously reported that PU.1, which is an ETS family transcription factor and essential for myeloid and lymphoid development, functions as a tumor suppressor in myeloma cells. PU.1 induces growth arrest and apoptosis of myeloma cell lines. In this study, we found that low-dose lenalidomide and pomalidomide up-regulate PU.1 expression through inducing demethylation of the PU.1 promoter. In addition, IMiDs inhibited DNMT1, DNMT3a, and DNMT3b activities in vitro. Furthermore, lenalidomide and pomalidomide decreased the methylation status of the whole genome in myeloma cells. Collectively, IMiDs exert demethylation activity through inhibiting DNMT1, 3a, and 3b, and up-regulating PU.1 expression, which may be one of the mechanisms of the anti-myeloma activity of IMiDs.

Although anti-T lymphocyte globulin-Fresenius (ATG-F) is commonly used as prophylaxis for graft-versus-host disease (GVHD), the appropriate dosage of ATG-F in the setting of a reduced-intensity conditioning (RIC) regimen has not been determined. In the present study, we retrospectively analyzed the clinical outcomes of 103 patients after unrelated bone marrow transplant (uBMT) with RIC regimens. RIC regimens consisted of purine analogue plus busulfan with low-dose TBI or ATG-F (5–10 mg/kg in total). Median age was 57 years (range 20–68). The incidence of grade II–IV acute GVHD and chronic GVHD with ATG-F was significantly lower than that with TBI 2 Gy (15 vs. 61 %, P < 0.05; 33 vs. 57 %, P < 0.05). The incidence of 2-year NRM with ATG-F was significantly lower than that with TBI 2 Gy (6 vs. 28 %, P < 0.05). There was no statistically significant difference in the cumulative incidence of 2-year relapse between the ATG-F and TBI 2 Gy groups (37 vs. 20 %, P = 0.13). In conclusion, the addition of low-dose ATG-F to GVHD prophylaxis in patients who received uBMT resulted in decreased incidence of acute and chronic GVHD, which led to a significantly reduced risk of NRM without compromising overall survival. The beneficial effect of low-dose ATG-F should be assessed in a prospective clinical trial.

PU.1 is an Ets family transcription factor, which is necessary for differentiation of both myeloid and lymphoid lineages. It was previously reported that conditional knockout of the upstream regulatory element (URE) located in 14 kb 5' of the PU.1 gene resulted in down-regulation of PU.1 expression in granulocytes and B lymphocytes by 80% compared to that of wild type and induced acute myeloid leukemia and CLL-like diseases in mice. Since the URE contains a suppressor region for PU.1 expression in T cells, such mice express PU.1 in T cells and develop T cell lymphoma. Thus, the failure of proper expression of PU.1 in certain differentiation stages in certain cell lineages appears to result in hematological malignancies. We previously reported that PU.1 is down-regulated in various myeloma cell lines. In addition, PU.1 is expressed in normal plasma cells and PU.1 is down-regulated in myeloma cells of certain myeloma patients, who appear to have poor prognosis. In those myeloma cell lines, the promoter and URE of the PU.1 gene are highly methylated. A demethylation agent, 5-aza-2'-deoxycytidine, induced PU.1 up-regulation, growth arrest, and apoptosis in myeloma cell lines, KMS12PE and KHM11. In addition, conditionally expressed PU.1 induced cell growth arrest and apoptosis in PU.1-low-negative myeloma cell lines, U266 and KMS12PE, suggesting that PU.1 is a tumor suppressor for myeloma cells. To elucidate the mechanisms of the cell growth arrest and apoptosis in myeloma cells induced by PU.1, we performed DNA microarray analysis to compare gene expression levels before and after PU.1 expression. Among cell-cycle related genes, p21WAF1/CIP1 was found up-regulated in U266 cells, while among apoptosis related genes, TRAIL was highly up-regulated in both U266 and KMS12PE cell lines. With further investigation, we concluded that PU.1 directly transactivated the TRAIL gene in myeloma cells, leading to apoptosis. Based on the DNA microarray data generated, we found that IRF4 is downregulated in U266 myeloma cells after PU.1 induction. It has been reported that knockdown of IRF4 induces apoptosis in myeloma cell lines. Therefore, we examined whether IRF4 was down-regulated in three myeloma cell lines, U266, KMS12PE, and KHM11 following PU.1 induction. Conditional expression of PU.1 by tet-off system induced IRF4 down-regulation in U266and KMS12PE cells. With lentiviral transduction method, ectopic expression of PU.1 also induced IRF4 down-regulation, cell-cycle arrest, and apoptosis in KHM11 cells. To investigate the role of IRF4 in PU.1-expressing U266 cells, we stably expressed IRF4, partially rescuing U266 cells from apoptosis. IRF4 is known to directly bind to the IRF7 promoter and down-regulate IRF7 expression in activated B cell-like (ABC) subtype of diffuse large B-cell lymphoma cells. Therefore, we examined whether IRF4 bound to the IRF7 promoter in KMS12PEand U266cells using chromatin immunoprecipitation assays. We found that IRF4 directly bound to the IRF7 promoter in both myeloma cell lines. When we overexpressed PU.1, IRF4 levels were decreased and the IRF4 binding to the IRF7 promoter was significantly reduced in those cell lines. Moreover, knockdown of IRF7 significantly rescued PU.1-expressing U266cells from apoptosis. These data strongly suggest that PU.1-induced apoptosis is associated with IRF4 down-regulation and subsequent IRF7 up-regulation in myeloma cells. Since IRF4 is essential transcription factor for myeloma cell survival, up-regulation of PU.1 by demethylation agents, including 5-aza-2'-deoxycytidine may serve as a promising therapeutic modality of multiple myeloma by inducing down-regulation of IRF4. Disclosures No relevant conflicts of interest to declare.

PU.1 is an essential transcription factor for hematopoiesis and important for differentiation of both myeloid and lymphoid lineages. In mice conditionally knocked-out of 3.4 kb length of the enhancer region located in14 kb 5’ upstream of the PU.1 gene (URE), PU.1 is down-regulated in myeloid cells and B cells by 20% of that of wild type, and such mice develop acute myeloid leukemia and CLL-like diseases. These data strongly suggest that PU.1 has tumor suppressor activity in hematopoietic cells. We previously reported that human PU.1 is down-regulated in the majority of myeloma cell lines through the methylation of the promoter and the 17 kb upstream enhancer region (URE) of the PU.1 gene that is homologous to that in 14 kb 5’ upstream of the murine PU.1 gene. Conditionally expressed PU.1 with tet-off system induced cell growth arrest and apoptosis in two myeloma cell lines, KMS12PE and U266, suggesting that the down-regulation of PU.1 is necessary for myeloma cell growth. We have also reported that PU.1 is expressed in normal plasma cells and in contrast, PU.1 is down-regulated in primary myeloma cells from a subset of myeloma patients, who appear to have poor prognosis. In the present study, to test whether PU.1 has tumor suppressor activity in vivo, we generated xenograft mouse models. 0.6 - 1 x 107 KMS12PE cells were subcutaneously injected in 16 immunodeficient mice (Rag2-/- Jak3-/- bulb/c). The mice were then administered doxycycline through drinking water. Half of the mice (N=8) stopped taking doxycycline when the tumor sizes reached 1 cm in diameter, whereas the other half (N=8) kept taking doxycycline. Although the tumors in the mice taking doxycycline continued to grow, the tumor growth in the mice not taking doxycycline significantly slowed down. Flow cytometry analysis of the tumors in the mice that stopped taking doxycycline revealed that the cells from the tumor had completely lost PU.1 expression. Moreover, when U266 cells conditionally expressing PU.1 were subcutaneously injected to another 10 mice and the same experiment was conducted, although the tumors in the mice taking doxycycline (N=5) kept growing, the tumors in the mice not taking doxycycline (N=5), did not grow any further. The present data suggest that PU.1 serves as a tumor a suppressor in the multiple myeloma cell lines as examined in vivo. Disclosures No relevant conflicts of interest to declare.

PU.1 is an Ets family transcription factor, which is essential for differentiation of both myeloid and lymphoid lineages. It was previously reported that conditional knockout of the upstream enhancer region (URE) located in 14 kb 5’ of the murine PU.1 gene resulted in down-regulation of PU.1 expression in granulocytes and B lymphocytes by 80% compared to that of wild type and induced acute myeloid leukemia and CLL-like diseases in mice. Therefore, down-regulation of PU.1 in myeloid and B cell lineages results in hematological malignancies. We previously reported that PU.1 is down-regulated in 5 out of 7 myeloma cell lines as well as primary myeloma cells from a subset of myeloma patients; that the promoter and the URE located in 17 kb 5’ of the human PU.1 gene that is homologous to that in 14 kb 5’ of murine PU.1 gene are highly methylated in these cell lines; and that conditionally expressed PU.1 with tet-off system induces cell growth arrest and apoptosis in myeloma cell lines, U266 and KMS12PE, suggesting that the down-regulation of PU.1 is necessary for myeloma cell growth. Here, to evaluate tumor suppressor activity of PU.1 in mature B and plasma cells in vivo, we generated Cγ1-Cre PU.1 knockout mice by crossing Cγ1-Cre and PU.1-loxP mice. We confirmed that PU.1 alleles were both conditionally deleted in the maturation stages of B cells from post germinal center B to plasma cells. By 18-24 months of age, about 77.7% (10 of 13) of the knockout mice had developed serum M proteins. To induce B cell differentiation to plasma cells, those mice were immunized with NP-CGG and 76.9% (20 of 26) of the mice developed serum M protein. ELISA of sera from those mice revealed that IgG was not elevated compared to those from the PU.1-loxP mice, which was thought because Cγ1-Cre locus fails to produce IgG1. Instead, a small number (5 of 20) of the mice showed relatively large amounts of IgM and/or IgA. When 11 such mice were sacrificed, 7 had developed splenomegaly and/or intestinal B cell lymphoma. Immunostaining revealed that B220+ cells had infiltrated into the tumors and various organs including the spleen, liver, and bone marrow. Those cells were monoclonal for κ chain and partly CD138 positive. When we transplanted those tumor cells into Rag2-/- Jak3-/- immunedeficient mice, all the mice died within 3 weeks. Thus, PU.1 apparently functions as a tumor suppressor in mature B cells and its deletion in late B cell maturation stages produces B cell lymphoma with M proteinemia. The remaining 4 mice developed high titer IgM and/or IgA levels and flow cytometry of bone marrow cells and splenocytes revealed that those cells were monoclonal for κ chain and positive for B220 and IgM and/or IgA, suggesting that those mice suffered from multiple myeloma or monoclonal gammopathy with undetermined sighnificance (MGUS). These data strongly suggest that conditional knockout of PU.1 in post germinal center B and plasma cells results in B cell lymphoma and plasma cell neoplasms related to multiple myeloma. Disclosures No relevant conflicts of interest to declare.

Abstract 2318 Introduction: ES has been well recognized to increase non-relapse mortality (NRM) in autologous hematopoietic cell transplantation (HCT). However, little information is available on ES in allogeneic HCT, particularly after reduced-intensity conditioning. To determine the incidence, risk factors and outcome of ES after RIST, we retrospectively reviewed the medical records of 285 patients (pts) who underwent RIST at our institution between 1999 and 2007. Patients and Methods: After excluding 37 pts who received cord blood transplantation or a second or subsequent allogeneic HCT, and those who experienced primary graft failure, 248 pts (male 153, female 95) with a median age of 55 y (range, 21–68) fulfilled the criteria of this study. The underlying diagnosis included lymphoma (106 pts; 43%), acute myeloid leukemia (59; 24%), myelodysplastic syndrome (51; 21%), and others (32; 13%). Ninety-two pts (37%) had a standard-risk disease such as acute leukemia or lymphoma in CR1, and 156 (63%) had a high-risk disease. The donor and stem cell source were related PBSC in 170 pts (69%), related BM in 8 (3%), and unrelated BM in 70 (28%). All of the pts received reduced-intensity conditioning with a purine analog and a busulfan-based regimen. With the use of G-CSF after HCT, neutrophil engraftment (ANC ≥500/μ l) was achieved at a median of 12 days (range, 5–28). ES was diagnosed when the patient showed at least 2 of the following symptoms within 96 h of neutrophil engraftment: (1) fever (>38.0°C) without an identifiable source of infection, (2) skin rash (>25% of body surface area) that was not due to a drug reaction, (3) weight gain (>2.5% of baseline body weight), and (4) hypoxia (sPO2 Results: Among the 248 pts, 45 (18%) developed ES at a median of 14 days (6-23) after allogeneic HCT. Symptoms consisted of fever (100%), skin rash (53%), weight gain (62%) and hypoxia (33%). The incidence of ES in recipients of unrelated donor grafts was significantly higher than that in recipients of related donor grafts (28% vs 14%, p=0.02), and male pts had a significantly higher incidence of ES than female pts (22% vs 12%, p=0.04). No significant difference in the incidence of ES was observed between groups stratified according to age, stem cell source, TNC or CD34+ cell dose, disease risk, GVHD prophylaxis, and the timing of engraftment. By a multivariate analysis, use of an unrelated donor (HR 2.3, 95%CI 1.3–4.1, p=0.007), pts with lymphoid malignancy (HR 2.0, 95%CI 1.1–3.7, p=0.03) and male pts (HR 2.0, 95%CI 1.0–4.0, p=0.04) were associated with a significantly increased risk of ES. Among the 40 pts who required systemic corticosteroid therapy, 31 (78%) achieved a complete response, and the remaining 9 (23%) responded partially. There was a trend toward a higher incidence of grade III-IV acute GVHD (27% vs 18%, p=0.10) in pts with ES, and the incidence of extensive chronic GVHD (69% vs 62%, p=0.04) was significantly higher in pts with ES. Overall survival (OS) and non-relapse mortality (NRM) were not significantly different between the two groups, after a median follow-up of 53 months (range, 2–108) in surviving patents. A multivariate analysis showed that pts with high-risk disease (NRM, HR 1.9, 95%CI 1.1–3.3, p=0.01; OS, HR 2.5, 95%CI 1.6–3.8, p Conclusions: ES is a rather common complication after RIST, especially in recipients of unrelated donor grafts. Although ES shows an initial good response to corticosteroid therapy, ES may have a negative impact on survival, especially in pts with standard-risk disease, and this effect may be related to the occurrence of GVHD. The development of an optimal treatment for ES may improve the outcome of pts who have received RIST by reducing GVHD-related mortality. Disclosures: No relevant conflicts of interest to declare.

Abstract 3508 Background: Allo-HCT is a therapeutic option for patients (pts) with relapsed or refractory B-cell non-Hodgkin lymphoma (B-NHL). However, the outcome of allo-HCT with a reduced-intensity conditioning (RIC) regimen for TL remains controversial, and no previous reports have compared the outcomes after allo-HCT for FL, TL, and DLBCL in the rituximab era. Patients and Methods: We retrospectively analyzed 73 consecutive pts with FL (n=33), TL (n=18), or DLBCL (n=22) who received allo-HCT at our institute between January 2000 and December 2008. We defined TL as DLBCL that was histologically proven in pts with pre- (n=8) or co- (n=10) existing FL. The median age of the 73 pts was 47 years (range, 26–67). The median duration from diagnosis to HCT was 38 months (range, 6–175). The median number of prior chemotherapy regimens was 4 (range, 1–10): 57 pts (78%) had received prior rituximab, and 23 (32%) had received high-dose chemotherapy with autologous HCT prior to allo-HCT. The disease status at allo-HCT was CR or PR/refractory; 23 (32%)/50 (68%) for all pts, 10/23 for FL, 7/11 for TL, and 6/16 for DLBCL. The age-adjusted international prognostic index (aaIPI) at HCT was high or high-intermediate risk in 21 pts (28%), and FLIPI at HCT was high risk in 11 pts with FL (15%). The median level of serum albumin at HCT was 4.2 g/dL (range, 2.7–5.1). A myeloablative conditioning regimen was used for 14 pts (19%), and a RIC regimen was used for 59 pts (81%). The donor and stem cell source were related peripheral blood stem cells in 44 pts (60%), related bone marrow in 2 (3%), unrelated bone marrow in 21 (29%), and cord blood in 6 (8 %). Results: With a median follow-up of 68 months in surviving pts, the 5-year estimated overall survival (OS; Figure) and progression-free survival (PFS) were 58% and 54% for all pts, 80% and 71% for FL, 67% and 67% for TL, and 20% and 17% for DLBCL, respectively. The 5-year cumulative incidences of relapse/disease progression (PD) and non-relapse mortality were 25% and 39% for all pts, 10% and 22% for FL, 24% and 13% for TL, and 50% and 67% for DLBCL, respectively. Grade III-IV acute GVHD occurred in 25% of all pts, and OS was significantly worse in such pts [hazard ratio (HR) 2.5 (95%CI 1.2–5.3), p=0.02]. Extensive chronic GVHD (cGVHD) occurred in 53% of pts who survived 100 days or longer, and OS for patients with extensive cGVHD was significantly worse than that in pts without extensive cGVHD [HR 4.5 (1.3-15.6), p=0.02]. The cause of death included PD in 10 pts, GVHD in 5, infection in 4, non-infectious lung complication in 5, cerebral infarction or hemorrhage in 2, and unknown in 3. No pts with FL died of PD, and no pts with TL who had survived for 7 months after HCT relapsed thereafter. By a multivariate analysis, the OS for DLBCL was significantly worse than that of TL [HR 4.8 (1.7-13.2), p=0.002]. OS for FL was not significantly different from that of TL [HR 0.74 (0.2-2.4), p=0.6]. Other factors that influenced OS were aaIPI at HCT [high or high-intermediate risk, HR 3.7 (1.6-8.5), p=0.002] and the serum albumin level at HCT [ Conclusion: In the rituximab era, pts with TL showed more favorable outcomes after allo-HCT compared to those with DLBCL, and there was no significant difference in OS between FL and TL. AaIPI and the serum albumin level at HCT may be useful surrogate markers that influence OS for pts with B-NHL after allo-HCT. Allo-HCT, mainly with the use of a RIC regimen, might be a promising option for pts with relapsed or refractory FL and TL. Disclosures: No relevant conflicts of interest to declare.

Abstract 3353 Poster Board III-241 [Background] Renal dysfunction is a life-threatening complication after hematopoietic stem cell transplantation, and the incidence of acute and chronic renal dysfunction after non-myeloablative transplantation is reportedly, 40 to 50% and 16 to 35%, respectively. In this study, we evaluated this complication after reduced-intensity stem cell transplantation (RIST) at a single institute. [Patients and Methods] We retrospectively reviewed the medical records of 286 patients (median age, 54 years; range, 21-68) with various hematological disorders who underwent RIST between 1999 and 2007, using a conditioning regimen that consisted of busulfan (oral 8 mg/kg or iv 6.4 mg/kg) and fludarabine (180 mg/m2, n=214) or cladribine (0.66 mg/kg, n=72). Sixty-seven patients also received 2-4 Gy of total body irradiation (TBI). The diagnosis included AML (n=77), ALL (n=9), MDS (n=56), malignant lymphoma (n=116), CML (n=14), and other (n=14). Whereas 188 patients were transplanted from a related donor (BM n=8, PB n=180), 98 were transplanted from an unrelated donor (BM n=80, PB n=1, CB n=17). GVHD prophylaxis consisted of cyclosporine (CSP, starting dose 3 mg/kg/day civ, target whole blood conc. 250-350 ng/ml, n=235) or tacrolimus (starting dose 0.03mg/kg/day civ, target whole blood conc. 10-20 ng/ml, n=51), with (n=131) or without (n=155) methotrexate, and 71 patients also received anti-human T-lymphocyte immunoglobulin (ATG, Fresenius, 5-10 mg/kg). Renal function was assessed in terms of the serum creatinine concentration and the estimated glomerular filtration rate (eGFR) as calculated by the Modification of Diet in Renal Disease equation (MDRD) for our population (eGFR=0.741*175*Age-0.203*Cr-1.154, *0.742, if female). Acute renal failure (ARF) within 100 days was categorized as grade 0 (decrease in eGFR of 25% but [Results] The median follow-up in surviving patients was 746 days (87-3291). The numbers of patients who developed grade 1, 2 and 3 ARF were 139, 72 and 9, respectively. The cumulative incidence of grade 2-3 ARF was 29 % at 100 days after RIST. The overall survival was significantly better in patients with grade 0-1 ARF than in those with grade 2-3 ARF (62% vs 42% at 2 years, p [Conslusion] We found that ARF was significantly associated with a higher mortality after busulfan-based RIST, and that preceding grade 2-3 ARF led to the occurrence of CKD in surviving patients, which highlights the importance of preventing ARF. This study also indicated that the incidence of acute and chronic renal complications was lower in our population compared to previously reported data from Western countries. Therefore, ethnicity should be taken into account when designing future international clinical trials. Disclosures: No relevant conflicts of interest to declare.