Citations

Abstract Abstract 1746 Diagnosis of essential thrombocythemia (ET) has been updated in the last World Health Organization (WHO) classification, that provides a guideline to distinguish ET from early/prefibrotic primary myelofibrosis. These two conditions differ in term of disease evolution and survival (Barbui et al, J. Clin. Oncol. 2011). To design a prognostic model for survival in WHO-defined ET (International Prognostic Score for Essential Thrombocythemia, IPSET), we studied 891 patients with strict WHO diagnostic criteria. Demographics have been presented elsewhere (Barbui et al, J. Clin. Oncol. 2011). We tested the prognostic impact on survival of age, prior thrombosis, leukocyte count, platelet count, hemoglobin level, JAK mutational status, splenomegaly. Harrell's C concordance statistics were used to set the best cutoff levels of continuous variables in order to predict survival. Univariate Cox proportional hazard regression showed that age over 60 years (P<.0001), leukocyte count greater than 11 x109/L (P<.0001), anemia (P=.04), platelet count greater than 1000 x109/L (P<.004) and prior history of thrombosis (P< 0001) were significant risk factors for survival. Age over 60 years (hazard ratio-HR- 6.5, 95% CI: 3.9–10.7; P<.0001), leukocyte count greater than 11 × 109/L (HR: 3.1, 95% CI: 2–4.7; P<.0001) and prior history of thrombosis (HR: 2.9, 95% CI: 1.9–4.5; P< 0001) retained statistical significance on survival by multivariable analysis and were included in the new prognostic model. We assigned each factor an integer weight close to the corresponding HR in the multivariable Cox regression: weight 2 for age over 60 years; weight 1 for leukocyte count greater than 11 x109/L and for prior thrombosis. Finally, we defined the IPSET score by allocating patients into three risk categories with significantly different survival according to the sum of weights: low risk (sum of weights=0; n= 342; median survival not reached), intermediate risk (sum=1-2; N=374; median survival 24.5 years), and high risk (sum=3-4, n=158; median survival 13.8 years). Fisher exact test did not reveal a difference in the distribution of the causes of death among IPSET categories. We validated the model in two independent cohorts: one from Germany (132 WHO-defined ET) and another from France (234 ET patients not strictly diagnosed according to WHO). Log rank test and Cox regression showed significant differences in term of survival among IPSET categories in both series. Finally, we designed an age-specific IPSET model for patients younger than 60 years (IPSET-y). Using the same methodology, we found that age over 45 years (weight 2), leukocyte count greater than 11 × 109/L (weight 1) and prior history of thrombosis (weight 1) were independent risk factors for survival. IPSET-y defined three risk categories (LR, sum=0; IR, sum=1-2; HR, sum=3–4) with a median survival not reached in LR and IR, and of 22.3 years in HR. In conclusion, IPSET, based on age over 60 years, leukocyte count greater than 11 x109/L and history of thrombosis allows prognostic assessment of WHO-defined ET. The validation process makes IPSET applicable in all patients phenotypically appearing as ET. IPSET models may be useful for treatment decision-making. Disclosures: Vannucchi: Italfarmaco: Consultancy; Novartis: Honoraria. Gisslinger:AOP Orphan Pharmaceuticals AG: Research Funding.

Abstract Abstract 3846 INTRODUCTION There is strong evidence indicating that the clear-cut separation of prefibrotic primary myelofibrosis (PMF) from essential thrombocythemia (ET) by consequent application of the World Health Organization (WHO) 2008 criteria is reflected in different, well defined clinical pictures and divergent prognoses (Barbui et al, JCO 2011,Thiele et al, Blood 2011). Very recently the specific risk profile for arterial and venous thrombosis in WHO- diagnosed ET was published (Carobbio et al, Blood 2011). In PMF so far all published data on vascular events were exclusively based on overt disease manifestations until now there are no data available regarding prefibrotic stages. Consequently, we aimed to evaluate the corresponding risk profile of patients with WHO-diagnosed prefibrotic PMF. METHODS A total number of 264 patients with WHO-defined prefibrotic PMF derived from either the Medical University of Vienna or an International Database (Barbui et al, JCO 2011) were studied. Nonfatal thrombotic events considered in this study were reported as rates per 100 patient-years and included transient ischemic attacks, thrombotic cerebrovascular accidents, coronary artery disease, myocardial infarction, peripheral arterial disease, deep vein thrombosis of peripheral vasculature, pulmonary embolism, and abdominal large vein thrombosis. Cardiovascular risks factors considered, comprised of arterial hypertension, diabetes mellitus and tobacco use. To evaluate risk factors for total thrombosis and for arterial and venous events in particular multivariate Cox- regression analysis including the co-variables sex, age, previous thrombotic event, laboratory parameters measured at diagnosis and need for cytoreductive and/or antiplatelet therapy during follow-up was calculated. P values less than 0.05 were considered as statistically significant. RESULTS After a median follow- up of 5.8 years (range0.0 – 27.2), the total rate of non fatal thrombotic events was 2.1% patient-years (95% CI, 1.5–2.8); the incidence of arterial events was higher (1.7% patient- years) than of venous events (0.6% patient-years).Considering thrombosis in general a higher white blood cell (WBC) count enhances the risk significantly (p=0.005; HR 1.15). This is also true in arterial events in particular (p=0.047; HR 1.12). A lower platelet count is associated with a higher risk for thrombotic events; for thrombosis in general this association is of borderline significance (p=0.056; HR 0.99), for arterial thrombosis in particular of significance (p= 0.042; HR 0.99). A lower hemoglobin level is associated with a higher risk for venous thrombosis (p=0.007; HR 0.59). CONCLUSION Leukocytosis appears as a risk factor for thrombosis in general and also for arterial thrombosis in particular in WHO-diagnosed prefibrotic PMF. Moreover, higher platelet counts seem to decrease significantly the risk for thrombotic events in general and arterial thrombosis in particular. Anemia is associated with a higher risk for venous thrombosis. These observations are partly in line with recently published findings in WHO-diagnosed ET (Carobbio et al,2011) and might indicate the existence of a specific risk profile for thrombotic events in prefibrotic PMF. This is the first study reporting data on the risk profile for thrombosis in WHO-diagnosed prefibrotic PMF. Certainly these findings ask for validation in a larger patient population. Disclosures: Gisslinger: Novartis: Speakers Bureau; Celgene Austria: Research Funding, Speakers Bureau; AOP-Orphan Pharmaceuticals AG: Speakers Bureau. Vannucchi:Novartis: Honoraria.

Abstract Background:Recurrent mutations in ATM, JAK1/3 and STAT5B genes have been identified in T-cell prolymphocytic leukemia (T-PLL), a mature T cell leukemia with poor survival. However, much remains to be understood regarding the dysregulated pathways involved in the pathogenesis of this aggressive disease. Here, we integrated the analyses of whole exome sequencing (WES) and transcriptomes of a cohort of 12 T-PLL samples to gain further insights into molecular mechanisms of this malignancy. Methods: Leukemic cells were isolated from peripheral blood or bone marrow samples of T-PLL patients. Tumor DNA and RNA, and germline DNA were extracted from purified leukemic T cells and bone marrow derived stromal cells, respectively. WES (n=12) and transcriptome analysis (n=10) were performed and data analyzed with published standard methods (Robinson et al. 2010 and DePristo et al. 2011) Results: 7 paired tumor and germline DNA and 5 tumor-only DNA samples were used for WES analysis. Mutations in ATM and TET2 were detected in 4 (33%) and 1 (8%) patients, respectively. JAK3 (p.M511I, p.Q501H and p.Q503H) or STAT5B (2 p.T628S and 1 p.N642H) mutations each occurred in 3 (25%) cases and were mutually exclusive, consistent with prior reports. Importantly, we found several novel mutations in genes with regulatory roles in the NOTCH signaling pathway. Specifically, 2 somatic mutations p.A3V and p.A3S in NOTCH2 and 2 other mutations (p.S244L and p.A1414V) in NOTCH4 were identified in 4 (33%) patients. One mutation was in the EGF- like and another one in the NODP domain critical for NOTCH-mediated cellular differentiation. Two (16.7%) novel missense mutations (p.G174D and p.V836I) were found in MAML2. Three missense mutations (2 p.S583N and 1 p.R190H) occurred in MAML1. Both MAML2 and MAML1 are essential cofactors of the NOTCH signaling pathway. In addition, a somatic mutation in the NOTCH signal regulator DTX2 (p.G268D) was detected. Altogether 7 (58.3%) patients harbored mutations in genes with a regulatory role in the NOTCH pathway. Among the epigenetic modifiers, we found deletions and point mutations in KDM6B and KDM6A in 4 (30%) patients including 2 codon deletions in KDM6B (p.X751Val) and 1 missense mutation each in KDM6B (p.R1016Q) and KDM6A (p.V510G). KDM6A and KDM6B are histone H3 lysine 27 demethylases known to be involved in regulation of DNA repair and play an important role in embryonic differentiation. Transcriptome analyses of 10 T-PLL cases versus normal CD3+ T cells from 5 healthy donors revealed 706 up-regulated and 655 down-regulated genes. Consistent with prior data, TCL1A and TCL1B were significantly overexpressed (23.7 and 13.1 fold, respectively). Using Ingenuity Pathway Analysis, we found PTEN Signaling, glutamate receptor, and axonal guidance signaling to be among the top 3 upregulated pathways. The top upstream regulators implicated for the up-regulated signals were FGF, Wnt/β-catenin and TNF. The top 3 down-regulated pathways were granulocyte adhesion and diapedesis, IL-17A in psoriasis and IL-10 signaling. The top regulators for the down-regulated pathways were LPS, TNF and IFNg. Wnt/β-catenin and Human embryonic stem cell pluripotency signaling were among the top 20 up-regulated pathways. Many genes involved in the regulation of Wnt signal pathway were included in the above pathways, including Wnt ligands (Wnt9A, Wnt4), transmembrane receptors (CDH1, LRP5, FZD6, FZD7, SMO), cytoplasmic factor (AXIN2), and nuclear factors (MYC, SOX12, SOX8, SOX18, CCND1). Summary: Our study identified recurrent mutations in the NOTCH signaling pathway as well as dysregulated embryonic developmental pathway, e.g. Wnt/NOTCH as newly implicated molecular mechanisms in T-PLL pathogenesis for further functional studies. Additionally, novel (KDM6A and KDM6B) and known mutations (ATM, TET2) in chromatin regulatory genes underscore the importance of epigenetic dysregulation in the tumorigenesis of T-PLL. Disclosures Parikh: Pharmacyclics: Honoraria, Research Funding. Mustjoki:Ariad: Research Funding; Bristol-Myers Squibb: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; Novartis: Honoraria, Research Funding. Ding:Merck: Research Funding.

Abstract Abstract 457 Introduction- The 2008 World Health Organization (WHO) diagnostic criteria for myeloproliferative neoplasms (MPN) underscore the role of bone marrow (BM) morphology in distinguishing essential thrombocythemia (ET) from early, and at times prefibrotic, primary myelofibrosis (PMF) that clinically presents like ET. The value of such a distinction in predicting clinical outcome has been questioned by some investigators. Study Design- Clinician scientists and hematopathologists from seven international centers of excellence for ET convened to design a clinicopathologic database of patients locally diagnosed and treated as ET. Study eligibility criteria included availability of treatment-naïve BM specimens obtained within one year of diagnosis. All bone marrows subsequently underwent a central blinded re-review by the author of the pertinent WHO chapter (JT) who applied strict WHO guidelines to identify cases of early PMF that were spuriously diagnosed as ET. Results- Revision of the BM biopsies according to the WHO morphological criteria confirmed ET in 891 patients (81%). Diagnosis was revised to early, prefibrotic PMF in 180 patients (16%). The remaining 33 (3%) BM specimens were qualitatively inadequate for accurate classification or represented unclassified cases. i) At presentation, early PMF, as opposed to true ET, was characterized by higher leukocyte (p<0.0001) and platelet (p=0.002) counts, lower hemoglobin (p=0.01) and hematocrit (p=0.001) levels, higher serum lactate dehydrogenase level (p<0.0001), higher circulating CD34+ cell count (p=0.03) and higher rate of palpable splenomegaly. JAK2V617F mutational frequency was 60% in each of the two groups. ii) Median follow-up was 6.2 years for ET and 7.0 years for early PMF. During this period, the rates of arterial (1.2-1.4% patients/year) and venous (0.6 patients/year) thrombotic complications were similar in the two groups. However, patients with early PMF, as compared to those with ET, were more likely to develop overt myelofibrosis (1% vs. 0.5% patients/year; RR=2.0, p=0.04) or acute leukemia (0.6% vs. 0.1% patients/year; RR=5.2, p=0.001). Cumulative leukemic transformation rate at 10 and 15 years was 0.7% and 2.1% in true ET versus 5.8% and 11.7% in PMF Similarly, survival was significantly worse in patients with early PMF (mortality rate: 2.7% vs. 1.3% patients/year; RR=2.1, p=0.002).The 10 and 15-years overall survival rates were: 89% and 80% in true ET versus 76% and 59% in PMF. On multivariable analysis, other risk factors for poor survival were age > 60 years (HR=6.3, p<0.0001), a leukocyte count of > 11×109/L (HR=2.13, p<0.0001) and history of thrombosis (HR=3.0, p<0.0001). Conclusions- The current study validates the clinical relevance of strict adherence to WHO criteria in the diagnosis of ET and provides seminal information on the survival and risk of leukemic transformation in strictly WHO-defined ET, which appears to be substantially better than previously assumed. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 2958 PURPOSE: Recent advances in understanding of the molecular alterations that occur at the genetic and epigenetic levels in Multiple Myeloma (MM) have led to major leaps in identifying molecular pathways that regulate progression and resistance to therapeutic agents. However, despite great scientific advances at the genomic level, studies to identify signaling pathways deregulated at the functional proteomic level in MM are limited. Using an antibody-based protein microarray technique, we identified Citron Rho Interacting Kinase (CRIK) as a protein that was highly expressed in primary multiple myeloma (MM) cells compared to normal plasma cell. We therefore sought to investigate the functional role of CRIK in MM cells. Methods: Primary CD138+ sorted MM cells were obtained from the bone marrow of patients after informed consent. We determined the protein expression level of 512 polypeptides in 12 samples of newly diagnosed patients with MM and 4 healthy control using high-throughput proteomic analysis with antibody-based protein microarray (Clontech, CA). MM.1S, OPM2, RPMI8226, and INA6 were used to perform functional validation. Protein expression has been studied by immunoblotting. Gene expression analysis has been assessed using the Affymetrix U133A platform and qPCR. Lentivirus was used to knockdown CRIK in MM cell lines (MM.1S, RPMI8226, OPM2, and INA6). DNA synthesis, cell survival, cell cycle profiling and apoptosis were assessed by BrdU, MTT, PI and Apo2.7 staining, and flow cytometry analysis, respectively. Results: We first showed that CRIK was overexpressed in 12 patients with MM compared to normal CD138+ cells obtained from healthy controls using high-throughput protein microarray. We further confirmed CRIK expression using immunohistochemistry in the same samples of MM patients. We next correlated CRIK gene expression level (CIT) with prognosis using previously published gene expression datasets and found that CRIK correlated with poor prognosis. Knockdown of CRIK in MM cell lines led to an anti-proliferative and pro-apoptotic effect in all MM cell lines tested. Indeed, CRIK-knockdown MM cells were characterized by a reduction of 60–80% in the proliferation rate, supported by reduction of DNA synthesis and G2/M phase cell cycle arrest. Moreover, induction of cytotoxicity of caspase-3, caspase-8, caspase-9, and parp cleavage was also demonstrated in CRIK knockdown cells compared to scramble probe transfected cells. We also showed that CRIK knockdown led to cytokinesis in MM cell lines, indicating a possible mechanism of inhibition of proliferation of these cells. Conclusion: In this study, we show that MM cells express a high level of a novel protein CRIK, and that inhibition of this protein leads to significant inhibition of proliferation and survival of MM cells. CRIK could be a critical therapeutic target in MM. Disclosures: Anderson: Millennium Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Ghobrial:Celgene: Membership on an entity's Board of Directors or advisory committees; Millennium: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees.

Abstract Background In the recent International Prognostic Score for Thrombosis in essential thrombocythemia (IPSET-thrombosis), age and history of thrombosis were confirmed as independent risk factors for future thrombosis and the study also identified independent prothrombotic role for cardiovascular (CV) risk factors and JAK2 V617F mutation (Barbui et al. Blood 2012). Methods In the current study, we re-analyzed the original IPSET-thrombosis data in 1019 patients with WHO-defined ET in whom JAK2 mutational status was available, in order to quantify the individual contributions of JAK2 mutations and CV risk factors in conventionally-assigned low and high risk ET, as well as in age- versus thrombosis-defined high risk status. Results After a median follow-up of 6.8 and 5.0 years in conventionally-assigned low- and high-risk patients, respectively, the overall annual rate of total thrombosis (108 events) in conventionally-assigned low- and high-risk patients was 1.11%-pt/y (CI 0.81-1.52) and 2.46%-pt/y (CI 1.94-3.11) respectively (p=0.001), and the difference was mainly due to a higher frequency of arterial thrombosis in high-risk patients (p<0.001).The influence of JAK2 mutational status and CV-risk factors on the rate of thrombosis in conventionally assigned low- and high-risk groups is presented in the table. Table 1. Additional risk factors N (%) Event Rate % pts/yr (95% CI) P-value P-value P-value trend Low risk 506 (50) 39 1.11 (0.81-1.52) None 200 (40) 7 0.44 (0.21-0.92) ref Cardiovascular risk factor 36 (7) 3 1.05 (0.34-3.25) 0.220 0.227 JAK2V617F 213 (43) 21 1.59 (1.04-2.44) 0.001 0.217 Both 52 (10) 8 2.57 (1.29-5.15) <0.001 ref <0.001 High risk 513 (50) 69 2.46 (1.94-3.11) None 111 (22) 10 1.44 (0.78-2.68) ref Cardiovascular risk factor 44 (9) 4 1.64 (0.62-4.37) 0.909 0.067 JAK2V617F 222 (43) 30 2.36 (1.65-3.38) 0.168 0.082 Both 136 (27) 25 4.17 (2.82-6.17) 0.011 ref 0.005 The number of major arterial and venous thrombosis was reported as rates per 100 patient-years and the difference among groups was assessed by Mantel Cox log-rank test i) Conventionally-assigned low-risk group. Amongst 506 patients, 200 (40%) displayed neither JAK2 mutation nor CV risk factors and their annual rate of thrombosis was 0.44%, as opposed to 1.05% in the presence of CV risk factors (P=NS), 1.59% in the presence of JAK2 mutation (p=0.001) and 2.57% in the presence of both CV risk factors and JAK2 mutation (P<0.001). There was no significant difference when low-risk patients with both JAK2 mutation and CV risk factors were compared with either those with CV risk factors only (p=0.227) or those with JAK2 mutation only (p=0.217). ii) Conventionally assigned high-risk group: The absence or presence of one or both of the aforementioned additional risk factors for thrombosis were documented in 111 (22%), 44 (9%), 222 (43%) and 136 (27%) patients, respectively, with corresponding annual rates of thrombosis at 1.44%, 1.64%, 2.36% and 4.17% (Table). High-risk patients with both risk factors had a significantly higher risk of thrombosis compared to their counterparts with the absence of JAK2 mutations and CV risk factors (p=0.011). Additional analysis revealed limited enhancement of thrombosis risk by either JAK2 mutations or CV risk factors or both in patients whose high-risk status was defined by the presence of thrombosis history, regardless of age (P=NS). In contrast, the presence of JAK2 mutations, with or without CV risk factors, might have affected thrombosis risk in patients where high-risk status was defined by age alone (p=0.05). Conclusions The current study suggests the possibility of considering four risk categories in ET: "very low risk" group (age ≤60 years and without thrombosis history, JAK2 mutations or CV risk factors); "low risk" (age ≤60 years and without thrombosis history but with JAK2 mutations or CV risk factors); "intermediate risk" (age>60 years but without thrombosis history or JAK2 mutations); and "high risk" (thrombosis history at any age or JAK2 -mutated patients who are older than 60 years of age). Treatment recommendations for each one of the above-mentioned new risk categories should be examined in the context of prospective controlled studies. Disclosures Barbui: Novartis: Speakers Bureau. Vannucchi:Novartis Pharmaceuticals Corporation: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Shire: Speakers Bureau; Baxalta: Membership on an entity's Board of Directors or advisory committees. Buxhofer-Ausch:AOP Orphan: Research Funding. De Stefano:Novartis: Research Funding, Speakers Bureau; Janssen Cilag: Research Funding; Shire: Speakers Bureau; GlaxoSmithKline: Speakers Bureau; Bruno Farmaceutici: Research Funding; Roche: Research Funding; Amgen: Speakers Bureau; Celgene: Speakers Bureau. Gisslinger:Janssen Cilag: Honoraria, Speakers Bureau; AOP ORPHAN: Consultancy, Honoraria, Research Funding, Speakers Bureau; Geron: Consultancy; Sanofi Aventis: Consultancy; Celgene: Consultancy, Honoraria, Research Funding, Speakers Bureau; Novartis: Honoraria, Research Funding, Speakers Bureau.

Abstract Malignant B-cells characteristically home to the bone marrow and lymph nodes. However, the mechanisms by which cells are recruited into and mobilized from the bone marrow/lymph nodes into the peripheral blood are not well understood. Chemokines such as SDF-1 and it receptor CXCR4 play a central role for lymphocyte trafficking and homing. Downstream activation of the PI3K pathway by chemokines has been implicated in the migration of many cell types. We recently demonstrated that CXCR4 expression correlates significantly with disease progression in CLL. Patients with Rai stage 4 had a higher expression of CXCR4 when compared to patients with Rai stage 0. The expression of CXCR4 was not found on CLL B cells resident within the lymph nodes implying that there may have been downregulation of CXCR4. In this study, we explore the molecular mechanisms involved in homing and migration of B-CLL cells in response to CXCR4 and investigated the role of the PI3K pathway in migration of CLL cells in response to SDF-1. Boyden chamber in vitro migration assays were used with primary CLL peripheral blood cells and the MEK1 CLL cell line. In addition, we expressed fluorescent YFP-CXCR4 in the cells and used confocal microscopy to visualize changes in the subcellular location of the fluorescent CXCR4 before and after SDF-1 stimulation. Inhibitors of the PI3K pathway such as the PI3K inhibitor LY294002 (10uM, one hour pretreatment) and the mTOR inhibitor, rapamycin (200nM overnight) were used. SDF-1 induced a dose dependent migration of primary CLL cells and MEK1 cells, indicating functional CXCR4 receptors. MEK 1 cells transfected with YFP-CXCR4 demonstrated surface localization on the cells. 3-Dimensional and continuous live imaging after SDF-1 stimulation for 30 minutes demonstrated alterations in the CXCR4-YFP leading to its capping and internalization subcellularly. Pretreatment of the cells with PI3K pathway inhibitors led to inhibition of migration with LY294002 but not with rapamycin. Confocal microscopy demonstrated abrogation of subcellular localization in the presence of LY294002 but not with rapamycin with the addition of SDF-1. These results demonstrate that CLL cells express functional CXCR4 receptora and that the PI3K pathway is essential for SDF-1 dependent CLL migration. In addition, we demonstrate that the CXCR4 receptor is internalized in response to SDF-1 stimulation indicating that CLL cells downregulate the CXCR4 receptor once they home to the bone marrow or lymph nodes where there is abundant SDF-1 in the microenvironment. This leads to the confinement of the cells in the microenvironment preventing further migration of the cells outside of the bone marrow/lymph nodes. Supported in part by CA97274

Abstract Malignant plasma cells characteristically home to the bone marrow (BM). However, the mechanisms by which cells are recruited into and mobilized from the bone marrow into the peripheral blood (PB) are not well understood. In this study, we explore the molecular mechanisms involved in homing and migration of plasma cells in response to CXCR4 and investigated the role of the PI3K pathway in migration of MM cells in response to SDF-1. CXCR4 surface expression was determined by FACS analysis (PE CXCR4, Pharmingen) using samples from bone marrow and peripheral blood of patients diagnosed with multiple myeloma (MM), monoclonal gammopathy of undetermined significance (MGUS) and primary systemic amyloidosis (AL). All results were expressed as percent expression in gated CD38+ and CD45+ cells. Boyden chamber in vitro migration assays were performed using Kas6/1MM cells. In addition, live confocal microscopy was used to visualize changes in the subcellular location of YFP-fluorescent CXCR4 before and after SDF-1 stimulation. Cells were pretreated with 10mM LY294002 or 200nM rapamycin to assess the effect of inhibition of PI3K or mTOR on CXCR4 subcellular localization. Immunoblotting was performed to confirm inhibition of the PI3K pathway. Comparisons between groups was performed using Mann-Whitney testing. The median CXCR4 expression is described in table 1. There was a significant difference between expression of BM CXCR4 in MM and MGUS (p=0.02). SDF-1 induced dose dependent migration of Kas 6/1 cells indicating a functional CXCR4 receptor. MM cells transfected with YFP-CXCR4 demonstrated surface localization on the cells. 3-Dimensional and continuous live imaging after SDF-1 stimulation for 30 minutes demonstrated alterations in the CXCR4-YFP leading to its capping, internalization subcellularly, and production of pseudopodia in response to SDF-1. This process was abrogated with pretreatment with LY294002 and rapamycin. These data demonstrate for the first time that the surface expression of CXCR4 is markedly elevated in the peripheral blood as compared to the bone marrow. Once in the bone marrow, and with the presence of excess SDF-1, the receptor becomes internalized and downregulated. In contrast to MM, CXCR4 expression on plasma cells in the bone marrow of normal and MGUS patients was higher. In addition, we demonstrate that the process of CXCR4 subcellular localization is abrogated by the administration of PI3K inhibitors LY294002 and rapamycin. These data suggest that CXCR4 expression is required for MM cells to circulate, and that downregulation occurs in the BM leading to immobilization of the cells. Future clinical trials using CXCR4 inhibitors, or inhibitors of PI3K and mTOR to prevent the homing and migration of MM cells into the bone marrow may be explored. This was supported in part by CAP50 CA97274. CXCR4 expression N=45 Median CXCR4% expression of total plasma cells Range MM BM (n=23) 27 4.3–90.1 MM PB (n=5) 91 60–95.5 MGUS BM (n=6) 65 41–78.6 AL BM (n=7) 46 17.5–71.6 Normal BM (n=4) 59 6.3–69.5 Kas6/1 cell line 100 -

Abstract Background . Cell-free DNA (cfDNA) sequencing enables serial temporal sampling, which offers the possibility of following the dynamics of biomarkers and clonal evolution in Multiple Myeloma (MM) over time. The use of cfDNA in clinical practice as a molecular biomarker and for monitoring response/resistance is dependent on a comprehensive profile of matched cfDNA and tumor DNA (tDNA) samples. Here we performed Ultra-Low Pass Whole Genome Sequencing (ULP-WGS) followed by whole-exome sequencing (WES) and targeted deep sequencing of matched cfDNA/tDNA samples from MM patients. Methods. We performed next generation sequencing of matched cfDNA/tDNA samples for 63 patients with newly diagnosed or relapsed MM, SMM, or MGUS. Libraries were constructed using the Kappa Hyper kit and sequenced by ultra-low-pass whole-genome sequencing (ULP-WGS, 0.1x coverage) to quantify tumor fraction within cfDNA. WES was performed on 30 matched samples cfDNA/tDNA/germline DNA from 10 patients with more than 5% of tumor fraction. Libraries were hybridized to the Nextera Rapid Capture Exome kit (Illumina) and then sequenced on HiSeq 4000 (Illumina). Targeted deep sequencing was performed on 32 matched cfDNA/tDNA samples from 16 patients using the HaloPlex HS technology (Agilent), allowing for molecular barcoding. Libraries were constructed according to the manufacturer's instructions and sequenced on HiSeq 2500 (Illumina). Sequencing data were analyzed using the Firehose pipelines, including MuTect, ABSOLUTE, ReCapSeg, GISTIC and MutSig. Results. We first used a cost-effective approach to establish the tumor content of cfDNA in a large-scale manner by ULP-WGS. Among 63 tested samples (53 MM, 6 SMM and 4 MGUS patient samples), the tumor fraction within cfDNA ranged from 0 to 81% with a mean of 10%. About 43% of these samples had tumor fraction greater than 5% within cfDNA. To assess whether cfDNA can capture the genetic diversity of MM and inform clinical management, we performed WES of matched cfDNA/tDNA/germline DNA samples for 10 patients (mean target coverage 194x). Copy number alterations (CNAs) assessed by WES (ReCapSeg) were consistent between cfDNA and tumor DNA. Similarly, focal CNAs assessed by GISTIC were consistent between tDNA and cfDNA. We then examined the overlap of somatic single nucleotide variants (SSNVs) between WES of cfDNA and matched tDNA. We found, on average, 100% of the clonal and 96% of the subclonal (range 54-100%) SSNVs that were detected in the tumor were confirmed to be present in cfDNA. Similarly, for mutations detected in the cfDNA, we found, on average, 100% of the clonal and 99% of the subclonal (range 98-100%) SSNVs were confirmed in the tumor. To assess whether targeted deep sequencing of cfDNA could be a good proxy for tumor biopsy we used a targeted deep sequencing approach of known MM driver genes. Libraries were prepared using unique molecular barcodes to avoid duplication rates, for 32 matched cfDNA/tDNA samples from 16 patients with MM. The mean target coverage was 596x. We found similar frequencies of altered MM driver genes in both cfDNA and tDNA, including KRAS, NRAS, and TP53, indicating that cfDNA can be used for precision medicine. Conclusions. Our study demonstrates that both WES and targeted deep sequencing of cfDNA are consistently representative of tumor DNA alterations in terms of CNAs, focal CNAs and SSNVs. This approach could therefore be used to longitudinally follow clonal evolution across the course of the disease and precision medicine in patients with MM. Disclosures Palumbo: Takeda: Employment, Honoraria; Janssen Cilag: Honoraria. Kumar:Noxxon Pharma: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Millennium: Consultancy, Research Funding; Skyline: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Research Funding; Kesios: Consultancy; Glycomimetics: Consultancy; BMS: Consultancy; Array BioPharma: Consultancy, Research Funding; Sanofi: Consultancy, Research Funding; AbbVie: Research Funding; Onyx: Consultancy, Research Funding. Roccaro:Takeda Pharmaceutical Company Limited: Honoraria. Facon:Amgen: Consultancy, Speakers Bureau; Novartis: Consultancy; Janssen: Consultancy, Speakers Bureau; Bristol: Consultancy; Millenium/Takeda: Consultancy; Celgene: Consultancy, Speakers Bureau; Karyopharm: Consultancy. Ghobrial:Celgene: Honoraria, Research Funding; BMS: Honoraria, Research Funding; Noxxon: Honoraria; Novartis: Honoraria; Takeda: Honoraria; Amgen: Honoraria.

Abstract Introduction: IgM-secreting myeloma is rare, encompassing about 1% of all the myeloma cases. Given its rarity, the characteristics and survival of these patients have not been extensively studied. Therefore, we carried out a multicenter retrospective study in patients with IgM myeloma. Methods: The study protocol was reviewed and approved by the Institutional Review Board of each participating institution. Clinical data were gathered and included age, sex, hemoglobin, calcium, LDH, estimated glomerular filtration rate (GFR), presence of lytic bone lesions, International Staging System score, cytogenetic abnormalities, final outcome and overall survival (OS) time. OS was defined as the time in months from diagnosis to last follow-up or death. The Chi-square and the rank-sum tests were used to compare categorical and continuous variables, respectively. The Kaplan-Meier method was used to estimate OS and the log-rank waas used to compare groups. The Cox proportional-hazard regression method was used to fit univariate and multivariate survival models, reported as hazard ratio (HR) with 95% confidence intervals (CI). All reported p-values are two-sided, and were considered significant if less than 0.05. Results: A total of 159 patients with IgM myeloma from 20 centers from Europe, USA and Latin America were included in this analysis. Patients were diagnosed between 1996 and 2015. The median age at diagnosis was 65 years (range 37-86 years) with a male predominance (68%). The median serum IgM level was 2510 mg/dl (range 27-12,100 mg/dl) with 25% of patients having a serum IgM within normal limits but an IgM monoclonal spike detectable in serum electrophoresis. Hemoglobin levels <10 g/dl were seen in 49 patients (32%), serum calcium was elevated in 24 (16%), estimated GFR of 60 ml/min or less in 56 (37%), lytic lesions were detected in 86 (58%), and serum LDH was elevated in 28 (24%). ISS scores of 1, 2 and 3 were seen in 53 (36%), 63 (43%) and 31 (21%) of patients, respectively. Although immunohistochemistry and/or flow cytometry data were limited, CD20 expression was seen in 15/26 (58%) and cyclin D1 in 10/15 (67%) patients. The most common cytogenetic abnormalities were t(11;14) in 26/67 (39%), del13q in 25/76 (33%) and del17p in 6/76 (8%) patients. 149 patients (94%) received at least one line of systemic therapy for myeloma of which 13 (9%) received rituximab as part of initial therapy. After a median follow-up of 47 months, 74 patients (47%) have died. The median OS was 62 months (95% CI 51-79 months). Cause of death was known in 38 patients, and the most common was myeloma progression (74%). IN the univariate analysis, prognostic factors associated with a worse OS were age (HR 1.03, 95% CI 1.01-1.06; p=0.01) and ISS score (ISS 2: HR 1.43, 95% CI 0.83-2.48; p=0.2, and ISS 3: HR 3.03, 95% CI 1.54-5.98; p=0.001, using ISS 1 as reference group), while male sex was associated with a better OS (HR 0.56, 95% CI 0.34-0.90; p=0.02). Hemoglobin, calcium, estimated GFR and lytic lesions were not associated with OS. In the multivariate analysis, male sex was associated with a better OS (HR 0.57, 95% CI 0.35-0.95; p=0.03) and ISS with worse OS (ISS 2: HR 1.57, 95% CI 0.89-2.74; p=0.12, and ISS 3: HR 2.76, 95% CI 1.38-5.55; p=0.004, using ISS 1 as reference group). Conclusion: Patients with IgM myeloma apparently present with similar clinical characteristics as patients with non-IgM myeloma. Pathologically, CD20 and cyclin D1 expression is common. The most common cytogenetic abnormalities identified were t(11;14) and del13q. Survival does not appear shorter than non-IgM myeloma patients, and the ISS appears to have similar prognostic value. Disclosures Castillo: Millennium: Research Funding; Janssen: Honoraria; Otsuka: Consultancy; Biogen: Consultancy; Abbvie: Research Funding; Pharmacyclics: Honoraria. Ghobrial:Celgene: Honoraria, Research Funding; BMS: Honoraria, Research Funding; Novartis: Honoraria; Takeda: Honoraria; Noxxon: Honoraria; Amgen: Honoraria. Hájek:Celgene: Consultancy, Research Funding; Amgen: Consultancy, Honoraria, Research Funding; Janssen: Honoraria; BMS: Honoraria; Takeda: Consultancy. Hungria:International Myeloma Foundation Latin America: Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy; Amgen: Consultancy; Roche: Consultancy; Bristol: Consultancy; Janssen: Consultancy, Speakers Bureau. Niesvizky:Celgene: Consultancy, Research Funding, Speakers Bureau; Takeda: Consultancy, Research Funding, Speakers Bureau; Onyx: Consultancy, Research Funding, Speakers Bureau. Reagan:Alexion: Honoraria; Seattle Genetics: Membership on an entity's Board of Directors or advisory committees. Richardson:Celgene: Membership on an entity's Board of Directors or advisory committees. Spicka:Janssen Cilag: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Consultancy, Honoraria; BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Millenium: Honoraria. Gertz:Celgene: Honoraria; Med Learning Group: Honoraria, Speakers Bureau; Research to Practice: Honoraria, Speakers Bureau; Alnylam Pharmaceuticals: Research Funding; Novartis: Research Funding; Prothena Therapeutics: Research Funding; Ionis: Research Funding; NCI Frederick: Honoraria; Sandoz Inc: Honoraria; GSK: Honoraria; Annexon Biosciences: Research Funding.