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Disease progression and relapse in multiple myeloma is dependent on the ability of the multiple myeloma plasma cells (PC) to reenter the circulation and disseminate throughout the bone marrow. Increased bone marrow hypoxia is associated with increased recirculation of multiple myeloma PCs. Accordingly, we hypothesized that during chronic hypoxia, activation of HIF-2α may overcome the bone marrow retention signal provided by stromal-derived CXCL12, thereby enabling dissemination of multiple myeloma PCs. Here we demonstrate that HIF-2α upregulates multiple myeloma PC CXCL12 expression, decreasing migration toward CXCL12 and reducing adhesion to mesenchymal stromal cells in vitro. We also found that HIF-2α strongly induced expression of the chemokine receptor CCR1 in multiple myeloma PCs. CCR1 activation potently induces multiple myeloma PC migration toward CCL3 while abrogating the multiple myeloma PC migratory response to CXCL12. In addition, increased CCR1 expression by multiple myeloma PCs conferred poor prognosis in newly diagnosed multiple myeloma patients and was associated with an increase in circulating multiple myeloma PCs in these patients. Taken together, our results suggest a role for hypoxia-mediated CCR1 upregulation in driving the egress of multiple myeloma PCs from the bone marrow. Targeting CCR1 may represent a novel strategy to prevent dissemination and overt relapse in multiple myeloma. Cancer Res; 77(20); 5452–63. ©2017 AACR.

Table of genes dysregulated with overexpression of HIF-2alpha in LP-1 cells

Supplementary Figure Legends and Methods

Supp. Figure 3. CCR1 expression is upregulated by hypoxia in human MM cell lines

GSEA for genes upregulated by overexpression of HIF-2alpha in LP-1 cells

Supp. Figure 5. Cell surface expression of CXCR4 and CCR1 in newly diagnosed MM patients

Supp. Figure 1. Overexpression of HIF-2α and CXCL12 in the HMCLs LP-1 and RPMI-8226

Supp. Figure 2. Migration towards CXCL12 and cell surface CXCR4 expression is downregulated by CXCL12 treatment

Supp. Figure 4. CXCL12 does not inhibit response to CCL3 in human MM cell lines

Multiple myeloma (MM) disease progression is dependent on the ability of MM plasma cells (PC) to egress from the bone marrow (BM), enter the circulation and disseminate to distal BM sites. Expression of the chemokine CXCL12 by BM stromal cells is crucial for MM PC retention within the BM. However, the mechanisms which overcome CXCL12-mediated retention to enable dissemination are poorly understood. We have previously identified that treatment with the CCR1 ligand CCL3 inhibits the response to CXCL12 in MM cell lines, suggesting that CCL3/CCR1 signaling may enable egress of MM PC from the BM. Here, we demonstrated that CCR1 expression was an independent prognostic indicator in newly diagnosed MM patients. Furthermore, we showed that CCR1 is a crucial driver of dissemination in vivo, with CCR1 expression in the murine MM cell line 5TGM1 being associated with an increased incidence of bone and splenic disseminated tumors in C57BL/KaLwRij mice. Furthermore, we demonstrated that CCR1 knockout in the human myeloma cell line OPM2 resulted in a >95% reduction in circulating MM PC numbers and BM and splenic tumor dissemination following intratibial injection in NSG mice. Therapeutic targeting of CCR1 with the inhibitor CCX9588 significantly reduced OPM2 or RPMI-8226 dissemination in intratibial xenograft models. Collectively, our findings suggest a novel role for CCR1 as a critical driver of BM egress of MM PC during tumor dissemination. Furthermore, these data suggest that CCR1 may represent a potential therapeutic target for the prevention of MM tumor dissemination.

RBC-transfusion dependency (RBC-TD) is an independent prognostic factor for poor overall survival (OS) in the WHO classification-based prognostic scoring system (WPSS) for MDS patients. However, WPSS did not include cytopenia, whereas revised International Prognostic Scoring System (IPSS-R) did not include RBC-TD. Thus, neither of these prognostic scoring systems incorporates both cytopenia and RBC-TD. We aimed to test whether RBC-TD adds prognostic value to the IPSS-R. We analyzed MDS patients not treated with disease-modifying therapy, and enrolled in SA-MDS Registry (derivation cohort; n = 295) and Dusseldorf registry (Germany; validation cohort; n = 113) using time-dependent Cox proportional regression and serial landmark analyses. In the derivation cohort, RBC-TD patients had inferior OS compared to RBC transfusion-independent (RBC-TI) patients (P

Acute erythroid leukemia (AEL) is a high-risk leukemia of poorly understood genetic basis, with controversy regarding diagnosisin the spectrum of myelodysplasia and myeloid leukemia. We compared genomic features of 159 childhood and adult AEL cases with non-AEL myeloid disorders and defined five age-related subgroups with distinct transcriptional profiles: adult, TP53mutated; NPM1 mutated; KMT2A mutated/rearranged; adult, DDX41 mutated; and pediatric, NUP98 rearranged. Genomic features influenced outcome, with NPM1 mutations and HOXB9 overexpression being associated with a favorable prognosis andTP53, FLT3 or RB1 alterations associated with poor survival. Targetable signaling mutations were present in 45% of cases and included recurrent mutations of ALK and NTRK1, the latter of which drives erythroid leukemogenesis sensitive to TRK inhibition.This genomic landscape of AEL provides the framework for accurate diagnosis and risk stratification of this disease, and the rationale for testing targeted therapies in this high-risk leukemia. Refereed/Peer-reviewed

Disease progression and relapse in multiple myeloma is dependent on the ability of the multiple myeloma plasma cells (PC) to reenter the circulation and disseminate throughout the bone marrow. Increased bone marrow hypoxia is associated with increased recirculation of multiple myeloma PCs. Accordingly, we hypothesized that during chronic hypoxia, activation of HIF-2α may overcome the bone marrow retention signal provided by stromal-derived CXCL12, thereby enabling dissemination of multiple myeloma PCs. Here we demonstrate that HIF-2α upregulates multiple myeloma PC CXCL12 expression, decreasing migration toward CXCL12 and reducing adhesion to mesenchymal stromal cells in vitro. We also found that HIF-2α strongly induced expression of the chemokine receptor CCR1 in multiple myeloma PCs. CCR1 activation potently induces multiple myeloma PC migration toward CCL3 while abrogating the multiple myeloma PC migratory response to CXCL12. In addition, increased CCR1 expression by multiple myeloma PCs conferred poor prognosis in newly diagnosed multiple myeloma patients and was associated with an increase in circulating multiple myeloma PCs in these patients. Taken together, our results suggest a role for hypoxia-mediated CCR1 upregulation in driving the egress of multiple myeloma PCs from the bone marrow. Targeting CCR1 may represent a novel strategy to prevent dissemination and overt relapse in multiple myeloma. Cancer Res; 77(20); 5452–63. ©2017 AACR.

Pacritinib (SB1518) is a Janus kinase 2 (JAK2), JAK2(V617F), and Fms-like tyrosine kinase 3 inhibitor that does not inhibit JAK1. It demonstrated a favorable safety profile with promising efficacy in phase 1 studies in patients with primary and secondary myelofibrosis (MF). This multicenter phase 2 study further characterized the safety and efficacy of pacritinib in the treatment of patients with MF. Eligible patients had clinical splenomegaly poorly controlled with standard therapies or were newly diagnosed with intermediate- or high-risk Lille score. Patients with any degree of cytopenia were eligible. Thirty-five patients were enrolled. At entry, 40% had hemoglobin

Introduction: Anemia is one of the commonest presenting features of MDS and approximately 30-40% of patients require regular RBC-transfusion. RBC-transfusion dependency (RBC-TD) is a poor-prognostic factor independent of revised International Prognostic Scoring System (IPSS-R) (Hiwase et al ASH 2014). Although RBC transfusion increases the risk of alloimmunization, there is limited literature characterizing this risk in MDS patients as compared to other hematological disorders (such as thalassemia). Methods: This retrospective study assessed the alloimmunization rate in 784 MDS and AML (20-30% blasts) patients registered in the South Australian-MDS registry (SA-MDS registry) between 1991 and 2015. RBC-TD was defined as ≥1 unit of RBC transfused every eight weeks for four months according to WHO based Prognostic Scoring System. The cumulative incidence of RBC-alloimmunization was calculated using competing risk analysis (death being the competing risk). Factors associated with increased rate of RBC antibody formation were investigated by Cox regression analysis. Results: The median age of the 784 patients at diagnosis was 75 years with 66% males. The estimated median follow up time was 7.3 years. 70% of patients (549/784) were diagnosed with primary MDS, while the remaining patients were diagnosed with AML (20-30% blasts; n=57), CMML (n=91) or therapy-related myeloid neoplasm (T-MN; n=87). At last follow-up 30% patients were alive, 67% were deceased and 3% were lost to follow-up. During the study period, 658 (84%) patients required ≥1 unit of RBC transfusion and median RBC units transfused were 29 (range 0-708). The WPSS definition of RBC-TD was met in 47% (366/784 patients), while 36% (282/784) patients required intermittent RBC-transfusions (RBC-TI). During follow up, 83 (13%) patients formed 155 RBC-alloantibodies and 50% of these cases (42/83) developed >1 RBC-alloantibody. Autoantibodies were also detected in 31 cases, mainly in association with RBC-alloantibodies (n=27; complex alloimmunization) while 4 cases had only autoantibodies. Interestingly, in 19/27 of cases autoantibodies were detected only after alloimmunization. The pathophysiologic mechanism of this remains unclear. The most common alloantibody specificities were Rh (57%) and Kell (21%) (Table 1). The median interval between 1st RBC transfusion and antibody detection was 10 (0.2-225) months. In 9 cases (6 females) alloantibodies were detected prior to the 1st unit of RBC-transfused. The incidence of RBC alloimmunization reached a plateau at 16% by 100 units of RBC (Fig. 1A), however 80% of antibodies were detectable by 30-40 RBC units transfused. It indicates that most "responders" will form antibodies during the first 30-40 units of RBC transfused. Since most chronically transfused MDS patients do not form RBC alloantibodies it is important from a clinical and resource-utilization standpoint to identify who is at greatest risk of RBC alloimmunization. Multivariate analysis using Cox-regression model was performed. The only factor which was associated with significantly higher risk of RBC alloimmunization was RBC-TD (HR 2.52; p=0.0005). Age, sex, IPSS-R category and number of RBC units transfused did not independently predict alloimmunization rate. Using competing risk analysis, the cumulative incidence of RBC-alloimmunization was significantly higher in RBC-TD group compared to RBC-TI group (p=0.0004; Fig. 1B). Conclusion: RBC-alloimmunization is a substantial risk in MDS patients, especially in RBC-transfusion dependent cases. Extended phenotype matching (D,C,c,E,e and Kell) could have prevented alloantibody formation in 79% of alloimmunized MDS patients. Table 1. Specificity of 155 RBC-alloantibodies Table 1. Specificity of 155 RBC-alloantibodies Disclosures Yeung: Ariad: Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding.

Acute Myeloid Leukemia (AML) remains a clinical challenge, with most patients dying of relapsed disease. The complete biological basis of relapse remains unclear. Genetic lesions and heterogeneity have been proposed as key drivers of clinical outcome, yet do not fully explain leukemia relapse. Epigenomic dysregulation is a hallmark of newly diagnosed AML. Plasticity is a core property of the epigenome, enabling cells to adapt to stressful conditions, independent of genetic alterations. Hence we asked whether epigenomic plasticity might contribute to AML progression, have functional consequences and be independent of genetic influences in AML (a question that has not been addressed for any tumor type). Methods. We formed an international consortium to collect and profile paired diagnosis and relapse AML specimens. We extracted DNA and RNA from 138 clinically annotated AML patient samples. We obtained matched germline DNA as genetic controls, and fourteen normal CD34+ specimens as DNA methylation and transcriptome controls. We performed methylome sequencing (ERRBS), genomic sequencing (exomes and targeted resequencing) and transcriptomic (RNA-seq) profiling. For a single patient, more intensive multi-layer profiling (whole genome sequencing, ERRBS, RNA-seq and single cell RNA-seq) was performed at five serial time points. We quantified epigenetic allelic heterogeneity (epialleles) using a novel approach that employs entropy equations (MethClone), and validated epiallele composition using orthogonal methods. Some of the major conclusions are: 1) Epigenetic allelic diversity is an independent variable linked to clinical outcome. Statistically significant epiallele shift (ΔS 2) Promoter epialleles are linked to hypervariable transcriptional regulation. We observed substantial change in epiallele burden at relapse versus diagnosis. A subset of the eloci localized to gene promoters. High promoter epiallele variance was significantly associated with high transcriptional variance (p 3) AML patients can be classified according to epigenetic allele progression at relapse. K-means clustering based on epiallele shift at diagnosis versus relapse distributed patients into three classes: those with reduced, increasing or stable epiallele burden. Strikingly, there was no correlation between epiallele changes and the patterns of genomic evolution. Furthermore, there was no correlation between epiallele patterns acquired with mutations in epigenetic modifiers or other recurrently mutated genes in AML. 4) Epigenetic heterogeneity upon disease relapse is divergent from the genetic landscape. Integrating whole genome sequencing and methylome analysis we observed that a) significant increases in epigenetic heterogeneity precede significant changes in the abundance of somatic mutations; b) whereas a high number of somatic mutations were shared across all time points, epialleles exhibited dominance of distinct and unique eloci at each time point; and c) the variant epiallele frequency decreased earlier in progression than somatic mutation variant allele frequency, suggesting that epigenetic clonal diversification can precede genetic clonal evolution. Summary. Based on our results we propose that epigenetic allele diversity allows populations of leukemia cells to sample transcriptional states more freely thus creating the potential for greater evolutionary fitness. This provides an additional independent mechanism of plasticity that can explain the resilient nature of AML to adapt and survive exposure to chemotherapy drugs, independent of genetic heterogeneity. Disclosures Perl: Actinium Pharmaceuticals: Consultancy; Asana Biosciences: Consultancy; Arog Pharmaceuticals: Consultancy; Ambit/Daichi Sankyo: Consultancy; Astellas US Pharma Inc.: Consultancy. Becker:Millenium: Research Funding. Lewis:Roche: Honoraria, Other: Travel; Amgen: Other: Travel. Levine:Loxo Oncology: Membership on an entity's Board of Directors or advisory committees; CTI BioPharma: Membership on an entity's Board of Directors or advisory committees; Foundation Medicine: Consultancy.

Multiple myeloma (MM) disease progression is dependent on the ability of MM plasma cells (PCs) to egress from the bone marrow (BM), enter the circulation and disseminate to distal BM sites. Expression of the chemokine CXCL12 by BM stromal cells is crucial for MM PC retention within the BM. However, the mechanisms which overcome CXCL12-mediated retention to enable dissemination are poorly understood. We have previously identified that treatment with the CCR1 ligand CCL3 inhibits the response to CXCL12 in MM cell lines, suggesting that CCL3/CCR1 signalling may enable egress of MM PC from the BM. Here, we demonstrated that CCR1 expression was an independent prognostic indicator in newly diagnosed MM patients. Furthermore, we showed that CCR1 is a crucial driver of dissemination in vivo, with CCR1 expression in the murine MM cell line 5TGM1 being associated with an increased incidence of bone and splenic disseminated tumours in C57BL/KaLwRij mice. Furthermore, we demonstrated that CCR1 knockout in the human myeloma cell line OPM2 resulted in a >95% reduction in circulating MM PC numbers and BM and splenic tumour dissemination following intratibial injection in NSG mice. Therapeutic targeting of CCR1 with the inhibitor CCX9588 significantly reduced OPM2 or RPMI-8226 dissemination in intratibial xenograft models. Collectively, our findings suggest a novel role for CCR1 as a critical driver of BM egress of MM PCs during tumour dissemination. Furthermore, these data suggest that CCR1 may represent a potential therapeutic target for the prevention of MM tumour dissemination. Refereed/Peer-reviewed