ALBERT

Description: Key Points Histamine and serotonin induce, but subsequently truncate, angiogenesis via a thrombspondin-1–mediated negative feedback loop.

Description: Multiple myeloma (MM) is 2-3 times more common among African-Americans compared to non-Hispanic whites. The 2-3-fold increased risk among family members of cases suggests a genetic contribution to risk. Genome-wide association studies (GWAS) in populations of European ancestry have identified seven novel risk loci at 2p23.3 (rs6746082), 3q26.2 (rs10936599), 3p22.1 (rs1052501), 6p21.32 (rs2285803), 7p15.3 (rs4487645), 17p11.2 (rs4273077) and 22q13.1 (rs877529) (Broderick, et al. Nat Genet, 2011, Chubb, et al. Nat Genet, 2013), three of which were replicated in another European series (Martino et al., Br J Haematol, 2012). Here we examined the index signals and conducted fine-mapping for each locus in a case-control study of 1,049 multiple myeloma cases and 7,084 controls of African ancestry to identify better markers of risk and novel independent loci in seven previously reported regions in this high risk population. Incident cases were recruited from 10 clinical centers and SEER cancer registries from 2011 to 2013 and genotyped using the Illumina HumanCore GWAS array. Control data were obtained from previous genome-wide studies of breast and prostate cancer, genotyped using the Illumina 1M-Duo in 4425 male controls from the African Ancestry Prostate Cancer Consortium (consisting of 14 independent studies) and 2632 female controls from a breast cancer GWAS of African-American women (consisting of 9 independent studies). Imputation to 1000 Genomes (March 2012 release) was conducted for regions around six of the previously identified single nucleotide polymorphisms [SNPs] (the HLA region harboring rs2285803 is still being imputed, results will be presented). A case-control analysis of SNPs/indels 〉1% frequency within 250 kb of each index variant was conducted using unconditional multivariable logistic regression adjusting for age, sex and five leading principal components. Region-specific alpha levels were determined through permutation tests. The minimum alpha level across the six regions was α=0.002. All previously reported risk variants were common in African-Americans (minor allele frequency [MAF] 〉0.05). For five of the six SNPs, we had ≥94% power to detect the same effect observed in non-Hispanic whites, and 64% power for the less common variant rs10936599 (MAF=0.07). We observed directionally consistent effects (odds ratio [OR]〉1) for the six risk variants tested, with three replicating at p≤0.05 (7p15.3, p=1.4x10-7; 17p11.2, p=0.05; 22q13.1, p=0.02). For three of the six regions, we observed better markers of risk in African-Americans that were correlated with the index SNP in Europeans (7p15.3, rs56333627, p=1.5x10-5, r2=0.89; 17p11.2, rs34562254, p=2.9x10-3, r2=0.90; 22q13.1, rs2092410, p=1.1x10-4 r2=.71). The missense variant identified in the 17p11.2 region (rs34562254, Pro251Leu) is located in TNFRSF13B, which encodes the protein TACI, a B cell surface receptor which plays a role in B cell maturation, apoptosis and antibody production by inducing activation of transcription factors including NFAT and NFκβ. In addition, there is evidence suggesting that TACI is involved in MM pathogenesis. Our results demonstrate that many of the risk loci for MM found in European ancestry populations are also risk loci in men and women of African ancestry and that by fine-mapping, we are able to identify variants that better capture risk in populations of African ancestry. Disclosures Terebelo: Celgene Corp: Membership on an entity's Board of Directors or advisory committees. Lonial:Millennium: The Takeda Oncology Company: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Onyx Pharmaceuticals: Consultancy, Research Funding.

Description: TP53 mutation (TP53mut) associates with poor survival in AML patients. However, the risk of residual TP53mut has not fully characterized. We found there are around 3% of patients have detectable residual (less than 25%) TP53mut reads from TCGA AML patient exon sequencing data under current sequencing depth. Importantly, these patients also showed worse outcome as compared to the TP53 wild type patients. We therefore studied the effect of residual p53 mutation using two AML cell lines, OCI-AML2 and MV4-11. Both cell lines have been characterized as p53 wild type cells. However, a distinct p53 single hotspot mutation transcripts were detected in low frequency with RNA-seq analysis in both cells. TP53mut cells isolated from the parental cells show higher drug tolerance and have higher population of stem cell maker positive cells, a characteristic of chemoresistant cells. When mixed with p53 wild type cells, the TP53mut cells also show survival advantage under chemo-drug pressure in vitro and vivo (Fig. A), suggesting its advantage to become chemoresistant cells. Interestingly, the chemo-drug resistant cell lines derived from both lines have homogeneous TP53mut at same spot as parental residual mutation cells. Further, we found two p53 target genes p21 and GADD45A contribute to cell survival and chemoresistance. Decrease of these genes leads to cell less sensitive upon chemo-drug treatment. We previously showed that histone deacetylase inhibitor Romidepsin can resensitize chemoresistant cells. Here we further show that Romidepsin can reactivate p53 targeted genes which are failed to be activated by mutant p53 (Fig. B), including p21 and GADD45A, through increasing gene promotor histone acetylation. Moreover, it can preferentially target p53 mutant cell subpopulation (Fig. C). Therefore, either single treatment or combination with chemotherapy drug, Romidepsin can potentially cure or prevent residual p53 mutation caused chemoresistance and relapse in patient. Taking together, our study raise importance on previous under looked residual p53 mutation in AML patient and shed lights on therapeutic strategies for treatments on chemoresistance. Figure Disclosures No relevant conflicts of interest to declare.

Description: Background: Hospitalized medically ill patients are at risk for venous thromboembolism (VTE) for at least 45 days after discharge. This observation prompted the MAGELLAN and MARINER trials, which evaluated the efficacy and safety of rivaroxaban for extended thromboprophylaxis. In MAGELLAN, rivaroxaban (10 mg once daily) started in hospital and continued for 35 days was compared with a 10±4 day course of enoxaparin (40 mg once daily) followed by placebo. In MARINER, a 45-day course of rivaroxaban (10 mg once daily for those with creatinine clearance [CrCl] ≥50ml/min and 7.5 mg once daily for those with CrCl 30-

Description: Background: Acutely ill medical patients with a history of cancer are at risk of venous thromboembolic events (VTE) in hospital and after discharge. Rivaroxaban was evaluated for VTE prevention in acutely ill medical patients in two randomized clinical trials of extended thromboprophylaxis with rivaroxaban. MAGELLAN (NCT00571649) included patients with active cancer undergoing treatment as well as those with only a history of cancer while the MARINER study (NCT02111564) only included patients with a history of cancer but not active cancer. In MAGELLAN treatment began in hospital (rivaroxaban 10mg QD for 35±4 days vs enoxaparin for 10±4 days followed by placebo), whereas in MARINER, treatment began at discharge (rivaroxaban 10mg QD or 7.5mg QD for those with baseline creatinine clearance 30-

Description: Several HOX loci associated long noncoding RNAs (lncRNAs) have been shown to regulate transcription of HOX genes through influencing epigenetic landscape. Especially, the posterior HOXA domain associated lncRNA HOTTIP acts as an epigenetic regulator that recruits WDR5/MLL complex to coordinate active chromatin modifications and HOXA genes expression in the development of animal digits. Despite HOX genes, especially HOXA genes, are highly expressed in many acute myeloid leukemia (AML) patients, it remains largely unknown whether and how HOTTIP lncRNA regulates hematopoietic stem cell (HSC) function and contributes to leukemogenesis. We showed previously that disruption of the CTCF boundary located between HOXA7 and HOXA9 genes (CBS7/9) resulted in reduced lncRNA HOTTIP and HOXA genes expression in MLL rearranged AML suggesting that HOTTIP may play a role in ectopic expression of the posterior HOXA gene. We employed a pooled CRISPR-Cas9 KO library to specifically screen lncRNAs in four HOX gene loci and identify HOTTIP as acritical regulator in controlling oncogenic HOX chromatin signature and associated gene expression patterns in AML by collaborating with posterior HOXA chromatin boundary. HOTTIP is upregulated in AML patients with MLL-rearrangement or NPM1 mutation. AML patients with high HOTTIP expression exhibits a significantly shortened survival compared to low HOTTIP expressing patients. To test whether HOTTIP acts to coordinate posterior chromatin domain and HOXA genes activation in AML, we manipulated HOTTIP lncRNA expression levels in the MLL-AF9 rearranged MOLM13 by loss-of-function KO and gain-of function rescue, as well as carried out genome wide chromatin and transcriptomic analysis to intterrogate the role of HOTTIP in control of AML specific posterior HOXA chromatin domain. We found that knock-out of HOTTIP lncRNA led to a loss of active chromatin structure and invasion of repressive H3K27me3 mark over the posterior HOXA domain. HOTTIP KO attenuated progression of AML in the transplanted AML mouse model resembling the effect of CBS7/9 boundary disruption, while transcriptional activation of HOTTIP lncRNA in the CBS7/9 boundary-disrupted AML cells restored HOXA locus chromatin signature and gene expression as well as reversed the CBS7/9-mediated anti-leukemic effects. To further determine the role of HOTTIP lncRNA in regulating HSC function and leukemogenesis, we generated transgenic mice that expresses Hottip lncRNA under the control of the hematopoietic specific Vav1 enhancer and promoter. The Hottip transgenic (Tg) mice exhibited increased WBC and neutrophil counts and developed splenomegaly indicating that enforced expression of Hottip lncRNA resulted in perturbation of hematopoiesis. Furthermore, overexpression of Hottip lncRNA in mice bone marrow hematopoietic compartment strongly perturbed hematopoietic stem and progenitor cell (HSC/HPC) function by altering self-renewal and differentiation property of HSC/HPCs through affecting homeotic gene associated oncogenic transcription program. Approximately 20% of Hottip lncRNA transgenic mice developed abnormal hematopoietic phenotypes resembling AML-like disease. RNA-seq and ATAC-seq analysis indicated that overexpression of Hottip enhanced promoter chromatin accessibility and stimulates transcription of genes and pathways involved in HSC function and leukemogenesis, including WNT signaling, hematopoietic cell lineage, cell cycle, Hoxa9, Hoxa13, and Meis1, Runx1, and Twist1 genes. Thus, Hottip lncRNA overexpression acts as an oncogenic event to promote HSC self-renewal and HPC proliferation by reprograming leukemic associated chromatin signature and transcription programs. Disclosures No relevant conflicts of interest to declare.

Description: Background: Asymptomatic proximal deep-vein thrombosis (ASxDVT) is an efficacy endpoint that has been used for several decades in clinical trials evaluating thromboprophylaxis with anticoagulants. Previous studies have suggested the finding of ASxDVT on routine ultrasonography is associated with increased subsequent all-cause mortality (ACM). We evaluated the relationship between ASxDVT and subsequent ACM using the data from the MAGELLAN study (NCT00571649), a randomized clinical trial that evaluated rivaroxaban compared with enoxaparin followed by placebo for the prevention of venous thromboembolism (VTE) in acutely ill medical patients in which routine compression ultrasonography was performed at Day 10 and at Day 35. Patients were followed up through 90 days. Methods: A post hoc analysis was performed using patients who received at least one dose of study drug and had an adequate ultrasound result at Day 10 or Day 35 (modified intent-to-treat population, mITT). Patients were categorized into one of three mutually exclusive groups: (1) those without VTE; (2) those with symptomatic VTE (SxVTE); and (3) those with an ASxDVT. If patients had an ASxDVT followed by an SxVTE event, they were categorized into the ASxDVT group. Baseline covariates (age, sex, race, BMI, diabetes, creatinine clearance, heart failure, acute ischemic stroke, acute infectious disease, inflammatory disease, acute respiratory insufficiency, history of VTE, history of cancer, history of anemia and assigned treatment group) were tested for association with ACM (p