ALBERT

Description: Multiple myeloma (MM) is a plasma cell dyscrasia characterized by bone marrow infiltration of clonal plasma cells. The recent literature has clearly demonstrated clonal heterogeneity in terms of both the genomic and transcriptomic signature of the tumor. Of note, novel studies have also highlighted the importance of the functional cross-talk between the tumor clone and the surrounding bone marrow milieu, as a relevant player of MM pathogenesis. These findings have certainly enhanced our understanding of the underlying mechanisms supporting MM pathogenesis and disease progression. Within the specific field of small non-coding RNA-research, recent studies have provided evidence for considering microRNAs as a crucial regulator of MM biology and, in this context, circulating microRNAs have been shown to potentially contribute to prognostic stratification of MM patients. The present review will summarize the most recent studies within the specific topic of microRNAs and circulating microRNAs in MM.

Description: Background: Extramedullary disease (EMD), strictly defined as an infiltrate of clonal plasma cells at an anatomic site distant from the bone marrow or adjacent soft tissue in a patient with underlying multiple myeloma, is an uncommon manifestation of multiple myeloma. Comparatively little is known about this disease entity, with no large case series published in the last decade. Patients and Methods: 663 consecutive patients with multiple myeloma who underwent autologous or allogeneic stem cell transplantation at a single, large, academic medical center in the United States from January 2005 to December 2011 were assessed for the presence or absence of EMD, as well as baseline demographic and biochemical characteristics, treatment regimens, and response to therapy. Results: A cohort of 55 patients with biopsy-proven EMD was identified, comprising 8.3% of the total study population. Among the patients with EMD, 13 (23.6%) were found to have EMD at the time of initial presentation, while the remainder developed EMD during the course of their illness. Patients with EMD received a median of 5 different treatment regimens during the course of their illness, most commonly with combinations of dexamethasone, thalidomide, lenalidomide, and bortezomib, as well as autologous hemotopoietic stem cell transplantation. Patients had received a median of 3 lines of therapy prior to experiencing an extramedullary relapse. Patients with EMD had markedly elevated maximum serum LDH levels (median 613.5 units/L) and low minimum hemoglobin levels (median 7.8 g/dL). Common cytogenetic abnormalities included deletion 13q, deletion 11q, t(11;14), and deletion 17p. Available immunohistochemical data suggest that EMD specimens had frequent expression of CXCR4, CD44, and CD56. The median overall survival data of these patients was 3.2 years (range, 0.9-9.5) and the median time from diagnosis of EMD to death was 0.5 years (range, 0.002-3.2). Conclusions: This report describes a large series of multiple myeloma patients with EMD who were treated in the era of stem cell transplant at a single academic medical center. Further studies to examine the molecular characteristics of extramedullary multiple myeloma are necessary to better define this entity and characterize therapeutic options that can prolong survival in this otherwise very vulnerable population. Disclosures Ghobrial: Millennium/Takeda: Membership on an entity's Board of Directors or advisory committees; Onyx: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees. Laubach:Novartis: Research Funding; Onyx Pharmaceuticals: Research Funding. Schlossman:Millennium: Consultancy. Mitsiades:Millennium Pharmaceuticals: Consultancy, Honoraria; Celgene: Consultancy, Honoraria; Amgen: Research Funding; Johnson & Johnson: Research Funding; DFCI: patent submission on stromal co-culture technologies Patents & Royalties.

Description: Introduction: Recent data show that Multiple Myeloma (MM) always progresses from a precursor state (monoclonal gammopathy of undetermined significance [MGUS]/smoldering multiple myeloma [SMM]) to overt MM indicating that there is continuous dissemination/clonal evolution of tumor cells from the original stages of tumor development to the time of clinical presentation. A major challenge in understanding the progression and metastasis of MM is to distinguish alterations driving the tumor growth and evolution from passenger mutations. Genetic screens are powerful tools for assaying phenotypes and identifying causal genes in various hallmarks of cancer progression. The clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated (Cas) system has emerged as a powerful technology to efficiently and simultaneously perform genome editing of multiple genes. Here we report a genome-wide CRISPR/Cas9-mediated loss of function screen in a xenograft mouse model to investigate the essential drivers of tumor growth and metastasis in MM. Methods: Lentiviral particles from 2 subpools of a human sgRNA library (Avana), each containing 1 sgRNA per gene were introduced into MM1.S (Cas9+/GFP+/Luc+) cell line with the pre-determined amount of virus to achieve 30-50% infection efficiency, corresponding to a multiplicity of infection (MOI) of ~0.5-1. Cells were selected with puromycin for 5-7 days following infection to remove uninfected cells. Selected cells were injected subcutaneously into SCID-Beige mice on both flanks. Genomic DNA from pre-transplantation cells, early primary tumors (~3 weeks post tumor cell injection), late stage primary tumors and metastatic bone marrow samples were extracted. gDNA was amplified following adaptor ligation and barcoding of the samples and PCR products were subsequently sequenced on a HiSeq2000 (Illumina). Results: To investigate the sgRNA library dynamics in different sample types (pre-transplantation cells, early primary tumor, late primary tumor, and bone marrow metastasis), we compared the overall distributions of sgRNAs from all sequenced samples. The early tumor sample replicates of both subpools on average retained 77.3% and 94.7% of the sgRNAs found in the pre-transplanted cell populations, while the late primary tumors retained 59.4% and 65.6% of the sgRNAs respectively, compared to early tumors. Interestingly, only a small fraction of sgRNAs (1.1% and 3.4% of sgRNAs in the pre-transplantation cells, 10.7% and 7.2% of sgRNAs in the late primary tumors for the 2 subpools respectively) were detected in the metastatic bone marrow samples. Using gene set enrichment analysis (GSEA), we found that the gene targets of the most enriched sgRNAs in the bone marrow samples were preferentially involved in important cellular processes, such as cell cycle regulation, protein translation, and several signaling pathways. Additionally we compared sgRNAs present in early primary tumor versus pre-transplantation cells and late primary tumor and found that many sgRNAs were depleted during tumor progression, indicating that their target genes were important for progression. These depleted sgRNAs in both stages mainly targeted genes involved in mTORC1 and DNA repair pathways, many of which are regulated by MYC and cell cycle related targets of E2F transcription factors. Conclusion: We established a platform for future in vivo Cas9 screens using the genome-wide CRISPR screening libraries to explore potential new targets in regulating tumor dissemination, colonization and metastasis in MM. In addition, this in vivo screening could potentially be used to investigate essential genes of response to targeted therapies or/and immunotherapies. Thus, CRISPR/Cas9-based in vivo screening is a powerful tool for functional genomics discoveries. Disclosures Roccaro: Takeda Pharmaceutical Company Limited: Honoraria. Ghobrial:BMS: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Novartis: Honoraria; Takeda: Honoraria; Noxxon: Honoraria; Amgen: Honoraria.

Description: Introduction Multiple myeloma (MM) is characterized by dissemination and accumulation of plasma cells in the bone marrow (BM), which promotes tumor cell growth and therapy resistance. ROBO1 is a conserved transmembrane receptor of the Ig superfamily with no intrinsic catalytic activity, and its role in MM pathogenesis is unknown. Material and Methods We first analyzed ROBO1 expression via western blot and/or immunohistochemistry (IHC). Gene expression profiling in a cohort of 170 newly diagnosed MM patients (IFM170) was used to compare ROBO1 expression across primary MM and BM stroma cells (BMSC), and normal BM plasma cells (PC). We used short hairpin RNA (shRNA) for stable ROBO1 knock down (KD) and CRISPR-Cas9 for ROBO1 knock out (KO). For protein structure-function and rescue studies, ROBO1 KO MM cells were transduced with a lentiviral vector expressing either full-length (FL) or truncated ROBO1 mutants devoid of extracellular (Cyt) or intracellular domain (DeltaCyt), including patient-derived truncating mutations, with a C-terminus triple FLAG tag. FLAG immunoprecipitation (IP) followed by mass spectrometry or western blotting and immunofluorescence (IF) were used to identify ROBO1 interacting partners and ROBO1 cellular localization. We used a hydrogel encapsulation system to study proliferation in a 3D system. To study extramedullary and intramedullary MM growth in vivo, WT and ROBO1 KO OPM2 were injected either subcutaneously (plasmacytoma model) or intra-medullary in femoral bones of donor mice which were then implanted subcutaneously in recipient SCID mice (µ-SCID model). PET-CT was used to assess tumor volume. Mouse tumors were retrieved for IHC and RNA extraction followed by RNA sequencing. To study dissemination and homing, KO and FL addback OPM2 cells were injected intravenously in SCID mice. Femurs and plasmacytoma were retrieved at endpoint for IHC. Results ROBO1 is highly expressed in human MM cell lines and primary MM cells with highest expression in cells carrying the high risk t(4;14) cytogenetic and low/absent expression in normal PC. Of human cancer cell lines, ROBO1 expression was limited to late B cell lineage; and ROBO1 KD was selectively cytotoxic against MM, but not other hematologic cancers. ROBO1 KO significantly decreases proliferation in a 3D culture system and tumor growth in extramedullary (mean tumor volume KO versus WT plasmacytoma: 457 versus 1323 mm3, p value= 0.02) and intramedullary (mean tumor volume KO versus WT: 823 versus 2684 mm3, p value= 0.001) murine models of human MM. ROBO1 KO MM cells show decreased adhesion to BM endothelial and BMSC, which is fully rescued by FL ROBO1 addback. To address whether ROBO1 loss alters dissemination/homing of MM cells in vivo, we injected mice intravenously with ROBO KO or FL addback OPM2 cells. While ROBO1 KO resulted in a modest, non-statistically significant prolongation in mouse OS (90 versus 75 days, respectively, p value 0.2), the pattern of disease was strikingly different. As expected, ROBO1 FL mice developed hindlimb paralysis with extensive BM infiltration with MM. Importantly, ROBO1 KO mice demonstrated reduced BM infiltration and developed solitary plasmacytoma. We next showed that ROBO1 C-terminus domain is necessary and sufficient to rescue ROBO1 KO proliferative defect while expression of ROBO1 truncations, including patient-derived frameshift mutations, acted as dominant negative. IP showed avid interaction of ROBO1 with ABL1. Interestingly, we showed that the cytosolic domain of ROBO1 undergoes cleavage and translocates to the nucleus, where its function is now being studied. Conclusions We show that ROBO1 is necessary for MM homing to the BM niche and for MM growth within and outside the BM space. ROBO1 cytosolic domain undergoes proteolytic cleavage and translocates to the nucleus and is necessary and sufficient to rescue ROBO1 KO defective proliferation. Based on our data, we propose a dual model for ROBO1 in MM: the full transmembrane receptor is involved in regulating adhesion, dissemination and homing of MM cells within the BM niche; the cleaved intracellular C-terminus domain participates in transcriptional regulation, promoting MM proliferation. These data suggest that ROBO1 C-terminus may be a novel molecular target in MM. Disclosures Roccaro: Celgene: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Associazione Italiana per al Ricerca sul Cancro (AIRC): Research Funding; Associazione Italiana per al Ricerca sul Cancro (AIRC): Research Funding; European Hematology Association: Research Funding; Transcan2-ERANET: Research Funding; European Hematology Association: Research Funding; AstraZeneca: Research Funding; Transcan2-ERANET: Research Funding; Amgen: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Research Funding. Ghobrial:Takeda: Consultancy; Sanofi: Consultancy; Amgen: Consultancy; BMS: Consultancy; Celgene: Consultancy; Janssen: Consultancy. Anderson:Sanofi-Aventis: Other: Advisory Board; Bristol-Myers Squibb: Other: Scientific Founder; Oncopep: Other: Scientific Founder; Amgen: Consultancy, Speakers Bureau; Janssen: Consultancy, Speakers Bureau; Takeda: Consultancy, Speakers Bureau; Celgene: Consultancy, Speakers Bureau.

Description: 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.

Description: Abstract 1826 Poster Board I-852 Patients with multiple myeloma (MM) typically present with the disease spread diffusely throughout the bone marrow (BM). This fact points to the role MM cell trafficking plays in disease progression. Like normal plasma cells, MM cell trafficking is directed by the cytokine, SDF-1 and its receptor, CXCR4. Using the small bicyclam molecule, AMD3100, to block the SDF-1/CXCR4 interaction, and in vivo flow cytometry to measure circulation time of MM cells in a xenograft model, we have previously shown that homing of injected AMD3100-treated MM cells to the bone marrow is perturbed. Soon after injection fewer AMD3100-treated than untreated MM cells are detected in mouse skull BM using in vivo fluorescence confocal microscopy. Furthermore, the combined treatment of established tumors with AMD3100 and bortezomib enhanced survival. Here we present data that the 2nd generation SDF-1/CXCR4 small monomacrocyclic inhibitor, AMD3465 behaves like its predecessor in blocking antibody binding to CXCR4 on MM cells, migration of MM cells toward SDF-1, and in vivo homing, but at concentrations 10-50 fold lower than AMD3100. Incubation with either 1uM AMD3465 or 50uM AMD3100 reduced antibody binding to CXCR4 on MM cells to isotype control levels. Likewise, treatment with AMD3465 reduced MM1S migration to 15% of that of untreated cells in a transwell migration assay. These in vitro effects translated in vivo into longer circulation times for AMD3465-treated MM cells than control cells. In vivo flow cytometry revealed that 40-50% of AMD3465-pre-treated cells remained in the circulation one hr after injection whereas untreated cells depleted to 20% of their original circulating cell count by that time. Future experiments will further describe the effect of AMD 3465 on MM cells in the BM microenvironment to answer whether AMD3465 can be used to mobilize MM cells from the BM environment or enhance survival when used in conjunction with therapeutic drugs. Disclosures Ghobrial: Millennium: Honoraria, Research Funding, Speakers Bureau; Celgene: Consultancy, Honoraria, Speakers Bureau; Novartis: Honoraria, Speakers Bureau.

Description: Background Increased bone marrow (BM) microvessel density (MVD) has been associated with progression of multiple myeloma (MM). Endothelial progenitor cells (EPCs) are circulating precursors with the capacity to differentiate into endothelial lineage cells through a process known as “vasculogenesis” thus contributing to vessel formation. The role of these cells in MM pathogenesis remains largely unexplored. We studied EPC BM mobilization in several MM mouse models (5TGM1, MM1S and Vk*MYC) during disease progression and quantified these cells in peripheral blood (PB) from patients at different stages of MM disease. Methods EPCs were quantified using flow cytometry (circulating CD34+ VEGFR2+ cells) in PB from mice injected intravenously (i.v.) with either murine MM 5TGM1-turboRFP+ cells or human MM1S-GFP+/luc+ cells. Circulating EPCs were also enumerated in PB from mice previously transplanted with BM from SCID/GFP mice (GFP-BM SCID mice) after the i.v. injection of 5TGM1-turboRFP+ cells as circulating GFP+ CD34+ VEGFR2+ cells. Peripheral blood samples were obtained from transgenic Vk*MYC mice affected by smoldering (s) MM (M-spike less than 6% of total protein on SPEP); active (a) MM (M-spike higher than 6% of total protein on SPEP); or healthy syngeneic mice, and examined for EPC levels through flow-cytometry (circulating CD34+ VEGFR2+ cells). Finally, the level of EPCs was evaluated in PB from healthy controls, smoldering (s) MM patients, in remission (r) and active (a) MM patients by using flow-cytometry (CD34+VEGFR2+ cells) and in vitro by performing endothelial colony forming assays [endothelial cells colony forming units (EC-CFUs) and endothelial colony forming cells (ECFCs)]. Results An increase in EPCs was evident starting one week after i.v. injection of tumor cells in both murine 5TGM1 and human MM1S orthotopic models. Compared to control mice, this EPC increase became significant (P

Description: Abstract 1804 Introduction: Phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway is a fundamental pathway for the regulation of cell proliferation, survival, adhesion, migration, and metabolism in a variety of physiological and pathological processes. The pathway and its downstream effectors are frequently activated in patients with acute leukemias, chronic leukemias, various types of lymphomas, and multiple myeloma (MM). In this study we investigated the expression of the different PI3K catalytic subunits in MM and effect of three different PI3K inhibitors on the interaction of MM cells with the bone marrow (BM) microenvironment. Methods and Results: First we characterized the baseline expression of the different PI3K-p110-alpha, beta, gamma and delta catalytic subunits in MM cell lines (MM1s, OPM1, OPM2, H929, RPMI, INA6, U266, and U266LR7) by immnunobloting. PI3K-p110-alpha was highly expressed in MM1s and RPMI8226; PI3K-p110-beta was highly expressed in all cell lines; PI3K-p110-gamma was highly expressed in OPM1 and OPM2; and PI3K-p110-delta was highly expressed in MM1s and INA6. Furthermore, we investigated BKM120, a novel pan-PI3K inhibitor (Novartis, Swizerland). MM cells (MM1s, H929, OPM1, and OPM2) were treated with increasing concentrations of BKM120 (0, 100, 250, 500 and 1000 nM) for 4 hrs, labeled with Calcein-AM, and applied to fibronectin adhesion plate, or to 96-well plate pre-coated with stroma. Cells were incubated for 1 hr at 37C, non-adherent cells were washed and MM adhesion was measured by fluorescence-reader. BKM120 reduced the adhesion of all MM cell lines to fibronectin and stromal cells in a dose-dependent manner. Mechanistically, BKM120 decreased the activation of adhesion-related signaling in MM cells induced by co-culture with stroma including pFAK, pSRC pCoffilin and pMyosin light chain, as detected by immunoblotting. Moreover, BKM120 inhibited the downstream signaling of PI3K: p-Akt, p-P70S6, and p-S6R and regulated the survival of MM cells with or without co-culture with Bone Marrow stroma (IC50- 1uM 48hrs) and caused cell cycle arrest, as detected by PI staining and analyzed by flow cytometry, and decreased the expression of cyclin D1, p-Rb and increased the expression of P27 and P21, as detected by immunoblotting. Furthermore, we compared the activity of BKM120 to other PI3K inhibitors NVP-BEZ-235, a dual PI3K/mTOR inhibitor (Selleck, Houston, TX); and CAL101, a potent PI3K-p110-delta inhibitor (Selleck, Houston, TX); we examined the effect of different PI3K inhibitors (BKM120 500nM, CAL101 500nM or NVP-BEZ-235 100nM) on adhesion of MM1s cells to fibronectin, and found that the three inhibitors decreased the adhesion. Similarly, down-regulation of the expression of the PI3K catalytic subunits in MM1s, using siRNA decreased the adhesion of MM cells to fibronectin. In addition, we tested the effect of inhibition of PI3K on chemotaxis of MM cells. MM1s cells treated with BKM120 500nM, CAL101 500nM or NVP-BEZ-235 100nM for 4hrs, or with knockdown of PI3K by siRNA were applied to the upper chamber of a Boyden-migration assay, and allowed to migrate towards media with or without SDF1 30nM or conditioned media from MM stroma in the lower chamber for 4hrs. Interestingly, BKM120, NVP-BEZ-235 and the PI3K knock down increased significantly the chemotaxis of MM cells towards SDF1 and BM stromal, while CAL-101 had no effect on chemotaxis. These results were in accord with the effect of the drugs on the surface expression of CXCR4; as both BKM120 and NVP-BEZ-235, but not CAL101, increased the expression of CXCR4 in MM cells. Conclusion: we characterized the basal expression of the different PI3K catalytic subunits in MM cells lines, and showed that BKM120 inhibited PI3K signaling including proliferation and cell cycle in MM cells. BKM120 inhibited MM adhesion; an effect which was observed in NVP-BEZ-235 and CAL101, while only BKM120 and NVP-BEZ-235 increased the chemotaxis and CXCR4 surface expression of MM cells. These findings suggest that BKM120 can be used for regulation of MM cell trafficking in vivo by disrupting adhesion of MM cells to the BM and inducting of mobilization, leading to increased sensitivity to therapeutic agents. Disclosures: Roccaro: Roche:. Ghobrial:Novartis: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Millennium: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Bristol-Myers Squibb: Research Funding; Noxxon: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding.

Description: Background. Measurement of serum M-spike is used to determine response to therapy and treatment free survival in Waldenstrom Macroglobulinemia (WM). However, there are many limitations to the use of IgM M-spike, and new sensitive markers are needed to determine early response or progression in these patients. We have previously shown that involved serum free light chain (sFLC) accurately diagnosed patients with WM, and correlated with markers of poor prognosis, specifically beta- 2 microglobulin (B2M). In this study, we sought to determine the role of levels of involved in the response to therapy in patients with WM treated on clinical trials, and compare it to the response observed using the traditional M-spike measurement. Methods. We prospectively studied involved sFLC in 61 WM patients enrolled on 2 clinical trials, at diagnosis (N=8) and with relapse/refractory disease (N=53). Patients were treated on one of two clinical trials: either perifosine (N=30; given 150mg oral daily) or combination of bortezomib and rituximab (N=30; given IV bortezomib 1.6mg/m2 at days 1, 8, 15 q 28 days × 6 cycles and rituxan 375 mg/m2 at days 1, 8, 15, 22 on cycles 1 and 4). Response was assessed after cycle 2, confirmed on 2 consecutive measurements, and included minor response (MR), partial response (PR) or complete remission (CR). Results. The baseline characteristics of the patients were as follows: the median age was 65 years (44–83), male/female ratio 2.38, serum B2M 3.0mg/L (1.00–7.30), hemoglobin 11.0g/dL (7.00–14.90), platelet count 216 ×109/mm3 (46–563), serum M-spike 2.24g/L (0.41–4.62), and involved sFLC 95.2mg/L (4.92–868). The WM International staging system (WM-ISS) showed that 28% of patients had low ISS, 31% intermediate, and 41% high ISS scores. The overall response rate for the entire cohort was 62.3%, assessed by M-spike measurement (MR=23, PR=13, nCR=2). The overall response rate using involved sFLC level was 72.1% (MR=14, PR=29, and CR=1), (p

Description: Key Points C1013G/CXCR4 acts as an activating mutation in WM leading to enhanced tumor growth, and as an inducer of drug resistance. BMS936564/MDX1338, a novel anti-CXCR4 moAb, successfully targets WM cells, either C1013G/CXCR4 mutated or wild-type.