Bergsagel, P. Leif

Abstract Dysregulation of D type cyclins is an almost universal event in multiple myeloma. Overexpression of cyclin D1 may occur by chromosomal translocation of t(11:14)(q13:32), and also in association with hyperdiploidy. To investigate the role of cyclin D1 in the growth of human myeloma cell lines, we used both shRNA plasmid constructs, and an siRNA Smartpool against cyclin D1 and compared to control cells transfected with anti-GFP or GAPDH constructs. siRNA was electroporated into multiple myeloma cell lines overexpressing cyclin D1 (KMS12PE, U266, H929) which gave a 50–60% transfection efficiency, assessed using a GFP plasmid. Successful reduction in levels of cyclin D1 was confirmed by western blotting and normalization to a beta actin standard. Cyclin D1 protein in sh- or siRNA transfected cells was reduced on average to 32% of that in cells transfected with an anti-GAPDH or anti-GFP siRNA. In individual experiments reduction of cyclin D1 protein to as little as 10% of control was observed. However, we found no sign of increased apoptosis by Annexin V/Propidium iodide staining. Furthermore, cell cycle analysis by ethidium bromide staining and flow cytometry revealed no significant change in the cell cycle of sh- or siRNA transfected cells when compared to control cells. qPCR analysis revealed no acute compensatory increase in the RNA levels of other D-type cyclins (D2, D3) following reduction of cyclin D1 levels. These results may be explained by the residual presence of sufficient cyclin D1 protein for cell cycle progression. An alternative explanation is that changes that frequently occur in myeloma to other cell cycle regulators, for example p16(INK4a) and Rb are able to circumvent cell cycle effects of reducing cyclin D1protein. These results suggest that the human myeloma cell lines tested are not acutely sensitive to cyclin D1 level.

Abstract Abstract 3884 Poster Board III-820 Background and Objective Thalidomide/dexamethasone (thal/dex) combination has shown high activity in newly diagnosed multiple myeloma (MM) (Rajkumar SV. at al, J Clin Oncol 2006;24:431-436). In newly diagnosed patients, lenalidomide/dexamethasone (len/dex) has demonstrated superiority compared with high-dose dexamethasone alone (Zonder JA et al, Blood 2007;110:77). Although both thal/dex and len/dex are active in newly diagnosed MM, no randomized trial has been reported comparing these two regimens, and unfortunately none are ongoing or planned. We compared the efficacy and the toxicity of thal/dex and len/dex as primary therapy in 411 newly diagnosed MM patients treated at the Mayo Clinic. Patients and methods 411 consecutive patients seen at Mayo Clinic between 2001 and 2008, who received induction with thal/dex (n=183) or len/dex (n=288) were retrospectively studied. Thalidomide was given at a dose ranging from 100 mg/day to 400 mg/day continuously; the lenalidomide dose was 25 mg/day, days 1-21 on a 28-day cycle. All patients received dexamethasone, either at high-dose (40 mg orally on days 1-4, 9-12, and 17-20) or at low-dose (40 mg orally day 1, 8, 15, 22); each cycle was repeated every 4 weeks. In addition, a case-matched subgroup analysis that adjusted for age, gender and transplantation status was performed among patients who received high-dose dexamethasone comparing the thal/dex (n=72) and len/dex (n=72) groups. Outcome was analyzed on an intention-to-treat basis. The Chi-square or the rank sum tests were used to compare variables. Time-to-event analysis was performed using the Kaplan-Meier method and all comparisons were determined by the log-rank test and by the Cox proportional hazards model. Results On intention-to-treat analysis, of 411 patients, 80.3% versus 61.2% patients, respectively in the len/dex group and in the thal/dex group (p < 0.001), achieved at least a partial response. A significant difference between the 2 groups was found in terms of both very good partial response or better (34.2% vs 12.0%, p < 0.001) and complete response rate (13.6% vs 3.3%, p < 0.001). Duration of therapy was significantly longer in len/dex patients as compared to thal/dex patients: 36.7% vs 12.6% of patients who did not stop treatment to receive SCT were still receiving therapy at 1 year (p < 0.001).Time-to-progression was significantly better in the len/dex group than in patients receiving thal/dex (median 27.4 vs 17.2 months, HR 0.64; 95% CI 0.44-0.93; p = 0.019). Similarly, progression-free-survival was significantly higher in len/dex patients (median 26.7 vs 17.1 months, HR 0.69; 95% CI 0.48-0.98; p = 0.036). This translated into an increase in overall survival (OS) (median not reached for len/dex group compared to 57.2 months in thal/dex patients, HR 0.60; 95% CI 0.40-0.92; p = 0.018). Survival advantages were evident in patients presenting with International Staging System Stage (ISS) I/II (HR 0.57; 95% CI 0.32-1.00; p = 0.052) at diagnosis but not in patients with ISS stage III in subgroup analysis. There was a trend toward better OS in len/dex group compared to thal/dex group both for patients who underwent transplant and for patients who did not. A similar rate of patients experienced at least one grade 3 or higher adverse event (57.5% vs 54.6% in len/dex and thal/dex groups, respectively, p = 0.568). However, the toxicity profile was different in the two groups: major grade 3-4 toxicities of len/dex were hematological, in particular neutropenia (14% with len/dex vs 0.6% with thal/dex, p<0.001) while the most common toxicities in thal/dex were venous thromboembolism (15.3% vs 9.2%, p = 0.058) and peripheral neuropathy (10.4% vs 0.9%, p < 0.001). The data on efficacy and safety shown above were also confirmed in the subgroup case-matched analysis which included only high-dose dexamethasone patients. Conclusions This cohort study shows the superiority of len/dex in terms of response rates and survival, compared to thal/dex. The toxicity profile of the 2 regimens is different and len/dex treatment, although more active, was not associated with increased toxicity (grade 3-4 AEs). These data need to be carefully evaluated and randomized prospective phase III studies are necessary to confirm these results and determine the optimal initial therapy for MM. Disclosures: Off Label Use: research drugs in combination to standard care. Lacy:celgene: Research Funding. Gertz:celgene: Honoraria; genzyme: Honoraria; millenium: Honoraria; amgen: Honoraria. Kumar:celgene: Research Funding; millenium: Research Funding; bayer: Research Funding; Novartis: Research Funding; Genzyme: Research Funding. Dispenzieri:celgene: Research Funding. Bergsagel:amgen: Membership on an entity's Board of Directors or advisory committees; genetech: Membership on an entity's Board of Directors or advisory committees; merck: Research Funding; celgene: Membership on an entity's Board of Directors or advisory committees. Witzig:celgene: Research Funding. Fonseca:medtronic: Consultancy; genzyme: Consultancy; celgene: Consultancy; amgen: Consultancy; BMS: Consultancy; otsuka: Consultancy. Greipp:celgene: Research Funding.

Abstract Abstract 429 Background: Patients with MM who have progressed after multiple novel agents have limited treatment options. Pomalidomide (CC4047) is the newest immunomodulatory (IMiD) agent that has demonstrated response rates of 63% in a Phase 2 trial of Pom/dex in patients with relapsed MM (in press, JCO). To better define the response rate in this group, we treated an additional cohort of patients who were truly resistant/refractory to lenalidomide. Methods: To be eligible, patients must:be refractory to lenalidomide therapy defined as relapsing on or within 60 days of stopping lenalidomide. Pomalidomide was given orally 2 mg daily on days 1–28 of a 28-day cycle. Dexamethasone was given orally at a dose of 40 mg daily on days 1, 8, 15 and 22 of each cycle. Response was assessed by the International Myeloma Working Group Uniform Response criteria. All patients received aspirin 325 mg daily as prophylaxis against DVT. Pom/dex regimen would be declared promising if we observed at least 4 confirmed responses out of 34 patients based on a single stage Fleming design. Results: 34 patients (23 male and 11 female) resistant/refractory to lenalidomide were enrolled. The median age was 62 years (range, 39-77). The median time from diagnosis to enrollment was 62 months (range 8-179). 12 patients had high risk molecular markers including loss of 17p (6 pts), t(4;14) (1 pt) and del 13 by cytogenetics (5 pts). 70% had ≥3 prior regimens including 38% with ≥5 prior regimens; 56% had prior thalidomide, 59% had prior bortezomib, and 68% had prior SCT. Toxicity (at least possibly related to treatment) was mild and consisted primarily of myelosuppression: grade 3/4 neutropenia (21%); grade 3 thrombocytopenia (9%); and grade 3 anemia (12%). Grade 3/4 non-hematologic toxicities occurred in 24%: pneumonia (3%), non-infectious pneumonitis (3%), hyperglycemia (3%), edema(3%), fatigue(9%) skin rash(3%). Neuropathy occurred in 18% (12% grade 1; 6% grade 2). No thromboembolic events have occurred so far. Nine (26%) patients were confirmed responders (all PR), surpassing the threshold for a positive trial, and 18 (53%) had SD. With a median follow-up of 4 months (range:0-8), 65% remain progression free; 88% remain alive; and 12% have died, all due to progressive MM. Conclusions: Pom/dex is active and well tolerated in this heavily pre-treated population of lenalidomide-refractory MM patients. The majority of patients have not progressed and objective responses are seen in 26%. This study confirms that pomalidomide has non-cross resistance with lenalidomide and offers benefit for patients who have relapsed after other novel therapies. Disclosures: Lacy: Celgene: Research Funding. Gertz:celgene: Honoraria; millenium: Honoraria, Membership on an entity's Board of Directors or advisory committees. Kumar:celgene: Honoraria; millenium: Honoraria, Membership on an entity's Board of Directors or advisory committees. Bergsagel:Genentech, Inc.: Consultancy; Amgen: Consultancy; Celgene: Consultancy; Merck: Research Funding. Stewart:Takeda-Millenium, Celgene, Novartis, Amgen: Consultancy; Takeda, Millenium: Research Funding; Genzyme, Celgene, Millenium, Proteolix: Honoraria.

Abstract Multiple myeloma (MM) is a tumor of isotype-switched plasma cells that accumulate in the bone marrow, replacing normal plasma cells and leading to bone destruction and marrow failure. It is often preceded by a stable monoclonal gammopathy (MG) with limited (<10%) bone marrow plasmacytosis that progresses stochastically to MM at a rate of between 1–2% per year. Primary genetic events thought to be associated with disease initiation are present at similar frequencies in both MG and MM. In approximately 40% of cases, there are recurrent chromosome translocations involving the immunoglobulin heavy chain gene that have the hallmarks of being mediated by errors in switch recombination (90%) or somatic hypermutation (10%). These involve recurrent loci that fall into three categories: Cyclin D (15% CCND1 at 11q13, <1% CCND2 at 12p13, 2% CCND3 at 6p21), MAF (5% c-maf at 16q23, 2% MAFB at 20q12, <1% MAFA at 8q24.3), and MMSET (usually with FGFR3 at 4p16, 15%). Approximately one-half of cases are hyperdiploid (48–75 chromosomes) with trisomies involving chromosomes 3, 5, 7, 9, 11, 15, 19 and 21. A unifying feature of MM is dysregulated expression of a cyclin D gene, either directly by Ig gene translocation, by transactivation by MAF (CCND2), or by unknown mechanisms (MMSET – CCND2, Hyperdiploid – CCND1). Interestingly, about 2% of patients express no cyclin D, and one-half of these patients have bi-allelic deletion of RB, highlighting the critical role of the CCND/RB axis in the pathogenesis of MM. Deletion of chromosome 13 is seen in one-half of MM but is much more common in the tumors that express CCND2 (>80%) than in those that express CCND1 (~30%). Although with largely redundant functions, CCND1 has additional ability to antagonize RB not shared by CCND2, suggesting that CCND2 tumors may be more critically dependent on the absolute level of RB protein. A variety of secondary genetic events associated with disease progression occur with a similar frequency in hyperdiploid and non-hyperdiploid tumors (17p loss or p53 mutations, RAS mutations, secondary Ig translocations, MYC translocations, and inactivation of p18INK4c or RB1). In contrast, a promiscuous array of mutations that activate the NFKB pathway are less common in hyperdiploid MM, which, nonetheless, has high levels of presumably ligand-dependent NFKB activity and appears particularly dependent on the bone marrow microenvironment. Both some of the primary (MAF, MMSET) and secondary (17p deletion) genetic events are associated with a poor prognosis with melphalan-based regimens and appear to benefit from the early introduction of bortezomib.

Abstract Abstract 616 Background: We have shown the three drug combination of cyclophosphamide, bortezomib and dexamethasone (CyBorD) to be highly active therapy in newly diagnosed myeloma while allowing stem cell harvest and transplantation (Reeder et al. Leukemia 2009; 23:1337-1341). However, twice weekly bortezomib and high dose dexamethasone have been shown to cause significant toxicities. In a prospective Phase II we modified CyBorD by using bortezomib once weekly and reducing the dexamethasone to “low dose dex” after the first two cycles in an attempt to reduce toxicity (cohort 2). We report the efficacy and toxicity of this modified regimen and compare the results to standard CyBorD (cohort 1). Patients and methods: 63 untreated symptomatic patients were enrolled on this Phase II trial (33 on cohort 1 and 30 on cohort 2). All are evaluable for response and toxicity. Treatment on cohort 2 consisted of oral cyclophosphamide 300 mg/m2 and IV bortezomib 1.5 mg/m2 days 1, 8, 15 and 22 and dexamethasone 40 mg by mouth days 1-4, 9-12, 17-20 in cycles 1 and 2, then 40 mg po days 1, 8, 15, 22 in cycles 3 and beyond. Cohort 1 used standard dosing of bortezomib and high dose dexamethasone throughout. Each cycle was 28 days. Acyclovir and a quinolone antibiotic prophylaxis were routinely used. Patients were evaluated for response and toxicity every cycle and were offered stem cell harvest and transplant after the 4th cycle but could continue up to 12 cycles maximum. Results: The median age for all 63 patients was 61 (36-74) years and 48% were female. Durie-Salmon stages were 47% II and 50% III and ISS stages I 43%, II 36%, and III 21%. Twenty-four percent of patients were genetic high risk (t(4;14) or deletion 17). Cohorts I and II were matched for age, gender and ECOG PS. ISS stages were higher in cohort 1 than cohort 2 (II/III 67% vs. 44%). The intent to treat (ITT) ORR (≥PR) for all 63 patients (cohorts 1 and 2) is 90% with 60% ≥VGPR. For cohort 2 (modified CyBorD) the ITT overall response (≥PR) was 93% (CR: 5, nCR: 7, VGPR: 6, PR: 10) with 60% ≥VGPR and 40% ≥ nCR. Those completing all 4 cycles of therapy had 92% ORR (24/26) and 65% (17/26) ≥VGPR. A comparison of response rates in cohorts 1 and 2 is shown in table 1. These high and comparable response rates were associated with fewer grade 3+ adverse events (AE's) than in cohort 1 (37% vs. 48%) and no grade 3 peripheral neuropathy (PN). The median follow-up for all 63 patients is 12.4 (2.8-29.2) months and 95% of patients are alive with 87% free from progression. Conclusions: Modified CyBorD with weekly bortezomib and reduced dexamethasone retains the high activity seen in standard CyBorD, but is less toxic and more convenient. Interestingly, this modified regimen allowed higher overall doses of bortezomib (5.2 vs. 6.0 mg/m2 per cycle) yet overall neuropathy rates were similar. This combination of a weekly alkylating agent with bortezomib and dexamethasone is well tolerated and produces high response rates in newly diagnosed patients with multiple myeloma. Disclosures: Reeder: Millennium (MPI): Research Funding; Celgene: Research Funding. Reece:Ortho Biotech: Honoraria, Research Funding. Chen:Celgene: Honoraria, Research Funding; Ortho Biotech: Honoraria. Hentz:Millennium (MPI): Research Funding. Fonseca:Otsuka: Consultancy; BMS: Consultancy; Amgen: Consultancy; Medtronic: Consultancy; Genzyme: Consultancy. Bergsagel:Merck: Research Funding; Amgen: Consultancy; Genentech: Consultancy; Celgene: Consultancy. Stewart:Proteolix: Honoraria; Millennium (MPI): Research Funding.

Abstract In approximately 50% of Multiple Myeloma (MM), translocation of non random genes into the IgH locus is believed to be the seminal event in the pathogenesis of the disease. Another 50% of cases are hyperdiploid and trisomic to certain autosomes, but do not harbor any translocation and thus are believed to have genetic alterations in unidentified loci. These observations, together with the finding of somatic mutations in FGFR3, N- and K-RAS, MYC, TP53 and CDKN2C/p18INK4C during the later stages of MM indicate that defective signaling pathways likely play a role in the progression of this malignancy. Of relevance then, in recent years recurrent mutations in kinases have frequently been implicated in malignancies including notably colon cancer and melanoma. We have therefore begun a comprehensive effort to sequence the tyrosine kinome for mutations and genetic polymorphisms in MM. Of particular interest are 90 receptor tyrosine kinases, 43 receptor tyrosine kinase-like, 5 receptor guanylate cyclase, and a lipid kinase. We report here results from our pilot high throughput exon scanning in 32 human MM cell lines which initially focused on 13 kinases known to be somatically mutated in human cancers. To date we have expanded this effort to assess 30 genes with sequence obtained which currently spans 80% coverage of the kinase domains of these genes. A total of 1.9 million bp have been sequenced across 235 exons. No recurrent mutations have been identified in the kinase domains of the cancer-associated genes: SRC, ILK1, KIT, GUCY2F, PDGFRA; in the genetic disorder-associated kinases: BTK, EPHA4, LAMA2, EPHB6, ACVR2; and in the mutation hot spots of frequently mutated cancer gene PIK3CA. A novel missense mutation is however identified upstream of the kinase domain of FGFR3 changing a Ser residue to Arg at codon 433. This residue, which is conserved across species and in FGFR1 and FGFR2, has not been reported in myeloma and in thanatophoric dysplasia, but the biological significance of this mutation is unknown. Several single nucleotide polymorphisms were identified in the coding regions of some of these kinases. Notably, synonymous polymorphisms in the kinase domains of EPHA4, PDGFRA3, KIT, MLK1, ILK1, NTRK3, FLT3, ABL1, FES, MLK4, and EGFR1 were identified that changed a codon but not the amino acid. More importantly, we identified non-synonymous amino acid variations in the kinase domains of EPHA4, GUCY2F, PTK2, and PIK3CA genes that are more likely to effect variability in the activity of these kinases. In summary, no recurrent kinase mutations of significance in Myeloma development or progression have yet been identified. Sequencing of the known cancer associated kinases in MGUS and hyperdiploid MM patients is now underway and our data set is being expanded to include all 139 kinases.

Abstract Background: The combination of lenalidomide and dexamethasone (RD) has been shown to be highly effective as initial therapy for multiple myeloma. More recently, a phase III trial demonstrated improved survival with use of lenalidomide and low dose dexamethasone (Rd). Further improvements by incorporating other active agents may increase the depth of response and may improve long-term outcome. We report the results from a phase II trial combining lenalidomide and low dose dexamethasone with cyclophosphamide (RCd) as initial therapy for newly diagnosed MM. Methods: The trial was initiated in July 2006 and completed the initial target accrual of 33 patients by July 2007 (Cohort 1). Due to high rate of dose reductions in cohort 1, between July 2007 and May 2008 an additional 20 patients were enrolled with lower doses of cyclophosphamide (Cohort 2). The treatment protocol consisted of lenalidomide given orally at a dose of 25 mg daily on days 1–21 of a 28-day cycle. Dex was given orally at a dose of 40 mg on days 1, 8, 15, and 22 of each cycle. Cyclophosphamide at a dose of 300 mg/m2 was given on days 1, 8, and 15 of each cycle in cohort 1 and 300 mg on days 1, 8, and 15 of each cycle in cohort 2. Patients also received an aspirin once daily as thromboprophylaxis. Response was defined as a decrease in serum monoclonal (M) protein by 50% or higher and a decrease in urine M protein by at least 90% or to a level less than 200 mg/24 hours. Responses were assessed on intent to treat basis. Results: 53 patients were enrolled. The median age was 64 years (range, 37–82). 14 patients (29%) had ISS stage III disease. The median number of cycles was 4 (range: 1 – 20). The best response based on all enrolled patients on an intent to treat basis was 83%, including CR:1 (2%), VGPR: 20 (38%), PR: 23 (43%), and less than PR: 9 (17%). The CR plus VGPR rate was 40%. Among the 20 patients in cohort 2 who were enrolled after optimization of the cyclophosphamide dosing, 16 (80%) have already achieved a partial response or better with 17 patients in this cohort still receiving study treatment. Overall, 25 of the 53 enrolled patients have discontinued study treatment. Reasons for ending treatment are: completed study per protocol (14), disease progression (5), adverse event (3) and alternate treatment (3). This includes 3 patients from cohort 2, one completed treatment per protocol, one went to alternate therapy and one patient went off for progression. Hematological toxicity was the most common with grade 4 toxicity seen in 8 patients (only 1 from cohort 2). Non-hematological toxicities included neuropathy, diarrhea, cystitis, and thrombosis. There were 6 patients with grade 4 non-hematological toxicities (none from cohort 2) attributed to the drug (thrombosis, confusion, depression and sepsis). Thirteen patients had dose adjustments, most commonly due to hematological toxicity attributed to lenalidomide or cyclophosphamide. One patient has died off study, of intracranial hemorrhage. The median follow-up for the remaining patients is 7.8 months. Conclusions: The combination of lenalidomide, cyclophosphamide, and dexamethasone (RCd) has excellent activity in the setting of newly diagnosed myeloma. Seventeen patients continue on study and the response rates are likely to be higher with additional followup. Myelosuppression was a significant toxicity leading to dose reductions and cycle delays, and is lower with decreased dose of CTX in cohort 2 without any apparent loss of responses.

Abstract Background: Thalidomide and its analogue lenalidomide have high response rates among patients with newly diagnosed as well as previously treated myeloma. Pomalidomide (CC4047) is the newest immunomodulatory (IMiD) agent that has shown single-agent activity in phase I studies. We report on the first Phase 2 trial of pomalidomide combined with low dose dexamethasone (Pom/dex) in patients with relapsed or refractory multiple myeloma. Methods: 37 patients (21 male and 16 female) were enrolled. Pomalidomide was given orally 2 mg daily on days 1–28 of a 28-day cycle. Dexamethasone was given orally at a dose of 40 mg daily on days 1, 8, 15 and 22 of each cycle. Response was assessed by the International Myeloma Working Group Uniform Response criteria. All patients received aspirin 325 mg daily as prophylaxis against DVT. Results: The median age was 66 years (range, 40 – 88). All patients were evaluable for response and toxicity, and all analysis were done on intent to treat basis. All patients had received prior therapy; 38% had 3 prior regimens; 35% had 2 prior regimens and 27% had one prior regimen. 76% had previous autologous stem cell transplant (ASCT) and 24% had 2 prior ASCT. 62% had previous IMiD therapy. Toxicity was mild and consisted primarily of myelosuppression. Grade 3 neutropenia occurred in 31%; grade 3 thrombocytopenia 3%; grade 3 anemia 3 %. Other grade 3/4 toxicities seen in less than 5% pts included: diarrhea, atrial fibrillation, pneumonia, dehydration and renal insufficiency. 16 % had grade 1/2 neuropathy. No grade 3 neuropathy was seen and there have been no thromboembolic events. Thirty (81%) patients are continuing study treatment. Seven patients have discontinued treatment due to: disease progression (5), died on study (1) and the medical doctor’s discretion (1). Twenty three of 37 patients (62%) achieved an objective response to therapy; including 9 (24%) with VGPR; 14 patients (38%) with PR; 6 (16%) with stable disease. Objective responses were seen in 4 of 13 patients (29%) who were refractory to lenalidomide. Conclusions: Pomalidomide plus dexamethasone (Pom/dex) is highly active and well tolerated for treatment of relapsed/refractory multiple myeloma with an objective responserate of 62%, including a 29% response rate among patients who are lenalidomiderefractory.

Abstract Abstract 604 We have conducted a pilot study to interrogate both CpG hyper- and hypomethylation in Multiple Myeloma (MM) using the Illumina GoldenGate (GG) BeadArrayTM high-throughput assay. Specifically, we utilized the Illumina Methylation Cancer Panel I, which spans 1,505 CpG loci selected from 807 genes including known tumor suppressor genes and oncogenes. To date we have profiled 50 CD138+ MM specimens, 4 MM cell lines and 6 normal CD138+ plasma cell samples (each representing a pool of 3-5 individuals) obtained from the bone marrow of patients who have undergone hip or knee replacement surgeries. We have obtained highly reproducible and reliable DNA methylation profiles with an average r2 of greater than 0.98 when the β values were compared between technical replicates. Further, we generated an internal control panel for the array by performing methylation specific PCR (MSP) to determine the methylation status of several genes found on the array (CDKN2A, E-Cadherin, MGMT, hMLH1) in 4 MM cell lines. A differential methylation analysis was conducted between normal plasma cells and MM samples using the BeadStudio Methylation Module v3.2. Differential scores for each CpG locus on the array were generated that correspond to significant differences between groups. Scores greater than (hypermethylation) or less than (hypomethylation) 13 represent ‘Diff scores' that are statistically significant (p values < 0.05) and this cut-off threshold is used to determine differentially methylated loci. Globally, when comparing MM to normal plasma cells, hypomethylation occurred at 42% of probes on the array, and was more common than hypermethylation, which occurred at only 21% of probes. Interestingly, 77% of probes situated in non-CpG islands were hypomethylated compared to 26% or probes in CpG islands. On the contrary hypermethylation occurred mainly in CpG islands (26% of probes) whereas only 7.4% of probes in non-CpG islands were considered hypermethylated. A total of 946 CpG loci were differentially methylated between normal plasma cells and MM. Among the most significantly differentially methylated CpG loci between normal plasma cells and MM were FZD9, ALOX12, MMP-3, MMP-8, and p16. Array comparative genomic hybridization (aCGH) data availabel for this same sample set was used to generate a hyperdiploid index for each sample by identifying those samples with whole chromosome gains at minimally three odd numbered chromosomes. There were 751 CpG loci that were differentially methylated between hypderdiploid and non-hyperdiploid tumors with WEE1, FRZB, ELK1, CLDN4, and SHH being among the most significant. We also applied the pathway enrichment analysis tool GeneGo v5 (Agilent) to these data, which identified cell adhesion/ECM remodeling, developmental pathways and several immune response pathways as the most significantly enriched pathways between normal and plasma cells with ephrin signaling pathways in the context of cell adhesion as the most significantly enriched pathway between hyperdiploid and non-hyperdiploid tumors. We hope to integrate methylation data with orthogonal datasets including gene expression, aCGH, and DNA sequence data being developed as part of the MMRF Genomics Initiative. Further validation of hits will also be followed up by functional studies to assess the true biological relevance of differentially methylated genes. This study represents one of the first methylome interrogation studies in MM and points towards global hypomethylation as possibly an important mechanism driving myelomagenesis. Our data also suggest that differential methylation of genes may be a significant determinant of hyperdiploid biology. Determining the set of critical genes and pathways based on the myeloma methylome is likely to lead to an improved understanding of biological mechanisms involved in myelomagenesis, ultimately leading to new and improved methods of diagnosing and treating this disease. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 3788 Poster Board III-724 Multiple myeloma (MM) is a malignancy characterized by clonal expansion and accumulation of long-lived plasma cells within the bone marrow. Phosphatidylinositol 3' kinase (PI3K) -mediated signaling is frequently dysregulated in cancer and controls fundamental cellular functions such as cell migration, growth, survival and development of drug resistance in many cancers, including MM, and therefore represents an attractive therapeutic target. Here, we demonstrate in vitro, that a potent and selective pan-isoform PI3Kinhibitor, GDC-0941, modulates the expected pharmacodynamic markers, inhibits cell-cycle progression and induces apoptosis; overcomes resistance to apoptosis in MM cells conferred by IGF-1 and IL-6; and is additive or synergistic with current standard of care drugs including dexamethasone, melphalan, lenolidamide and bortezomib. In cell lines we find sensitivity to GDC-0941 is positively correlated with pathway activation as determined by phospho-AKT-specific flow-cytometry and Western-blot analysis. Preliminary results indicate apoptosis of MM cells is correlated with increased expression of the proapoptotic BH3-only protein BIM; mechanisms of increased apoptosis in MM will be further explored and an update presented. We further extend these in vitro findings to show that GDC-0941 has activity as a single agent in vivo and combines well with standard of care agents in several murine xenograft models to delay tumor progression and prolong survival. Our results suggest that GDC-0941 may combine well with existing therapies, providing a framework for the clinical use of this agent, and a rational approach to improving the efficacy of myeloma treatment. Disclosures: Munugalavadla: Genentech: Employment, Patents & Royalties. Berry:Genentech: Employment, Patents & Royalties. Du:Genentech, Inc.: Employment, Equity Ownership. Mariathasan:Genentech: Employment, Patents & Royalties. Slaga:Genentech: Employment, Patents & Royalties. Sun:Genentech Inc.: Employment. Chesi:Genentech, Inc.: Consultancy; Amgen: Consultancy; Celgene: Consultancy; Merck: Research Funding. Bergsagel:Genentech: Consultancy; Amgen: Consultancy; Celgene: Consultancy; Merck: Research Funding. Ebens:Genentech, Inc.: Employment, Equity Ownership, Patents & Royalties.