Fonseca, Rafaël

Previously, we have shown that centrosome amplification is common in multiple myeloma and is already present in monoclonal gammopathy of undetermined significance (MGUS), suggesting an early role in myelomagenesis. In addition, we derived a gene expression based centrosome index (CI) that correlated closely with centrosome amplification detected by immunofluorescence. We also showed in a heterogeneously treated and relatively small cohort of patients that the CI is an independent prognostic factor. In this study, we validated the prognostic significance of a gene expression based centrosome index (CI) in 2 large cohorts of homogenously treated myeloma patients entered into clinical trials. Cohort 1 consisted of newly diagnosed patients from the University of Arkansas for Medical Science (UAMS) entered treated with total therapy II. These patients have gene expression profiling performed on purified CD138+ plasma cells from pre-treatment bone marrow cells using the Affymetrix U133plus chip (data available from Gene Expression Omnibus). Cohort 2 consisted of relapsed or refractory patients entered into bortezomib trials. These patients have GEP performed on purified CD138+ PCs using the Affymetrix U133A and B chip as part of a pharmacogenomics study (data kindly provided by Millenium Pharmaceuticals). Expression values extracted using the MAS 5.0 software are log-transformed, median centered and analyzed using Genespring 7.0 (Agilent Technologies). Survival is calculated from date of entry into trial till death in both cohorts. In the UAMS dataset, a high CI is significantly associated with shorter survival and emerged as an independent prognostic factor with t(4;14) (detected by spike FGFR3/MMSET expression) when entered into a multivariate Cox proportional hazard analysis (other variables entered included CKS1B expression above median and elevated gene expression based proliferation index, both of which were significantly associated with shorter survival on univariate but not multivariate analysis). In the bortezomib cohort, a high CI is again significantly associated with shorter survival, and this effect is independent of response to bortezomib. Therefore, a high CI is a powerful independent prognostic factor in both newly diagnosed and relapsed patients even in patients treated by intensive therapy (total therapy II) and novel agents (bortezomib). We next compared the gene expression profiles of tumors with high and low CI, to define the molecular phenotype of these aggressive tumors and identify possible novel therapeutic targets. Tumors with high CI over-expressed genes coding for proteins associated with the centrosome (TUBG1, CETN2, TACC3, NEK2, PRKRA, STK6, AURKB and PLK4), cell cycle (CCNB1, CCNB2, CCND2, E2F2, CDC gene family, CDK5, CDK6, CDKN2C), proliferation (RAN, CKS1B, TOP2A, TTK, TYMS, MCM gene family, ASPM), involve in DNA repair / G2 cell cycle checkpoints (BRCA1, CHEK1, CHEK2, MAD2L1, BUB1, BUB1B, FANCD2, REV1L), kinetochore and microtubule attachment (AURKB, BIRC5, CENPA, CENPE, CENPH, ZWINT), genes coding for cancer testis antigens (GAGE and MAGE family) and implicated in other cancer (PTP4A3, EZH2). Consistent with this, the most significantly associated Gene Ontology biological process are cell cycle, mitosis, proliferation, DNA repair, microtubule related In particular, aurora kinases are significantly over-expressed in patients with high CI and may represent novel therapeutic targets in these patients with very poor prognosis.

Abstract The study of genomic aberrations in chronic lymphocytic leukemia (CLL) has yielded critical information, now routinely used for the prognostication of patients. An unbiased search for genome wide areas of copy number change is needed to identify possible primary genetic events in CLL and to elucidate their relationship to other known cytogenetic factors, such as deletions of 13q14, 11q23 and 17p13 and trisomy 12. Here we report on a study where we used a 60-mer oligo array-based Comparative Genomic Hybridization (aCGH, 44B platform from Agilent Technologies, Palo Alto, CA). We observed the most common genetic aberrations in CLL and in similar frequencies as would be predicted for CLL (e.g. 44% showing deletions of chromosome 13q14). Among those patients, 45% had no apparent other aberration. Of great interest, small bi-allelic deletions of chromosome 13, which predominantly involved the DLEU1 and DLEU2 locus, were detected in 4 patients (16%). Deletions of 11q23 were observed in 6 cases (24%), and while some involved the ATM locus one did not, casting doubt on the precise gene deregulated by these deletions. Large deletions of the whole 17p-arm were detected in three cases (12%). Trisomy 12 was present in only two cases (8%). No other trisomies were detected and also small regions of copy gain were uncommon. Monosomy of chromosomes 19, X and Y were present in three separate cases. Large deletions of chromosome 2p were seen in two cases, but an additional case had a small deletion involving the ALK gene. This case also had a breakpoint at chromosome 5 involving the NMP1 locus, suggestive of a t(2;5). A recent study (Mayr et al., Blood 2006) indicates that chromosomal translocations in CLL are present in 33% and were associated with a dismal prognosis. In our analysis we detected several breakpoints indicative of translocations. Detailed study is necessary to elucidate possible molecular events associated with these translocations. Other small regions of DNA copy loss were found at several locations throughout the genome. Regions of interest are shown in the table. In summary we show that multiple areas of recurrent genomic gain and loss can be identified in clonal cells of CLL and should lead to further insights into the understanding of disease pathogenesis. Chromosome Location Gene(s) of interest Loss 6q24.3 LATS Loss 10q23.3 LG11 Loss 10q24.2 PAX2, WNT8B, TLX1, POLL, NFKB2 Loss 11p15.4 PPFIBP2 Loss 12p13 TNFRSF1A and 7 Loss 15q22.1 TCF12 Loss 19p13.3 BAX, RUVBL2 Loss 20q11.2 TP53INP2 Loss 20q13.1 WFDC13

Abstract Background: An abnormal free light chain (FLC) indicating the presence of excess monoclonal FLC is associated with an increased risk of progression of monoclonal gammopathy of undetermined significance (MGUS) to multiple myeloma (MM) or related disorder. In addition, the risk of progression rises with increasingly abnormal FLC ratio, suggesting that the mechanism for markedly abnormal FLC ratios may be different compared to ratios closer to normal range. We hypothesized that as in light chain MM (in which IgH expression is completely lost), a more markedly abnormal FLC ratio is a marker for IgH translocations (TCs) involving 14q32. We tested this hypothesis using data obtained from gene expression profiling (GEP) to identify the presence of specific IgH TCs and correlating them to serum FLC ratio. Methods: We examined data from 128 GEPs from pts with MM (92), smoldering MM (13), MGUS (9) and primary amyloidosis (14). Presence of IgH translocations were identified using the specific probes for the partner chromosome TC sites, namely FGFR3/MMSET (4p16), cyclin D3 (6p21), cyclin D1 (11q13), c-maf (16q23), and mafB (20q12) as previously described. FLC estimation was carried out on stored serum samples from these patients using the serum FLC assay (FreeliteH, The Binding Site Limited, UK) performed on a Dade-Behring Nephelometer. Based on the established reference range, kappa/lambda FLC ratio <0.26 or >1.65 were defined as abnormal indicating the presence of monoclonal lambda and kappa FLC, respectively. The monoclonal LC isotype was considered the involved FLC isotype, and the opposite LC type as the uninvolved FLC type. Differential expression of genes was examined using Genespring 7.2 software. Results: Among the 92 pts with MM, 36 (42%) had evidence of one of the 5 primary IgH TCs: 20 pts with 11q13 (22%), 7 pts with 4p16 (8%), 4 pts with16q23 (4%), 3 pts with 20q12 (3%), and 2 patients with 6p21 (2%). Among the 11 pts with MM with an FLC ratio of > 1000, 8 (72%) had an IgH TC. The proportion of pts with an FLC ratio >1000 was significantly higher in pts with an IgH TCcompared to those without, 22% vs 5% respectively, P=0.02. The mean FLC ratio was 1728 (range; 1.6 to 31,008) in patients with an IgH TC vs. 412 (1–11340) for those without IgH TCs, P=0.09. Similarly in pts with MGUS, SMM or AL all three pts with a ratio > 50 had evidence of an IgH translocation. compared to 14/33 with lower ratio. The mean FLC ratio was 29 (range;1 to 209) in pts with an IgH TC vs. 9.1 (1–41) for those without IgH TCs, P=0.1. We correlated the results of FISH tests where available (122 of 128 pts) to determine the ability of GEP to identify IgH TCs. IgH translocation identified by the GEP could be detected on FISH in 42 of 47 patients (89%). Correspondingly, 61 of 75 patients (81%) without an IgH translocation on GEP had a similar result by FISH as well. We compared the GEP of MM pts with FLC ratio of >500 to the rest and identified 34 genes which were 2 fold differentially expressed between the two groups. Conclusion: By combining GEP data and serum FLC measurements, we show that very high FLC ratios is associated with IgH translocations. However, the correlation is not absolute, likely reflecting that markedly abnormal FLC ratios may be mediated through other mechanisms including increasing tumor load. To further explore this we analyzed differentially expressed genes between patients with high and low ratios and identified a set of 34 genes, which are currently being studied further.

Abstract Immunoglobulin (Ig) light chain (LC)-associated amyloidosis (AL) is a fatal plasma cell (PC) disorder characterized by the overproduction of Ig light chains that deposit in an abnormal conformation as amyloid throughout the body. Lambda LC are involved in amyloid deposition 2–3 times more often than kappa LC, and certain LC Ig variable genes are more frequently involved than others and influence clinical presentation and outcome. AL is a potential complication of any immunoglobulin clonal process, but is most often pathologically associated with minimal clonal expansion of PC, as seen in monoclonal gammopathy of undetermined significance. It is much less commonly observed in patients with multiple myeloma (MM). Because of this, and to our knowledge, there are no cell lines that have been established from AL patients, an experimental tool that would be of great value in studying amyloid formation and the biology of amyloid producing PC. In this study, we have established two cell lines from a 50 yr old female initially diagnosed with AL. Upon initial diagnosis, the BM aspirate consisted of 27% IgG λPC with a PC labeling index (PCLI) of 1.9% and a κ to λratio of <0.1. Amyloid was present in periosteal vessel walls and in the fat aspirate. The first cell line, ALMC-1, was established from BM mononuclear cells isolated from the diagnostic aspirate. The patient received a peripheral blood stem cell transplant (PBSCT) 2 months later, but relapsed within 100 days post-PBSCT with symptomatic myeloma. At relapse, the patient’s BM aspirate consisted of 70% λ+ PC and a PCLI of 20%; the second cell line, ALMC-2 was established from this aspirate. IgVL and IgVH analysis revealed that both cell lines expressed identical sequences and used IgVλ 6–57*01, IgλJ3*02, and IgλC3*03: both used the IgVH VH3–21 gene and the extent of somatic mutation was approximately 4%. Both cell lines produce significant FLC, and studies are currently underway to characterize in vitro amyloid production. We next used fluorescence in situ hybridization (FISH) to identify the genetic defects in this patient’s tumor population before and after transition to symptomatic MM. The initial BM aspirate at time of diagnosis of AL revealed approximately 30% of the PC had clear evidence of c-MYC gene amplification. In the subsequent draws as well as in both cell lines, 100% c-MYC amplification was identified, consistent with clonal selection. FISH analysis also revealed that 40% of cells had p53 deletion upon initial diagnosis, whereas the subsequent samples and cell lines were 100% for p53 deletion. All cells also had an IgH translocation that did not involve any commonly observed chromosome partners. Lastly, we have characterized the cytokine responsiveness of both cell lines. Although some differences are observed between ALMC-1 and ALMC-2, IL-6 and IGF-1 stimulated growth in both cell lines to varying degrees and both lines expressed autocrine IGF-I. In summary, our initial characterization of ALMC-1 and ALMC-2 predicts that these unique cell lines will prove to be an invaluable tool to better understand AL, from the combined perspectives of amyloidogenic protein structure and amyloid formation, genetics, and cell biology. Insight gained from this model system may eventually have an impact in the clinical arena by providing a better understanding of this incurable disease.

Translocations involving immunoglobulin (Ig) loci and chromosome 13 monosomy (Δ13) are frequent cytogenetic findings in multiple myeloma (MM). Similar chromosomal aberrations have been identified in the monoclonal gammopathy of undetermined significance (MGUS), but their prevalence and significance remain uncertain. Bone marrow from 72 patients with MGUS (n = 62) and smoldering MM (n = 10) was evaluated for translocations between the Ig heavy chain (IgH) and chromosomes 4, 11, and 16, translocations involving Ig light chain–lambda (IgL-λ, and Δ13. Fluorescence in situ hybridization (FISH) analysis was done on clonal plasma cells (PCs) detected by immunofluorescence (cIg-FISH) of the cytoplasmic light chain. We also studied cells for cyclin D1 and FGFR3 up-regulation by immunohistochemistry and immunofluorescence, respectively. Twenty-seven (46%) of 59 patients had IgH translocations, and 4 (11%) of 37 had an IgL-λ translocation. A t(11;14)(q13;q32) was found in 15 (25%) of 59 patients, a t(4;14)(p16.3;q32) in 9% of patients, and a t(14;16)(q32;q23) in 5% of patients. All patients with t(4;14)(p16.3;q32) tested (n = 3) had intense cytoplasmic fluorescence with an anti-FGFR3 antibody. PC nuclear staining of cyclin D1 was only observed in patients with t(11;14)(q13;q32); Δ13 was detected in the clonal PCs in 50% of patients. The percentage of abnormal PCs varied with any given abnormality. No obvious clinical or biologic correlations were associated with these chromosome abnormalities. Similar translocations are found in both MGUS and MM, including t(4;14)(p16.3;q32) and t(14;16)(q32;q23). Moreover, Δ13 is common in MGUS and unlikely to play a predominant role in the evolution of MGUS to MM.

Abstract In an attempt to identify novel genetic abnormalities in multiple myeloma (MM) we analyzed 68 MM patient samples and 42 human myeloma cell lines (HMCL) with high-resolution (60kb) array-based comparative genomic hybridization (aCGH). We concentrated on bi-allelic genomic deletions with the expectation that these regions might contain novel tumor suppressor genes and identified a common abnormality at 14q32. Fine mapping of the 14q32 microdeletion by PCR demonstrated a 45 kb minimal deletion encompassing two genes; TRAF3, a negative regulator of the non-canonical NF-kB pathway, and AMN. To determine the frequency of copy number abnormalities of this region a cohort of 161 patients were screened with a FISH probe mapping to the minimally deleted region. This identified 7 (4.4%) patients with bi-allelic deletion and 19 (11.8%) patients with a single copy of the target region. Sequencing of all TRAF3 coding exons in 62 patients and 42 HMCL identified inactivating mutations in 9 patient samples and 4 HMCL. Overall, the incidence of TRAF3 inactivation, bi-allelic deletion or mutation, is 7/42 (16.7%) in HMCL and 12/62 (19.4%) in patients, making it one of the most common genetic abnormalities identified in MM. Importantly, dysregulation of NF-kB pathways is a common event in MM, but the mechanism for this dysregulation is largely unknown. Although TRAF3 is a negative regulator of the non-canonical NF-kB pathway it has not previously been implicated in cancer. Therefore, we tested the tumor suppressor function of TRAF3 by reintroducing TRAF3 into HMCL harboring TRAF3 abnormalities using an adenovirus gene transfer system. Expression of TRAF3 in HMCL with TRAF3 abnormalities rapidly reversed cellular processing of NFKB2 from p100 (an inactive isoform) to p52 (active) and additionally led to a 60% reduction in cellular proliferation (range, 10–89%) associated with Go/G1 cell cycle arrest and induction of cell death by apoptosis. At 48 hrs post infection the proportion of cells entering S-phase or G2/M declined by 31% (range, 8.1–56.1) and the proportion undergoing apoptosis increased by 28% (range 11.7–47.4%). In contrast, over-expression of TRAF3 in control HMCL without TRAF3 abnormalities had no effect. Overall, TRAF3 is identified as a novel tumor suppressor that regulates the non-canonical NF-kB pathway and is inactivated in ~ 20% of MM patients. Given the involvement of the NF-kB pathway in multiple human malignancies and the near constitutive expression of TRAF3 we propose that inactivation of TRAF3, a novel tumor suppressor identified for the first time in this study, may occur in other cancers. In this regard, we have recently identified a Burkitt lymphoma cell line that does not express TRAF3 and thus has constitutive processing of p100 to p52. The clinical and therapeutic consequences of this finding and its frequency in other tumor types are currently the focus of further investigation. In conclusion, the abnormalities identified in this study represent the first mutations identified that cause constitutive NF-kB activation in MM.

Abstract Plasma cell leukemia (PCL) is an aggressive and rare hematological malignancy that can originate either as primary disease (pPCL) or as a leukemic transformation of multiple myeloma (MMLT). We report here on the clinical characteristics, survival and genetic studies of 80 patients with PCL treated at a single institution (including 41 with pPCL and 39 with MMLT) and make comparisons with 439 newly diagnosed cases of multiple myeloma (MM). From our results pPCL presents a decade earlier than MMLT (54.7 vs 65.3 years) and despite substantially poorer clinical and laboratory parameters at presentation (hepatomegaly 32% vs 11%, leukocytes 31.6 vs 20.9, β2M 8.5 vs 4.3) pPCL appears more responsive to conventional combination chemotherapy (VAD, VBMVP or VBAP) than MMLT and is associated with significantly longer survival (median 18.4 vs 3 months). Comparison of pPCL groups treated with combination chemotherapy (n=21) or with other regimens (40% MP, 10% Thal/Dex, 20% other, 30% none)(n=20) identifies no substantial pre-treatment differences between the groups although a higher proportion of patients who received combination chemotherapy subsequently proceeded to stem cell transplantation (30 vs 10%). Importantly, survival of pPCL patients treated initially with combination chemotherapy (median 13.9, mean 27.3 months) was significantly longer compared with patients who did not receive combination chemotherapy (median 5.2, mean 9.9 months)(p=0.035) with 2 long term survivors (> 7 years) in the chemotherapy group. By comparison, patients with MMLT received less active therapy for their leukemic disease than did patients with pPCL (21% VAD, VBMVP or VBAP; 18% MP). Treated MMLT patients showed selection bias for younger age (60.9 vs 66.4 years) and lack of bone disease (0 vs 65%)(p<0.01); however despite this, median survival was disappointingly short for MMLT patients in the treatment group and was not significantly improved compared with non-treated patients (2.3 vs 0.8 months)(p=0.34). Assessment of novel therapies in PCL is therefore urgently required. Karyotype analysis and targeted genetic studies demonstrate that IgH translocations are present with high frequency in both pPCL and MMLT (71 vs 86%) compared with MM (~50%). Notably, IgH translocation in pPCL is almost exclusively targeted at chromosome 11 (cyclin D1) belying its importance in establishing the phenotype. IgH translocation in MMLT is primarily to chromosome 11 [71%], but also targets chromosomes 4 (FGFR3/MMSET) [13%] and 16 (cMaf) [20%], recapitulating MM. Abnormalities of chromosomes 3,5,7,9,11,13,15 and 19 are present equally in all 3 disorders. Deletion of 17p13 (p53) shows strong selection pressure in the leukemias (pPCL 53.8%, MMLT 48.8%, MM 10.7%) and is complemented by p53 mutation (23%). Notably, pPCL tumors show lower rates of Ras mutation (12 vs 40%) and p14 (0 vs 31%) or p16 (25 vs 40%) promoter methylation than MMLT. Together these results therefore indicate that pPCL and MMLT are fundamentally different plasma cell disorders with distinctive biology, genetic abnormalities and treatment responses.

Abstract Background: Patients with early stage myeloma are typically observed without therapy until symptomatic disease occurs. We have reported early results of therapy with single-agent thalidomide as initial therapy for early stage multiple myeloma in an attempt to delay progression to symptomatic disease (Leukemia2003;17:775–9). We now report the long-term results of this phase II trial. Methods: Thirty-one patients with smoldering or indolent multiple myeloma were enrolled between April 1999–March 2002. All pts had bone marrow (BM) plasma cells >=10% and measurable disease defined as serum monoclonal (M) protein >=2gm/dL and/or urine M protein >=400mg/24 hours. Two patients were deemed ineligible because they were found to have received prior therapy for myeloma and were excluded from analysis. Thalidomide was initiated at a dose of 200 mg/day and increased as tolerated by 200 mg/day every 2 weeks to a maximum dose of 800 mg/day. The dose of thalidomide was decreased as needed to minimize toxicity. Treatment was continued until disease progression or serious toxicity, except for patients achieving less than a minor response (<25% paraprotein reduction) to therapy in whom therapy was stopped at one year. Response was defined as a decrease in serum and urine monoclonal (M) protein by 50% or higher. If the serum M protein was unmeasurable, a 90% or higher decrease in urine M protein was required. Responses need to be confirmed at least 4 weeks apart. Results: Ten patients (34%) had indolent myeloma, including 4 patients with lytic bone lesions, 3 patients with anemia (Hb <11gm/dL), and 3 patients with both anemia and lytic bone lesions. Median follow up of living patients is 5.6 years (range, 4.0–7.1 years). Of the twenty-nine eligible patients, ten (34%) had a partial response to therapy with at least 50% or greater reduction in serum and urine monoclonal (M) protein. Three patients are still on study and receiving therapy. The remaining have gone off-study: seven patients (27%)had progressive disease while on therapy; other reasons for ending study treatment included completed therapy per protocol (2 pts), patient refusal (2pts), toxicity (8 pts), alternate treatment (3 pts), other medical problems (1 pt), died on study (1 pt), and other (2 pts). The median time to progression (TTP) was 3.2 years (95% CI 2.1–5.6 yrs). Median progression free survival (PFS) was 3.0 yrs (95% CI 2.0–5.1 yrs). Median overall survival has not been reached; 5 year survival rate by the Kaplan Meier method is 60%. Major grade 3–4 non-hematologic adverse events at any time during therapy were noted in 34% of patients; this includes 14% with grade 4 toxicity. Grade 3–4 toxicities occurring in more than one patient include neuropathy (2 pts) and sinus bradycardia (2 pts). Conclusions: Thalidomide has activity in asymptomatic myeloma. This approach must be further tested in randomized trials to determine if the survival estimates are superior to observation. Given the activity of thalidomide, trials are also needed with lenalidomide.

Abstract The t[4;14] simultaneously deregulates fibroblast growth factor receptor 3 (FGFR3) and MMSET in 15% of patients (pts) with Multiple Myeloma (MM). Although oncogenic, FGFR3 expression is lost in ~25% of t[4;14] pts on gene expression profiling while MMSET is always retained. The t[4;14] is highly associated with poor prognosis, furthermore FGFR3 kinase inhibitors are in Phase I trials, thus detection of t[4;14] pts is increasingly important. The Multiple Myeloma Research Consortium (MMRC) therefore evaluated 4 competing methodologies for the diagnostic detection of t[4;14]. Bone marrow (BM) samples were collected in uniform fashion from 85 pts. FGFR3 immunocytochemistry (ICC) and flow cytometry (FC) were performed at the retrieval site, while split samples were shipped to the MMRC tissue bank and processed under GLP conditions. Processed samples were analyzed by cIg-FISH and quantitative IgH-MMSET RT-PCR (QPCR) on unsorted BM and blood. Of 60 samples with sufficient plasma cells for analysis, 8 were FISH +ve [13.3%]. Low % BM plasma cells prevented successful FISH in 25% of samples reflecting large volume harvests and hemodilution. Analysis was conducted in a blinded fashion. With FISH as the gold standard for detection of t[4;14] the sensitivity and specificity of the other diagnostic tests are: BM QPCR is most sensitive (7 of 8 FISH positive detected) and specific (42/43 negatives correctly identified). QPCR on peripheral blood is ongoing. FC is more sensitive to the detection of FGFR3 protein than ICC. Correlation between FC and ICC was only 0.46. Interestingly, 6 of 7 evaluable pts here and 13/14 (92%) in an expanded analysis of FISH +ve patients also expressed the FGFR3 protein. Given the discrepancy between this finding and previously reported loss of FGFR3 expression in 25% of pts we further explored t[4;14] stability. Clonal selection/heterogeneity was determined by the % plasma cells in each pt. with an unbalanced translocation (loss of one der chromosome). In 42 t[4;14] pts, 13 (31%) had a balanced translocation(>75% of cells with a double fusion), 14 (33%) had an unbalanced translocation (>75% cells with only one signal), and 15 (36%) had a chimeric picture. This heterogeneous pattern is suggestive of an evolution towards an unbalanced translocation. Despite this survival did not differ between pts with balanced or unbalanced translocation. Conclusions: These results indicate that the t[4;14] is highly heterogeneous with respect to balanced versus unbalanced translocations, which likely evolve over time. For detection, cIg-FISH continues to be the gold standard diagnostic methodology but may be limited by low plasma cell numbers in dilute BM or during MM remission. QPCR and FC appear most sensitive and specific for presence of t[4;14] and FGFR3 protein expression respectively. Surprisingly (given prior evidence of loss of FGFR3 expression in 25% of pts) 92% of t[4;14] pts in this series expressed FGFR3 protein. # Analyzed % Positive Sensitivity Specificity FISH 60 13 - - QPCR 65 14 87.5 97.6 Flow 82 15 85.7 91 ICC 85 15 62.5 92

Abstract Introduction A unique biological characteristic of MM plasma cells (PCs) is the substantial production of immunoglobulin proteins. This process requires disulfide bond formations that in turn generate large amounts of H2O2. The Trx-TrxR reductase system exists to combat this oxidative stress; however, cytotoxicity can occur when the cells' antioxidative capacity is overwhelmed. Recently, we demonstrated that IMiDs inhibit peroxidase-mediated decomposition of H2O2, and that lenalidomide sensitivity in MM correlates with the degree of antioxidative capacity (Sebastian et al. 2015 ASH). In this study we sought to better understand this inhibitory process. Methods We used various human MM cell lines with different sensitivity to lenalidomide. Cell viability was assessed by the MTT assay. Antioxidative capacity was measured via the total cellular oxidation of reduced flavin adenine dinucleotide (FADH2) and reduced nicotinamide adenine dinucleotide (NAD(P)H) after H2O2treatment. A CRBN CRISPR/Cas9 KO plasmid was used to generate CRBN knockout cells and lentivirus system was used to over-express CRBN in MM cells. Results We found that IMiDs inhibit TrxR mediated intracellular H₂O₂ decomposition in a CRBN dependent fashion. Unlike lenalidomide, the direct TrxR inhibitor auranofin was very effective in inducing cell death in MM cell lines, in a CRBN independent fashion. By using MM.1R isogeneic cells with and without CRBN, and the CRBN-overexpressing OCIMY-5 cell line (transfected with wt-CRBN) we showed that auranofin treatment caused cytotoxicity irrespective of CRBN level of expression, while lenalidomide was only effective in CRBN expressing cells. Clinically achievable concentrations of auranofin treatment induced cell signals similar to lenalidomide, including degradation of IKZF1, IKZF3. As with lenalidomide, the sensitivity of CRBN expressing cell lines to auranofin correlated with their basal antioxidative capacity (MM.1S cells are sensitive and have with lower anti-oxidative capacity while RPMI-8226 is resistant due to its high anti-oxidative capacity). We also found that targeting Trx (downstream effector of TrxR) with the direct inhibitor PX12 overcame this cellular anti-oxidative capacity and inhibited cell proliferation in both RPMI-8226 and MM.1S in a CRBN independent fashion. Combination of auranofin with bortezomib showed a synergistic effect, but only in cells with lower anti-oxidative capacity. In contrast, PX-12, showed a synergistic effect with bortezomib in all analyzed MM cells lines, irrespective of their anti-oxidative capacity and CRBN expression. Conclusions IMiDs inhibit TrxR-mediated intracellular H2O2decomposition in CRBN expressing MM. While the direct TrxR inhibitor, auranofin, bypassed the CRBN requirement for inducing cytotoxicity in MM, its cytotoxic effect could be overcome by the cells antioxidative capacity. Direct Trx inhibition (such as PX-12) seems like a potent strategy for MM therapy to overcome cellular CRBN requirements and higher anti-oxidative capacity cells. Disclosures Bergsagel: Novartis: Research Funding; Amgen, BMS, Novartis, Incyte: Consultancy. Stewart:celgene: Consultancy. Fonseca:Patent Pending: Patents & Royalties: The use of calcium isotopes as biomarkers for bone metabolisms; Patent Pending: Patents & Royalties: The use of calcium isotopes as biomarkers for bone metabolisms; Janssen: Consultancy; Bayer: Consultancy; Millennium, a Takeda Company: Consultancy; Millennium, a Takeda Company: Consultancy; BMS: Consultancy; Millennium, a Takeda Company: Consultancy; Patent: Patents & Royalties: Prognostication of MM based on genetic categorization of FISH of the disease; Celgene: Consultancy; AMGEN: Consultancy; Patent: Patents & Royalties: Prognostication of MM based on genetic categorization of FISH of the disease; Millennium, a Takeda Company: Consultancy; Novartis: Consultancy; Celgene: Consultancy; Patent: Patents & Royalties: Prognostication of MM based on genetic categorization of FISH of the disease; Janssen: Consultancy; Patent: Patents & Royalties: Prognostication of MM based on genetic categorization of FISH of the disease; Bayer: Consultancy; AMGEN: Consultancy; Patent Pending: Patents & Royalties: The use of calcium isotopes as biomarkers for bone metabolisms; Novartis: Consultancy; AMGEN: Consultancy; Sanofi: Consultancy; AMGEN: Consultancy; Sanofi: Consultancy; BMS: Consultancy; Patent Pending: Patents & Royalties: The use of calcium isotopes as biomarkers for bone metabolisms.