Citations

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.

The median survival in primary systemic (AL) amyloidosis is less than 18 months. No published series of patients with AL amyloidosis have reported survival of more than 10 years. The records of all Mayo Clinic patients with a diagnosis of AL amyloidosis between January 1, 1966 and March 1, 1987 were reviewed. Patients with secondary amyloidosis, familial amyloidosis, senile systemic amyloidosis, and localized amyloidosis were excluded. During the 21 years of the study, 841 patients with AL amyloidosis were seen. Of these, 29 were excluded because the diagnosis was made at autopsy, and 2 others were excluded because no follow-up data were available. Actuarial survival for the 810 patients was 51% at 1 year, 16% at 5 years, and 4.7% at 10 years. Thirty patients survived for 10 years or more after the histologic diagnosis of AL amyloidosis; all received alkylating-agent therapy. In 14 patients, the monoclonal protein disappeared from the serum or urine. Of 10 patients with nephrotic syndrome, 4 had an objective response. Congestive heart failure, older age, creatinine value of 2 mg/dL or more, bone marrow plasma cell value of 20% or more, platelet count of 500 × 109/L or less, and the presence of peripheral neuropathy were underrepresented in the 10-year survivors and are unfavorable prognostic features. Five percent of patients with AL amyloidosis survived for 10 years or more.

Abstract Background: Multiple myeloma remains incurable with current approaches and newer therapies are needed to improve the outcome of these patients. While monoclonal antibody based therapies have been successful in some of the hematological malignancies, such approaches have had limited efficacy in the setting of myeloma. Thymoglobulin (polyclonal rabbit antithymocyte globulin, Genzyme) (Thymo) has been extensively evaluated in the setting of allogeneic blood and marrow transplantation and solid organ transplants. Given the polyclonal nature of this product, with antibodies against different B cell antigens, we evaluated the in vitro and in vivo activity of Thymo in myeloma. Methods: MM cell lines were cultured in RPMI 1640 containing 10% fetal bovine serum supplemented with L-Glutamine, penicillin, and streptomycin. The KAS-6/1 cell line was also supplemented with 1 ng/ml IL-6. Cytotoxicity following drug treatment was measured using the MTT viability assay. Apoptosis was measured by flow cytometry using Annexin V/PI in cell lines and Apo 2.7 in primary patient plasma cells. Shifts in expression of a variety of different B cell and plasma cell antigens were examined on several different myeloma cell lines following Thymo treatment in order to identify the potential antigenic targets. In vivo activity of thymo was evaluated in a SCID plasmacytoma model injected with RPMI myeloma cell lines. Results: rATG was cytotoxic in vitro to several MM cell lines (RPMI 8226, U266, OPM1, OPM2) including the IL-6 dependent cell line Kas6/1 with LC50 of around 1 mg/mL. Additionally, thymo was cytotoxic MM cell lines resistant to conventional agents such as doxorubicin (Dox40), melphalan (LR5) and dexamethasone (MM1R). Thymo induced apoptosis in MM cell lines and in patient derived primary myeloma cells. When tested in combination with other anti-myeloma agents an additive effect was seen with doxorubicin, PS341 and melphalan. Using competitive flow cytometry, we identified CD138, CD38, Cd45, CD126, CD49d (VLA4), as well as CD20 as antigens likely to be targeted by Thymo. Tumor bearing mice injected with Thymo at two different doses (5 mg/kg and 10 mg/kg for five days) had significantly delayed tumor growth compared to non-injected mice, and this translated into a better survival for these mice. Mice receiving 10 mg/kg dose had a slower tumor growth compared to 5 mg/kg dose (Figure). Conclusions: Thymoglobulin has promising in vitro and in vivo activity in the setting of myeloma. These studies will provide the rational for future clinical development of this agent in myeloma alone or in combination with other agents. Based on these results, we are in the process of initiating a clinical trial combining Thymo with Melphalan. Figure Figure

Abstract Background: Renal insufficiency of varying severity including end stage renal disease requiring dialysis is often a presenting manifestation of multiple myeloma (MM). While many patients (pts) improve following initiation of therapy for MM, a considerable number of pts proceed to stem cell transplant with less than optimal renal function. It is not clear whether the outcome of their transplants differs from pts with normal renal function. Methods: The MM transplant database was searched to identify pts with a Creatinine clearance (Crcl) of less than 50 ml/min/m2 (study cohort). These pts were then matched to two pts each with a clearance of ≥ 50 ml/min/m2 (control cohort), based on cytogenetic abnormalities (normal vs. abnormal), circulating plasma cells (yes vs. no), age at transplant, % of plasma cells at transplant, plasma cell labeling index, time to transplant from diagnosis and the disease status at transplant, the factors used in that order of importance. Results: Eighty pts with a Crcl < 50 ml/min were identified and matched to 160 pts with Crcl ≥ 50 ml/min. The pts were matched for the above factors and the two groups were similar in terms of their other baseline features except CRP and B2M, both of which were lower in the control group. Pts with reduced renal function were more likely to receive dose reduced melphalan for conditioning (32.5%) compared to the control group (2%; P < 0.0001). The outcomes from the stem cell transplant were similar in both the groups. 96% of pts obtained an objective response to stem cell transplant in each of the groups with no difference in the time to response; and a complete response was seen in 38.5% and 36.6% of the study and control cohorts respectively (P=NS). The median post transplant progression free survival was 18.2 months and 18.4 mos respectively for the study cohort and the control group (P=0.4). However, the median overall survival from transplant was shorter for the study cohort (30.7 mos vs. 60 mos for the controls; P = 0.007; Figure). The time to platelet and neutrophil engraftment was not different between the groups. In terms of transplant related toxicity, the median days hospitalized was higher in the study group (5 days vs. 9.5 days; P=0.003) as was the incidence of grade 3 and 4 mucositis (8% vs. 23%; P= 0.0008). Six pts (7.5%) had treatment related deaths in the study group compared to 3 pts (2%) among the controls (P=0.03), the majority of the deaths being infection related. Conclusion: Here we demonstrate that pts with MM and reduced renal function derive disease free survival comparable to those with normal renal function, despite the increased use of reduced dose Melphalan for conditioning. The toxicity is clearly increased in the presence of abnormal renal function. Interestingly, the overall survival was inferior among the pts with reduced renal function. One possible explanation for this observation is the decreased availability of novel therapies for salvage among pts with reduced renal function as many of them would not be eligible for clinical trials due to reduced renal function. Figure Figure

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 Plasma cell (PC) proliferative disorders vary in behavior ranging from MGUS, a usually indolent disorder, to multiple myeloma, an aggressive disease with poor long-term survival. Detecting PC immunoglobulin (Ig) light chain restriction is commonly used to demonstrate PC clonality and establish the diagnosis. Furthermore, greater degrees of peripheral blood (PB) and/or bone marrow (BM) involvement are associated with more aggressive disease types and, therefore, are adverse prognostic indicators. Flow cytometric immunophenotyping (FCIP) is often used for detecting PC Ig light chain restriction. Shortcomings of FCIP as traditionally performed include its relative insensitivity and its underestimation of PC number. For these reasons, the FCIP PC clonality assessment in our laboratory is currently supplemented with a slide-based immunofluorescence (IF) technique. Recent advances in flow cytometry have led to the development of powerful instruments and reagents, potentially enhancing the ability of FCIP to analyze PC clones. In this study a newly available single tube, 6-color FCIP approach for detecting and enumerating monotypic PCs was compared to the current combined FCIP/IF assay. 94 PB and 124 BM samples were analyzed by combined FCIP/IF and single tube 6-color FCIP assays. For PB, FCIP/IF used 2-color CD38-PE/ CD45-PerCP FCIP to enumerate PCs and slide based IF to detect Ig light chain restriction. For BM FCIP/IF used two 4-color FCIP tubes (Tube1: cytoplasmic (cy)-kappa Ig-FITC/CD20-PE/CD45-PerCP/CD38-APC; Tube 2: cy-lambda Ig-FITC/CD56-PE/CD45-PerCP/CD38 APC) and slide-based IF to confirm clonality. These FCIP assays were performed on a FACSCaliber. The single tube, 6-color FCIP assay used the following fluorochrome-antibody combination: cy-kappa Ig-FITC/cy-lambda Ig-PE/CD138-PerCP-Cy5.5/CD38-APC/CD19-PE-Cy7/CD45-APC-Cy7 with data acquired on a FACSCanto. The results are summarized in Tables 1 & 2, the concordance between the methods was high. All false-negative 6-color FCIP results were attributable to the use of isotonic lysis for cell isolation. When limiting the comparison to the ficolled cells alsoused for FCIP/IF, 6-color FCIP was consistently more sensitive. The 6-color assay also allowed for the discriminition between CD19-positive polytypic PCs and CD19-negative monotypic PCs and the detection of CD45-positive monotypic PC subsets which were often present and which were not identified in the combined FCIP/IF approach. Estimates of PB disease burden generated from the 6-color technique were similar to those determined from the FCIP/IF data which have previously been shown to be of prognositic significance. 6-color FCIP allows for the rapid, sensitive detection of monotypic PCs. The ability of 6-color FCIP to detect phenotypically distinct clonal PC subsets enhances the sensitivity and may provide prognositically significant data through both more complete cell enumeration and charactarization. Given these advantages, 6-color FCIP may eventually supplant traditional FCIP methods of PC analysis. Method Comparsion in BM Bone Marrow 6-color FCIP 6-color FCIP Positive negative total Positive = clone detected; negative = no clone detected. FCIP/IF Positive 81(65%) 3(2%) 84 FCIP/IF Negative 5(4%) 35(28%) 40 Total 86 38 124 Method Comparsion in PB Peripheral Blood 6-color FCIP 6-color FCIP Positive negative total Positive = clone detected; negative = no clone detected. FCIP/IF positive 24(26%) 7(7%) 31 FCIP/IF negative 9(10%) 54(57%) 63 total 33 61 94

Abstract Background: Myeloma remains incurable due to a stem cell/proliferative component that responds poorly to standard treatments. We have shown that aberrant IL-1beta stimulates the generation of paracrine IL-6, a central myeloma growth factor. A Phase II trial was completed using IL-1 receptor antagonist (IL-1Ra/Anakinra), which inhibits paracrine IL-6 production, and low dose Dexamethasone (Dex), which decreases IL-1 levels through myeloma cell apoptosis, in patients with SMM/IMM. SMM/IMM patients are most likely to benefit from anti-cytokine therapy in order to delay/prevent the development of active myeloma. Methods: Patients that had ≥ 10% bone marrow plasma cells and/or an IgG or IgA M-spike ≥ 3 g/dL and did not require immediate chemotherapy were eligible. All patients received 100 mg of IL-1Ra SQ qd for 6 months unless clinical progression occurred. Non-progressors were allowed to continue on therapy with IL-1Ra alone. Low dose Dex (20 mg qweek) was added after 6 months of IL-1Ra or for evidence of clinical progression; the dose was adjusted based on response/toxicity. Results: To investigate the effects of IL-1Ra and Dex alone and in combination in vitro, we co-cultured IL-1beta transduced +/− myeloma cells with stromal cells +/− dexamethasone, IL-1Ra, or both for 48 hours and quantitated the percent apoptotic cells by flow cytometry and IL-6 production by ELISA. The results showed that: 1) IL-1Ra was superior to Dex at inhibition of IL-6 but caused no myeloma apoptosis; 2) Dex induced apoptosis was inhibited by IL-6 3) Dex and IL-1Ra combined induced maximal IL-6 inhibition and apoptosis of myeloma cells. In the clinical trial, data were available on 47 patients; smoldering (79%) / indolent (21%). All patients received IL-1Ra initially and 20/47 subsequently received IL-1Ra/Dex. Seven patients had a decrease in the plasma cell labeling index (PCLI), a marker of cell proliferation, on IL-1Ra alone which paralleled a decrease in the high sensitivity C-reactive protein (CRP). Interestingly, in one patient treated with Dex alone for 6 months, Dex induced a decrease in the M-protein and IL-1 levels, however, the PCLI and CRP values increased. The IL-1Ra/Dex combination has resulted in stability of disease in the majority of the 47 patients; 28 continue on therapy with a median overall progression-free survival (PFS) of 37.5 months. Four of the 47 pts achieved a minor response (MR) with IL-1Ra alone, and an additional 6 pts achieved a MR/PR after addition of dex. The continuous measure of % reduction in CRP was significantly associated with time to progression (p=0.02). Similarly, those patients who had a >5% decrease in serum M protein also had a longer PFS (p<0.001). Of note, 2 patients with high PCLI values of 6.4 and 3.0, characteristic of poor prognosis, responded with a reduction in the PCLI values and continue on combination therapy for 3 and 1.5 years, respectively with stable disease. Conclusion: Agents such as IL-1Ra that specifically inhibit paracrine IL-6 production are more effective at targeting the proliferative component than apoptosis inducing agents such as Dex; the combination may be especially useful in patients that have an elevated PCLI at presentation.