ALBERT

Description: Background: B-cell maturation antigen (BCMA) serves as one of the receptors for B-cell activating factor (BAFF) or a proliferation-inducing ligand (APRIL), which are members of the tumor necrosis factor (TNF) family that promote survival of B-cells, including neoplastic B cells from chronic lymphocytic leukemia (CLL) patients (pts). We have found that BCMA is increased in plasma or serum from patients with multiple myeloma (MM). The level of serum BCMA found among MM pts associates with clinical status and predicts overall survival (OS). However, it is not known whether plasma (p) BCMA levels are elevated in pts with other B-cell malignancies, such as CLL. We examined plasma from healthy adults and pts with CLL for pBCMA and associated the observed levels in CLL pts with disease characteristics and/or known prognostic markers, such as white blood cell counts (WBC), serum β2-M, CLL-cell expression of mutated (M) or unmutated (U) immunoglobulin heavy-chain variable region (IGHV) or ZAP-70, or CLL-cytogenetic markers. We also examined the relationship between pBCMA and time from diagnosis (DX) or sample collection (SC) to initial treatment (treatment-free survival (TFS)) or OS. Methods: We examined the archived, plasma samples of 171 pts with CLL that were collected upon initial presentation to UCSD for studies on factors that could associate with disease outcome. Pts received therapy if they satisfied International Workshop on CLL (IWCLL) criteria for treatment. We examined serial plasma samples from a subset of these pts (n = 21) collected soon after DX, prior to first treatment, after treatment, and at relapse after therapy. We also assessed plasma samples of 76 healthy adults. We determined the pBCMA levels using a polyclonal anti-BCMA antibody in an ELISA available from R&D Systems (Minneapolis, MN). We used Mann-Whitney analysis to assess for associations between the relative pBCMA levels and disease characteristics assessed at the time of SC and Kaplan-Meier analysis to assess the relationship between measured pBCMA and TFS (median 4.1 years) and OS (median follow-up 7.8 years). Results: The median level of pBCMA in pts with CLL obtained from pts that were untreated at the time of first determination of pBCMA levels, regardless of whether they subsequently received therapy (n = 166; 58.54 ng/mL), was higher than that of healthy adults (n = 76; 6.32 ng/mL, P 〈 0.0001). The median pBCMA levels of samples from pts with CLL-cells that used M-IGHV (n = 87; median 42.13 ng/mL), or that lacked expression of ZAP-70 (n = 88; median 42.59 ng/mL), was lower than that of pts with CLL-cells that used U-IGHV (n = 84; 87.46 ng/mL, P 〈 0.0001), or that expressed ZAP-70 (n = 83; median 87.38 ng/mL, P 〈 0.0001). The median pBCMA level of pts with CLL cells that had del(13q) (n = 83; 46.57 ng/mL) was lower than that of pts with CLL cells that did not have detectable del(13q) (n = 77; 73.8 ng/mL; P = 0.0002). The median pBCMA of pts with CLL cells with del(17p) (n = 16; 77.23 ng/mL) appeared lower than that of pts without detectable del(17p) (n = 144; 51.77 ng/mL), but did not reach significance (P = 0.09). The TFS was longer (overall median time from SC to treatment: 2.36 years) among pts with pBCMA levels in the lowest three quartiles (median 3.72 years; range of pBCMA 13.21 - 104.69 ng/mL) when compared to patients with pBCMA in the highest quartile (median 0.67 years; range of pBCMA 110.1 - 782.97 ng/mL; P 〈 0.0001). Serial pBCMA levels consistently correlated with changes in clinical status among pts (n = 21) who had a pBCMA sample taken within three months of the determination of their clinical status. CLL pts with a pBCMA in the highest quartile had a significantly shorter OS when compared to pts with pBCMA levels in the lower three quartiles (P = 0.023). Conclusions: This is the first study to show that BCMA levels are increased in the plasma of CLL pts. We also demonstrate that the pBCMA levels correlate with other known prognostic indicators of CLL, such as IGHV mutational status, ZAP-70 expression and chromosomal abnormalities. CLL pts with higher pBCMA levels have a shorter TFS and OS. Furthermore, changes in pBCMA levels show consistent correlation with changes in the pts' clinical status during treatment. In summary, pBCMA appears to be a new plasma biomarker to monitor the disease course of CLL patients and determine their outcome. Disclosures Kipps: Pharmacyclics Abbvie Celgene Genentech Astra Zeneca Gilead Sciences: Other: Advisor.

Description: Background: Waldenström's macroglobulinemia (WM) is an incurable B-cell lymphoplasmacytic lymphoma. B-cell maturation antigen (BCMA) serves as one of the receptors for B-cell activating factor (BAFF) or a proliferation-inducing ligand (APRIL), which are members of the tumor necrosis factor (TNF) family that can induce activation of NF-κB and promote survival of B cells, including neoplastic B cells. We previously showed that serum BCMA levels are elevated in multiple myeloma (MM) patients, and correlated with disease status and overall survival (OS). In this study, we sought to determine whether BCMA levels are elevated in the serum of WM patients, track with conventional WM tumor markers, and correlate with disease status and OS. Methods: Data was obtained on a total of 67 WM patients who received treatment in one of two clinics that specialize in the treatment of WM. Serum BCMA levels were determined with a polyclonal anti-BCMA antibody using an ELISA (R&D Systems, Minneapolis, MN). Mann-Whitney analysis was used to measure differences in serum BCMA levels between WM patients and healthy subjects as well as the clinical status of WM patients. Using Kaplan-Meier analysis, OS (median follow up 5.1 years) in WM patients was measured from the time of the first assessment of serum BCMA levels in each patient. In addition, serum BCMA levels were compared to serum M-protein and IgM levels in 12 patients, serially, during their individual courses of treatment. Results: We compared serum BCMA levels for all 67 patients, including 27 untreated WM patients to healthy subjects (n = 76). Serum BCMA levels were markedly elevated in all WM patients (median 79.53 ng/mL), including those who were untreated (median 82.72 ng/mL) versus healthy subjects (median 6.32 ng/mL, p 〈 0.0001 for both comparisons). Serum BCMA values were compared to both serum M-protein and IgM levels in 12 WM patients during their disease course. Serum BCMA levels consistently correlated with changes in both of these established WM serum markers during their course of disease. Serum BCMA levels of WM patients also correlated with patient disease status at the time of sample collection. Specifically, serum from patients achieving 〉 partial response (PR, n = 12) showed significantly lower levels of BCMA than samples from patients with either stable disease (SD, n = 8, p = 0.030) or progressive disease (PD, n = 21, p = 0.0004). OS (median 12.5 years) was determined among patients in the highest serum BCMA quartile (n=16; quartile range 128.91-812.48 ng/mL) and compared to levels in the lower three quartiles (n = 48; range 20.13-128.85 ng/mL). Notably, OS was shorter among patients in the top quartile compared to those in the other three quartiles (p = 0.02). Conclusions: This is the first study to demonstrate that serum BCMA levels are elevated in Waldenström's macroglobulinemia patients. Importantly, serum BCMA levels correlated with both serum IgM and M-protein levels, as well as tracked with these established WM biomarkers for individual patients during their course of disease. Additionally, patients with levels of BCMA in the highest quartile exhibited shorter OS. Thus, serum BCMA represents a new serum biomarker to predict outcome and monitor patients with Waldenström's macroglobulinemia. Disclosures No relevant conflicts of interest to declare.

Description: Introduction: B-cell maturation antigen (BCMA) has been shown to be highly expressed on the surface of tumor cells from patients (pts) with multiple myeloma (MM) and chronic lymphocytic leukemia (CLL) and is the target for therapeutic approaches in these diseases. Our group has shown that serum and plasma levels of BCMA correlate with disease status and survival in MM and CLL patients. We have recently shown that solubilized BCMA prevents its ligand B cell activating factor (BAFF) from binding and stimulating B-cells to produce polyclonal antibody. Recently, γ-secretase has been identified as the enzyme that leads to shedding of BCMA from off of B-cells. Gamma secretase is a multi-subunit protease complex that includes four individual proteins: presenilin-1 (PSEN1), nicastrin, anterior pharynx-defective 1 (APH-1), and presenilin enhancer 2 (PEN-2). CD147 is as a non-essential regulator of the complex. We examined gene expression of PSEN1, APH-1, PEN-2, and CD147 in MM pts with progressive (PD) and in complete remission (CR). We also determined the effects of the gamma secretase inhibitor (GSI) LSN424354 (Eli Lilly), a selective small-molecule inhibitor, on solubilized BCMA levels in MM and CLL tumor cells. Methods: Bone marrow (BM) mononuclear cells (MCs) were isolated from MM pts following Western Institutional Review Board (WIRB) approval and informed consent in accordance with the Declaration of Helsinki. Total RNA was extracted using the Qiagen RNeasy kit (Qiagen, Louisville, KY 40219) following the manufacturer's instructions. Quantitative PCR (qPCR) was applied to measure the relative abundance of human PSEN1, APH-1, PEN-2, and CD147 mRNA compared to that of the housekeeping gene HPRT mRNA. qPCR was performed using TaqMan technology on an OneStepPlus instrument (Life Technology, Grand Island, NY 14072) and followed the standard procedure. Peripheral blood MCs were obtained from patients with CLL. The human MM LAGκ-1A xenograft was grown in the left superficial gluteal muscle of SCID mice for six weeks and removed. Single-cell suspensions were prepared. LAGκ-1A or CLL tumor cells were treated with the GSI LSN424354 in a concentration dependent fashion, and BCMA levels were determined using an ELISA (R&D Systems, Minneapolis, MN) assay. MM tumor cells were treated with the LSN424354 and performed non-radioactive MTS cell proliferation assay following a standard MTS protocol. Results: qPCR showed PEN-2 gene expression was slightly increased among MM patients in PD compared to those in CR or normal subjects whereas there was no change in expression of the PSEN1 or APH1 genes. CD147 gene expression was markedly increased in MM pts in PD (n=25) compared to those in CR (n=18; P=0.005) or MGUS (n=9; P=0.005). Next, we determined the effect of the GSI LSN424354 on cultured MM or CLL tumor cells. The GSI inhibitor LSN424354 markedly reduced BCMA levels (〉 90%) in supernatants from human MM LAGκ-1A cells after 5 days of tissue culture in a dose dependent fashion at concentrations ranging from 100 pM to 10 nM. Similarly, freshly obtained CLL tumor cells exposed to LSN424354 at concentrations similarly from 100 pM to 10 nM also showed a marked reduction (also 〉 90%) in supernatant BCMA levels. Notably, MTS assay results showed LSN424354 did not inhibit cell proliferation in MM or CLL tumor cells at concentrations up to 100 nM. Conclusion: Gamma secretase sheds BCMA off of B-cells. CD147, a regulator of gamma secretase activity, shows markedly higher gene expression in MM pts with PD compared to those in CR or MGUS individuals. The GSI LSN424354 reduces solubilized BCMA from tumor cells from CLL patients and human MM xenografts. Since CD147 has been shown to be present in serum, we are currently evaluating CD147 in serum samples from pts with MM and other plasma cell dyscrasias. In addition, we are examining the expression of BCMA on the surface of tumor cells from MM and CLL pts following exposure to BCMA, whether this GSI by reducing solubilized BCMA levels can reverse the immune dysfunction in mice bearing MM, and improve the efficacy of anti-BCMA antibody therapies. Disclosures Berenson: OncoTracker: Employment, Equity Ownership.