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Abstract: Concurrent Bruton tyrosine kinase and BCL2 inhibition has not yet been investigated in Waldenström macroglobulinemia (WM). We performed an investigator-initiated trial of ibrutinib and venetoclax in symptomatic treatment-naïve patients with MYD88-mutated WM. Patients received ibrutinib 420 mg once daily (cycle 1), followed by a ramp-up of venetoclax to 400 mg daily (cycle 2). The combination was then administered for 22 additional 4-week cycles. The attainment of very good partial response (VGPR) was the primary end point. Forty-five patients were enrolled in this study. The median baseline characteristics were as follows: age 67 years, serum IgM 43 g/L, and hemoglobin 102 g/L. Seventeen patients (38%) carried CXCR4 mutations. Nineteen patients (42%) achieved VGPR. Grade 3 or higher adverse events included neutropenia (38%), mucositis (9%), and tumor lysis syndrome (7%). Atrial fibrillation occurred in 3 (9%), and ventricular arrhythmia in 4 (9%) patients that included 2 grade 5 events. With a median follow-up of 24.4 months, the 24-month progression-free survival (PFS) and overall survival (OS) rates were 76% and 96%, respectively, and were not impacted by CXCR4 mutations. The median time on therapy was 10.2 months, and the median time after the end of therapy (EOT) was 13.3 months. Eleven of the 12 progression events occurred after EOT, and the 12-month PFS rates after EOT were 79%; 93% if VGPR was attained, and 69% for other patients (P = .12). Ibrutinib and venetoclax induced high VGPR rates and durable responses after EOT, although they were associated with a higher-than-expected rate of ventricular arrhythmia in patients with WM, leading to early study treatment termination. This trial was registered at www.clinicaltrials.gov as #NCT04273139., (© 2024 American Society of Hematology. Published by Elsevier Inc. Licensed under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0), permitting only noncommercial, nonderivative use with attribution. All other rights reserved.)

Activating mutations in MYD88 promote malignant cell growth and survival through hematopoietic cell kinase (HCK)-mediated activation of Bruton tyrosine kinase (BTK). Ibrutinib binds to BTKCys481 and is active in B-cell malignancies driven by mutated MYD88. Mutations in BTKCys481, particularly BTKCys481Ser, are common in patients with acquired ibrutinib resistance. We therefore performed an extensive medicinal chemistry campaign and identified KIN-8194 as a novel dual inhibitor of HCK and BTK. KIN-8194 showed potent and selective in vitro killing of MYD88-mutated lymphoma cells, including ibrutinib-resistant BTKCys481Ser-expressing cells. KIN-8194 demonstrated excellent bioavailability and pharmacokinetic parameters, with good tolerance in rodent models at pharmacologically achievable and active doses. Pharmacodynamic studies showed sustained inhibition of HCK and BTK for 24 hours after single oral administration of KIN-8194 in an MYD88-mutated TMD-8 activated B-cell diffuse large B-cell lymphoma (ABC DLBCL) and BCWM.1 Waldenström macroglobulinemia (WM) xenografted mice with wild-type BTK (BTKWT)- or BTKCys481Ser-expressing tumors. KIN-8194 showed superior survival benefit over ibrutinib in both BTKWT- and BTKCys481Ser-expressing TMD-8 DLBCL xenografted mice, including sustained complete responses of >12 weeks off treatment in mice with BTKWT-expressing TMD-8 tumors. The BCL_2 inhibitor venetoclax enhanced the antitumor activity of KIN-8194 in BTKWT- and BTKCys481Ser-expressing MYD88-mutated lymphoma cells and markedly reduced tumor growth and prolonged survival in mice with BTKCys481Ser-expressing TMD-8 tumors treated with both drugs. The findings highlight the feasibility of targeting HCK, a key driver of mutated MYD88 pro-survival signaling, and provide a framework for the advancement of KIN-8194 for human studies in B-cell malignancies driven by HCK and BTK., (© 2021 by The American Society of Hematology.)

MYD88 and CXCR4 mutations are common in Waldenström macroglobulinemia (WM). Mutated CXCR4 (CXCR4Mut) impacts BTK-inhibitor response. We conducted a phase 1 trial of the CXCR4-antagonist ulocuplumab with ibrutinib in this first-ever study to target CXCR4Mut in WM. Ibrutinib was initiated at 420 mg/d with cycle 1 and continued until intolerance or progression; ulocuplumab was given cycles 1 to 6, with a 3 + 3 dose-escalation design. Each cycle was 4 weeks. Thirteen symptomatic patients, of whom 9 were treatment-naive patients were enrolled. Twelve were evaluable for response. At best response, their median serum immunoglobulin M declined from 5574 to 1114 mg/dL; bone marrow disease decreased from 65% to 10%, and hemoglobin increased from 10.1 to 14.2 g/dL (P < .001). The major and VGPR response rates were 100% and 33%, respectively, with VGPRs observed at lower ulocuplumab dose cohorts. Median times to minor and major responses were 0.9 and 1.2 months, respectively. With a median follow-up of 22.4 months, the estimated 2-year progression-free survival was 90%. The most frequent recurring grade ≥2 adverse events included reversible thrombocytopenia, rash, and skin infections. Ulocuplumab dose-escalation did not impact adverse events. The study demonstrates the feasibility of combining a CXCR4-antagonist with ibrutinib and provides support for the development of CXCR4-antagonists for CXCR4Mut WM. This trial was registered at www.clinicaltrials.gov as #NCT03225716., (© 2021 by The American Society of Hematology.)

Acquired ibrutinib resistance due to BTK Cys481 mutations occurs in B-cell malignancies, including those with MYD88 mutations. BTK Cys481 mutations are usually subclonal, and their relevance to clinical progression remains unclear. Moreover, the signaling pathways that promote ibrutinib resistance remain to be clarified. We therefore engineered BTK Cys481Ser and BTK WT expressing MYD88-mutated Waldenström macroglobulinemia (WM) and activated B-cell (ABC) diffuse large B-cell lymphoma (DLBCL) cells and observed reactivation of BTK-PLCγ2-ERK1/2 signaling in the presence of ibrutinib in only the former. Use of ERK1/2 inhibitors triggered apoptosis in BTK Cys481Ser -expressing cells and showed synergistic cytotoxicity with ibrutinib. ERK1/2 reactivation in ibrutinib-treated BTK Cys481Ser cells was accompanied by release of many prosurvival and inflammatory cytokines, including interleukin-6 (IL-6) and IL-10 that were also blocked by ERK1/2 inhibition. To clarify if cytokine release by ibrutinib-treated BTK Cys481Ser cells could protect BTK WT MYD88-mutated malignant cells, we used a Transwell coculture system and showed that nontransduced BTK WT MYD88-mutated WM or ABC DLBCL cells were rescued from ibrutinib-induced killing when cocultured with BTK Cys481Ser but not their BTK WT -expressing counterparts. Use of IL-6 and/or IL-10 blocking antibodies abolished the protective effect conferred on nontransduced BTK WT by coculture with BTK Cys481Ser expressing WM or ABC DLBCL cell counterparts. Rebound of IL-6 and IL-10 serum levels also accompanied disease progression in WM patients with acquired BTK Cys481 mutations. Our findings show that the BTK Cys481Ser mutation drives ibrutinib resistance in MYD88-mutated WM and ABC DLBCL cells through reactivation of ERK1/2 and can confer a protective effect on BTK WT cells through a paracrine mechanism., (© 2018 by The American Society of Hematology.)

The link between inflammation and cancer is particularly strong in Waldenström macroglobulinemia (WM), a diffuse large B-cell lymphoma wherein the majority of patients harbor a constitutively active mutation in the innate immune-signaling adaptor myeloid differentiation primary response 88 (MyD88). MyD88Leu265Pro (MyD88 L265P ) constitutively triggers the myddosome assembly providing a survival signal for cancer cells. Here, we report detection and a functional role of MyD88 in the extracellular vesicles (EVs) shed from WM cells. MyD88 L265P was transferred via EVs into the cytoplasm of the recipient mast cells and macrophages, recruiting the endogenous MyD88 that triggered the activation of proinflammatory signaling in the absence of receptor activation. Additionally, internalization of EVs containing MyD88 L265P was observed in mice with an effect on the bone marrow microenvironment. MyD88-loaded EVs were detected in the bone marrow aspirates of WM patients thus establishing the physiological role of EVs for MyD88 L265P transmission and shaping of the proinflammatory microenvironment. Results establish the mechanism of transmission of signaling complexes via EVs to propagate inflammation as a new mechanism of intercellular communication., (© 2018 by The American Society of Hematology.)

Ibrutinib produces high response rates and durable remissions in Waldenström macroglobulinemia (WM) that are impacted by MYD88 and CXCR4 WHIM mutations. Disease progression can develop on ibrutinib, although the molecular basis remains to be clarified. We sequenced sorted CD19 + lymphoplasmacytic cells from 6 WM patients who progressed after achieving major responses on ibrutinib using Sanger, TA cloning and sequencing, and highly sensitive and allele-specific polymerase chain reaction (AS-PCR) assays that we developed for Bruton tyrosine kinase ( BTK ) mutations. AS-PCR assays were used to screen patients with and without progressive disease on ibrutinib, and ibrutinib-naïve disease. Targeted next-generation sequencing was used to validate AS-PCR findings, assess for other BTK mutations, and other targets in B-cell receptor and MYD88 signaling. Among the 6 progressing patients, 3 had BTK Cys481 variants that included BTK Cys481Ser(c.1635G>C and c.1634T>A) and BTK Cys481Arg(c.1634T>C) Two of these patients had multiple BTK mutations. Screening of 38 additional patients on ibrutinib without clinical progression identified BTK Cys481 mutations in 2 (5.1%) individuals, both of whom subsequently progressed. BTK Cys481 mutations were not detected in baseline samples or in 100 ibrutinib-naive WM patients. Using mutated MYD88 as a tumor marker, BTK Cys481 mutations were subclonal, with a highly variable clonal distribution. Targeted deep-sequencing confirmed AS-PCR findings, and identified an additional BTK Cys481Tyr(c.1634G>A) mutation in the 2 patients with multiple other BTK Cys481 mutations, as well as CARD11 Leu878Phe(c.2632C>T) and PLCγ2 Tyr495His(c.1483T>C) mutations. Four of the 5 patients with BTK C481 variants were CXCR4 mutated. BTK Cys481 mutations are common in WM patients with clinical progression on ibrutinib, and are associated with mutated CXCR4 ., (© 2017 by The American Society of Hematology.)

Whole-genome sequencing has identified highly prevalent somatic mutations including MYD88, CXCR4, and ARID1A in Waldenström macroglobulinemia (WM). The impact of these and other somatic mutations on transcriptional regulation in WM remains to be clarified. We performed next-generation transcriptional profiling in 57 WM patients and compared findings to healthy donor B cells. Compared with healthy donors, WM patient samples showed greatly enhanced expression of the VDJ recombination genes DNTT, RAG1, and RAG2, but not AICDA Genes related to CXCR4 signaling were also upregulated and included CXCR4, CXCL12, and VCAM1 regardless of CXCR4 mutation status, indicating a potential role for CXCR4 signaling in all WM patients. The WM transcriptional profile was equally dissimilar to healthy memory B cells and circulating B cells likely due increased differentiation rather than cellular origin. The profile for CXCR4 mutations corresponded to diminished B-cell differentiation and suppression of tumor suppressors upregulated by MYD88 mutations in a manner associated with the suppression of TLR4 signaling relative to those mutated for MYD88 alone. Promoter methylation studies of top findings failed to explain this suppressive effect but identified aberrant methylation patterns in MYD88 wild-type patients. CXCR4 and MYD88 transcription were negatively correlated, demonstrated allele-specific transcription bias, and, along with CXCL13, were associated with bone marrow disease involvement. Distinct gene expression profiles for patients with wild-type MYD88, mutated ARID1A, familial predisposition to WM, chr6q deletions, chr3q amplifications, and trisomy 4 are also described. The findings provide novel insights into the molecular pathogenesis and opportunities for targeted therapeutic strategies for WM.

Activating mutations in MYD88 are present in ∼95% of patients with Waldenström macroglobulinemia (WM), as well as other B-cell malignancies including activated B-cell (ABC) diffuse large B-cell lymphoma (DLBCL). In WM, mutated MYD88 triggers activation of Bruton tyrosine kinase (BTK). Ibrutinib, a pleiotropic kinase inhibitor that targets BTK, is highly active in patients with mutated MYD88. We observed that mutated MYD88 WM and ABC DLBCL cell lines, as well as primary WM cells show enhanced hematopoietic cell kinase (HCK) transcription and activation, and that HCK is activated by interleukin 6 (IL-6). Over-expression of mutated MYD88 triggers HCK and IL-6 transcription, whereas knockdown of HCK reduced survival and attenuated BTK, phosphoinositide 3-kinase/AKT, and mitogen-activated protein kinase/extracellular signal-regulated kinase signaling in mutated MYD88 WM and/or ABC DLBCL cells. Ibrutinib and the more potent HCK inhibitor A419259, blocked HCK activation and induced apoptosis in mutated MYD88 WM and ABC DLBCL cells. Docking and pull-down studies confirmed that HCK was a target of ibrutinib. Ibrutinib and A419259 also blocked adenosine triphosphate binding to HCK, whereas transduction of mutated MYD88 expressing WM cells with a mutated HCK gatekeeper greatly increased the half maximal effective concentration for ibrutinib and A419259. The findings support that HCK expression and activation is triggered by mutated MYD88, supports the growth and survival of mutated MYD88 WM and ABC DLBCL cells, and is a direct target of ibrutinib. HCK represents a novel target for therapeutic development in MYD88-mutated WM and ABC DLBCL, and possibly other diseases driven by mutated MYD88., (© 2016 by The American Society of Hematology.)

Waldenström macroglobulinemia (WM) is a rare lymphoma characterized by the accumulation of IgM-producing lymphoplasmacytic cells. Although WM patients can experience prolonged remissions, the disease invariably recurs. Therefore, novel treatments associated with higher success rates and lower toxicity profiles are needed. The discovery of recurrent mutations in the MYD88 and CXCR4 genes has unraveled potential therapeutic targets in WM patients. As a result of these findings and based on the design and execution of a prospective clinical trial, the FDA granted approval to ibrutinib, an oral Bruton tyrosine kinase (BTK) inhibitor, to treat patients with symptomatic WM. The present review focuses on potential therapies that could change the landscape of treatment of patients with WM, specifically focusing on inhibitors or antagonists or the proteasome, BTK, CD38, BCL2 and the CXCR4 and MYD88 genes themselves. Novel agents with novel mechanisms of action should be evaluated in the context of carefully designed clinical trials., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Bortezomib frequently produces severe treatment-related peripheral neuropathy (PN) in Waldenström's macroglobulinemia (WM). Carfilzomib is a neuropathy-sparing proteasome inhibitor. We examined carfilzomib, rituximab, and dexamethasone (CaRD) in symptomatic WM patients naïve to bortezomib and rituximab. Protocol therapy consisted of intravenous carfilzomib, 20 mg/m2 (cycle 1) and 36 mg/m(2) (cycles 2-6), with intravenous dexamethasone, 20 mg, on days 1, 2, 8, and 9, and rituximab, 375 mg/m(2), on days 2 and 9 every 21 days. Maintenance therapy followed 8 weeks later with intravenous carfilzomib, 36 mg/m(2), and intravenous dexamethasone, 20 mg, on days 1 and 2, and rituximab, 375 mg/m(2), on day 2 every 8 weeks for 8 cycles. Overall response rate was 87.1% (1 complete response, 10 very good partial responses, 10 partial responses, and 6 minimal responses) and was not impacted by MYD88(L265P) or CXCR4(WHIM) mutation status. With a median follow-up of 15.4 months, 20 patients remain progression free. Grade ≥2 toxicities included asymptomatic hyperlipasemia (41.9%), reversible neutropenia (12.9%), and cardiomyopathy in 1 patient (3.2%) with multiple risk factors, and PN in 1 patient (3.2%) which was grade 2. Declines in serum IgA and IgG were common. CaRD offers a neuropathy-sparing approach for proteasome inhibitor-based therapy in WM. This trial is registered at www.clinicaltrials.gov as #NCT01470196., (© 2014 by The American Society of Hematology.)

Whole genome sequencing has revealed activating somatic mutations in MYD88 (L265P) and CXCR4 in Waldenström macroglobulinemia (WM). CXCR4 somatic mutations in WM are the first ever reported in human cancer and are similar to nonsense (NS) and frameshift (FS) germline mutations found in warts, hypogammaglobulinemia, infections and myelokathexis (WHIM) syndrome. We genotyped lymphoplasmacytic cells from 175 WM patients and observed significantly higher bone marrow (BM) disease involvement, serum immunoglobulin-M levels, and symptomatic disease requiring therapy, including hyperviscosity syndrome in those patients with MYD88(L265P)CXCR4(WHIM/NS) mutations (P < .03). Patients with MYD88(L265P)CXCR4(WHIM/FS) or MYD88(L265P)CXCR4(WILDTYPE (WT)) had intermediate BM and serum immunoglobulin-M levels; those with MYD88(WT)CXCR4(WT) showed lowest BM disease burden. Fewer patients with MYD88(L265P) and CXCR4(WHIM/FS or NS) vs MYD88(L265P)CXCR4(WT) presented with adenopathy (P < .01), further delineating differences in disease tropism based on CXCR4 status. Neither MYD88 nor CXCR4 mutations correlated with SDF-1a (RS1801157) polymorphisms in 54 patients who were genotyped for these variants. Unexpectedly, risk of death was not impacted by CXCR4 mutation status, but by MYD88(WT) status (hazard ratio 10.54; 95% confidence interval 2.4-46.2, P = .0018). Somatic mutations in MYD88 and CXCR4 are important determinants of clinical presentation and impact overall survival in WM. Targeted therapies directed against MYD88 and/or CXCR4 signaling may provide a personalized treatment approach to WM.

The genetic basis for Waldenström macroglobulinemia (WM) remains to be clarified. Although 6q losses are commonly present, recurring gene losses in this region remain to be defined. We therefore performed whole genome sequencing (WGS) in 30 WM patients, which included germline/tumor sequencing for 10 patients. Validated somatic mutations occurring in >10% of patients included MYD88, CXCR4, and ARID1A that were present in 90%, 27%, and 17% of patients, respectively, and included the activating mutation L265P in MYD88 and warts, hypogammaglobulinemia, infection, and myelokathexis-syndrome-like mutations in CXCR4 that previously have only been described in the germline. WGS also delineated copy number alterations (CNAs) and structural variants in the 10 paired patients. The CXCR4 and CNA findings were validated in independent expansion cohorts of 147 and 30 WM patients, respectively. Validated gene losses due to CNAs involved PRDM2 (93%), BTG1 (87%), HIVEP2 (77%), MKLN1 (77%), PLEKHG1 (70%), LYN (60%), ARID1B (50%), and FOXP1 (37%). Losses in PLEKHG1, HIVEP2, ARID1B, and BCLAF1 constituted the most common deletions within chromosome 6. Although no recurrent translocations were observed, in 2 patients deletions in 6q corresponded with translocation events. These studies evidence highly recurring somatic events, and provide a genomic basis for understanding the pathogenesis of WM.

Myeloid differentiation factor 88 (MYD88) L265P somatic mutation is highly prevalent in Waldenström macroglobulinemia (WM) and supports malignant growth through nuclear factor κB (NF-κB). The signaling cascade(s) by which MYD88 L265P promotes NF-κB activation in WM remain unclear. By lentiviral knockdown or use of a MYD88 inhibitor, decreased phosphorylation of the NF-κB gatekeeper IκBα and survival occurred in MYD88 L265P-expressing WM cells. Conversely, WM cells engineered to overexpress MYD88 L265P showed enhanced survival. Coimmunoprecipitation studies identified Bruton tyrosine kinase (BTK) complexed to MYD88 in L265P-expressing WM cells, with preferential binding of MYD88 to phosphorylated BTK (pBTK). Increased pBTK was also observed in WM cells transduced to overexpress L265P vs wild-type MYD88. Importantly, MYD88 binding to BTK was abrogated following treatment of MYD88 L265P-expressing cells with a BTK kinase inhibitor. Inhibition of BTK or interleukin-1 receptor-associated kinase 1 and 4 (IRAK-1 and -4) kinase activity induced apoptosis of WM cells, and their combination resulted in more robust inhibition of NF-κB signaling and synergistic WM cell killing. The results establish BTK as a downstream target of MYD88 L265P signaling, and provide a framework for the study of BTK inhibitors alone, and in combination with IRAK inhibitors for the treatment of WM.

In this issue of Blood, Poulain et al demonstrate the high prevalence of the MYD88 L265P somatic mutation in patients with Waldenstrom macroglobulinemia (WM) and provide insight into its biological relevance in the growth and survival of WM.

Anemia often prompts therapy in Waldenström macroglobulinemia (WM), although is not fully explained by bone marrow disease involvement in many patients. Hepcidin regulates gut absorption and distribution of iron and is elevated and associated with anemia in WM. Since hepcidin evaluation remains experimental, we initiated an American Board of Internal Medicine (ABIM) practice improvement project to determine baseline transferrin saturation (TSAT) levels in untreated anemic patients with WM. Among 108 patients with WM evaluated, 56 (52%) had a TSAT level ≤ 20%, which included 25 (23%) patients with severely depressed TSAT levels (≤ 10%). Sixteen patients with TSAT levels ≤ 10% received parenteral iron, and 14 of these patients showed improved hematocrit values (28.75% to 32.75%; P < .0001), mean corpuscular volume (MCV) (84.7 to 89.9; P = .006), and TSAT levels (8.1% to 21.2%; P < .0001). Anemia in 8 of these patients was previously refractory to oral iron therapy. Routine screening of iron saturation levels may therefore identify patients with WM and severe iron deficiency who may be candidates for parenteral iron therapy., (Copyright © 2013 Elsevier Inc. All rights reserved.)

By whole-genome and/or Sanger sequencing, we recently identified a somatic mutation (MYD88 L265P) that stimulates nuclear factor κB activity and is present in >90% of Waldenström macroglobulinemia (WM) patients. MYD88 L265P was absent in 90% of immunoglobulin M (IgM) monoclonal gammopathy of undetermined significance (MGUS) patients. We therefore developed conventional and real-time allele-specific polymerase chain reaction (AS-PCR) assays for more sensitive detection and quantification of MYD88 L265P. Using either assay, MYD88 L265P was detected in 97 of 104 (93%) WM and 13 of 24 (54%) IgM MGUS patients and was either absent or rarely expressed in samples from splenic marginal zone lymphoma (2/20; 10%), CLL (1/26; 4%), multiple myeloma (including IgM cases, 0/14), and immunoglobulin G MGUS (0/9) patients as well as healthy donors (0/40; P < 1.5 × 10(-5) for WM vs other cohorts). Real-time AS-PCR identified IgM MGUS patients progressing to WM and showed a high rate of concordance between MYD88 L265P ΔCT and BM disease involvement (r = 0.89, P = .008) in WM patients undergoing treatment. These studies identify MYD88 L265P as a widely present mutation in WM and IgM MGUS patients using highly sensitive and specific AS-PCR assays with potential use in diagnostic discrimination and/or response assessment. The finding of this mutation in many IgM MGUS patients suggests that MYD88 L265P may be an early oncogenic event in WM pathogenesis.

Unlabelled: Familial disease is common in Waldenström macroglobulinemia (WM). We examined the impact of familial disease status on treatment outcome in WM and observed that familial disease was associated with inferior outcomes. However patients with familial WM receiving a bortezomib-containing regimen showed improved treatment outcomes vs. those receiving non–bortezomib-containing regimens. Bortezomib-containing regimens may therefore represent a more optimal treatment approach for patients with familial WM., Background: We examined the impact of familial predisposition on treatment outcome in 135 patients with Waldenström macroglobulinemia (WM), 26.7% of whom had first- or second-degree relatives with a B-cell lymphoproliferative disorder., Patients and Methods: All patients were rituximab naive and received a rituximab-containing regimen. There were no significant differences in baseline characteristics between cohorts., Results: Overall response (93.9% vs. 75.0%; P = .029) and complete response/very good partial response (CR/VGPR) (23.2% vs. 16.7%; P < .0001), time to progression (TTP) (45.5 vs. 21 months; P = .015) and time to next therapy (TTNT) (50.0 vs. 33.0 months; P = .024) favored patients with sporadic WM. By multivariate analysis, familial predisposition was an independent marker for disease progression (hazard ratio, 0.554). Patients with familial but not sporadic disease exhibited better responses, including CR/VGPR attainment (P = .0006) and a trend for longer progression-free survival (> 33 vs. 20.6 months; P = .08), with bortezomib-containing therapy., Conclusion: The findings convey that familial predisposition is an important determinant of treatment outcome in WM. Prospective studies to confirm these observations are needed., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Background: Little is known about the epidemiology and etiology of Waldenstrom macroglobulinemia (WM). Despite several studies of the relation between family history and B-cell disorders and WM, family history of non-hematologic cancers has not been systematically investigated. We thus examined associations of family history of breast, colorectal, lung, ovarian, and prostate cancers with WM., Methods: All probands aged 20-79 years with bone marrow biopsy-confirmed diagnosis of WM between May 1, 1999 and January 1, 2010 at the Bing Center for Waldenstrom Macroglobulinemia were eligible for inclusion in our analysis. We reviewed medical records for eligible probands to determine family history of cancer (defined as a cancer diagnosis for ≥1 first-degree relative(s) of the proband). Using expected values constructed from the United States National Health Interview Survey, we estimated age- and race-standardized rate ratios (RRs) for family history of breast, colorectal, lung, ovarian, and prostate cancers by WM subtype., Results: Family history of prostate cancer had the largest overall rate ratio (RR=1.4, 95% confidence limits [CL]: 1.1, 1.7), and among sporadic cases, family history of prostate and breast cancer had the largest rate ratios (prostate: RR=1.3, 95% CL: 1.1, 1.7; breast: RR=1.3, 95% CL: 1.2, 1.6)., Conclusion: Our study suggests that it may be worthwhile to pursue these associations in a case-control study with uniform selection and data collection for cases and controls, and at least some record-based information on family history., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

CD52 is expressed on malignant cells in lymphoplasmacytic lymphoma (LPL), including IgM-secreting Waldenström macroglobulinemia (WM). We examined the activity of alemtuzumab in 28 symptomatic LPL (27 IgM and 1 IgA) patients. The median prior number of therapies for these patients was 2 (range, 0-5) and 43% had refractory disease. Patients received alemtuzumab at 30 mg IV 3 times weekly for up to 12 weeks after test dosing, and also received hydrocortisone, acyclovir, and Bactrim or equivalent prophylaxis. Patients had a complete response (n = 1), a partial response (n = 9), or a MR (n = 11) for an overall and major response rate of 75% and 36%, respectively. Median serum Ig decreased from 3510 to 1460 mg/dL (P < .001 at best response). With a median follow-up of 64 months, the median time to progression was 14.5 months. Hematologic and infectious complications, including CMV reactivation, were more common in previously treated patients and were indirectly associated with 3 deaths. Long-term follow-up revealed late-onset autoimmune thrombocytopenia (AITP) in 4 patients at a median of 13.6 months after therapy, which contributed to 1 death. Alemtuzumab is an active therapy in patients with LPL, but short- and long-term toxicities need to be carefully weighed against other available treatment options. Late AITP is a newly recognized complication of alemtuzumab in this patient population. This study is registered at www.clinicaltrials.gov as NCT00142181.

We recently described paratarg-7 (P-7), a protein of unknown function, as the target of 15% of immunoglobulin A (IgA) and IgG paraproteins in monoclonal gammopathy of undetermined significance (MGUS) and multiple myeloma. To determine the frequency of P-7 as a paraprotein target in IgM-MGUS and Waldenström macroglobulinemia (WM), sera from patients with IgM-MGUS/WM were tested for reactivity with recombinant P-7 by enzyme-linked immunoabsorbent assay. The specificity of the paraprotein-mediated reaction was shown by absorption studies and cloning of the respective B-cell receptor. The paraproteins of 18 (9 WM and 9 IgM-MGUS) of 161 patients (11%) reacted with P-7. Isoelectric focusing and phosphatase treatment showed that P-7 was hyperphosphorylated (pP-7) in all patients with an anti-P-7-specific IgM paraprotein tested. Because only 4 of 200 healthy controls (2%) were carriers of pP-7, pP-7 carrier state is associated with a significantly increased risk (odds ratio = 6.2; P = .001) for developing IgM-MGUS/MW. Family analyses showed that the pP-7 carrier state is inherited as a dominant trait. After IgA/IgG-MGUS and multiple myeloma, IgM-MGUS/WM is the second neoplasia associated with pP-7 carrier state. The dominant inheritance of pP-7 explains cases of familial IgM-MGUS/WM and enables the identification of family members at increased risk.

Soluble CD27 (sCD27) is produced by Waldenström's macroglobulinemia (WM) cells, with high levels found in WM patients which may facilitate disease expansion. Matrix metalloproteinases (MMP) may facilitate sCD27 release by cleavage of CD27. By gene expression analysis, we observed significantly higher transcription levels of MMP-8 and MMP-9, with 58.5 and 16.7 fold increase in mean transcription levels in WM cells relative to healthy donor peripheral blood B cells (P = .04, and .05, respectively). We developed a model for study of sCD27 release by transfecting BCWM.1 WM cells and BL2126 lymphoblastic B cells, both of which express MMP-8 and MMP-9 with a vector expressing FLAG-tagged CD27 (pFLAG-CD27) which in the presence of phorbol myristate acetate resulted in ≥ 10-fold increase in sCD27 release. MMP inhibitors against MMP-8, but not MMP 2, 3, or 9 blocked release of sCD27. The results suggest that MMP-8 may play a role in the pathogenesis of WM, and that its inhibition may be of therapeutic value in WM., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Waldenström's macroglobulinemia (WM) patients often present with anemia as their primary disease manifestation that may be related to hepcidin, an important regulator of iron homeostasis. We therefore determined hepcidin levels in 53 WM patients, and 20 age-matched healthy patient donors by hepcidin-25 ELISA. Serum hepcidin levels were elevated in WM patients versus healthy patients (P=.04), and correlated with BM disease involvement (P=.004), beta-2-microglobulin levels (P=.029), and inversely with hemoglobin (P=.05). No correlation with serum iron indices was observed, though in patients with high hepcidin levels, increased iron deposition in bone marrow macrophages was observed. Importantly, hepcidin transcripts and protein were produced by primary WM cells. Hepcidin levels correlated with serum IL-6 (P<.001) and C-Reactive Protein (P=.033) levels. The results of this study implicate hepcidin as a contributor to anemia in WM, and suggest that an iron re-utilization defect accompanies hepcidin overproduction leading to its sequestration in WM patients.

We studied the role of histone deacetylase inhibitors in Waldenstrom's macroglobulinemia (WM). Gene expression profiling of bone marrow CD19+ cells from 30 patients and 10 healthy donors showed overexpression of HDAC4, HDAC9, and Sirt5, with validation of HDAC9 overexpression by q-PCR in primary and BCWM.1 cells. Suberoylanilide hydroxamic acid, trichostatin A, panobinostat, and sirtinol demonstrated dose-dependent killing of BCWM.1 cells. TSA showed the greatest potency with IC50 of 70 nM. Importantly, HDAC9 activity was decreased following TSA treatment suggesting an essential role for this HDAC in WM therapy. The combination of bortezomib plus HDAC inhibitors resulted in at least additive tumor cell killing in BCWM.1 cells. TSA and bortezomib-induced apoptosis depended on a similar set of caspase activation, whereas their effect on cell cycle regulators was distinctly different. These results provided a framework for examining HDAC inhibitors as monotherapy, as well as combination therapy with bortezomib in WM.

Waldenstrom macroglobulinemia (WM) is an incurable low-grade lymphoma characterized by bone marrow (BM) involvement of IgM secreting lymphoplasmacytic cells. The induction of unfolded protein response (UPR) genes ("physiologic" UPR) enables cells to differentiate into professional secretory cells capable of production of high amounts of endoplasmic reticulum (ER)-processed proteins, such as immunoglobulins. Ultimately, the initially cytoprotective UPR triggers an apoptotic cascade if ER stress is not corrected, called proapoptotic/terminal UPR. We show that WM cells inherently express the physiologic UPR machinery compared with normal BM cells, and that increased ER stress leads to proapoptotic/terminal UPR in WM cells. We therefore examined tunicamycin, ER stress inducer, for potential antitumor effects in WM. Tunicamycin induced significant cytotoxicity, apoptosis and cell-cycle arrest, and inhibited DNA synthesis in WM cell lines and primary BM CD19(+) cells from patients with WM with an inhibitory concentration (IC(50)) of 0.5 microg/mL to 1 microg/mL, but not in healthy donor cells. Importantly, coculture of WM cells in the context of the BM microenvironment did not inhibit tunicamycin-induced cytotoxicity. Finally, we demonstrate that ER stress inducer synergizes with other agents used in the treatment of WM. These preclinical studies provide a framework for further evaluation of ER stress inducing agents as therapeutic agents in WM.

Waldenström macroglobulinemia (WM) is a B-cell malignancy characterized by an IgM monoclonal gammopathy and bone marrow (BM) infiltration with lymphoplasmacytic cells (LPCs). Excess mast cells (MCs) are commonly present in WM, and provide growth and survival signals to LPCs through several TNF family ligands (CD40L, a proliferation-inducing ligand [APRIL], and B-lymphocyte stimulator factor [BLYS]). As part of these studies, we demonstrated that WM LPCs secrete soluble CD27 (sCD27), which is elevated in patients with WM (P < .001 vs healthy donors), and serves as a faithful marker of disease. Importantly, sCD27 stimulated expression of CD40L on 10 of 10 BM MC samples and APRIL on 4 of 10 BM MC samples obtained from patients with WM as well as on LAD2 MCs. Moreover, the SGN-70 humanized monoclonal antibody, which binds to CD70 (the receptor-ligand partner of CD27), abrogated sCD27 mediated up-regulation of CD40L and APRIL on WM MCs. Last, treatment of severe combined immunodeficiency-human (SCID-hu) mice with established WM using the SGN-70 antibody blocked disease progression in 12 of 12 mice, whereas disease progressed in all 5 untreated mice. The results of these studies demonstrate a functional role for sCD27 in WM pathogenesis, along with its utility as a surrogate marker of disease and a target in the treatment of WM.

Thalidomide enhances rituximab-mediated, antibody-dependent, cell-mediated cytotoxicity. We therefore conducted a phase 2 study using thalidomide and rituximab in symptomatic Waldenstrom macroglobulinemia (WM) patients naive to either agent. Intended therapy consisted of daily thalidomide (200 mg for 2 weeks, then 400 mg for 50 weeks) and rituximab (375 mg/m(2) per week) dosed on weeks 2 to 5 and 13 to 16. Twenty-five patients were enrolled, 20 of whom were untreated. Responses were complete response (n = 1), partial response (n = 15), and major response (n = 2), for overall and major response rate of 72% and 64%, respectively, on an intent-to-treat basis. Median serum IgM decreased from 3670 to 1590 mg/dL (P < .001), whereas median hematocrit rose from 33.0% to 37.6% (P = .004) at best response. Median time to progression for responders was 38 months. Peripheral neuropathy to thalidomide was the most common adverse event. Among 11 patients experiencing grade 2 or greater neuropathy, 10 resolved to grade 1 or less at a median of 6.7 months. Thalidomide in combination with rituximab is active and produces long-term responses in WM. Lower doses of thalidomide (ie,

The presence of valine (V) at position 158 of FcgammaRllla (CD16) is known to improve clinical response to rituximab in indolent non-Hodgkin lymphoma (NHL). Little is known about the basic mechanisms for this observation. We examined natural killer (NK) cells from healthy donors representing the FcgammaRIIIa-158 polymorphic subgroups (V/V, V/F, and F/F) for gene transcript and cell surface CD16 expression, rituximab binding, and rituximab-dependent NK cell-mediated cytotoxicity. We observed higher levels of FcgammaRIIIa transcripts among individuals with the FcgammaRIIIa-158 V/V versus V/F or F/F genotype (P < .001); increased cell surface CD16 expression by quantitative flow cytometry on NK cells from individuals expressing at least one valine at FcgammaRIIIa-158 versus F/F (P = .029); as well as augmented rituximab binding and rituximab-mediated, antibody-dependent cellular cytotoxicity (ADCC). These results suggest that individuals expressing at least one valine at FcgammaRIIIa-158 might, in part, have better clinical outcomes due to increased CD16 expression, rituximab binding, and rituximab-mediated ADCC.

Background: Familial clustering of B-cell disorders among Waldenström's macroglobulinemia (WM) patients has been reported, though the frequency and any differences in disease manifestation for familial patients remain to be defined., Patients and Methods: We therefore analyzed clinicopathological data from 257 consecutive and unrelated WM patients. Forty-eight (18.7%) patients had at least one first-degree relative with either WM (n = 13, 5.1%), or another B-cell disorder including non-Hodgkin's lymphoma (n = 9, 3.5%), myeloma (n = 8, 3.1%), chronic lymphocytic leukemia (n = 7, 2.7%), monoclonal gammopathy of unknown significance (n = 5, 1.9%), acute lymphocytic leukemia (n = 3, 1.2%) and Hodgkin's disease (n = 3, 1.2%). Patients with a familial history of WM or a plasma cell disorder (PCD) were diagnosed at a younger age and with greater bone marrow involvement., Results: Deletions in 6q represented the only recurrent structural chromosomal abnormality and were found in 13% of patients, all non-familial cases. Interphase FISH analysis demonstrated deletions in 6q21-22.1 in nearly half of patients, irrespective of familial background., Conclusions: The above results suggest a high degree of clustering for B-cell disorders among first-degree relatives of patients with WM, along with distinct clinical features at presentation based on familial disease cluster patterns. Genomic studies to delineate genetic predisposition to WM are underway.