McMaster, Mary L.

Introduction: WM is a rare subtype of lymphoma, identified by the presence of IgM paraprotein, infiltration of clonal, small lymphoplasmacytic B cells in the bone marrow, and the somatic mutation, MYD88 L265P, which is observed in over 90% of WM patients. We previously identified two rare variants at 6p25.3 (EXOC2) and 14q32.13 (TCL1) that were significantly associated with an increased risk of WM/LPL (PMID: 30305637). However, the genetic basis for WM/LPL predisposition remains largely unknown. We conducted the largest WM/LPL GWAS to discover further germline susceptibility loci for WM/LPL. Methods: Our meta-analysis discovery set included 1,707 cases and 58,328 controls of European ancestry from the InterLymph Consortium, genotyped on a high-density SNP array and imputed to TOPMed, providing over 10 million common variants for association testing. Germline genetic loci with suggestive significance (P<5x10-6) were selected for replication in four independent sets (570 cases and 771,770 controls; UK Biobank, Copenhagen Hospital Biobank, FinnGen, Mayo Clinic), giving us a total of 2,277 WM/LPL cases and 831,098 controls. Conditional and sensitivity analyses were performed considering family history and sex. A transcriptome-wide association study (TWAS) was performed using FUSION with expression quantitative trait loci (eQTL) data from GTEx and Young Finns Study in whole blood, lymphocytes, and other tissues. Functional annotations were done using FUMA, F-MAGMA, FORGE, and OpenTarget. Colocalization was measured using CoLoC with whole blood gene expression data. Results & Discussion: We identified 11 germline genetic loci associated with WM/LPL risk that replicated and reached genome-wide significance (P< 5x10-8), including the two known loci on 6p25.3 and 14q32.13 and nine novel loci in the following regions: 6p25.3 (n=2 independent loci), 2q37.1, 9p13.2, 6p21.32, 10q23.31, 16q21, 1p31.1, and 15q15.1. Four of the discovered variants showed strong associations with WM/LPL [odds ratios (ORs) >10]. Enrichment was observed for enhancer and promoter elements in B-cells (FDR q < 0.01), and gene-based and colocalization analyses identified several potential biological pathways. Colocalization analyses show the intronic PAX5 risk variant on 9p (OR=1.5, P= 2.3x10-25) associated with whole blood eQTL expression of PAX5, which plays an essential role in regulating lymphoid progenitors to the B-lymphocyte lineage, as well as RP11-297B17.3 (RNA gene, antisense to PAX5). In addition, GWAS have shown this variant is in linkage disequilibrium (LD) with GWAS loci for CD20 on IgD+ CD38- B cell that represents a specific immunophenotype that helps identify and characterize B cells involved with WM and other similar conditions. The 2q37.1 (SP140) locus (OR=1.6, P=1.2x10-33) contains variants linked to chronic lymphocytic leukemia (CLL) and autoimmune diseases, including multiple sclerosis and Crohn's disease. This locus is important in chromatin-mediated gene regulation, suggesting a significant role in the immune system. The specific variant influences exon-skipping and potentially protein expression, altering the gene's function. The variants on 10q23.31 in FAS (OR=1.3, P=4.4x10-13) and 15q15.1 (OR=1.2, P=8.5x10-11) in BCL2 modifying factor (BMF), are in strong LD with known CLL susceptibility variants. The 15q variant is also linked with multiple lymphoid leukemia GW significant SNPs. Sex-specific analyses identified one novel locus at 20q13.33 associated with the expression of ZGPAT and UCKL1 in males (OR=1.9, P=9.5x10-10). TWAS identified associations with CRHR1 and CDKN2A; overexpression of both are shown to be associated with an increased risk of WM/LPL. Expression of CDKN2A has been linked to childhood acute lymphoblastic leukemia, while CRHR1 has been associated with breast cancer risk. Conclusions: Our study, the largest GWAS of WM to date, has identified 11 susceptibility loci, including two previously known and nine novel regions. The findings underscore the genetic complexity of WM, with the PAX5 and SP140 loci implicated in both chromatin-mediated gene regulation and immune system functions. These insights not only enhance our understanding of WM predisposition but also pave the way for future research focused on functional understanding of these loci, potentially leading to new therapeutic strategies.

Abstract Chronic lymphocytic lymphoma (CLL) has one of the highest familial risks among cancers. Monoclonal B-cell lymphocytosis (MBL), the precursor to CLL, has a higher prevalence (13%-18%) in families with 2 or more members with CLL compared with the general population (5%-12%). Although, the rate of progression to CLL for high-count MBLs (clonal B-cell count ≥500/µL) is ∼1% to 5%/y, no low-count MBLs have been reported to progress to date. We report the incidence and natural history of MBL in relatives from CLL families. In 310 CLL families, we screened 1045 relatives for MBL using highly sensitive flow cytometry and prospectively followed 449 of them. MBL incidence was directly age- and sex-adjusted to the 2010 US population. CLL cumulative incidence was estimated using Kaplan-Meier survival curves. At baseline, the prevalence of MBL was 22% (235/1045 relatives). After a median follow-up of 8.1 years among 449 relatives, 12 individuals progressed to CLL with a 5-year cumulative incidence of 1.8%. When considering just the 139 relatives with low-count MBL, the 5-year cumulative incidence increased to 5.7%. Finally, 264 had no MBL at baseline, of whom 60 individuals subsequently developed MBL (2 high-count and 58 low-count MBLs) with an age- and sex-adjusted incidence of 3.5% after a median of 6 years of follow-up. In a screening cohort of relatives from CLL families, we reported progression from normal-count to low-count MBL to high-count MBL to CLL, demonstrating that low-count MBL precedes progression to CLL. We estimated a 1.1% annual rate of progression from low-count MBL, which is in excess of that in the general population.

Abstract Waldenström macroglobulinemia (WM) is a unique subset of lymphoplasmacytic lymphoma (LPL) that is defined by the presence of an LPL infiltrate in the bone marrow together with a monoclonal IgM protein in the serum. A somatic activating mutation, MYD88 L265P, occurs in 85+% of WM and in 25%-50% of patients with the precursor condition, IgM monoclonal gammopathy of undetermined significance (MGUS); however, germline MYD88 mutations have not been observed in WM patients, and the genetic basis for WM predisposition remains undefined. To identify novel WM susceptibility loci we conducted a two-stage genome-wide association study (GWAS) in over 450 WM cases and 4300 controls of European ancestry. Discovery (stage 1) included 217 WM cases (40% familial) and 3798 controls genotyped on the Illumina Omni Express or Illumina Omni2.5 platforms following standard quality control procedures. The genotyped data were imputed using the Haplotype Reference Consortium panel as a reference and analyzed using logistic regression. In stage 1, we identified three loci on chromosomes 6, 14 and 3 significantly associated (P<5.0x10-8) with risk of WM. Eleven promising SNPs in these and other suggestive loci (P<5.0x10-7) were selected for replication (stage 2) in 269 WM or LPL cases (4% familial) and 571 controls, and genotyping was conducted using standard methods on Taqman and Sequenom platforms or Sanger sequencing (1 SNP). Preliminary results confirm replication of the chromosome 6 locus. Stratification on familial status will illuminate the contribution of familial disease. These results will provide insight into the underlying genetic basis of WM susceptibility. Citation Format: Mary L. McMaster, Sonja I. Berndt, Shengchao A. Li, Susan Slager, Joseph Vijai, Charles C. Chung, Bin Zhu, Laurie Burdette, Brenda Birmann, Elizabeth E. Brown, James R. Cerhan, Karin Ekstrom-Smedby, Henrik Hjalgrim, Geffen Kleinstern, Brian K. Link, James McKay, Alain Monnereau, Lindsay M. Morton, Alexandra Nieters, Nathaniel Rothman, Christine F. Skibola, Alex Smith, Lauren R. Teras, Claire M. Vajdic, Roel Vermeulen, Belynda Hicks, Lynn R. Goldin, Neil E. Caporaso. A genome-wide association study of Waldenström macroglobulinemia/lymphoplasmacytic lymphoma demonstrates association with chromosome 6 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1318. doi:10.1158/1538-7445.AM2017-1318

SummaryThe diagnosis of Waldenström macroglobulinaemia (WM) can be challenging given the variety of signs and symptoms patients can present. Furthermore, once the diagnosis of WM is established, the initial evaluation should be thorough as well as appropriately directed. During the 8th International Workshop for WM in London, United Kingdom, a multi‐institutional task force was formed to develop consensus recommendations for the diagnosis and initial evaluation of patients with WM. In this document, we present the results of the deliberations that took place to address these issues. We provide recommendations for history‐taking and physical examination, laboratory studies, bone marrow aspiration and biopsy analysis and imaging studies. We also provide guidance on the initial evaluation of special situations, such as anaemia, hyperviscosity, neuropathy, Bing‐Neel syndrome and amyloidosis. We hope these recommendations serve as a practical guidance to clinicians taking care of patients with a suspected or an established diagnosis of WM.