Analysis of 6q deletion in Waldenstrom macroglobulinemia

Time to Move to the Single-Cell Level: Applications of Single-Cell Multi-Omics to Hematological Malignancies and Waldenström's Macroglobulinemia-A Particularly Heterogeneous Lymphoma

Single-cell sequencing techniques have become a powerful tool for characterizing intra-tumor heterogeneity, which has been reflected in the increasing number of studies carried out and reported. We have rigorously reviewed and compiled the information about these techniques inasmuch as they are relative to the area of hematology to provide a practical view of their potential applications. Studies show how single-cell multi-omics can overcome the limitations of bulk sequencing and be applied at all stages of tumor development, giving insights into the origin and pathogenesis of the tumors, the clonal architecture and evolution, or the mechanisms of therapy resistance. Information at the single-cell level may help resolve questions related to intra-tumor heterogeneity that have not been previously explained by other techniques. With that in mind, we review the existing knowledge about a heterogeneous lymphoma called Waldenström's macroglobulinemia and discuss how single-cell studies may help elucidate the underlying causes of this heterogeneity.

6q deletion in Waldenström macroglobulinaemia negatively affects time to transformation and survival

Deletion of the long arm of chromosome 6 (del6q) is the most frequent cytogenetic abnormality in Waldenström macroglobulinaemia (WM), occurring in approximately 50% of patients. Its effect on patient outcome has not been completely established. We used fluorescence in situ hybridisation to analyse the prevalence of del6q in selected CD19+ bone marrow cells of 225 patients with newly diagnosed immunoglobulin M (IgM) monoclonal gammopathies. Del6q was identified in one of 27 (4%) cases of IgM-monoclonal gammopathy of undetermined significance, nine of 105 (9%) of asymptomatic WM (aWM), and 28/93 (30%) of symptomatic WM (sWM), and was associated with adverse prognostic features and higher International Prognostic Scoring System for WM (IPSSWM) score. Asymptomatic patients with del6q ultimately required therapy more often and had a shorter time to transformation (TT) to symptomatic disease (median TT, 30 months vs. 199 months, respectively, P < 0·001). When treatment was required, 6q-deleted patients had shorter progression-free survival (median 20 vs. 47 months, P < 0·001). The presence of del6q translated into shorter overall survival (OS), irrespective of the initial diagnosis, with a median OS of 90 compared with 131 months in non-del6q patients (P = 0·01). In summary, our study shows that del6q in IgM gammopathy is associated with symptomatic disease, need for treatment and poorer clinical outcomes.

Waldenstrom's macroglobulinemia in the era of immunotherapy

Waldenstrom macroglobulinemia (WM) is a lymphoplasmacytic lymphoma that presents with symptomatic anemia, thrombocytopenia, constitutional symptoms, extramedullary disease and rarely hyperviscosity syndrome. The presence of both IgM monoclonal protein and ≥10% monoclonal lymphoplasmacytic cells is required for the diagnosis. MyD88 is present in 67-90% of patients but is not pathognomonic for WM. Many patients who fulfill the criteria of WM are asymptomatic and do not require treatment. Recent advances in the understanding of the biology of WM have paved the way for new treatment options. The use of novel agents with or without rituximab enables the use of effective chemotherapy-free regiments upfront and in the relapsed setting. New targeted treatments such as venetoclax and CXCR4 antagonists are being investigated.

Waldenstrom Macroglobulinemia: Genomic Aberrations and Treatment

Waldenström macroglobulinemia (WM) is a rare, indolent, and monoclonal immunoglobulin M-associated lymphoplasmacytic disorder with unique clinicopathologic characteristics. Over the past decade, remarkable progress has occurred on both the diagnostic and therapeutic fronts in WM. A deeper understanding of the disease biology emanates from the seminal discoveries of myeloid differentiation primary response 88 (MYD88) L265P somatic mutation in the vast majority of cases and C-X-C chemokine receptor, type 4, mutations in about a third of patients. Although WM remains an incurable malignancy, and the indications to initiate treatment are largely unchanged, the therapeutic armamentarium continues to expand. Acknowledging the paucity of high-level evidence from large randomized controlled trials, herein, we evaluate the genomic aberrations and provide a strategic framework for the management in the frontline as well as the relapsed/refractory settings of symptomatic WM.

How I treat Waldenström macroglobulinemia

Waldenström macroglobulinemia (WM) is a B-cell neoplasm manifested by the accumulation of clonal immunoglobulin (Ig)M-secreting lymphoplasmacytic cells. MYD88 and CXCR4 warts, hypogammaglobulinemia, infections, myelokathexis syndrome-like somatic mutations are present in >90% and 30% to 35% of WM patients, respectively, and impact disease presentation, treatment outcome, and overall survival. Familial predisposition is common in WM. Asymptomatic patients should be observed. Patients with disease-related hemoglobin <10 g/L, platelets <100 × 10(9)/L, bulky adenopathy and/or organomegaly, symptomatic hyperviscosity, peripheral neuropathy, amyloidosis, cryoglobulinemia, cold-agglutinin disease, or transformed disease should be considered for therapy. Plasmapheresis should be used for patients with symptomatic hyperviscosity and before rituximab for those with high serum IgM levels to preempt a symptomatic IgM flare. Treatment choice should take into account specific goals of therapy, necessity for rapid disease control, risk of treatment-related neuropathy, immunosuppression and secondary malignancies, and planning for future autologous stem cell transplantation. Frontline treatments include rituximab alone or rituximab combined with alkylators (bendamustine and cyclophosphamide), proteasome inhibitors (bortezomib and carfilzomib), nucleoside analogs (fludarabine and cladribine), and ibrutinib. In the salvage setting, an alternative frontline regimen, ibrutinib, everolimus, or stem cell transplantation can be considered. Investigational therapies under development for WM include agents that target MYD88, CXCR4, BCL2, and CD27/CD70 signaling, novel proteasome inhibitors, and chimeric antigen receptor-modified T-cell therapy.

MYD88 L265P mutations are correlated with 6q deletion in Korean patients with Waldenström macroglobulinemia

Waldenström macroglobulinemia (WM) is a malignant lymphoplasma-proliferative disorder with IgM monoclonal gammopathy. A recent whole-genome study identified MYD88 L265P as the key mutation in WM. We investigated MYD88 mutations in conjunction with cytogenetic study in 22 consecutive Korean WM patients. Conventional G-banding and interphase fluorescence in situ hybridization (FISH) were performed at regions including 6q21 using bone marrow (BM) aspirates. Sixteen patients were subjected to Sanger sequencing-based MYD88 mutation study. Five patients (28%) showed cytogenetic aberrations in G-banding. The incidence of 6q21 deletion was 17% by conventional G-banding and 37% by FISH. Ten patients (45%) showed cytogenetic aberrations using FISH: 6q deletion in eight (37%) and IGH rearrangement in four (18%). Two patients had both the 6q deletion and IGH rearrangement, and two had only the IGH rearrangement. Eleven patients (69%) presented with the MYD88 L265P mutation. MYD88 mutations were significantly associated with the presence of 6q deletions (P = 0.037). Six patients with the 6q deletion for whom sequencing was possible were found to harbor MYD88 mutations. The MYD88 L265P mutation was also associated with increased lymphocyte burden in BM biopsy. This is the first report of high frequency MYD88 L265P mutations in Korean WM patients.

Genetic factors and pathogenesis of Waldenström's macroglobulinemia

Waldenström's macroglobulinemia (WM) is an indolent but incurable B-cell malignancy. Over the last decade, advances in the molecular field brought about by the use of high-throughput genomic analyses-including array-based comparative genomic hybridization and massively parallel genome sequencing-have considerably improved our understanding of the genetic basis of WM. Its pathogenesis, however, remains fragmented. Important steps have been made in elucidating the underlying aberrations and deregulated mechanisms of the disease, and thereby providing invaluable information for identifying biomarkers for disease diagnosis, risk stratification, and therapeutic approaches. We review the genetic basis of the disease.

Waldenström macroglobulinemia: from biology to treatment

Waldenström macroglobulinemia (WM) is distinct B-cell lymphoproliferative disorder primarily characterized by bone marrow infiltration of lymphoplasmacytic cells along with production of a serum monoclonal (IgM). In this review, we describe the biology of WM, the diagnostic evaluation for WM with a discussion of other conditions that are in the differential diagnosis and clinical manifestations of the disease as well as current treatment options. Within the novel agents discussed are everolimus, perifosine, enzastaurin, panobinostat, bortezomib and carfilzomib, pomalidomide and ibrutinib. Many of the novel agents have shown good responses and have a better toxicity profile compared to traditional chemotherapeutic agents, which makes them good candidates to be used as primary therapies for WM in the future.

Candidate genes of Waldenström's macroglobulinemia: current evidence and research

Waldenström's macroglobulinemia (WM) is a relatively uncommon, indolent malignancy of immunoglobulin M-producing B cells. The World Health Organization classifies it as a lymphoplasmacytic lymphoma and patients typically present with anemia, hepatosplenomegaly and diffuse lymphadenopathies. Historically, the genetic characterization of the disease has been hampered by the relatively low proliferative rate of WM cells, thus making karyotyping challenging. The use of novel technologies such as fluorescence in situ hybridization, gene array, and whole genome sequencing has contributed greatly to establishing candidate genes in the pathophysiology of WM and to identifying potential treatment targets, such as L265P MYD88. The discovery of microRNAs and the recognition of epigenetics as a major modulatory mechanism of oncogene expression and/or oncosuppressor silencing have aided in further understanding the pathogenesis of WM. Once thought to closely resemble multiple myeloma, a cancer of terminally differentiated, immunoglobulin-secreting plasma cells, WM appears to genetically cluster with other indolent B-cell lymphomas such as chronic lymphocytic leukemia/small cell lymphoma. The relative high incidence of familial cases of WM and other B-cell malignancies has been helpful in identifying high-risk gene candidates. In this review, we focus on the established genes involved in the pathogenesis of WM, with special emphasis on the key role of derangement of the nuclear factor kappa B signaling pathway and epigenetic mechanisms.

Lymphoplasmacytic lymphoma and Waldenström macroglobulinemia

Lymphoplasmacytic lymphoma (LPL) is a low-grade, B-cell neoplasm composed of small lymphocytes, plasmacytoid lymphocytes, and plasma cells that typically involve the bone marrow, and it is associated with an immunoglobulin M (IgM) gammopathy. The definition of Waldenström macroglobulinemia (WM) and its relationship to LPL has been confusing in the past. In addition, the diagnosis of LPL itself can be challenging because LPL lacks disease-specific morphologic, immunophenotypic, and genetic features to differentiate it from other mature B-cell neoplasms. Accurate diagnosis of LPL/WM rests on recognition of the differential diagnostic features between LPL and other diagnostic possibilities and the use of the recently refined definition of WM and its relationship with LPL: The presence of an IgM monoclonal gammopathy of any level in the setting of bone marrow involvement by LPL. This review summarizes the clinical, laboratory, and histologic features of LPL/WM, with particular emphasis on unique aspects of LPL/WM that may aid in accurate diagnosis.

Molecular pathogenesis of Waldenstrom's macroglobulinemia

Waldenström's macroglobulinemia is an indolent, lymphoproliferative disease, characterized by a heterogeneous lymphoplasmacytic bone marrow infiltrate and high immunoglobulin M production. While technological advances over the past several decades have dramatically improved the possibilities of studying the molecular basis of Waldenström's macroglobulinemia, the pathogenesis of the disease remains fragmented. Undoubtedly, research has been successful in uncovering underlying aberrations and deregulated mechanisms in this disease, providing useful information for identifying biomarkers for disease diagnosis, risk stratification and therapeutic intervention, but there is still a long way to go before the pathogenesis of Waldenström's macroglobulinemia is fully revealed. In addition, the low number of in vitro or in vivo models significantly challenges extensive analysis. In this manuscript, we review the molecular basis of this disease.

High-throughput genomic analysis in Waldenström's macroglobulinemia

Single-nucleotide polymorphism array (SNPa) and array-based comparative genomic hybridization (aCGH) are among the most sensitive genomic high-throughput screening techniques used in the exploration of genetic abnormalities in Waldenström's macroglobulinemia (WM). SNP and aCGH allow the identification of copy number abnormalities (CNA) at the kilobase level thus identifying cryptic genetic abnormalities unseen by lower-resolution approaches such as conventional cytogenetic or fluorescence in situ hybridization (FISH). CNA were identified in nearly 80% of cases by aCGH that delineated in addition minimal altered regions. At gene level, remarkable findings affecting genes involved in the regulation of the NF-kB signaling pathways were identified, such as biallelic inactivation of TNFAIP3 and TRAF3. SNPa also allowed characterization of copy neutral losses such as uniparental disomies (UPD), which is an important and frequent mechanism of gene alteration in cancer cells. Herein, we summarize the current knowledge of WM genomic basis using these high-throughput techniques.

[Waldenström's macroglobulinemia]

Waldenström's macroglobulinemia (WM) is a B-cell disorder characterized primarily by bone marrow infiltration with lymphoplasmacytic cells, along with the presence of an IgM monoclonal gammopathy in the blood. WM remains incurable with a median of 8-year of overall survival for patients with symptomatic WM. Treatment is postponed for asymptomatic patients and progressive anemia is the most common indication for initiation of treatment. The main therapeutic options include alkylating agents, nucleoside analogues, and rituximab, either alone or in combination. Studies involving new combination chemotherapy are ongoing and preliminary results are encouraging. However, there are several limitations to these approaches. The complete response rate is low and the treatment free survival is short in many patients, no specific agent or regimen has been shown to be superior to another, and no treatment has been specifically approved for WM. As such, new therapeutic agents are needed for the treatment of WM. In ongoing efforts, we and others have sought to exploit advances made in the understanding of the biology of WM so as to better target therapeutics for this malignancy. These efforts have led to the development of proteasome inhibitors as bortezomib, several Akt/mTor inhibitors, such as perifosine and Rad001. Many other agents and monoclonal antibodies are currently being tested in clinical trials and seem promising. This article provides an update of the current preclinical studies and clinical efforts for the development of novel agents in the treatment of WM.

Fluorescence immunophenotypic and interphase cytogenetic characterization of nodal lymphoplasmacytic lymphoma

Lymphoplasmacytic lymphoma (LPL) is a small B-cell lymphoma with plasmacytic differentiation that does not fulfill the criteria for any other small B-cell lymphoma. Cytogenetic characterization of nodal LPL is limited and the distinction from marginal zone lymphomas with plasmacytic differentiation can be problematic. Thus, 17 cases of lymph node-based LPL were studied with fluorescence immunophenotypic and interphase cytogenetics for the investigation of neoplasia (FICTION) using a CD79a antibody and probes to detect trisomies of chromosomes 3 (15 cases), 12 (16 cases), and 18 (17 cases); rearrangements (R) of IgH (10 cases), BCL6 (6 cases), PAX5 (7 cases), and MALT1 (16 cases); and deletion 6q21 (7 cases). Cases with IgH R were further studied with an IgH/BCL2 probe. In cases without FICTION studies, previously reported fluorescence in situ hybridization results for IgH, PAX5, and deletion 6q21 were available from prior studies. The histopathology, immunophenotype, and available clinical data were also reviewed. Three pathologic categories were recognized: 5 classic LPL, 5 vaguely nodular polymorphous (VN-P), and 7 other. Among the classic LPL, 4/4 had an IgM paraproteinemia, 5/5 had bone marrow involvement (BM+), and 1/5 had +MALT1. One of one VN-P LPL had an IgM paraprotein, 2/4 were IgM+, 2/4 IgG+, 1/3 had BM+, and 1/5 had an IgH R. Among the other cases, 2/3 had a paraprotein, 2/7 were IgM+, 5/7 IgG+, and 0/3 had BM+. Of these cases, 1 showed +12, 1 +18, and 1 IgH/BCL2 rearrangement plus +18. None of the 17 cases had a 6q21 deletion or +3. Therefore, with rare exception, lymph node-based LPL with classic or more varied histopathologic features does not have the cytogenetic abnormalities frequently associated with bone marrow-based LPL/Waldenstrom macroglobulinemia or many of the marginal zone lymphomas. The search for better objective inclusionary criteria for LPL must continue.