Defining Lymphoplasmacytic Lymphoma: Does MYD88L265P Define a Pathologically Distinct Entity Among Patients With an IgM Paraprotein and Bone Marrow-Based Low-Grade B-Cell Lymphomas With Plasmacytic Differentiation?

OBJECTIVES

Lymphoplasmacytic lymphoma (LPL) remains a poorly defined entity, even with the discovery of MYD88L265P mutations and association with Waldenström macroglobulinemia (WM). Among bone marrow (BM)-based, low-grade B-cell lymphoma with plasmacytic differentiation (LGBLPD) and immunoglobulin M (IgM) paraproteins, we sought to determine whether MYD88L265P defines a distinct entity and can help refine diagnostic criteria for LPL.

METHODS

BMs diagnosed with LGBLPD or LPL and serum IgM paraprotein were studied (2007-2013). Clinicopathologic features were reviewed and specimens were tested for MYD88L265P.

RESULTS

In total, 138 (87%) of 159 cases had MYD88L265P, and 158 of 159 were clinically considered WM. MYD88L265P cases had higher disease burden than MYD88WT. Features associated with MYD88L265P include increased mast cells and lymphocyte (not plasma cell)-predominant infiltrate. Hemosiderin, Dutcher bodies, and paratrabecular growth were not associated with MYD88L265P.

CONCLUSIONS

Our data support a clinicopathologic approach to LPL diagnosis and recognition that it may manifest with varying morphologies, phenotypes, and molecular features.

Genotype-Phenotype Correlation of Hereditary Erythrocytosis Mutations, a single center experience

Hereditary erythrocytosis is associated with high oxygen affinity hemoglobin variants (HOAs), 2,3-bisphosphoglycerate deficiency and abnormalities in EPOR and the oxygen-sensing pathway proteins PHD, HIF2α, and VHL. Our laboratory has 40 years of experience with hemoglobin disorder testing and we have characterized HOAs using varied protein and molecular techniques including functional assessment by p50 analysis. In addition, we have more recently commenced adding the assessment of clinically relevant regions of the VHL, BPGM, EPOR, EGLN1 (PHD2), and EPAS1 (HIF2A) genes in a more comprehensive hereditary erythrocytosis panel of tests. Review of our experience confirms a wide spectrum of alterations associated with erythrocytosis which we have correlated with phenotypic and clinical features. Through generic hemoglobinopathy testing we have identified 762 patients with 81 distinct HOA Hb variants (61 β, 20 α), including 12 that were first identified by our laboratory. Of the 1192 cases received for an evaluation specific for hereditary erythrocytosis, approximately 12% had reportable alterations: 85 pathogenic/likely pathogenic mutations and 58 variants of unknown significance. Many have not been previously reported. Correlation with clinical and phenotypic data supports an algorithmic approach to guide economical evaluation; although, testing is expanded if the suspected causes are negative or of uncertain significance. Clinical features are similar and range from asymptomatic to recurrent headaches, fatigue, restless legs, chest pain, exertional dyspnea and thrombotic episodes. Many patients were chronically phlebotomized with reported relief of symptoms. This article is protected by copyright. All rights reserved.

Lymphoplasmacytic Lymphoma With a Non-IgM Paraprotein Shows Clinical and Pathologic Heterogeneity and May Harbor MYD88 L265P Mutations

OBJECTIVES

Lymphoplasmacytic lymphoma (LPL) with non-immunoglobulin M (IgM) paraproteinemia remains poorly understood. The goal of this study was to investigate the clinicopathologic features of LPL in the bone marrow in patients with immunoglobulin G (IgG) or immunoglobulin A (IgA) paraproteins and evaluate MYD88 L265P mutation status to determine the relationship of these cases to Waldenström macroglobulinemia (WM).

METHODS

Bone marrows from LPL cases with IgG or IgA paraproteins diagnosed between January 1, 2007, and June 30, 2014, were retrieved from the clinical archive. Clinicopathologic features were retrospectively reviewed. MYD88 L265P mutation status was assessed by allele-specific polymerase chain reaction prospectively on all cases.

RESULTS

Of 27 cases, four were reclassified as multiple myeloma, all MYD88 mutation negative. MYD88 L265P mutations were present in 10 (43%) of 23 remaining cases. No association between MYD88 status and bone marrow morphologic or phenotypic features, including the presence of Dutcher bodies, mast cells, expression of CD19 by plasma cells, or hemosiderin, was identified, although these features were present in a subset of cases, similar to WM. Clinical features of WM such as hyperviscosity were uncommon in this group and did not correlate with MYD88 status.

CONCLUSIONS

Non-IgM LPLs are a clinically and pathologically heterogeneous group and often harbor MYD88 L265P mutation, albeit at a lower rate than classic WM. MYD88 status does not correlate with any specific pathologic or clinical manifestations.

Chemoimmunotherapy for relapsed/refractory and progressive 17p13-deleted chronic lymphocytic leukemia (CLL) combining pentostatin, alemtuzumab, and low-dose rituximab is effective and tolerable and limits loss of CD20 expression by circulating CLL cells

Chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL) patients with purine analog refractory disease or TP53 dysfunction still have limited treatment options and poor survival. Alemtuzumab-containing chemoimmunotherapy regimens can be effective but frequently cause serious infections. We report a Phase II trial testing the efficacy and tolerability of a short-duration regimen combining pentostatin, alemtuzumab, and low-dose high-frequency rituximab designed to decrease the risk of treatment-associated infections and to limit the loss of CD20 expression by CLL cells. The study enrolled 39 patients with progressive CLL that was either relapsed/refractory (n = 36) or previously untreated with 17p13 deletion (17p13-) (n = 3). Thirteen (33%) patients had both 17p13- and TP53 mutations predicted to be dysfunctional, and eight patients had purine analog refractory CLL without TP53 dysfunction. Twenty-six (67%) patients completed therapy, with only five (13%) patients having treatment-limiting toxicity and no treatment-related deaths. Twenty-two (56%) patients responded to treatment, with 11 (28%) complete responses (four with incomplete bone marrow recovery). Median progression-free survival was 7.2 months, time to next treatment was 9.1 months, and overall survival was 34.1 months. The majority of deaths (82%) were caused by progressive disease, including transformed diffuse large B-cell lymphoma (n = 6). Correlative studies showed that low-dose rituximab activates complement and natural killer cells without a profound and sustained decrease in expression of CD20 by circulating CLL cells. We conclude that pentostatin, alemtuzumab, and low-dose high-frequency rituximab is a tolerable and effective therapy for CLL and that low-dose rituximab therapy can activate innate immune cytotoxic mechanisms without substantially decreasing CD20 expression.

Matrix metalloproteinase-10 is a critical effector of protein kinase Ciota-Par6alpha-mediated lung cancer

Protein kinase Ciota (PKCiota) drives transformed growth of non-small cell lung cancer (NSCLC) cells through the Rho family GTPase Rac1. We show here that PKCiota activates Rac1 in NSCLC cells by formation of a PKCiota-Par6alpha complex that drives anchorage-independent growth and invasion through activation of matrix metalloproteinase-10 (MMP-10) expression. RNAi-mediated knockdown of PKCiota, Par6alpha or Rac1 expression inhibits NSCLC transformation and MMP-10 expression in vitro. Expression of wild-type Par6alpha in Par6alpha-deficient cells restores transformation and MMP-10 expression, whereas expression of Par6alpha mutants that either cannot bind PKCiota (Par6alpha-K19A) or couple to Rac1 (Par6alpha-DeltaCRIB) do not. Knockdown of MMP-10 expression blocks anchorage-independent growth and invasion of NSCLC cells and addition of catalytically active MMP-10 to PKCiota- or Par6alpha-deficient cells restores anchorage-independent growth and invasion. Dominant-negative PKCiota inhibits tumorigenicity and MMP-10 expression in subcutaneous NSCLC tumors. MMP-10 and PKCiota are coordinately overexpressed in primary NSCLC tumors, and tumor MMP-10 expression predicts poor survival in NSCLC patients. Our data define a PKCiota-Par6alpha-Rac1 signaling axis that drives anchorage-independent growth and invasion of NSCLC cells through induction of MMP-10 expression.

Sequence, expression and function of an mRNA encoding a soluble form of the human interleukin-6 receptor (sIL-6R)

Soluble receptors have been shown to be potent immunomodulators of their respective ligands. Since IL-6 is a central growth factor for myeloma cells, an sIL-6R may modulate IL-6 activity. We have previously reported a novel IL-6R mRNA from myeloma cells that exhibits a 94-nt deletion of the entire transmembrane domain from codons 356 (G-TG) to 387 (AG-G). The transmembrane domain deletion results in a shift in the translational reading frame with the insertion of 10 new amino acids followed by a stop codon. Sequence analysis shows the ligand-binding domain of the sIL-6R to be identical to that of the membrane-bound IL-6R up to the transmembrane domain deletion. The sIL-6R cDNA was expressed in QT-6 fibroblasts and PA-1 ovarian cells using the expression vector pCDM8. Supernates were immunoprecipitated with anti-IL-6R antibody and cells transfected with the sIL-6R cDNA produced a single band with a molecular weight of 50-55 kDa. This molecular weight corresponds to the size of the sIL-6R protein observed in normal human urine. Supernates were collected from mock or sIL-6R transfected PA-1 cells after 48 hours and assayed for their ability to stimulate or suppress the growth of an IL-6 dependent cell line, ANBL-6. Soluble IL-6R alone had no effect on the growth of the ANBL-6 cells. However, the growth of ANBL-6 cells by sIL-6R was potentiated in the presence of IL-6 and could be blocked by anti-IL-6 antibody. The above results suggest that, in the presence of IL-6, sIL-6R associates with gp130 leading to signal transduction and cell growth.