Molecular targets of glucocorticoids that elucidate their therapeutic efficacy in aggressive lymphomas

Glucocorticoids have been used for decades to treat lymphomas without an established mechanism of action. Using functional genomic, proteomic, and chemical screens, we discover that glucocorticoids inhibit oncogenic signaling by the B cell receptor (BCR), a recurrent feature of aggressive B cell malignancies, including diffuse large B cell lymphoma and Burkitt lymphoma. Glucocorticoids induce the glucocorticoid receptor (GR) to directly transactivate genes encoding negative regulators of BCR stability (LAPTM5; KLHL14) and the PI3 kinase pathway (INPP5D; DDIT4). GR directly represses transcription of CSK, a kinase that limits the activity of BCR-proximal Src-family kinases. CSK inhibition attenuates the constitutive BCR signaling of lymphomas by hyperactivating Src-family kinases, triggering their ubiquitination and degradation. With the knowledge that glucocorticoids disable oncogenic BCR signaling, they can now be deployed rationally to treat BCR-dependent aggressive lymphomas and used to construct mechanistically sound combination regimens with inhibitors of BTK, PI3 kinase, BCL2, and CSK.

Molecular Determinants of Sensitivity to Polatuzumab Vedotin in Diffuse Large B Cell Lymphoma

Polatuzumab Vedotin (Pola-V) is an antibody-drug conjugate directed to the CD79B subunit of the B cell receptor (BCR). When combined with conventional immunochemotherapy, Pola-V improves outcomes in DLBCL. To identify determinants of Pola-V sensitivity, we used CRISPR-Cas9 screening for genes that modulated Pola-V toxicity for lymphomas or the surface expression of its target, CD79B. Our results reveal the striking impact of CD79B glycosylation on Pola-V epitope availability on the lymphoma cell surface and on Pola-V toxicity. Genetic, pharmacological, and enzymatic approaches that remove sialic acid from N-linked glycans enhanced lymphoma killing by Pola-V. Pola-V toxicity was also modulated by KLHL6, an E3 ubiquitin ligase that is recurrently inactivated in germinal center derived lymphomas. We reveal how KLHL6 targets CD79B for degradation in normal and malignant germinal center B cells, thereby determining expression of the surface BCR complex. Our findings suggest precision medicine strategies to optimize Pola-V as a lymphoma therapeutic.

Response to Bruton's tyrosine kinase inhibitors in aggressive lymphomas linked to chronic selective autophagy

Diffuse large B cell lymphoma (DLBCL) is an aggressive, profoundly heterogeneous cancer, presenting a challenge for precision medicine. Bruton's tyrosine kinase (BTK) inhibitors block B cell receptor (BCR) signaling and are particularly effective in certain molecular subtypes of DLBCL that rely on chronic active BCR signaling to promote oncogenic NF-κB. The MCD genetic subtype, which often acquires mutations in the BCR subunit, CD79B, and in the innate immune adapter, MYD88L265P, typically resists chemotherapy but responds exceptionally to BTK inhibitors. However, the underlying mechanisms of response to BTK inhibitors are poorly understood. Herein, we find a non-canonical form of chronic selective autophagy in MCD DLBCL that targets ubiquitinated MYD88L265P for degradation in a TBK1-dependent manner. MCD tumors acquire genetic and epigenetic alterations that attenuate this autophagic tumor suppressive pathway. In contrast, BTK inhibitors promote autophagic degradation of MYD88L265P, thus explaining their exceptional clinical benefit in MCD DLBCL.

Targeting N-linked Glycosylation for the Therapy of Aggressive Lymphomas

Diffuse large B-cell lymphoma (DLBCL) can be subdivided into the activated B-cell (ABC) and germinal center B cell-like (GCB) subtypes. Self-antigen engagement of B-cell receptors (BCR) in ABC tumors induces their clustering, thereby initiating chronic active signaling and activation of NF-κB and PI3 kinase. Constitutive BCR signaling is essential in some GCB tumors but primarily activates PI3 kinase. We devised genome-wide CRISPR-Cas9 screens to identify regulators of IRF4, a direct transcriptional target of NF-κB and an indicator of proximal BCR signaling in ABC DLBCL. Unexpectedly, inactivation of N-linked protein glycosylation by the oligosaccharyltransferase-B (OST-B) complex reduced IRF4 expression. OST-B inhibition of BCR glycosylation reduced BCR clustering and internalization while promoting its association with CD22, which attenuated PI3 kinase and NF-κB activation. By directly interfering with proximal BCR signaling, OST-B inactivation killed models of ABC and GCB DLBCL, supporting the development of selective OST-B inhibitors for the treatment of these aggressive cancers.

SIGNIFICANCE

DLBCL depends on constitutive BCR activation and signaling. There are currently no therapeutics that target the BCR directly and attenuate its pathologic signaling. Here, we unraveled a therapeutically exploitable, OST-B-dependent glycosylation pathway that drives BCR organization and proximal BCR signaling. This article is highlighted in the In This Issue feature, p. 1749.

Effect of ibrutinib with R-CHOP chemotherapy in genetic subtypes of DLBCL

In diffuse large B cell lymphoma (DLBCL), tumors belonging to the ABC but not GCB gene expression subgroup rely upon chronic active B cell receptor signaling for viability, a dependency that is targetable by ibrutinib. A phase III trial ("Phoenix;" ClinicalTrials.gov: NCT01855750) showed a survival benefit of ibrutinib addition to R-CHOP chemotherapy in younger patients with non-GCB DLBCL, but the molecular basis for this benefit was unclear. Analysis of biopsies from Phoenix trial patients revealed three previously characterized genetic subtypes of DLBCL: MCD, BN2, and N1. The 3-year event-free survival of younger patients (age ≤60 years) treated with ibrutinib plus R-CHOP was 100% in the MCD and N1 subtypes while the survival of patients with these subtypes treated with R-CHOP alone was significantly inferior (42.9% and 50%, respectively). This work provides a mechanistic understanding of the benefit of ibrutinib addition to chemotherapy, supporting its use in younger patients with non-GCB DLBCL.

Overcoming Acquired Epigenetic Resistance to BTK Inhibitors

The use of Bruton tyrosine kinase (BTK) inhibitors to block B-cell receptor (BCR)-dependent NF-κB activation in lymphoid malignancies has been a major clinical advance, yet acquired therapeutic resistance is a recurring problem. We modeled the development of resistance to the BTK inhibitor ibrutinib in the activated B-cell (ABC) subtype of diffuse large B-cell lymphoma, which relies on chronic active BCR signaling for survival. The primary mode of resistance was epigenetic, driven in part by the transcription factor TCF4. The resultant phenotypic shift altered BCR signaling such that the GTPase RAC2 substituted for BTK in the activation of phospholipase Cγ2, thereby sustaining NF-κB activity. The interaction of RAC2 with phospholipase Cγ2 was also increased in chronic lymphocytic leukemia cells from patients with persistent or progressive disease on BTK inhibitor treatment. We identified clinically available drugs that can treat epigenetic ibrutinib resistance, suggesting combination therapeutic strategies.

Significance

In diffuse large B-cell lymphoma, we show that primary resistance to BTK inhibitors is due to epigenetic rather than genetic changes that circumvent the BTK blockade. We also observed this resistance mechanism in chronic lymphocytic leukemia, suggesting that epigenetic alterations may contribute more to BTK inhibitor resistance than currently thought.See related commentary by Pasqualucci, p. 555. This article is highlighted in the In This Issue feature, p. 549.

Insertion of atypical glycans into the tumor antigen-binding site identifies DLBCLs with distinct origin and behavior

Glycosylation of the surface immunoglobulin (Ig) variable region is a remarkable follicular lymphoma-associated feature rarely seen in normal B cells. Here, we define a subset of diffuse large B-cell lymphomas (DLBCLs) that acquire N-glycosylation sites selectively in the Ig complementarity-determining regions (CDRs) of the antigen-binding sites. Mass spectrometry and X-ray crystallography demonstrate how the inserted glycans are stalled at oligomannose-type structures because they are buried in the CDR loops. Acquisition of sites occurs in ∼50% of germinal-center B-cell-like DLBCL (GCB-DLBCL), mainly of the genetic EZB subtype, irrespective of IGHV-D-J use. This markedly contrasts with the activated B-cell-like DLBCL Ig, which rarely has sites in the CDR and does not seem to acquire oligomannose-type structures. Acquisition of CDR-located acceptor sites associates with mutations of epigenetic regulators and BCL2 translocations, indicating an origin shared with follicular lymphoma. Within the EZB subtype, these sites are associated with more rapid disease progression and with significant gene set enrichment of the B-cell receptor, PI3K/AKT/MTORC1 pathway, glucose metabolism, and MYC signaling pathways, particularly in the fraction devoid of MYC translocations. The oligomannose-type glycans on the lymphoma cells interact with the candidate lectin dendritic cell-specific intercellular adhesion molecule 3 grabbing non-integrin (DC-SIGN), mediating low-level signals, and lectin-expressing cells form clusters with lymphoma cells. Both clustering and signaling are inhibited by antibodies specifically targeting the DC-SIGN carbohydrate recognition domain. Oligomannosylation of the tumor Ig is a posttranslational modification that readily identifies a distinct GCB-DLBCL category with more aggressive clinical behavior, and it could be a potential precise therapeutic target via antibody-mediated inhibition of the tumor Ig interaction with DC-SIGN-expressing M2-polarized macrophages.

Compromised counterselection by FAS creates an aggressive subtype of germinal center lymphoma

Fas is highly expressed on germinal center (GC) B cells, and mutations of FAS have been reported in diffuse large B cell lymphoma (DLBCL). Although GC-derived DLBCL has better overall outcomes than other DLBCL types, some cases are refractory, and the molecular basis for this is often unknown. We show that Fas is a strong cell-intrinsic regulator of GC B cells that promotes cell death in the light zone, likely via T follicular helper (Tfh) cell-derived Fas ligand. In the absence of Fas, GCs were more clonally diverse due to an accumulation of cells that did not demonstrably bind antigen. FAS alterations occurred most commonly in GC-derived DLBCL, were associated with inferior outcomes and an enrichment of Tfh cells, and co-occurred with deficiency in HVEM and PD-L1 that regulate the Tfh-B cell interaction. This work shows that Fas is critically required for GC homeostasis and suggests that loss of Tfh-mediated counterselection in the GC contributes to lethality in GC-derived lymphoma.

Genome-wide Screens Identify Lineage- and Tumor-Specific Genes Modulating MHC-I- and MHC-II-Restricted Immunosurveillance of Human Lymphomas

Tumors frequently subvert major histocompatibility complex class I (MHC-I) peptide presentation to evade CD8+ T cell immunosurveillance, though how this is accomplished is not always well defined. To identify the global regulatory networks controlling antigen presentation, we employed genome-wide screening in human diffuse large B cell lymphomas (DLBCLs). This approach revealed dozens of genes that positively and negatively modulate MHC-I cell surface expression. Validated genes clustered in multiple pathways including cytokine signaling, mRNA processing, endosomal trafficking, and protein metabolism. Genes can exhibit lymphoma subtype- or tumor-specific MHC-I regulation, and a majority of primary DLBCL tumors displayed genetic alterations in multiple regulators. We established SUGT1 as a major positive regulator of both MHC-I and MHC-II cell surface expression. Further, pharmacological inhibition of two negative regulators of antigen presentation, EZH2 and thymidylate synthase, enhanced DLBCL MHC-I presentation. These and other genes represent potential targets for manipulating MHC-I immunosurveillance in cancers, infectious diseases, and autoimmunity.

Abstract PO-22: Compromised counterselection by FAS creates a lethal subtype of germinal center lymphoma

Fas is highly expressed on germinal center (GC) B cells, and mutations of FAS have been reported in diffuse large B-cell lymphoma (DLBCL); however, the function of Fas in the GC remains controversial. Although GC-derived DLBCL has better overall outcomes to therapy than other DLBCL types, some cases are refractory and the molecular basis for this is often unknown. We show that Fas is a strong cell-intrinsic regulator of GC B cells that promotes B-cell death in the light zone likely via T follicular helper (Tfh) cell-derived Fas ligand. In the absence of Fas, GCs were more clonally diverse due to an accumulation of cells that did not demonstrably bind antigen. We found that FAS alterations occurred most commonly in the GC-derived genetic subtype of DLBCL, EZB. FAS alterations in EZB were associated with inferior outcomes and an enrichment of Tfh cells. Alterations in FAS co-occurred with deficiency in HVEM and PD-1 ligands that regulate the Tfh-B cell interaction and were associated with increased diversity of B-cell receptor variable genes across samples. This work shows that Fas is critically required for GC homeostasis and suggests that loss of Tfh-mediated counterselection in the GC contributes to lethality in a distinct subtype of GC-derived lymphoma.

Citation Format: Raud Razzaghi, Shreya Agarwal, Nikita Kotlov, Olga Plotnikova, Krystle Nomie, Da Wei Huang, George W. Wright, Moyi Li, Katsuyoshi Takata, Chen Yao, John J. O'Shea, James D. Phelan, Stefania Pittaluga, David W. Scott, Jagan R. Muppidi. Compromised counterselection by FAS creates a lethal subtype of germinal center lymphoma [abstract]. In: Proceedings of the AACR Virtual Meeting: Advances in Malignant Lymphoma; 2020 Aug 17-19. Philadelphia (PA): AACR; Blood Cancer Discov 2020;1(3_Suppl):Abstract nr PO-22.

Characteristics of Breast Ducts in Normal-Risk and High-risk Women and Their Relationship to Ductal Cytologic Atypia

Breast ductal cytologic atypia is an important risk factor for sporadic breast cancer. Characterization of the associated normal breast tissue is needed to develop additional methods of risk assessment and new targets for breast cancer prevention. We conducted a prospective clinical trial evaluating women at normal-risk or at high-risk for sporadic breast cancer. Breast ductal cells were collected and studied cytologically and by gene expression profiling, and breast ductal architectural changes were studied by breast ductal endoscopy (BDE) and breast MRI. One hundred and forty subjects were studied, 70 at high risk (RR, 2.0-4.6) and 70 at normal risk. Cytologic atypia was present in 22.9% of high-risk and 25.7% of normal-risk subjects. Ductal endoscopy was performed in 89 subjects and revealed benign intraductal abnormalities, primarily intraductal fibrous webbing suggesting chronic inflammation, in 40.4% of high-risk and 5.4% of normal-risk subjects, respectively (P ₂ = 0.0002). Two high-risk subjects with atypia and no normal-risk subjects with atypia developed invasive breast cancer. Gene expression profiling of ductal cells showed comparable gene expression profiles without enriched expression of previously defined oncogenic signatures in subjects with cellular atypia compared with those without atypia, and in high-risk subjects compared with normal-risk subjects (FDR > 0.5). Cytologic ductal atypia in normal-risk subjects does not appear to be of clinical significance. Atypia in women at high risk may be associated with benign and malignant breast ductal abnormalities; these characteristics of high-risk ductal cells may not be reflected in gene expression profiles.

Inhibition of Bruton tyrosine kinase in patients with severe COVID-19

Patients with severe COVID-19 have a hyperinflammatory immune response suggestive of macrophage activation. Bruton tyrosine kinase (BTK) regulates macrophage signaling and activation. Acalabrutinib, a selective BTK inhibitor, was administered off-label to 19 patients hospitalized with severe COVID-19 (11 on supplemental oxygen; 8 on mechanical ventilation), 18 of whom had increasing oxygen requirements at baseline. Over a 10-14 day treatment course, acalabrutinib improved oxygenation in a majority of patients, often within 1-3 days, and had no discernable toxicity. Measures of inflammation – C-reactive protein and IL-6 – normalized quickly in most patients, as did lymphopenia, in correlation with improved oxygenation. At the end of acalabrutinib treatment, 8/11 (72.7%) patients in the supplemental oxygen cohort had been discharged on room air, and 4/8 (50%) patients in the mechanical ventilation cohort had been successfully extubated, with 2/8 (25%) discharged on room air. Ex vivo analysis revealed significantly elevated BTK activity, as evidenced by autophosphorylation, and increased IL-6 production in blood monocytes from patients with severe COVID-19 compared with blood monocytes from healthy volunteers. These results suggest that targeting excessive host inflammation with a BTK inhibitor is a therapeutic strategy in severe COVID-19 and has led to a confirmatory international prospective randomized controlled clinical trial.

A Probabilistic Classification Tool for Genetic Subtypes of Diffuse Large B Cell Lymphoma with Therapeutic Implications

The development of precision medicine approaches for diffuse large B cell lymphoma (DLBCL) is confounded by its pronounced genetic, phenotypic, and clinical heterogeneity. Recent multiplatform genomic studies revealed the existence of genetic subtypes of DLBCL using clustering methodologies. Here, we describe an algorithm that determines the probability that a patient's lymphoma belongs to one of seven genetic subtypes based on its genetic features. This classification reveals genetic similarities between these DLBCL subtypes and various indolent and extranodal lymphoma types, suggesting a shared pathogenesis. These genetic subtypes also have distinct gene expression profiles, immune microenvironments, and outcomes following immunochemotherapy. Functional analysis of genetic subtype models highlights distinct vulnerabilities to targeted therapy, supporting the use of this classification in precision medicine trials.

Gene Expression Profiling of Mediastinal Gray Zone Lymphoma and Its Relationship to Primary Mediastinal B-cell Lymphoma and Classical Hodgkin Lymphoma

Mediastinal gray zone lymphoma (MGZL) has immunopathologic features between classical Hodgkin lymphoma (cHL) and primary mediastinal thymic B-cell lymphoma (PMBL), leading to uncertainty regarding its biological relationship to these entities. We performed gene expression profiling from patients with MGZL (20), cHL (18), and PMBL (17) and show MGZL clusters between cHL and PMBL. Expression signatures reveal germinal B-cell and IFN regulatory factor 4 (IRF4) signatures were relatively low in MGZL and cHL compared with PMBL, indicating downregulation of the B-cell program in MGZL, a hallmark of cHL. T-cell and macrophage signatures were higher in MGZL and cHL compared with PMBL, consistent with infiltrating immune cells, which are found in cHL. The NFκB signature was higher in MGZL than PMBL, and like cHL, MGZL and PMBL express NFκB inducing kinase (NIK), indicating noncanonical signaling. These findings indicate that while MGZL has distinctive clustering, it is biologically closer to cHL.

Regulation of B cell receptor-dependent NF-κB signaling by the tumor suppressor KLHL14

The KLHL14 gene acquires frequent inactivating mutations in mature B cell malignancies, especially in the MYD88L265P, CD79B mutant (MCD) genetic subtype of diffuse large B cell lymphoma (DLBCL), which relies on B cell receptor (BCR) signaling for survival. However, the pathogenic role of KLHL14 in DLBCL and its molecular function are largely unknown. Here, we report that KLHL14 is in close proximity to the BCR in the endoplasmic reticulum of MCD cell line models and promotes the turnover of immature glycoforms of BCR subunits, reducing total cellular BCR levels. Loss of KLHL14 confers relative resistance to the Bruton tyrosine kinase (BTK) inhibitor ibrutinib and promotes assembly of the MYD88-TLR9-BCR (My-T-BCR) supercomplex, which initiates prosurvival NF-κB activation. Consequently, KLHL14 inactivation allows MCD cells to maintain NF-κB signaling in the presence of ibrutinib. These findings reinforce the central role of My-T-BCR-dependent NF-κB signaling in MCD DLBCL and suggest that the genetic status of KLHL14 should be considered in clinical trials testing inhibitors of BTK and BCR signaling mediators in DLBCL.

Genome-wide discovery of somatic coding and noncoding mutations in pediatric endemic and sporadic Burkitt lymphoma

Although generally curable with intensive chemotherapy in resource-rich settings, Burkitt lymphoma (BL) remains a deadly disease in older patients and in sub-Saharan Africa. Epstein-Barr virus (EBV) positivity is a feature in more than 90% of cases in malaria-endemic regions, and up to 30% elsewhere. However, the molecular features of BL have not been comprehensively evaluated when taking into account tumor EBV status or geographic origin. Through an integrative analysis of whole-genome and transcriptome data, we show a striking genome-wide increase in aberrant somatic hypermutation in EBV-positive tumors, supporting a link between EBV and activation-induced cytidine deaminase (AICDA) activity. In addition to identifying novel candidate BL genes such as SIN3A, USP7, and CHD8, we demonstrate that EBV-positive tumors had significantly fewer driver mutations, especially among genes with roles in apoptosis. We also found immunoglobulin variable region genes that were disproportionally used to encode clonal B-cell receptors (BCRs) in the tumors. These include IGHV4-34, known to produce autoreactive antibodies, and IGKV3-20, a feature described in other B-cell malignancies but not yet in BL. Our results suggest that tumor EBV status defines a specific BL phenotype irrespective of geographic origin, with particular molecular properties and distinct pathogenic mechanisms. The novel mutation patterns identified here imply rational use of DNA-damaging chemotherapy in some patients with BL and targeted agents such as the CDK4/6 inhibitor palbociclib in others, whereas the importance of BCR signaling in BL strengthens the potential benefit of inhibitors for PI3K, Syk, and Src family kinases among these patients.

Taming the Heterogeneity of Aggressive Lymphomas for Precision Therapy

Genomic analyses of diffuse large B cell lymphoma (DLBCL) are revealing the genetic and phenotypic heterogeneity of these aggressive lymphomas. In part, this heterogeneity reflects the existence of distinct genetic subtypes that acquire characteristic constellations of somatic genetic alterations to converge on the DLBCL phenotype. In parallel, functional genomic screens and proteomic analyses have identified multiprotein assemblies that coordinate oncogenic survival signaling in DLBCL. In this review, we merge these recent insights into a unified conceptual framework with implications for the design of precision medicine trials in DLBCL.

A gene signature that distinguishes conventional and leukemic nonnodal mantle cell lymphoma helps predict outcome

Mantle cell lymphoma (MCL) is an aggressive B-cell malignancy, but some patients have a very indolent evolution. This heterogeneous course is related, in part, to the different biological characteristics of conventional MCL (cMCL) and the distinct subgroup of leukemic nonnodal MCL (nnMCL). Robust criteria to distinguish these MCL subtypes and additional biological parameters that influence their evolution are not well defined. We describe a novel molecular assay that reliably distinguishes cMCL and nnMCL using blood samples. We trained a 16-gene assay (L-MCL16 assay) on the NanoString platform using 19 purified leukemic samples. The locked assay was applied to an independent cohort of 70 MCL patients with leukemic presentation. The assay assigned 37% of cases to nnMCL and 56% to cMCL. nnMCL and cMCL differed in nodal presentation, lactate dehydrogenase, immunoglobulin heavy chain gene mutational status, management options, genomic complexity, and CDKN2A/ATM deletions, but the proportion with 17p/TP53 aberrations was similar in both subgroups. Sequential samples showed that assay prediction was stable over time. nnMCL had a better overall survival (OS) than cMCL (3-year OS 92% vs 69%; P = .006) from the time of diagnosis and longer time to first treatment. Genomic complexity and TP53/CDKN2A aberrations predicted for shorter OS in the entire series and cMCL, whereas only genomic complexity was associated with shorter time to first treatment and OS in nnMCL. In conclusion, the newly developed assay robustly recognizes the 2 molecular subtypes of MCL in leukemic samples. Its combination with genetic alterations improves the prognostic evaluation and may provide useful biological information for management decisions.

A multiprotein supercomplex controlling oncogenic signalling in lymphoma

B cell receptor (BCR) signalling has emerged as a therapeutic target in B cell lymphomas, but inhibiting this pathway in diffuse large B cell lymphoma (DLBCL) has benefited only a subset of patients¹. Gene expression profiling identified two major subtypes of DLBCL, known as germinal centre B cell-like and activated B cell-like (ABC)^2,3, that show poor outcomes after immunochemotherapy in ABC. Autoantigens drive BCR-dependent activation of NF-κB in ABC DLBCL through a kinase signalling cascade of SYK, BTK and PKCβ to promote the assembly of the CARD11-BCL10-MALT1 adaptor complex, which recruits and activates IκB kinase^4-6. Genome sequencing revealed gain-of-function mutations that target the CD79A and CD79B BCR subunits and the Toll-like receptor signalling adaptor MYD88^5,7, with MYD88(L265P) being the most prevalent isoform. In a clinical trial, the BTK inhibitor ibrutinib produced responses in 37% of cases of ABC¹. The most striking response rate (80%) was observed in tumours with both CD79B and MYD88(L265P) mutations, but how these mutations cooperate to promote dependence on BCR signalling remains unclear. Here we used genome-wide CRISPR-Cas9 screening and functional proteomics to determine the molecular basis of exceptional clinical responses to ibrutinib. We discovered a new mode of oncogenic BCR signalling in ibrutinib-responsive cell lines and biopsies, coordinated by a multiprotein supercomplex formed by MYD88, TLR9 and the BCR (hereafter termed the My-T-BCR supercomplex). The My-T-BCR supercomplex co-localizes with mTOR on endolysosomes, where it drives pro-survival NF-κB and mTOR signalling. Inhibitors of BCR and mTOR signalling cooperatively decreased the formation and function of the My-T-BCR supercomplex, providing mechanistic insight into their synergistic toxicity for My-T-BCR⁺ DLBCL cells. My-T-BCR supercomplexes characterized ibrutinib-responsive malignancies and distinguished ibrutinib responders from non-responders. Our data provide a framework for the rational design of oncogenic signalling inhibitors in molecularly defined subsets of DLBCL.

Genetics and Pathogenesis of Diffuse Large B-Cell Lymphoma

BACKGROUND

Diffuse large B-cell lymphomas (DLBCLs) are phenotypically and genetically heterogeneous. Gene-expression profiling has identified subgroups of DLBCL (activated B-cell-like [ABC], germinal-center B-cell-like [GCB], and unclassified) according to cell of origin that are associated with a differential response to chemotherapy and targeted agents. We sought to extend these findings by identifying genetic subtypes of DLBCL based on shared genomic abnormalities and to uncover therapeutic vulnerabilities based on tumor genetics.

METHODS

We studied 574 DLBCL biopsy samples using exome and transcriptome sequencing, array-based DNA copy-number analysis, and targeted amplicon resequencing of 372 genes to identify genes with recurrent aberrations. We developed and implemented an algorithm to discover genetic subtypes based on the co-occurrence of genetic alterations.

RESULTS

We identified four prominent genetic subtypes in DLBCL, termed MCD (based on the co-occurrence of MYD88L265P and CD79B mutations), BN2 (based on BCL6 fusions and NOTCH2 mutations), N1 (based on NOTCH1 mutations), and EZB (based on EZH2 mutations and BCL2 translocations). Genetic aberrations in multiple genes distinguished each genetic subtype from other DLBCLs. These subtypes differed phenotypically, as judged by differences in gene-expression signatures and responses to immunochemotherapy, with favorable survival in the BN2 and EZB subtypes and inferior outcomes in the MCD and N1 subtypes. Analysis of genetic pathways suggested that MCD and BN2 DLBCLs rely on "chronic active" B-cell receptor signaling that is amenable to therapeutic inhibition.

CONCLUSIONS

We uncovered genetic subtypes of DLBCL with distinct genotypic, epigenetic, and clinical characteristics, providing a potential nosology for precision-medicine strategies in DLBCL. (Funded by the Intramural Research Program of the National Institutes of Health and others.).

A Phase 2/3 Multicenter, Randomized, Open-Label Study to Compare the Efficacy and Safety of Lenalidomide Versus Investigator's Choice in Patients with Relapsed or Refractory Diffuse Large B-Cell Lymphoma

Purpose: Randomized, multicenter, open-label, phase 2/3 trial investigating lenalidomide versus investigator's choice (IC) in relapsed/refractory diffuse large B-cell lymphoma (DLBCL).Experimental Design: Patients with DLBCL who received ≥2 prior therapies were stratified by DLBCL subtype [germinal center B-cell (GCB) vs. non-GCB; determined by immunohistochemistry (IHC)] and then randomized 1:1 to lenalidomide (25 mg/day, 21 days of 28-day cycle) or IC (gemcitabine, rituximab, etoposide, or oxaliplatin). Crossover to lenalidomide was permitted for IC-treated patients with radiologically confirmed progressive disease. The primary endpoint was overall response rate (ORR). Progression-free survival (PFS), overall survival, and subtype analysis [GCB vs. activated B-cell (ABC)] using gene expression profiling (GEP) were exploratory endpoints.Results: Stage 1: 102 DLBCL patients (by IHC: non-GCB, n = 54; GCB, n = 48) received ≥1 dose of lenalidomide or IC. Hematologic treatment-emergent adverse events with lenalidomide versus IC included neutropenia (42.6%; 36.4%), anemia (33.3%; 47.3%), thrombocytopenia (24.1%; 43.6%), and leukopenia (5.6%; 12.7%), respectively. Overall, lenalidomide-treated patients had an ORR of 27.5% versus 11.8% in IC (ORRs were similar regardless of IHC-defined DLBCL subtype). Median PFS was increased in patients receiving lenalidomide (13.6 weeks) versus IC (7.9 weeks; P = 0.041), with greater improvements in non-GCB patients (15.1 vs. 7.1 weeks, respectively; P = 0.021) compared with GCB (10.1 vs. 9.0 weeks, respectively; P = 0.550).Conclusions: The clinical benefit of lenalidomide monotherapy in DLBCL patients was more evident in the non-GCB subtype. Exploratory analyses suggest that this preferential benefit was more pronounced in the GEP-defined ABC population, demonstrating a need for additional studies of lenalidomide in DLBCL using GEP subtyping. Clin Cancer Res; 23(15); 4127-37. ©2017 AACR.

New Molecular Assay for the Proliferation Signature in Mantle Cell Lymphoma Applicable to Formalin-Fixed Paraffin-Embedded Biopsies

Purpose Mantle cell lymphoma is an aggressive B-cell neoplasm that displays heterogeneous outcomes after treatment. In 2003, the Lymphoma/Leukemia Molecular Profiling Project described a powerful biomarker-the proliferation signature-using gene expression in fresh frozen material. Herein, we describe the training and validation of a new assay that measures the proliferation signature in RNA derived from routinely available formalin-fixed paraffin-embedded (FFPE) biopsies. Methods Forty-seven FFPE biopsies were used to train an assay on the NanoString platform, using microarray gene expression data of matched fresh frozen biopsies as a gold standard. The locked assay was applied to pretreatment FFPE lymph node biopsies from an independent cohort of 110 patients uniformly treated with rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone. Seventeen biopsies were tested across three laboratories to assess assay reproducibility. Results The MCL35 assay, which contained a 17-gene proliferation signature, yielded gene expression of sufficient quality to assign an assay score and risk group in 108 (98%) of 110 archival FFPE biopsies. The MCL35 assay assigned patients to high-risk (26%), standard-risk (29%), and low-risk (45%) groups, with different lengths of overall survival (OS): a median of 1.1, 2.6, and 8.6 years, respectively (log-rank for trend, P < .001). In multivariable analysis, these risk groups and the Mantle Cell Lymphoma International Prognostic Index were independently associated with OS ( P < .001 for both variables). Concordance of risk assignment across the three independent laboratories was 100%. Conclusion The newly developed and validated MCL35 assay for FFPE biopsies uses the proliferation signature to define groups of patients with significantly different OS independent of the Mantle Cell Lymphoma International Prognostic Index. Importantly, the analytic and clinical validity of this assay defines it as a reliable biomarker to support risk-adapted clinical trials.

Targeting Non-proteolytic Protein Ubiquitination for the Treatment of Diffuse Large B Cell Lymphoma

Chronic active B cell receptor (BCR) signaling, a hallmark of the activated B cell-like (ABC) subtype of diffuse large B cell lymphoma (DLBCL), engages the CARD11-MALT1-BCL10 (CBM) adapter complex to activate IκB kinase (IKK) and the classical NF-κB pathway. Here we show that the CBM complex includes the E3 ubiquitin ligases cIAP1 and cIAP2, which are essential mediators of BCR-dependent NF-κB activity in ABC DLBCL. cIAP1/2 attach K63-linked polyubiquitin chains on themselves and on BCL10, resulting in the recruitment of IKK and the linear ubiquitin chain ligase LUBAC, which is essential for IKK activation. SMAC mimetics target cIAP1/2 for destruction, and consequently suppress NF-κB and selectively kill BCR-dependent ABC DLBCL lines, supporting their clinical evaluation in patients with ABC DLBCL.

Prognostic Significance of Diffuse Large B-Cell Lymphoma Cell of Origin Determined by Digital Gene Expression in Formalin-Fixed Paraffin-Embedded Tissue Biopsies

PURPOSE

To evaluate the prognostic impact of cell-of-origin (COO) subgroups, assigned using the recently described gene expression-based Lymph2Cx assay in comparison with International Prognostic Index (IPI) score and MYC/BCL2 coexpression status (dual expressers).

PATIENTS AND METHODS

Reproducibility of COO assignment using the Lymph2Cx assay was tested employing repeated sampling within tumor biopsies and changes in reagent lots. The assay was then applied to pretreatment formalin-fixed paraffin-embedded tissue (FFPET) biopsies from 344 patients with de novo diffuse large B-cell lymphoma (DLBCL) uniformly treated with rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) at the British Columbia Cancer Agency. MYC and BCL2 protein expression was assessed using immunohistochemistry on tissue microarrays.

RESULTS

The Lymph2Cx assay provided concordant COO calls in 96% of 49 repeatedly sampled tumor biopsies and in 100% of 83 FFPET biopsies tested across reagent lots. Critically, no frank misclassification (activated B-cell-like DLBCL to germinal center B-cell-like DLBCL or vice versa) was observed. Patients with activated B-cell-like DLBCL had significantly inferior outcomes compared with patients with germinal center B-cell-like DLBCL (log-rank P < .001 for time to progression, progression-free survival, disease-specific survival, and overall survival). In pairwise multivariable analyses, COO was associated with outcomes independent of IPI score and MYC/BCL2 immunohistochemistry. The prognostic significance of COO was particularly evident in patients with intermediate IPI scores and the non-MYC-positive/BCL2-positive subgroup (log-rank P < .001 for time to progression).

CONCLUSION

Assignment of DLBCL COO by the Lymph2Cx assay using FFPET biopsies identifies patient groups with significantly different outcomes after R-CHOP, independent of IPI score and MYC/BCL2 dual expression.

Essential role of the linear ubiquitin chain assembly complex in lymphoma revealed by rare germline polymorphisms

Constitutive activation of NF-κB is a hallmark of the activated B cell-like (ABC) subtype of diffuse large B-cell lymphoma (DLBCL), owing to upstream signals from the B-cell receptor (BCR) and MYD88 pathways. The linear polyubiquitin chain assembly complex (LUBAC) attaches linear polyubiquitin chains to IκB kinase-γ, a necessary event in some pathways that engage NF-κB. Two germline polymorphisms affecting the LUBAC subunit RNF31 are rare among healthy individuals (∼1%) but enriched in ABC DLBCL (7.8%). These polymorphisms alter RNF31 α-helices that mediate binding to the LUBAC subunit RBCK1, thereby increasing RNF31-RBCK1 association, LUBAC enzymatic activity, and NF-κB engagement. In the BCR pathway, LUBAC associates with the CARD11-MALT1-BCL10 adapter complex and is required for ABC DLBCL viability. A stapled RNF31 α-helical peptide based on the ABC DLBCL-associated Q622L polymorphism inhibited RNF31-RBCK1 binding, decreased NF-κB activation, and killed ABC DLBCL cells, credentialing this protein-protein interface as a therapeutic target.

SIGNIFICANCE

We provide genetic, biochemical, and functional evidence that the LUBAC ubiquitin ligase is a therapeutic target in ABC DLBCL, the DLBCL subtype that is most refractory to current therapy. More generally, our findings highlight the role of rare germline-encoded protein variants in cancer pathogenesis.

Abstract LB-248: IRF4 as a critical regulator and potential therapeutic target in ABC type diffuse large B-cell lymphoma

Interferon regulatory factor 4 (IRF4) is a transcriptional regulator with crucial roles in the development of lymphocytes and implicated in malignant transformation. Recently, we have demonstrated that cell lines derived from cancers of plasma cell origin (i.e., multiple myeloma) are addicted to an anomalous gene expression program driven by the wild-type IRF4. Here, we show that an aggressive malignancy of mature B-cells, the activated B-cell-like type of diffuse large B-cell lymphoma (ABC-DLBCL), also requires IRF4 for survival. With an integrative analysis of genome-wide IRF4 localization (ChIP-Seq) assays and gene expression profiling, we identify IRF4 target genes in ABC-DLBCL as members of diverse pathways related to B-cell biology and oncogenesis, largely distinct from the IRF4 targets in multiple myeloma cells. For instance, we identify CARD11, an adaptor in the NF-κB pathway, as a target of IRF4 in ABC-DLBCL, and confirm this by cell-based reporter assays. This novel regulatory mechanism complements the established aspects of ABC-DLBCL pathobiology, where NF-κB pathway is constitutively active and indispensable, and drives IRF4 expression. Furthermore, we find enrichment for a composite ETS-IRF DNA motif in IRF4 binding regions in ABC-DLBCL, suggesting cooperative activity between IRF4 and ETS transcription factor(s). Supporting this, we demonstrate through complementation assays that critical amino acids on IRF4 and the ETS factor SPIB, notably those residues important for their interaction, are essential for the survival of ABC-DLBCL, but not multiple myeloma cells. Taken together we show that ABC-DLBCL cells are addicted to the transcription factor IRF4, in part through a positive feedback mechanism involving CARD11, NF-κB, and IRF4. In addition, our results suggest therapeutic potential for targeting the IRF4-ETS interaction interface in ABC-DLBCL.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-248. doi:10.1158/1538-7445.AM2011-LB-248

Cooperative epigenetic modulation by cancer amplicon genes

Chromosome band 9p24 is frequently amplified in primary mediastinal B cell lymphoma (PMBL) and Hodgkin lymphoma (HL). To identify oncogenes in this amplicon, we screened an RNA interference library targeting amplicon genes and thereby identified JAK2 and the histone demethylase JMJD2C as essential genes in these lymphomas. Inhibition of JAK2 and JMJD2C cooperated in killing these lymphomas by decreasing tyrosine 41 phosphorylation and increasing lysine 9 trimethylation of histone H3, promoting heterochromatin formation. MYC, a major target of JAK2-mediated histone phosphorylation, was silenced after JAK2 and JMJD2C inhibition, with a corresponding increase in repressive chromatin. Hence, JAK2 and JMJD2C cooperatively remodel the PMBL and HL epigenome, offering a mechanistic rationale for the development of JAK2 and JMJD2C inhibitors in these diseases.

Chromosomal alterations detected by comparative genomic hybridization in subgroups of gene expression-defined Burkitt's lymphoma

BACKGROUND

Burkitt's lymphoma is an aggressive B-cell lymphoma characterized by typical morphological, immunophenotypic and molecular features. Gene expression profiling provided a molecular signature of Burkitt's lymphoma, but also demonstrated that a subset of aggressive B-cell lymphomas not fulfilling the current World Health Organization criteria for the diagnosis of Burkitt's lymphoma nonetheless show a molecular signature of Burkitt's lymphoma ('discrepant Burkitt's lymphoma'). Given the different treatment of Burkitt's lymphoma and diffuse large B-cell lymphomas we investigated molecular differences within gene expression-defined Burkitt's lymphoma.

DESIGN AND METHODS

We studied tumors from 51 Burkitt's lymphoma patients, comprising 26 with classic Burkitt's lymphoma, 17 with atypical Burkitt's lymphoma and 8 with 'discrepant Burkitt's lymphoma', by comparative genomic hybridization and gene expression profiling.

RESULTS

Classic and atypical Burkitt's lymphoma (excluding 'discrepant Burkitt's lymphoma'), in adult and pediatric cases do not differ in underlying genomic imbalances or gene expression suggesting that these subgroups are molecularly homogeneous. 'Discrepant Burkitt's lymphoma', however, differ dramatically in the absolute number of alterations from classic/atypical Burkitt's lymphoma and from diffuse large B-cell lymphoma. Moreover, this category includes lymphomas that carry both the t(14;18) and t(8;14) translocations and are clinically characterized by presentation in adult patients and an aggressive course.

CONCLUSIONS

Pediatric and adult Burkitt's lymphoma are molecularly homogeneous, whereas 'discrepant Burkitt's lymphoma' differ in underlying genetic and clinical features from typical/atypical Burkitt's lymphoma. 'Discrepant Burkitt's lymphoma' may therefore form a distinct genetic subgroup of aggressive B-cell lymphomas, which show poor response to multi-agent chemotherapy.

Oncogenic CARD11 mutations in human diffuse large B cell lymphoma

Diffuse large B cell lymphoma (DLBCL) is the most common form of non-Hodgkin's lymphoma. In the least curable (ABC) subtype of DLBCL, survival of the malignant cells is dependent on constitutive activation of the nuclear factor-kappaB (NF-kappaB) signaling pathway. In normal B cells, antigen receptor-induced NF-kappaB activation requires CARD11, a cytoplasmic scaffolding protein. To determine whether CARD11 contributes to tumorigenesis, we sequenced the CARD11 gene in human DLBCL tumors. We detected missense mutations in 7 of 73 ABC DLBCL biopsies (9.6%), all within exons encoding the coiled-coil domain. Experimental introduction of CARD11 coiled-coil domain mutants into lymphoma cell lines resulted in constitutive NF-kappaB activation and enhanced NF-kappaB activity upon antigen receptor stimulation. These results demonstrate that CARD11 is a bona fide oncogenein DLBCL, providing a genetic rationale for the development of pharmacological inhibitors of the CARD11 pathway for DLBCL therapy.

Aberrant immunoglobulin class switch recombination and switch translocations in activated B cell-like diffuse large B cell lymphoma

To elucidate the mechanisms underlying chromosomal translocations in diffuse large B cell lymphoma (DLBCL), we investigated the nature and extent of immunoglobulin class switch recombination (CSR) in these tumors. We used Southern blotting to detect legitimate and illegitimate CSR events in tumor samples of the activated B cell-like (ABC), germinal center B cell-like (GCB), and primary mediastinal B cell lymphoma (PMBL) subgroups of DLBCL. The frequency of legitimate CSR was lower in ABC DLBCL than in GCB DLBCL and PMBL. In contrast, ABC DLBCL had a higher frequency of internal deletions within the switch mu (Smu) region compared with GCB DLBCL and PMBL. ABC DLBCLs also had frequent deletions within Sgamma and other illegitimate switch recombinations. Sequence analysis revealed ongoing Smu deletions within ABC DLBCL tumor clones, which were accompanied by ongoing duplications and activation-induced cytidine deaminase-dependent somatic mutations. Unexpectedly, short fragments derived from multiple chromosomes were interspersed within Smu in one case. These findings suggest that ABC DLBCLs have abnormalities in the regulation of CSR that could predispose to chromosomal translocations. Accordingly, aberrant switch recombination was responsible for translocations in ABC DLBCLs involving BCL6, MYC, and a novel translocation partner, SPIB.

Appropriateness of some resampling-based inference procedures for assessing performance of prognostic classifiers derived from microarray data

The goal of many gene-expression microarray profiling clinical studies is to develop a multivariate classifier to predict patient disease outcome from a gene-expression profile measured on some biological specimen from the patient. Often some preliminary validation of the predictive power of a profile-based classifier is carried out using the same data set that was used to derive the classifier. Techniques such as cross-validation or bootstrapping can be used in this setting to assess predictive power, and if applied correctly, can result in a less biased estimate of predictive accuracy of a classifier. However, some investigators have attempted to apply standard statistical inference procedures to assess the statistical significance of associations between true and cross-validated predicted outcomes. We demonstrate in this paper that naïve application of standard statistical inference procedures to these measures of association under null situations can result in greatly inflated testing type I error rates. Under alternatives of small to moderate associations, confidence interval coverage probabilities may be too low, although for very large associations coverage probabilities approach their intended values. Our results suggest that caution should be exercised in interpreting some of the claims of exceptional prognostic classifier performance that have been reported in prominent biomedical journals in the past few years.

Molecular diagnosis of Burkitt's lymphoma

BACKGROUND

The distinction between Burkitt's lymphoma and diffuse large-B-cell lymphoma is crucial because these two types of lymphoma require different treatments. We examined whether gene-expression profiling could reliably distinguish Burkitt's lymphoma from diffuse large-B-cell lymphoma.

METHODS

Tumor-biopsy specimens from 303 patients with aggressive lymphomas were profiled for gene expression and were also classified according to morphology, immunohistochemistry, and detection of the t(8;14) c-myc translocation.

RESULTS

A classifier based on gene expression correctly identified all 25 pathologically verified cases of classic Burkitt's lymphoma. Burkitt's lymphoma was readily distinguished from diffuse large-B-cell lymphoma by the high level of expression of c-myc target genes, the expression of a subgroup of germinal-center B-cell genes, and the low level of expression of major-histocompatibility-complex class I genes and nuclear factor-kappaB target genes. Eight specimens with a pathological diagnosis of diffuse large-B-cell lymphoma had the typical gene-expression profile of Burkitt's lymphoma, suggesting they represent cases of Burkitt's lymphoma that are difficult to diagnose by current methods. Among 28 of the patients with a molecular diagnosis of Burkitt's lymphoma, the overall survival was superior among those who had received intensive chemotherapy regimens instead of lower-dose regimens.

CONCLUSIONS

Gene-expression profiling is an accurate, quantitative method for distinguishing Burkitt's lymphoma from diffuse large-B-cell lymphoma.

A random variance model for detection of differential gene expression in small microarray experiments

MOTIVATION

Microarray techniques provide a valuable way of characterizing the molecular nature of disease. Unfortunately expense and limited specimen availability often lead to studies with small sample sizes. This makes accurate estimation of variability difficult, since variance estimates made on a gene by gene basis will have few degrees of freedom, and the assumption that all genes share equal variance is unlikely to be true.

RESULTS

We propose a model by which the within gene variances are drawn from an inverse gamma distribution, whose parameters are estimated across all genes. This results in a test statistic that is a minor variation of those used in standard linear models. We demonstrate that the model assumptions are valid on experimental data, and that the model has more power than standard tests to pick up large changes in expression, while not increasing the rate of false positives.

AVAILABILITY

This method is incorporated into BRB-ArrayTools version 3.0 (http://linus.nci.nih.gov/BRB-ArrayTools.html).

SUPPLEMENTARY MATERIAL

ftp://linus.nci.nih.gov/pub/techreport/RVM_supplement.pdf

Bilateral fracture of the mandible in chronic lymphocytic leukaemia. Case report

The development of osteolytic bone lesions in patients with chronic lymphocytic leukaemia (CLL) is extremely rare and has not been reported to involve the mandible. A case of bilateral pathologic fracture of the mandible extensively involved with multiple bony deposits of CLL is reported.

A comparison of the mechanogram of the ankle jerk in men and women: observations using an adjustable dorsiflexing torque, high inertia mechanical filter and automatic readout system

An instrument of new design has been constructed to measure the contractions of the calf musculature resulting from a tap on the Achilles tendon. The instrument provides a predetermined and adjustable dorsiflexing torque from a printed motor, but the contractions are virtually isometric as the system is one of high inertia. Peak force, half-contraction time and half-relaxation time are monitored by electronic circuits equipped with digital output meters. Observations have been made on fifty-two male and forty-five female medical students. There were no significant differences in the peak torques generated by the contractions between the men and women students and no difference in the half-contraction times. The half-relaxation times of the women were, however, significantly longer than those of the men (P = 0.0001). In another group of students the EMG discharges following a tendon tap were recorded, there was no significant difference in the duration of the activity in men and women. Observations have also been made on twenty-three male and seventy female subjects whose mean ages were in the mid-sixties. The peak torques generated by the contractions were significantly higher in the women (P = 0.03). There was no difference in the half-contraction times, but the half-relaxation times of the women were significantly longer (P = 0.001). Possible reasons for the differences are discussed.

Neurophysiology of lower-limb function in hemiplegic children

Equinus in hemiplegic children is multifactorial. In some cases it is due to a short muscle, in others to simple foot-drop, tonic spasticity, rigidity, compensation for a short limb, fixed flexion contracture at the hip, dominantly inherited forefoot deformity, forefoot equinus secondary to chronic toe-walking, or abnormalities of the visco-elastic properties of the muscle, with true intramuscular contracture. This neurophysiological study confirms that hemiplegia in children is not a homogeneous condition. Some have tonic spasticity; some, although stiff, show electrical silence on stretching; some appear to have a short muscle, with no hypertonicity; and others have hypertonicity in relation to position (i.e. rigidity). A short muscle is not always associated with tonic spasticity with reciprocal inhibition. Weakness can occur without spasticity. Speed of movement of toes, ankle and hip is also significantly reduced.

The effects of neuromuscular stimulation on muscle tone at the knee in paraplegia

Resting muscle tone of the leg was measured in terms of thigh muscle stiffness and knee resonant frequency in muscles of spinal cord injured subjects who had been involved in an electrical neuromuscular stimulation training programme of the thigh muscles over at least 2 months. The thigh circumference of these patients was 6.6% larger than before training commenced (P less than 0.001) and showed increased muscle stiffness and resonant frequency compared to a similar group of paralysed subjects who had not used any neuromuscular stimulation. Resonant frequency and stiffness after the long-term training were similar to those of non-injured controls and therefore the stimulation programme seemed to reverse the effects of paralysis on muscle tone. Short periods of rest (30 min) caused increased muscle stiffness in non-injured controls and paralysed muscles trained by neuromuscular stimulation. Additional 15 min periods of neuromuscular stimulation further increased muscle stiffness in the trained muscles but also in the muscles of paralysed subjects who had no long-term neuromuscular training. In contrast, 15 min sessions of passive movement of the knee decreased muscle stiffness in long-term trained paralysed muscles and untrained paralysed muscles. Knee resonant frequency was also significantly decreased in the trained paralysed muscles. Results show that muscle tone varies depending on the amount of previous movement or rest and that although neuromuscular stimulation of paralysed muscles increases muscle stiffness and knee resonant frequency, it is in fact restoring such properties of the muscle to a state approaching that of non-injured controls.

Resonant frequency at the wrist in hypermobile women

The resonant frequency of the wrist has been measured in sixteen hypermobile and nine normal women at ten levels of peak torque. At the lowest level the results were identical but at the others the hypermobile values were lower. Damping and thixotropy appeared to be normal. In another group the grip strength of hypermobile subjects was similar to that of controls. The possibility that the connective tissue of the musculature of hypermobile subjects is of enhanced compliance is discussed.

Biodynamics of the ankle in spastic children--effect of chronic stretching of the calf musculature

The biodynamics of the feet of spastic children have been studied by estimating the resonant frequency using a printed motor to supply rhythmic torques. Changes induced when the muscles have been stretched by casting for four weeks are trivial or absent. The position of the feet, however, after the procedure became more nearly normal.

Purification of a cellular (granulocyte) and an extracellular (serum) phospholipase A2 that participate in the destruction of Escherichia coli in a rabbit inflammatory exudate

A granule-associated phospholipase A2 from rabbit polymorphonuclear leukocytes and a closely similar phospholipase A2 from rabbit serum have been purified to near homogeneity by ion-exchange and reverse-phase chromatography. The cellular (polymorphonuclear leukocyte) phospholipase A2 has been purified greater than 100,000-fold and the extracellular (serum) phospholipase A2 approximately 60,000-fold. The NH2-terminal amino acid sequence of the ascitic fluid phospholipase A2 that we have recently purified from inflammatory exudates produced in rabbits is nearly identical (15 of 16 residues) to that of the polymorphonuclear leukocyte phospholipase A2 and completely identical (19 of 19 residues) to that of the purified serum phospholipase A2. The functional properties of these three phospholipases A2 are indistinguishable. Each enzyme is active against Escherichia coli killed by the bactericidal/permeability-increasing protein of polymorphonuclear leukocyte, a property shared only by a subset of phospholipases A2. The presence of structurally and functionally very closely similar phospholipases A2 in the cellular and extracellular compartments of an inflammatory exudate is consistent with the apparent role of these enzymes in the destruction of certain microbial invaders during the acute inflammatory response.

Biodynamics of the wrist in rheumatoid arthritis--the enigma of stiffness

The wrist has been moved rhythmically in the horizontal plane by sinusoidal torques provided by a printed motor. Measurements have been made on normal subjects and subjects with rheumatoid arthritis. Both groups exhibited a resonance, the oscillations being greatest when the applied torque was of certain frequency. In both groups the resonant frequency fell to approximately the same constant value when the torque was raised. While the main relationships were similar a somewhat lower torque resulted in the lowering of resonant frequency in the patients. The relationship between applied torque and peak velocity at resonance was also studied. For a given torque the motion was greater in the patients. No objective signs of increased viscous or elastic stiffness were demonstrable at the wrist in patients with rheumatoid arthritis.

Muscle tone around the human knee in paraplegia

The thigh muscle tone of non-injured subjects and complete injury paraplegics has been investigated using torques, generated by a printed motor, to move the knee. The dynamic measure of resonant frequency (related to stiffness) together with a static measure of stiffness have shown the legs of non-injured subjects to respond non-linearly to decreasing torques. However, the complete paraplegics' legs did not respond non-linearly but showed constant resonant frequency and stiffness over the range of torques. Peak velocity at resonance (inversely related to damping) gradually increased with increasing torques in both groups. In addition, at a chosen baseline torque of 0.7 N m, resonant frequency and muscle stiffness were significantly lower and peak velocity significantly higher in the paraplegics compared to the non-injured subjects. Contrary to expectations the thigh muscles in established, complete paraplegia showed a lack of tonic EMG activity. In addition, whilst phasic stretch responses were occasionally seen there was no tonic activity in relation to continued stretch. Since muscles atrophy after paralysis, the smaller muscle bulk may contribute to the lower muscle tone.

Assessment of human hemiplegic spasticity by a resonant frequency method

The resonant frequency of the wrist has been measured in hemiplegic subjects and was higher on the spastic side, indicating greater stiffness. The increased stiffness is associated with stretch reflex activity, which is absent in normal subjects. The increased stiffness of spasticity in most of the patients did not exaggerate the sharpness of tuning as there was a compensatory rise in damping. Increased damping will contribute to the subjective assessment of muscular hypertonicity. Measurements of resonant frequency and damping are essential in assessing muscular hypertonicity.