Germinal center-specific protein human germinal center associated lymphoma directly interacts with both myosin and actin and increases the binding of myosin to actin

HGAL inhibits lymphoma dissemination by interacting with multiple Cytoskeletal proteins

In vivo experiments demonstrate that HGAL expression in lymphoma decreases tumor dissemination and prolongs animal survival.

HGAL inhibits cell motility by interacting with multiple cytoskeletal proteins, thereby affecting cell motility by multiple mechanisms.

Human germinal center–associated lymphoma (HGAL) is an adaptor protein specifically expressed in germinal center lymphocytes. High expression of HGAL is a predictor of prolonged survival of diffuse large B-cell lymphoma (DLBCL) and classic Hodgkin lymphoma. Furthermore, HGAL expression is associated with early-stage DLBCL, thus potentially limiting lymphoma dissemination. In our previous studies, we demonstrated that HGAL regulates B-cell receptor signaling and cell motility in vitro and deciphered some molecular mechanisms underlying these effects. By using novel animal models for in vivo DLBCL dispersion, we demonstrate here that HGAL decreases lymphoma dissemination and prolongs survival. Furthermore, by using an unbiased proteomic approach, we demonstrate that HGAL may interact with multiple cytoskeletal proteins thereby implicating a multiplicity of effects in regulating lymphoma motility and spread. Specifically, we show that HGAL interacts with tubulin, and this interaction may also contribute to HGAL effects on cell motility. These findings recapitulate previous observations in humans, establish the role of HGAL in dissemination of lymphoma in vivo, and explain improved survival of patients with HGAL-expressing lymphomas.

Transcriptome integration analysis and specific diagnosis model construction for Hodgkin's lymphoma, diffuse large B-cell lymphoma, and mantle cell lymphoma

Transcriptome differences between Hodgkin's lymphoma (HL), diffuse large B-cell lymphoma (DLBCL), and mantle cell lymphoma (MCL), which are all derived from B cell, remained unclear. This study aimed to construct lymphoma-specific diagnostic models by screening lymphoma marker genes. Transcriptome data of HL, DLBCL, and MCL were obtained from public databases. Lymphoma marker genes were screened by comparing cases and controls as well as the intergroup differences among lymphomas. A total of 9 HL marker genes, 7 DLBCL marker genes, and 4 MCL marker genes were screened in this study. Most HL marker genes were upregulated, whereas DLBCL and MCL marker genes were downregulated compared to controls. The optimal HL-specific diagnostic model contains one marker gene (MYH2) with an AUC of 0.901. The optimal DLBCL-specific diagnostic model contains 7 marker genes (LIPF, CCDC144B, PRO2964, PHF1, SFTPA2, NTS, and HP) with an AUC of 0.951. The optimal MCL-specific diagnostic model contains 3 marker genes (IGLV3-19, IGKV4-1, and PRB3) with an AUC of 0.843. The present study reveals the transcriptome data-based differences between HL, DLBCL, and MCL, when combined with other clinical markers, may help the clinical diagnosis and prognosis.

Conditional expression of HGAL leads to the development of diffuse large B-cell lymphoma in mice

Diffuse large B-cell lymphomas (DLBCLs) are clinically and genetically heterogeneous tumors. Deregulation of diverse biological processes specific to B cells, such as B-cell receptor (BCR) signaling and motility regulation, contribute to lymphomagenesis. Human germinal center associated lymphoma (HGAL) is a B-cell-specific adaptor protein controlling BCR signaling and B lymphocyte motility. In normal B cells, it is expressed in germinal center (GC) B lymphocytes and promptly downregulated upon further differentiation. The majority of DLBCL tumors, primarily GC B-cell types, but also activated types, express HGAL. To investigate the consequences of constitutive expression of HGAL in vivo, we generated mice that conditionally express human HGAL at different stages of hematopoietic development using 3 restricted Cre-mediated approaches to initiate expression of HGAL in hematopoietic stem cells, pro-B cells, or GC B cells. Following immune stimulation, we observed larger GCs in mice in which HGAL expression was initiated in GC B cells. All 3 mouse strains developed DLBCL at a frequency of 12% to 30% starting at age 13 months, leading to shorter survival. Immunohistochemical studies showed that all analyzed tumors were of the GC B-cell type. Exon sequencing revealed mutations reported in human DLBCL. Our data demonstrate that constitutive enforced expression of HGAL leads to DLBCL development.

Genomic Amplification and Functional Dependency of the Gamma Actin Gene ACTG1 in Uterine Cancer

Sarcomere and cytoskeleton genes, or actomyosin genes, regulate cell biology including mechanical stress, cell motility, and cell division. While actomyosin genes are recurrently dysregulated in cancers, their oncogenic roles have not been examined in a lineage-specific fashion. In this report, we investigated dysregulation of nine sarcomeric and cytoskeletal genes across 20 cancer lineages. We found that uterine cancers harbored the highest frequencies of amplification and overexpression of the gamma actin gene, ACTG1. Each of the four subtypes of uterine cancers, mixed endometrial carcinomas, serous carcinomas, endometroid carcinomas, and carcinosarcomas harbored between 5~20% of ACTG1 gene amplification or overexpression. Clinically, patients with ACTG1 gains had a poor prognosis. ACTG1 gains showed transcriptional patterns that reflect activation of oncogenic signals, repressed response to innate immunity, or immunotherapy. Functionally, the CRISPR-CAS9 gene deletion of ACTG1 had the most robust and consistent effects in uterine cancer cells relative to 20 other lineages. Overall, we propose that ACTG1 regulates the fitness of uterine cancer cells by modulating cell-intrinsic properties and the tumor microenvironment. In summary, the ACTG1 functions relative to other actomyosin genes support the notion that it is a potential biomarker and a target gene in uterine cancer precision therapies.

Interplay between HGAL and Grb2 proteins regulates B-cell receptor signaling

Human germinal center (GC)-associated lymphoma (HGAL) is an adaptor protein expressed in GC B cells. HGAL regulates cell motility and B-cell receptor (BCR) signaling, processes that are central for the successful completion of the GC reaction. Herein, we demonstrate phosphorylation of HGAL by Syk and Lyn kinases at tyrosines Y80, Y86, Y106Y107, Y128, and Y148. The HGAL YEN motif (amino acids 107-109) is similar to the phosphopeptide motif pYXN used as a binding site to the growth factor receptor-bound protein 2 (Grb2). We demonstrate by biochemical and molecular methodologies that HGAL directly interacts with Grb2. Concordantly, microscopy studies demonstrate HGAL-Grb2 colocalization in the membrane central supramolecular activation clusters (cSMAC) following BCR activation. Mutation of the HGAL putative binding site to Grb2 abrogates the interaction between these proteins. Further, this HGAL mutant localizes exclusively in the peripheral SMAC and decreases the rate and intensity of BCR accumulation in the cSMAC. Furthermore, we demonstrate that Grb2, HGAL, and Syk interact in the same complex, but Grb2 does not modulate the effects of HGAL on Syk kinase activity. Overall, the interplay between the HGAL and Grb2 regulates the magnitude of BCR signaling and synapse formation.

Cigarette Smoke Condensate Exposure Changes RNA Content of Extracellular Vesicles Released from Small Airway Epithelial Cells

Exposure to environmental tobacco smoke (ETS) is a known risk factor for the development of chronic lung diseases, cancer, and the exacerbation of viral infections. Extracellular vesicles (EVs) have been identified as novel mediators of cell–cell communication through the release of biological content. Few studies have investigated the composition/function of EVs derived from human airway epithelial cells (AECs) exposed to cigarette smoke condensate (CSC), as surrogates for ETS. Using novel high-throughput technologies, we identified a diverse range of small noncoding RNAs (sncRNAs), including microRNA (miRNAs), Piwi-interacting RNA (piRNAs), and transfer RNA (tRNAs) in EVs from control and CSC-treated SAE cells. CSC treatment resulted in significant changes in the EV content of miRNAs. A total of 289 miRNAs were identified, with five being significantly upregulated and three downregulated in CSC EVs. A total of 62 piRNAs were also detected in our EV preparations, with five significantly downregulated and two upregulated in CSC EVs. We used TargetScan and Gene Ontology (GO) analysis to predict the biological targets of hsa-miR-3913-5p, the most represented miRNA in CSC EVs. Understanding fingerprint molecules in EVs will increase our knowledge of the relationship between ETS exposure and lung disease, and might identify potential molecular targets for future treatments.

Analysis of human upstream open reading frames and impact on gene expression

The upstream open reading frame (uORF) is a post-transcriptional regulatory element in the 5' untranslated region (5'UTR), which modulates the translation levels of main open reading frame (mORF). Earlier studies showed that disturbed uORF-mediated translation control can result in drastic changes in translation levels of mORF, leading to genetic disorders. To date, there has been no systematic investigation into the relationship between variations in patients and uORF status. Here, taking the advantage of several datasets, including gene ontology (GO) annotations and sequence feature analysis, we have examined uORF impacts in human transcripts. GO annotations indicate that uORF-containing genes are enriched in certain features such as oncogenes and transcription factors. Sequence feature analysis reveals that uORF is a factor for determination of the translation initiation site (TIS) in human transcripts. We show that genes with uORFs have lower protein expression levels than genes without uORFs in multiple human tissues. Moreover, by examining three disease variation databases, we identified uORF-altering mutations from a total of 3,740,225 variations, which are highly suspected to be associated with changed levels of gene expression. For an experimental validation, we found four mutations with significant effects on protein expression but with only modest changes in transcription levels. These findings will provide researchers on related diseases with new insights into the importance of known mutations.

Gene expression profile analysis identifies metastasis and chemoresistance-associated genes in epithelial ovarian carcinoma cells

The purpose of this study was to identify genes that associated with higher ability of metastasis and chemotherapic resistance in epithelial ovarian carcinoma (EOC) cells. An oligonucleotide microarray with probe sets complementary to 41,000⁺ unique human genes and transcripts was used to determine whether gene expression profile may differentiate three epithelial ovarian cell lines (RMG-I-C, COC1 and HO8910) from their sub-lines (RMG-I-H, COCI/DDP and HO8910/PM) with higher ability of metastasis and chemotherapic resistance. Quantitative real-time PCR and immunohistochemical staining validated the microarray results. Hierarchic cluster analysis of gene expression identified 49 genes that exhibited ≥2.0-fold change and P value ≤0.05. Highly differential expression of GCET2, NLRP4, FOXP1 and SNX29 genes was validated by quantitative PCR in all cell line samples. Finally, FOXP1 was validated at the protein level by immunohistochemistry in paraffin embedded ovarian tissues (i.e., for metastasis, 15 primary EOC and 10 omental metastasis [OM]; for chemoresistance, 13 sensitive and 13 resistant EOC). The identification of higher ability of metastasis and chemotherapic resistance-associated genes may provide a foundation for the development of new type-specific diagnostic strategies and treatment for metastasis and chemotherapic resistance in epithelial ovarian cancer.

HGAL localization to cell membrane regulates B-cell receptor signaling

Human germinal center-associated lymphoma (HGAL) is specifically expressed only in germinal center (GC) B lymphocytes and GC-derived lymphomas. HGAL protein decreases lymphocyte motility by inhibiting the ability of myosin to translocate actin via direct interaction with F-actin and myosin II and by activating RhoA signaling via direct interactions with RhoA-specific guanine nucleotide exchange factors. HGAL protein also regulates B-cell receptor (BCR) signaling by directly binding to and enhancing Syk kinase activity and activation of its downstream effectors. Herein we demonstrate that HGAL protein can be myristoylated and palmitoylated and that these modifications localize HGAL to cellular membrane raft microdomains with distinct consequences for BCR signaling and chemoattractant-induced cell mobility. In BCR signaling, raft localization of HGAL facilitates interaction with Syk and modulation of the BCR activation and signaling, which induces HGAL phosphorylation and redistribution from lipid raft to bulk membrane and cytoplasm, followed by degradation. In contrast, HGAL myristoylation and palmitoylation avert its inhibitory effects on chemoattractant-induced cell motility. These findings further elucidate the growing and complex role of HGAL in B-cell biology and suggest that membrane-bound and cytoplasmic HGAL protein differently regulates distinct biological processes.

LMO2 and BCL6 are associated with improved survival in primary central nervous system lymphoma

Primary central nervous system lymphoma (PCNSL) is an aggressive sub-variant of non-Hodgkin lymphoma (NHL) with morphological similarities to diffuse large B-cell lymphoma (DLBCL). While methotrexate (MTX)-based therapies have improved patient survival, the disease remains incurable in most cases and its pathogenesis is poorly understood. We evaluated 69 cases of PCNSL for the expression of HGAL (also known as GCSAM), LMO2 and BCL6 - genes associated with DLBCL prognosis and pathobiology, and analysed their correlation to survival in 49 PCNSL patients receiving MTX-based therapy. We demonstrate that PCNSL expresses LMO2, HGAL(also known as GCSAM) and BCL6 proteins in 52%, 65% and 56% of tumours, respectively. BCL6 protein expression was associated with longer progression-free survival (P = 0·006) and overall survival (OS, P = 0·05), while expression of LMO2 protein was associated with longer OS (P = 0·027). Further research is needed to elucidate the function of BCL6 and LMO2 in PCNSL.

Germinal centre protein HGAL promotes lymphoid hyperplasia and amyloidosis via BCR-mediated Syk activation

The human germinal centre associated lymphoma (HGAL) gene is specifically expressed in germinal centre B-lymphocytes and germinal centre-derived B-cell lymphomas, but its function is largely unknown. Here we demonstrate that HGAL directly binds Syk in B-cells, increases its kinase activity upon B-cell receptor stimulation and leads to enhanced activation of Syk downstream effectors. To further investigate these findings in vivo, HGAL transgenic mice were generated. Starting from 12 months of age these mice developed polyclonal B-cell lymphoid hyperplasia, hypergammaglobulinemia and systemic reactive AA amyloidosis, leading to shortened survival. The lymphoid hyperplasia in the HGAL transgenic mice are likely attributable to enhanced B-cell receptor signalling as shown by increased Syk phosphorylation, ex vivo B-cell proliferation and increased RhoA activation. Overall, our study shows for the first time that the germinal centre protein HGAL regulates B-cell receptor signalling in B-lymphocytes which, without appropriate control, may lead to B-cell lymphoproliferation.

Discrete effects of A57G-myosin essential light chain mutation associated with familial hypertrophic cardiomyopathy

The functional consequences of the familial hypertrophic cardiomyopathy A57G (alanine-to-glycine) mutation in the myosin ventricular essential light chain (ELC) were assessed in vitro and in vivo using previously generated transgenic (Tg) mice expressing A57G-ELC mutant vs. wild-type (WT) of human cardiac ELC and in recombinant A57G- or WT-protein-exchanged porcine cardiac muscle strips. Compared with the Tg-WT, there was a significant increase in the Ca²⁺ sensitivity of force (ΔpCa₅₀ ≅ 0.1) and an ~1.3-fold decrease in maximal force per cross section of muscle observed in the mutant preparations. In addition, a significant increase in passive tension in response to stretch was monitored in Tg-A57G vs. Tg-WT strips indicating a mutation-induced myocardial stiffness. Consistently, the hearts of Tg-A57G mice demonstrated a high level of fibrosis and hypertrophy manifested by increased heart weight-to-body weight ratios and a decreased number of nuclei indicating an increase in the two-dimensional size of Tg-A57G vs. Tg-WT myocytes. Echocardiography examination showed a phenotype of eccentric hypertrophy in Tg-A57G mice, enhanced left ventricular (LV) cavity dimension without changes in LV posterior/anterior wall thickness. Invasive hemodynamics data revealed significantly increased end-systolic elastance, defined by the slope of the pressure-volume relationship, indicating a mutation-induced increase in cardiac contractility. Our results suggest that the A57G allele causes disease by means of a discrete modulation of myofilament function, increased Ca²⁺ sensitivity, and decreased maximal tension followed by compensatory hypertrophy and enhanced contractility. These and other contributing factors such as increased myocardial stiffness and fibrosis most likely activate cardiomyopathic signaling pathways leading to pathologic cardiac remodeling.

MicroRNAs and Glucocorticoid-Induced Apoptosis in Lymphoid Malignancies

The initial response of lymphoid malignancies to glucocorticoids (GCs) is a critical parameter predicting successful treatment. Although being known as a strong inducer of apoptosis in lymphoid cells for almost a century, the signaling pathways regulating the susceptibility of the cells to GCs are only partly revealed. There is still a need to develop clinical tests that can predict the outcome of GC therapy. In this paper, I discuss important parameters modulating the pro-apoptotic effects of GCs, with a specific emphasis on the microRNA world comprised of small players with big impacts. The journey through the multifaceted complexity of GC-induced apoptosis brings forth explanations for the differential treatment response and raises potential strategies for overcoming drug resistance.

Myosin regulatory light chain mutation found in hypertrophic cardiomyopathy patients increases isometric force production in transgenic mice

FHC (familial hypertrophic cardiomyopathy) is a heritable form of cardiac hypertrophy caused by mutations in genes encoding sarcomeric proteins. The present study focuses on the A13T mutation in the human ventricular myosin RLC (regulatory light chain) that is associated with a rare FHC variant defined by mid-ventricular obstruction and septal hypertrophy. We generated heart-specific Tg (transgenic) mice with ~10% of human A13T-RLC mutant replacing the endogenous mouse cardiac RLC. Histopathological examinations of longitudinal heart sections from Tg-A13T mice showed enlarged interventricular septa and profound fibrotic lesions compared with Tg-WT (wild-type), expressing the human ventricular RLC, or non-Tg mice. Functional studies revealed an abnormal A13T mutation-induced increase in isometric force production, no change in the force-pCa relationship and a decreased Vmax of the acto-myosin ATPase. In addition, a fluorescence-based assay showed a 3-fold lower binding affinity of the recombinant A13T mutant for the RLC-depleted porcine myosin compared with WT-RLC. These results suggest that the A13T mutation triggers a hypertrophic response through changes in cardiac sarcomere organization and myosin cross-bridge function leading to abnormal remodelling of the heart. The significant functional changes observed, despite a low level of A13T mutant incorporation into myofilaments, suggest a 'poison-peptide' mechanism of disease.

miR-155 regulates HGAL expression and increases lymphoma cell motility

HGAL, a prognostic biomarker in patients with diffuse large B-cell lymphoma and classic Hodgkin lymphoma, inhibits lymphocyte and lymphoma cell motility by activating the RhoA signaling cascade and interacting with actin and myosin proteins. Although HGAL expression is limited to germinal center (GC) lymphocytes and GC-derived lymphomas, little is known about its regulation. miR-155 is implicated in control of GC reaction and lymphomagenesis. We demonstrate that miR-155 directly down-regulates HGAL expression by binding to its 3'-untranslated region, leading to decreased RhoA activation and increased spontaneous and chemoattractant-induced lymphoma cell motility. The effects of miR-155 on RhoA activation and cell motility can be rescued by transfection of HGAL lacking the miR-155 binding site. This inhibitory effect of miR-155 suggests that it may have a key role in the loss of HGAL expression on differentiation of human GC B cells to plasma cell. Furthermore, this effect may contribute to lymphoma cell dissemination and aggressiveness, characteristic of activated B cell-like diffuse large B-cell lymphoma typically expressing high levels of miR-155 and lacking HGAL expression.

PRDM1/Blimp1 downregulates expression of germinal center genes LMO2 and HGAL

Human germinal center-associated lymphoma (HGAL) and LIM domain only-2 (LMO2) are proteins highly expressed in germinal center (GC) B lymphocytes. HGAL and LMO2 are also expressed in GC-derived lymphomas and distinguish biologically distinct subgroups of diffuse large B-cell lymphomas (DLBCL) associated with improved survival. However, little is known about their regulation. PRDM1/Blimp1 is a master regulator of terminal B cell differentiation and may also function as a tumor suppressor in the pathogenesis of DLBCL, where it is frequently inactivated by mutations and deletions. We now demonstrate that both HGAL and LMO2 are directly regulated by the transcription repressor PRDM1. In vivo studies demonstrate that PRDM1 directly binds to the recognition sites within the upstream promoters of both HGAL and LMO2. PRDM1 binding suppresses endogenous protein and mRNA levels of HGAL and LMO2. In addition, promoter analysis reveals that site-specific binding of PRDM1 to the promoters is capable of repressing transcriptional activity. This inhibitory effect of PRDM1 suggests that it has a key role in the loss of HGAL and LMO2 expression upon differentiation of GC B cells to plasma cells and may also contribute to absence of HGAL and LMO2 expression in post-GC lymphoid tumors.