Protease activity of the API2-MALT1 fusion oncoprotein in MALT lymphoma development and treatment

The Multifaceted Role and Utility of MicroRNAs in Indolent B-Cell Non-Hodgkin Lymphomas

Normal B-cell development is a tightly regulated complex procedure, the deregulation of which can lead to lymphomagenesis. One common group of blood cancers is the B-cell non-Hodgkin lymphomas (NHLs), which can be categorized according to the proliferation and spread rate of cancer cells into indolent and aggressive ones. The most frequent indolent B-cell NHLs are follicular lymphoma and marginal zone lymphoma. MicroRNAs (miRNAs) are small non-coding RNAs that can greatly influence protein expression. Based on the multiple interactions among miRNAs and their targets, complex networks of gene expression regulation emerge, which normally are essential for proper B-cell development. Multiple miRNAs have been associated with B-cell lymphomas, as the deregulation of these complex networks can lead to such pathological states. The aim of the present review is to summarize the existing information regarding the multifaceted role of miRNAs in indolent B-cell NHLs, affecting the main B-cell subpopulations. We attempt to provide insight into their biological function, the complex miRNA-mRNA interactions, and their biomarker utility in these malignancies. Lastly, we address the limitations that hinder the investigation of the role of miRNAs in these lymphomas and discuss ways that these problems could be overcome in the future.

Canonical and Non-Canonical Roles of GRK2 in Lymphocytes

G protein-coupled receptor kinase 2 (GRK2) is emerging as a key integrative signaling node in a variety of biological processes ranging from cell growth and proliferation to migration and chemotaxis. As such, GRK2 is now implicated as playing a role in the molecular pathogenesis of a broad group of diseases including heart failure, cancer, depression, neurodegenerative disease, and others. In addition to its long-known canonical role in the phosphorylation and desensitization of G protein-coupled receptors (GPCRs), recent studies have shown that GRK2 also modulates a diverse array of other molecular processes via newly identified GRK2 kinase substrates and via a growing number of protein-protein interaction binding partners. GRK2 belongs to the 7-member GRK family. It is a multidomain protein containing a specific N-terminal region (referred to as αN), followed by a regulator of G protein signaling homology (RH) domain, an AGC (Protein kinase A, G, C serine/threonine kinase family) kinase domain, and a C-terminal pleckstrin homology (PH) domain. GPCRs mediate the activity of many regulators of the immune system such as chemokines and leukotrienes, and thus GRK proteins may play key roles in modulating the lymphocyte response to these factors. As one of the predominant GRK family members expressed in immune cells, GRK2's canonical and noncanonical actions play an especially significant role in normal immune cell function as well as in the development and progression of disorders of the immune system. This review summarizes our current state of knowledge of the roles of GRK2 in lymphocytes. We highlight the diverse functions of GRK2 and discuss how ongoing investigation of GRK2 in lymphocytes may inform the development of new therapies for diseases associated with lymphocyte dysregulation.

Holding All the CARDs: How MALT1 Controls CARMA/CARD-Dependent Signaling

The scaffold proteins CARMA1-3 (encoded by the genes CARD11, -14 and -10) and CARD9 play major roles in signaling downstream of receptors with immunoreceptor tyrosine activation motifs (ITAMs), G-protein coupled receptors (GPCR) and receptor tyrosine kinases (RTK). These receptors trigger the formation of oligomeric CARMA/CARD-BCL10-MALT1 (CBM) complexes via kinases of the PKC family. The CBM in turn regulates gene expression by the activation of NF-κB and AP-1 transcription factors and controls transcript stability. The paracaspase MALT1 is the only CBM component having an enzymatic (proteolytic) activity and has therefore recently gained attention as a potential drug target. Here we review recent advances in the understanding of the molecular function of the protease MALT1 and summarize how MALT1 scaffold and protease function contribute to the transmission of CBM signals. Finally, we will highlight how dysregulation of MALT1 function can cause pathologies such as immunodeficiency, autoimmunity, psoriasis, and cancer.

First-line antibiotic therapy in Helicobacter pylori-negative low-grade gastric mucosa-associated lymphoid tissue lymphoma

First-line antibiotic treatment for eradicating Helicobacter pylori (HP) infection is effective in HP-positive low-grade gastric mucosa-associated lymphoid tissue lymphoma (MALToma), but its role in HP-negative cases is uncertain. In this exploratory retrospective study, we assessed the outcome and potential predictive biomarkers for 25 patients with HP-negative localized gastric MALToma who received first-line HP eradication (HPE) therapy. An HP-negative status was defined as negative results on histology, rapid urease test, 13C urea breath test, and serology. We observed an antibiotic response (complete remission [CR], number = 8; partial remission, number = 1) in 9 (36.0%) out of 25 patients. A t(11;18)(q21;q21) translocation was detected in 7 (43.8%) of 16 antibiotic-unresponsive cases, but in none of the 9 antibiotic-responsive cases (P = 0.027). Nuclear BCL10 expression was significantly higher in antibiotic-unresponsive tumors than in antibiotic-responsive tumors (14/16 [87.5%] vs. 1/9 [11.1%]; P = 0.001). Nuclear NF-κB expression was also significantly higher in antibiotic-unresponsive tumors than in antibiotic-responsive tumors (12/16 [75.0%] vs. 1/9 [11.1%]; P = 0.004). A substantial portion of patients with HP-negative gastric MALToma responded to first-line HPE. In addition to t(11;18)(q21;q21), BCL10 and NF-κB are useful immunohistochemical biomarkers to predict antibiotic-unresponsive status in this group of tumors.

MALT1 promotes melanoma progression through JNK/c-Jun signaling

Mucosa-associated lymphoma antigen 1 (MALT1) is a lymphoma oncogene that regulates signal transduction as a paracaspase and an adaptor protein. Yet, the role of MALT1 in other solid cancers such as melanoma is not well-understood. Here, we demonstrate that MALT1 is overexpressed in malignant melanoma cells, and predicts a poor disease-free survival. MALT1 inhibition via shRNA-mediated gene silencing or pharmacologically with MI-2 compound markedly reduced cell growth and migration of A2058 and A375 melanoma cell lines in vitro. Subcutaneous tumor growth analysis revealed that MALT1 gene silencing significantly reduced tumor growth and metastasis to the lung. Consistently, the subcutaneous tumors with MALT1 loss had increased cell apoptosis and decreased proliferation. In addition, these tumors showed signs of mesenchymal–epithelial transition as indicated by the upregulation of E-cadherin and downregulation of N-cadherin and β1-intergrin. Further molecular analysis revealed that MALT1 is required for c-Jun and nuclear factor-κB (NF-κB) activation by tumor necrosis factor-α. Forced expression of the c-Jun upstream activator MKK7 reversed the cell growth and migration defects caused by MALT1 loss. In contrast, NF-κB activation via expression of p65ER, a fusion protein containing NF-κB p65 and the tamoxifen-responsive mutant estrogen receptor, induced minimal effects on cell proliferation, but diminished cell death induced by MALT1 loss and TRAIL treatment. Together, these findings demonstrate that MALT1 promotes melanoma cell proliferation and motility through JNK/c-Jun, and enhances melanoma cell survival through NF-κB, underscoring MALT1 as a potential therapeutic target and biomarker for malignant melanoma.

Exploring the interplay between autoimmunity and cancer to find the target therapeutic hotspots

Autoimmunity arises when highly active immune responses are developed against the tissues or substances of one's own body. It is one of the most prevalent disorders among the old-age population with prospects increasing with age. The major cause of autoimmunity and associated diseases is the dysregulation of host immune surveillance. Impaired repairment of immune system and apoptosis regulation can be seen as major landmarks in autoimmune disorders such as the mutation of p53 gene which results in rheumatoid arthritis, bowel disease which consequently lead to tissue destruction, inflammation and dysfunctioning of body organs. Cytokines mediated apoptosis and proliferation of cells plays a regulatory role in cell cycle and further in cancer development. Anti-TNF therapy, Treg therapy and stem cell therapy have been used for autoimmune diseases, however, with the increase in the use of immunomodulatory therapies and their development for autoimmune diseases and cancer, the understanding of human immune system tends to become an increasing requirement. Hence, the findings associated with the relationship between autoimmune diseases and cancer may prove to be beneficial for the improvement in the health of suffering patients. Here in, we are eliciting the underlying mechanisms which result in autoimmune disorders causing the onset of cancer, exploration of interactome to find the pathways which are mutual to both, and recognition of hotspots which might play important role in autoimmunity mediated therapeutics with different therapies such as anti-TNF therapy, Treg therapy and stem cell therapy.

The B-cell-activating factor signalling pathway is associated with Helicobacter pylori independence in gastric mucosa-associated lymphoid tissue lymphoma without t(11;18)(q21;q21)

We previously reported that activation of the B-cell-activating factor (BAFF) pathway upregulates nuclear factor-κB (NF-κB) and induces BCL3 and BCL10 nuclear translocation in Helicobacter pylori (HP)-independent gastric diffuse large B-cell lymphoma (DLBCL) tumours with evidence of mucosa-associated lymphoid tissue (MALT). However, the significance of BAFF expression in HP independence of gastric low-grade MALT lymphomas without t(11;18)(q21;q21) remains unexplored. Sixty-four patients who underwent successful HP eradication for localized HP-positive gastric MALT lymphomas without t(11;18)(q21;q21) were studied. BAFF expression was significantly higher in the HP-independent group than in the HP-dependent group [22/26 (84.6%) versus 8/38 (21.1%); p < 0.001]. Similarly, BAFF receptor (BAFF-R) expression (p = 0.004) and nuclear BCL3 (p = 0.004), BCL10 (p < 0.001), NF-κB (p65) (p = 0.001) and NF-κB (p52) (p = 0.005) expression were closely correlated with the HP independence of these tumours. Moreover, BAFF overexpression was significantly associated with BAFF-R expression and nuclear BCL3, BCL10, NF-κB (p65) and NF-κB (p52) expression. These findings were further validated in an independent cohort, including 40 HP-dependent cases and 18 HP-independent cases of gastric MALT lymphoma without t(11;18)(q21;q21). The biological significance of BAFF signalling in t(11;18)(q21;q21)-negative lymphoma cells was further studied in two types of lymphoma B cell: OCI-Ly3 [non-germinal centre B-cell origin DLBCL without t(11;18)(q21;q21) cell line] and MA-1 [t(14;18)(q32;q21)/IGH-MALT1-positive DLBCL cell line]. In both cell lines, we found that BAFF activated the canonical NF-κB and AKT pathways, and induced the formation of BCL10-BCL3 complexes, which translocated to the nucleus. BCL10 and BCL3 nuclear translocation and NF-κB (p65) transactivation were inhibited by either LY294002 or by silencing BCL3 or BCL10 with small interfering RNA. BAFF also activated non-canonical NF-κB pathways (p52) through tumour necrosis factor receptor-associated factor 3 degradation, NF-κB-inducing kinase accumulation, inhibitor of κB kinase (IKK) α/β phosphorylation and NF-κB p100 processing in both cell lines. Our data indicate that the autocrine BAFF signal transduction pathway contributes to HP independence in gastric MALT lymphomas without the t(11;18)(q21;q21) translocation. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

BIRC3 single nucleotide polymorphism associate with asthma susceptibility and the abundance of eosinophils and neutrophils

BACKGROUND AND OBJECTIVE

Aberrant apoptosis is a disease susceptibility mechanism relevant for asthma, whereby fragility of the airway epithelium and enhanced survival of inflammatory cells, contributes to its pathogenesis and prolongation. Cellular Inhibitor of Apoptosis Proteins (cIAP) suppress apoptosis, and participate in the immune response. In this study, single nucleotide polymorphisms (SNP) in the BIRC2 (codes cIAP1) and BIRC3 (cIAP2) genes were evaluated for an association with asthma.

METHODS

Caucasian asthmatic (n = 203) and control (n = 198) subjects were selected from participants in the North West Adelaide Health Study. SNPs (n = 9) spanning the consecutively positioned BIRC2 and BIRC3 genes, were selected using a haplotype tagging approach. Alleles and haplotype associations were analysed by logistic regression, assuming an additive genetic model, and adjusted for gender and atopy.

RESULTS

The frequency of the minor allele for the BIRC3 SNP rs3460 was significantly lower in asthmatics compared to the control cases (P = 0.046). BIRC3 SNPs rs7928663 and rs7127583 associated with a reduction in eosinophil and neutrophil abundance when assessed across the study population (multivariate P values = 0.002, and 0.005, respectively). Further, the frequency of a haplotype tagged by rs3460, rs7928663 and rs7127583 was reduced in the asthma sub group (P = 0.05), while the presence of the major allele for rs7928663 associated with an increased load of circulating eosinophils and neutrophils (multivariate P value = 0.001).

CONCLUSIONS

Polymorphisms in the BIRC3 gene, but not BIRC2, are associated with a protective effect with regards to asthma susceptibility, and a reduced load of inflammatory cells.

MALT1-ubiquitination triggers non-genomic NF-κB/IKK signaling upon platelet activation

We have recently shown that IKK complex plays an important non-genomic role in platelet function, i.e., regulates SNARE machinery-dependent membrane fusion. In this connection, it is well known that MALT1, whose activity is modulated by proteasome, plays an important role in the regulation of IKK complex. Therefore, the present studies investigated the mechanism by which IKK signaling is regulated in the context of the platelet proteasome. It was found that platelets express a functional proteasome, and form CARMA/MALT1/Bcl10 (CBM) complex when activated. Using a pharmacological inhibitor, the proteasome was found to regulate platelet function (aggregation, integrin activation, secretion, phosphatidylserine exposure and changes in intracellular calcium). It was also found to regulate thrombogenesis and physiologic hemostasis. We also observed, upon platelet activation, that MALT1 is ubiquitinated, and this coincides with the activation of the IKK/NF-κB-signaling pathway. Finally, we observed that the proteasome inhibitor blocks CBM complex formation and the interaction of IKKγ and MALT1; abrogates SNARE formation, and the association of MALT1 with TAK1 and TAB2, which are upstream of the CBM complex. Thus, our data demonstrate that MALT1 ubiquitination is critical for the engagement of CBM and IKK complexes, thereby directing platelet signals to the NF-κB pathway.

Systematic detection of noncanonical NF-κB activation

In unstimulated cells, NF-κB dimers usually exist as latent complexes in the cytoplasm with the IκB (inhibitor of NF-κB) proteins or IκB-like protein p100, the precursor of NF-κB2 mature form p52. Accordingly, there are two major mechanisms leading to NF-κB activation: inducible degradation of IκBs and processing of p100 to generate p52 (selective degradation of the C-terminal IκB-like sequence of p100), which are termed the canonical and noncanonical NF-κB pathways, respectively. While activation of the canonical NF-κB pathway plays critical roles in a wide range of biological processes, the noncanonical NF-κB pathway has important but more restricted roles in both normal and pathological processes. Systematic detection of the noncanonical NF-κB pathway activation is very important for understanding the physiological role of this pathway in biological processes, and for the diagnosis, prevention, and treatment of related diseases. We describe here the methods we employ to detect noncanonical NF-κB activation in cells and tissues. These methods are immunoblotting, co-immunoprecipitation, immunofluorescence, immunohistochemistry, chromatin immunoprecipitation (ChIP) analysis, and electrophoretic mobility shift assay (EMSA). Noncanonical NF-κB-induced gene expression changes can be determined by gene array analysis and quantitative real-time PCR.

MALT1 paracaspase: a unique protease involved in B-cell lymphomagenesis

SUMMARY MALT1 is a key regulator of adaptive immunity. MALT1-dependent signaling events control survival, proliferation and differentiation of lymphocytes in response to T- or B-cell receptor stimulation. MALT1 not only regulates physiological lymphocyte activation, but also controls oncogenic signaling in distinct lymphoid malignancies. The fusion protein API2–MALT1 generated by the chromosomal translocation t(11;18) acts as an oncoprotein in the late stages of mucosa-associated lymphoid tissue lymphoma. Moreover, MALT1 is critical for survival and proliferation of the activated B-cell type of diffuse large B-cell lymphomas, one of the most aggressive entities of malignant lymphomas. On the molecular level, MALT1 serves a dual role by functioning as a signaling adaptor and a protease. Both of these functions are critical for triggering the adaptive immune response and for promoting lymphomagenesis. Recent data emphasize that MALT1 is a promising drug target for the treatment of aggressive lymphomas.

Development of Bullous Disease during Treatment of Pulmonary Marginal Zone B-Cell Lymphoma

We describe an unusual case of severe pulmonary bullous disease developing during treatment of marginal zone B-Cell lymphoma (MALT) involving the pulmonary parenchyma. The patient originally presented with pneumonia-like symptoms along with hemoptysis and was diagnosed with MALT lymphoma after a video-assisted thoracic surgical (VATS) lung biopsy. Computed tomography (CT) of the chest at diagnosis revealed multiple opacities, but no bullous disease. During the ensuing 4 years, and while on chemotherapy for the MALT lymphoma, sequential CT and pulmonary function tests revealed the development of progressive bullous disease resulting in the replacement of large portions of the lung parenchyma with bilateral bullae. This complication is rare, has been reported only once before in a patient with concomitant amyloidosis, and may be related to activation of proteolytic enzymes by lymphoma cells or chemotherapeutic agents.