Mucosa-associated lymphoid tissue (MALT) lymphoma is specifically associated with t(11;18)(q21;q21), t(1;14)(p22;q32) and t(14;18)(q32;q21). t(11;18)(q21;q21) fuses the N-terminus of the API2 gene to the C-terminus of the MALT1 gene and generates a functional API2-MALT1 product. t(1;14)(p22;q32) and t(14;18)(q32;q21) bring the BCL10 and MALT1 genes respectively to the IGH locus and deregulate their expression. The oncogenic activity of the three chromosomal translocations is linked by the physiological role of BCL10 and MALT1 in antigen receptor-mediated NFkappaB activation. In this study, MALT1 and BCL10 expression was examined in normal lymphoid tissues and 423 cases of MALT lymphoma from eight sites, and their expression was correlated with the above translocations, which were detected by molecular and molecular cytogenetic methods. In normal B-cell follicles, both MALT1 and BCL10 were expressed predominantly in the cytoplasm, high in centroblasts, moderate in centrocytes and weak/negative in mantle zone B-cells. In MALT lymphoma, MALT1 and BCL10 expression varied among cases with different chromosomal translocations. In 9/9 MALT lymphomas with t(14;18)(q32;q21), tumour cells showed strong homogeneous cytoplasmic expression of both MALT1 and BCL10. In 12/12 cases with evidence of t(1;14)(p22;q32) or variants, tumour cells expressed MALT1 weakly in the cytoplasm but BCL10 strongly in the nuclei. In all 67 MALT lymphomas with t(11;18)(q21;q21), tumour cells expressed weak cytoplasmic MALT1 and moderate nuclear BCL10. In MALT lymphomas without the above translocations, both MALT1 and BCL10, in general, were expressed weakly in the cytoplasm. Real-time quantitative RT-PCR showed a good correlation between MALT1 and BCL10 mRNA expression and underlining genetic changes, with t(14;18)(q32;q21)- and t(1;14)(p22;q32)-positive cases displaying the highest MALT1 and BCL10 mRNA expression respectively. These results show that MALT1 expression pattern is identical to that of BCL10 in normal lymphoid tissues but varies in MALT lymphomas, with high cytoplasmic expression of both MALT1 and BCL10 characterizing those with t(14;18)(q32;q21).

Bcl10 plays an essential role in the adaptive immune response, because Bcl10-deficient lymphocytes show impaired Ag receptor-induced NF-κB activation and cytokine production. Bcl10 is a phosphoprotein, but the physiological relevance of this posttranslational modification remains poorly defined. In this study, we report that Bcl10 is rapidly phosphorylated upon activation of human T cells by PMA/ionomycin- or anti-CD3 treatment, and identify Ser138 as a key residue necessary for Bcl10 phosphorylation. We also show that a phosphorylation-deficient Ser138/Ala mutant specifically inhibits TCR-induced actin polymerization yet does not affect NF-κB activation. Moreover, silencing of Bcl10, but not of caspase recruitment domain-containing MAGUK protein-1 (Carma1) induces a clear defect in TCR-induced F-actin formation, cell spreading, and conjugate formation. Remarkably, Bcl10 silencing also impairs FcγR-induced actin polymerization and phagocytosis in human monocytes. These results point to a key role of Bcl10 in F-actin-dependent immune responses of T cells and monocytes/macrophages.

The most frequently recurring translocations in mucosa-associated lymphoid tissue (MALT) B-cell non-Hodgkin lymphoma, t(11;18)(q21;q21) and t(14;18)(q32; q21), lead to formation of an API2-MALT1 fusion or IgH-mediated MALT1 overexpression. Various approaches have implicated these proteins in nuclear factor B (NF- B IntroductionFour recurrent chromosomal translocations have been described in non-Hodgkin B-cell lymphoma of the mucosa-associated lymphoid tissue (MALT) type. Two of them, t(14;18)(q32;q21) and t(11; 18)(q21;q21), are found in 30% to 50% of extranodal MALT lymphomas. The former juxtaposes the MALT1 (MLT1 or paracaspase 1) gene to the IgH promoter region, resulting in the deregulation of MALT1 expression, whereas the latter creates a fusion between MALT1 and the inhibitor of apoptosis gene API2 (cIAP2/HIAP1). [1][2][3][4][5][6] Unlike the low-grade indolent MALT lymphomas that are dependent on the continuous presence of Helicobacter pylori, MALT lymphomas with translocations targeting the MALT1 gene can be found in cases without H pylori and are refractory to treatment against H pylori. 7,8 The other 2 much rarer translocations, t(1;14)(p22;q32) and t(1;2)(p22;p12), target the BCL10 gene on the short arm of chromosome 1. 9,10 MALT1 was independently identified as a member of the human paracaspase family and an interacting partner of B-cell lymphoma 10 (BCL10). 11 In vitro, MALT1 synergizes with BCL10 to enhance nuclear factor B activation, 12 and the association of the 2 proteins has been shown to mediate IB kinase (IKK) activation by facilitating the ubiquitinylation of the NF-B essential modulator (NEMO) by the ubiquitin-conjugating enzyme UBC13. 13 BCL10 also interacts with a group of proteins that contain an N-terminal caspase recruitment domain (CARD) domain and show overall structural homology to MAGUK (membrane-associated guanylate kinase) proteins. 14-17 These proteins were subsequently termed CARMA (CARD-containing MAGUK) proteins, of which CARMA1 (CARD11) expression is predominantly lymphoid specific. It has been shown recently that MALT1 not only interacts with BCL10 directly but also associates with CARMA1, suggesting that a complex containing MALT1, CARMA1, and BCL10 plays an important role in lymphoid cell signaling. 18 The critical function of MALT1 in lymphocyte signaling has been revealed by the analyses of MALT1-deficient mice, 19,20 whose T cells fail to proliferate in response to CD3/CD28 costimulation or to phorbol myristate acetate (PMA) and ionomycin. Similarly, B cells of MALT1 Ϫ/Ϫ mice fail to proliferate in response to immunoglobulin M (IgM), CD40, or lipopolysaccharide (LPS) stimulation. The lymphoid compartments of these mice showed severe reduction of marginal zone B cells and a lack of germinal center formation in spleens, as well as deregulated maturation of T-cell subsets in the thymus. The phenotype of MALT1-deficient mice closely resembles that of mice lacking Bcl10, in particular with respect to the lack of marginal zone B cells, and in the lack of response to T-a...

Immuno-oncology is an ever growing field that has seen important progress across the spectrum of cancers. Responses can be deep and durable. However, as only a minority of patients respond to checkpoint inhibition, predictive biomarkers are needed. Cancer is a genetic disease arising from the accumulation of somatic mutations in the DNA of affected cells. Tumor mutational burden (TMB), represents the number of somatic mutations in a tumor that form neoantigens, responsible for the immunogenicity of tumors. Randomized controlled trials have so far failed to show a survival benefit when stratifying patients by tissue TMB. TMB has also been evaluated in plasma (PTMB). PTMB is anticipated to represent the biology of the entire cancer, whereas obtaining tissue of an amenable primary or a metastatic lesion may be prone to sampling bias because of tumor heterogeneity. For this reason, we are evaluating the correlation between TMB and PTMB, and prospectively evaluating the impact of these biomarkers on clinical outcomes. We also discuss the technical difficulties inherent to performing and comparing these analyses. Furthermore, we evaluate the correlation between the evolution of PTMB during an immunotherapy treatment and response at 3 and 6 months, as we believe PTMB may be a dynamic biomarker. In this paper, we present results from the first 4 patients in this project.