Unknown,Transcriptomics,Genomics,Proteomics

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Identification of molecular mechanisms involved in pathogenesis of MALT lymphoma from small sample size

ABSTRACT: MALT lymphoma is characterized by t(11;18)(q21;q21)/API2-MALT1, t(1;14)(p22;q32)/BCL10-IGH and t(14;18)(q32;q21)/IGH-MALT1, which commonly activate the NF-ÎºB pathway. Gastric MALT lymphomas harboring such translocation do not respond to H. pylori eradication, while those without translocation can be cured by antibiotics. To understand the molecular mechanism of these different MALT lymphoma subgroups, we performed gene expression profiling analysis of 24 MALT lymphomas (15 translocation-positive, 9 translocation-negative). Gene set enrichment analysis (GSEA) of the NF-ÎºB target genes and 4394 additional gene sets covering various cellular pathways, biological processes and molecular functions showed that translocation-positive MALT lymphomas are characterized by an enhanced expression of NF-ÎºB target genes, particularly TLR6, CCR2, CD69 and BCL2, while translocation-negative cases were featured by active inflammatory and immune responses, such as IL8, CD86, CD28 and ICOS. Separate analyses of the genes differentially expressed between translocation-positive and negative cases and measurement of gene ontology term in these differentially expressed genes by hypergeometric test reinforced the above findings by GSEA. Finally, expression of TLR6, in the presence of TLR2, enhanced both API2-MALT1 and BCL10 mediated NF-ÎºB activation in vitro. Our findings provide novel insights into the molecular mechanism of MALT lymphomas with and without translocation, potentially explaining their different clinical behaviors. This study compares MALT with other lymphomas, namely follicular lymphomas (FL) and mantle cell lymphomas (MCL), and investigates the molecular mechanisms of the lymphomagenesis between translocation-positive versus -negative MALT lymphoma cases in order to derive the pathways leading to MALT lymphoma pathogenesis. The study uses fresh frozen tissues from 24 MALT lymphoma cases with 7 FL and 7 MCL. Samples were run on the HG-U133A, HG-U133B, and HG-U133 plus2 GeneChips.

ORGANISM(S): Homo sapiens

SUBMITTER: Christiane De Wolf-Peeters

PROVIDER: E-GEOD-16024 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:MALT lymphoma is characterized by t(11;18)(q21;q21)/API2-MALT1, t(1;14)(p22;q32)/BCL10-IGH and t(14;18)(q32;q21)/IGH-MALT1, which commonly activate the NF-κB pathway. Gastric MALT lymphomas harboring such translocation do not respond to H. pylori eradication, while those without translocation can be cured by antibiotics. To understand the molecular mechanism of these different MALT lymphoma subgroups, we performed gene expression profiling analysis of 24 MALT lymphomas (15 translocation-positive, 9 translocation-negative). Gene set enrichment analysis (GSEA) of the NF-κB target genes and 4394 additional gene sets covering various cellular pathways, biological processes and molecular functions showed that translocation-positive MALT lymphomas are characterized by an enhanced expression of NF-κB target genes, particularly TLR6, CCR2, CD69 and BCL2, while translocation-negative cases were featured by active inflammatory and immune responses, such as IL8, CD86, CD28 and ICOS. Separate analyses of the genes differentially expressed between translocation-positive and negative cases and measurement of gene ontology term in these differentially expressed genes by hypergeometric test reinforced the above findings by GSEA. Finally, expression of TLR6, in the presence of TLR2, enhanced both API2-MALT1 and BCL10 mediated NF-κB activation in vitro. Our findings provide novel insights into the molecular mechanism of MALT lymphomas with and without translocation, potentially explaining their different clinical behaviors. This study compares MALT with other lymphomas namely follicular and mantle cell lymphomas, and investigates the molecular mechanisms of the lymphomagenesis between translocation positive versus negative MALT lymphoma cases in order to derive the pathways leading to MALT lymphoma pathogenesis using GSEA, GO, dynamic pathway analysis as well as other bioinformatics analysis. Samples were run on the Affymetrix HG-U133A and HG-U133 plus2 GeneChips.

Project description:Proper regulation of nuclear factor κB (NF-κB) transcriptional activity is required for normal lymphocyte function, and deregulated NF-κB signaling can facilitate lymphomagenesis. We demonstrate that the API2-MALT1 fusion oncoprotein created by the recurrent t(11;18)(q21;q21) in mucosa-associated lymphoid tissue (MALT) lymphoma induces proteolytic cleavage of NF-κB–inducing kinase (NIK) at arginine 325. NIK cleavage requires the concerted actions of both fusion partners and generates a C-terminal NIK fragment that retains kinase activity and is resistant to proteasomal degradation. The resulting deregulated NIK activity is associated with constitutive noncanonical NF-κB signaling, enhanced B cell adhesion, and apoptosis resistance. Our study reveals the gain-of-function proteolytic activity of a fusion oncoprotein and highlights the importance of the noncanonical NF-κB pathway in B lymphoproliferative disease. This study compares nine t(11;18)-positive MALT lymphomas (8 from the stomach and 1 from lung) and eight translocation negative MALT lymphomas (all from the stomach) using gene set enrichment analysis (GSEA). All cases were subjected to Affymetrix U133A and U133B microarray analysis. The cases used in this study are the same cases used for the study by Hamoudi et al. (2010) entitled "Differential expression of NF-kB target genes in MALT lymphoma with and without chromosome translocation: insights into molecular mechanism" with GEO reference number: GSE18736 and PubMed ID: http://www.ncbi.nlm.nih.gov/pubmed/20520640 All cases were subjected to non-specific filtering to eliminate non-variant probes, then the U133A and U133B probes were collapsed and the collapsed set was subjected to GSEA using the NF-kB target gene set as described in Hamoudi et al. (2010) study mentioned above. The 34 samples in this study are identical to the ones done in the previous series except that the gene set enrichment was done on just those 34 samples and not the complete set.

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Identification of molecular mechanisms involved in pathogenesis of MALT lymphoma from small sample size

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