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High-throughput sequencing analysis of the chromosome 7q32 deletion reveals IRF5 as a potential tumour suppressor in splenic marginal-zone lymphoma

Autores: Fresquet Arnau, Vicente José; Robles Cortes, Eloy Francisco; Parker, A.; Martínez-Useros, J.; Mena, M.; Malumbres, R.; Aguirre Ena, Xabier; Catarino, S.; Arteta, D.; Osaba, L.; Mollejo, M.; Hernández-Rivas, J. M.; Calasanz Abinzano, María José; Daibata, M.; Dyer, M. J.; Prosper Cardoso, Felipe; Vizcarra, E.; Piris, M. A.; Oscier, D.; Martínez Climent, José Ángel
ISSN: 0007-1048
Volumen: 158
Número: 6
Páginas: 712 - 726
Fecha de publicación: 2012
Using high-resolution genomic microarray analysis, a distinct genomic profile was defined in 114 samples from patients with splenic marginal zone lymphoma (SMZL). Deletion or uniparental disomy of chromosome 7q were detected in 42 of 114 (37%) SMZLs but in only nine of 170 (5%) mature B-cell lymphomas (P < 0·00001). The presence of unmutated IGHV, genomic complexity, 17p13-TP53 deletion and 8q-MYC gain, but not 7q deletion, correlated with shorter overall survival of SMZL patients. Mapping studies narrowed down a commonly deleted region of 2·7 Mb in 7q32.1-q32.2 spanning a region between the SND1 and COPG2 genes. High-throughput sequencing analysis of the 7q32-deleted segment did not identify biallelic deletions/insertions or clear pathogenic gene mutations, but detected six nucleotide changes in IRF5 (n = 2), TMEM209 (n = 2), CALU (n = 1) and ZC3HC1 (n = 1) not found in healthy individuals. Comparative expression analysis found a fourfold down-regulation of IRF5 gene in lymphomas with 7q32 deletion versus non-deleted tumours (P = 0·032). Ectopic expression of IRF5 in marginal-zone lymphoma cells decreased proliferation and increased apoptosis in vitro, and impaired lymphoma development in vivo. These results show that cryptic deletions, insertions and/or point mutations inactivating genes within 7q32 are not common in SMZL, and suggest that IRF5 may be a haploinsufficient tumour suppressor in this lymphoma entity.