RESUMO
Gene expression profiling has identified two major molecular subtypes of diffuse large B-cell lymphoma (DLBCL) that are histologically indistinguishable but differ in cure rates. Here, we investigated whether the isotype of the B-cell receptor (BCR) expressed by the tumoral cells correlated with the molecular subtype and survival. Gene expression analysis clustered the 53 patients included in this study into three subgroups, 17 germinal center B-cell-like (GCB) cases, 26 activated B-cell-like (ABC) cases and 10 intermediate cases. The molecular subtype was correlated with the isotype, as 15/17 GCB cases expressed a secondary isotype (immunoglobulin (Ig)G or IgA), whereas 24/26 ABC cases expressed a primary isotype (IgM or IgD) (P<0.0001). There was a trend toward a worse outcome for patients with an ABC DLBCL and a shorter overall survival for patients with IgM+ tumor (P=0.21 and 0.014, respectively). Finally, fluorescence in situ hybridization (FISH) analysis revealed a striking asymmetric pattern, as the IGHM gene is conserved only on the productive IGH allele in most IgM+ tumors. Taken together, these data indicate that the isotype of the BCR is a reliable indicator for the GCB and ABC subtypes in DLBCL, and suggest that the conservation of an IgM is required for ABC DLBCL lymphomagenesis to occur.
Assuntos
Linfócitos B/patologia , Centro Germinativo/patologia , Linfoma Difuso de Grandes Células B/classificação , Linfoma Difuso de Grandes Células B/genética , Receptores de Antígenos de Linfócitos B/genética , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Biomarcadores Tumorais/genética , Biomarcadores Tumorais/metabolismo , Feminino , Perfilação da Expressão Gênica , Humanos , Técnicas Imunoenzimáticas , Cadeias Pesadas de Imunoglobulinas/genética , Imunoglobulina M/genética , Hibridização in Situ Fluorescente , Masculino , Pessoa de Meia-Idade , Análise de Sequência com Séries de Oligonucleotídeos , RNA Mensageiro/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Taxa de SobrevidaRESUMO
CD4+CD56+ haematodermic neoplasms (HDN) constitute a rare disease characterized by aggressive clinical behaviour and a poor prognosis. Tumour cells from HDN are leukaemic counterparts of plasmacytoid dendritic cells (pDCs). Despite increased knowledge of the ontogenetic origin of these tumours, the genetic causes and oncogenic signalling events involved in malignant transformation are still unknown. To delineate novel candidate regions and disease-related genes, we studied nine typical CD4+CD56+ HDN cases using genome-wide high-resolution array comparative genomic hybridization (CGH). Genomic imbalances, which were predominantly losses, were frequently detected. Gross genomic losses or gains involving an entire chromosome were observed in eight cases. The most frequent imbalances were deletions of chromosome 9, chromosome 13 and partial losses affecting 17p or 12p. Combinations of deletions of tumour suppressor genes (TSG), namely RB1, CDKN1B (p27), CDKN2A, (p16(ink4a), p14(arf)) or TP53 (p53), were observed in all cases. These results indicate that deletion events altering G1/S regulation are crucial for HDN oncogenesis. Furthermore, in addition to frequent sporadic gene losses, in one case we observed a 8q24 interstitial deletion that brought MYC closer to miR-30b/miR-30d, which may be related to their deregulation. Taken together, these results indicate that in addition to frequent G1/S checkpoint alterations, various genetic events could contribute to the chemoresistance of the tumour.
