[Acquired somatic mutations in non-coding region of bcl-6 gene in germinal center-type diffuse large B-cell lymphoma].

Objective To investigate the mutation of 5' non-coding region of bcl-6 gene in germinal center B-cell (GCB)subtype of diffuse large B-cell lymphoma(DLBCL). Methods t(14;18) detection and immunohistochemical staining (EnVision method) were performed in 60 cases of DLBCL, which were divided into GCB and non-GCB subtypes. Polymerase chain reaction (PCR) , single-strand conformation polymorphism and direct DNA sequencing were used to identify mutations in the 5' non-coding region of the bcl-6 gene. Results Seven of 60 cases showed t(14;18) translocation in the major breakpoint region. Using minimally acceptable criteria, 18 of 60 cases were probably to be germinal centre derived. Bcl-6 mutations were detected in 12 of 60 cases (20. 0%) of DLBCL, with a significantly higher frequency in the GCBsubgroups (7/18) than in the non-GCB subgroups (11.9%, 5/42) . Bcl-6 mutations occurred most frequently in + 363 and + 469 sites. An association of bcl-6 mutation and GCB subgroup was obtained.Conclusions The 5' regulatory region of the bcl-6 gene underwent less frequent somatic hypermutation during lymphomagenesis than the results of previous reports. Bcl-6 mutation occurred mostly in the GCBsubtype and detection of t(14 ;18) seems helpful in the classification of DLBCL. Key words: Lymphoma,large-cell, diffuse;  Germinal center;  Proto-oncogene proteins c-bcl-6; Translocation, genetic;  Mutation