A Novel Non-Immunoglobulin (non-Ig)/BCL6 Translocation in Diffuse Large B-Cell Lymphoma Involving Chromosome 10q11.21 Loci and Review on Clinical Consequences of BCL6 Rearrangements

BCL6 rearrangements (3q27) are the most common chromosomal abnormalities in diffuse large B-cell lymphoma (DLBCL), with numerous immunoglobulin (Ig) and non-Ig genes as partners. In DLBCL, the translocations occur predominantly in the "major breakpoint region" encompassing the first noncoding exon and a part of the first intron of BCL6; few cases with "alternative breakpoint cluster" located 245285 kb 5' BCL6 were also described. The regulatory sequences of known Ig and non-Ig partners replace the 5' untranslated region of the BCL6 in the same transcriptional orientation. Contrary to Ig/BCL6 fusions typical by high BCL6 gene expression, in non-Ig/BCL6 translocations were observed unexpectedly low BCL6 mRNA levels. From the clinical point of view, the survival rate of DLBCL patients with non-Ig partners is inferior to those with Ig/BCL6 translocations, suggesting that non-Ig/BCL6 fusion is a poor prognostic indicator. Hereby we provide comprehensive information about known non-Ig translocation partners and clinical consequences of BCL6 rearrangements in DLBCL. Moreover, we describe a novel reciprocal translocation t(3;10) in refractory patient with DLBCL with the breaking points at 5' untranslated region of BCL6 and 5' untranslated region of the RASGEF1A gene on chromosome 10q11.21 loci; this rearrangement was associated with low BCL6 and RASGEF1A gene expressions. Our patient harbouring dual chromosomal rearrangement involving BCL2 and BCL6 genes relapsed three-times and died soon; thus, further supporting the notion that non-Ig/BCL6 fusion is a poor prognostic indicator of DLBCL. There is evidence of prognostic value of BCL6 rearrangements also in rituximab era.