Cd44 Activation In Mature B-Cell Malignancies By A Novel Recurrent Igh Translocation

Using inverse polymerase chain reaction, we identified CD44, located on chromosome 11p13, as a novel translocation partner of IGH in 9 of 114 cases of gastric, nongastric extranodal, follicular, and nodal diffuse large B-cell lymphoma (DLBCL). Notably, these translocations involving IGHS mu were detected in follicular lymphomas and exclusively in germinal center B cell-like (GCB)-DLBCLs. CD44 is notexpressed in reactive GC B cells. The IGHS mu/CD44 translocations substitute S mu for the CD44 promoter and remove exon 1 of CD44, resulting in the overexpression of I mu-CD44 hybrid mRNA transcripts activated from derivative 11 that encode a new CD44 variant lacking the leader peptide and with a unique C-terminus (CD44 Delta Ex1). When overexpressed in vitro in the CD44(-) GCB-DLBCL cell line BJAB, CD44 Delta Ex1-green fluorescent protein localized to the cytoplasm and nucleus, whereas CD44s-green fluorescent protein (standard form) localized to the plasma membrane. The ectopic expression of CD44 Delta Ex1 in BJAB cells enhanced their proliferation rate and clonogenic ability, indicating a possible pathogenic role of the translocation. (Blood. 2010;115:2458-2461)