Novel bcl-2 breakpoints in patients with follicular lymphoma

Using genomic DNA from patients with follicular lymphoma, we performed polymerase chain reaction (PCR) amplifications to detect t(14;18) translocations. Unexpectedly large products of -1 kilobase (kb) were detected by gel electrophoresis in 2 of 50 positive cases. In these 2 cases, sequence analyses showed novel breakpoints in the 3' untranslated region of bcl-2, ~800 bp downstream of the major breakpoint region (mbr). The breakpoints in IgH occurred in J(H)4 in one patient and J(H)5 in the other. Sequences just upstream of the new bcl-2 breakpoints suggest a mechanism of translocation that may include minisatellite core-mediated recombination. In one of our two patients with novel bcl-2 breakpoints, the ~1 kb product obtained using conventional mbr primers was detectable only when a nested PCR was performed. These findings have important implications for diagnosis and minimal residual disease detection in t(14;18)-positive lymphomas.