We have cloned and sequenced a t(14;18) bcl-2 breakpoint cluster region which lies more than 12 kb 3' of the major breakpoint cluster region (mbr, located in the last exon of bcl-2), and 5' of the minor cluster region (mcr). Using probes of these separate regions, we have determined the frequency with which each of the breakpoint areas of bcl-2 is involved in translocation and are investigating whether the specific breakpoint of bcl-2 might influence clinical behavior of lymphomas. To determine whether point mutation in the bcl-2 ORF might be involved in deregulation of bcl-2, we have directly sequenced PCR-amplified DNA from eleven primary follicular lymphomas. As no mutations were found, we conclude that bcl-2 activation is not generally attributable to mutation in these sites. In continuing studies of the molecular biology of Hodgkin's disease, we applied PCR to the involved tissues of Hodgkin's disease and found positive bcl-2/JH sequences in 33%. Since our single bcl-2/mbr primer detects only 37% of follicular lymphoma, then many, perhaps most, cases of Hodgkin's disease contain t(14;18). Planned studies include investigation of bcl-2 expression using PCR-amplified CDNA and direct analysis of Reed-Sternberg cells for bcl-2 expression in intact tissue sections with an antibody we have raised to the bcl-2 protein. We have identified a novel T-delta gene rearrangement occurring in the majority of precursor B (""""""""common"""""""") ALL. To determine the mechanism of this rearrangement and its consequences, we are cloning and sequencing genomic DNA from a primary case of precursor B ALL which carries the delta rearrangement.
