Cloning of the t(11;14)(q13;q32) translocation breakpoints from two human leukemia cell lines

The t(11;14)(q13;q32) translocation has been associated with several subtypes of human leukemia and lymphoma. It has been proposed that this translocation activates a proto-oncogene designated BCL1. In an effort to better understand the mechanism by which this translocation leads to malignancy, we have studied this translocation in two human cell lines. MO1094 and MO2058 were derived from patients with prolymphocytic variants of chronic lymphocytic leukemia. Southern blotting of the MO2058 cell line documented that the translocation linked the Jh region in the immunoglobulin heavy chain gene to the previously described BCL1 major translocation cluster (MTC). Using the polymerase chain reaction, we cloned this translocation and showed that the chromosome 11 breakpoint was within 7 bp of two other samples reported previously. Southern blotting of the MO1094 cell line suggested that the translocation in this cell line might link Jh sequences to a new region in the BCL1 locus on chromosome 11. Therefore, the MO1094 breakpoint was cloned from a genomic library. Comparison with normal cloned DNA from the BCL1 locus showed that the chromosome 11 breakpoint occurred 24 kb telomeric of the MTC. This work reinforces the concept that translocation breakpoints in the BCL1 locus are scattered over at least 63 kb.