Expanded range of 11q13 breakpoints with differing patterns of cyclin D1 expression in B‐cell malignancies

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Abstract
We have analyzed the BCL1 locus in a series of 24 B‐cell tumors and cell lines with rearrangements of 11q13 (mostly t(11;14)(q13;q32) translocations). Using Southern hybridization and/or fluorescence in situ hybridization (FISH) on metaphase chromosomes, we have not only confirmed the scattering of the breakpoints between the BCL1 locus and the cyclin DI gene (CCND1), but also shown that some of the breakpoints could be as far as 500 kb on either side of the latter. Expression of CCND1 was not restricted to cases with t(11;14)(q13;q32), but was also associated with other 11q13 rearrangements, such as a t(8;11)(p22;q13). Whatever the alteration at 11q13, a correlation was observed between the expression of CCND1 and the presence of a breakpoint within 150 kb upstream of the gene. On the contrary, three samples, including a bona fide t(11;14) translocation and two cases with breakpoints located outside the BCL1‐CCND1 area, did not exhibit detectable levels of CCND1 transcripts. Our results raise the possibility that several discrete molecular events can take place at 11q13 in B‐cell malignancies.