LACK OF CLONAL BCRA2 GENE DELETION ON CHROMOSOME-13 IN CHRONIC LYMPHOCYTIC-LEUKEMIA

Chromosome 13q deletion is among the most common cytogenetic abnormali ties in chronic lymphocytic leukaemia (CLL). We investigated the 13q14 .3 deletion in 44 CLL patients by Southern blotting following purifica tion of clonal B CLL cells to >90%. Two sets of probes were used to in vestigate the site of clonal deletion, the D13S25 and D13S319 markers (at 13q14.3) and probes for exons 11 and 26-27 of the BRCA2 gene (at 1 3q12). Homozygous and heterozygous deletion at the 13q14.3 region was found in live and 17 patients, respectively Despite the recent report of the BRCA2, gene involvement in >80% of CLL patients, we failed to d etect a single case of homozygous or heterozygous deletion involving t he 13q12 region. Our data support previous findings that the 13q14.3, and not the 13q12 region, is the major site of candidate tumour suppre ssor gene(s) in CLL.