Identification and mapping of novel tumor suppressor loci on 6p in diffuse large B-cell non-Hodgkin's lymphoma

Allelic deletions have been thought to be indicators of the presence of tumor suppressor genes (TSGs). As indicated by this allelotype study using 39 highly informative microsatellite markers distributed among all autosomal chromosomes, frequent loss of heterozygosity (LOH) has been found at 6p in B-cell non-Hodgkin's lymphoma. To identify the commonly deleted regions (CDRs), we performed fine deletion mapping using 26 highly polymorphic microsatellite markers on 6p. The most frequent LOH occurred at D651721, where 9 of 18 of the informative cases (50%) had allelic losses. Seventeen of 32 cases (53%) exhibited LOH at least at one locus on 6p. Ten of these 17 cases showed interstitial deletions, and their LOH patterns indicated two CDRs on 6p; one between D6S1721 and D6S260 (at 6p23-24), and the other between D6S265 and D6S291 (at 6p21). The genetic distance of both CDRs was 6 cM. The CDKN1A (p21) gene is reported to be located within the interval of the CDR at 6p21, but no mutation of the gene was found in these 32 patients. These data suggested that these two loci might harbor novel putative TSGs responsible for the pathogenesis of malignant lymphoma. We have constructed a contig of yeast artificial chromosome (YAC) clones spanning the most frequent CDR at 6p23-24. This YAC contig can be used for fine physical mapping of the region and cloning of candidate TSGs.