Frequent alteration of the DF3 tumor-associated antigen gene in primary human breast carcinomas.

The gene for the human DF3 breast carcinoma-associated antigen contains a conserved (G + C)-rich 60-base pair tandem repeat and maps to chromosome 1q21-24. In the present study we isolated and characterized 1220 base pairs of nonrepetitive adjacent sequences. Multiple alleles were identified by fragment size. Signal intensity of hybrids with the tandem and unique sequence probes indicated that allelic variation is due to different numbers of repeats. Probes for both the tandem and the unique sequences were used to study the DF3 locus in human breast tumor DNAs. Seventy of 110 breast tumor DNAs were informative at the DF3 locus. Of these, 20 (29%) showed a loss of heterozygosity, while eight (11%) had an increased copy number of one allele. In some cases, the loss of heterozygosity or increased copy number did not extend to other markers on chromosome 1q or 1p. These data indicate that the chromosomal region around the DF3 locus is affected by mutations at high frequency.