Analysis of the estrogen receptor gene structure in human breast cancer

We studied the structure of the human estrogen receptor (ER) gene by Southern blot analysis in 34 tumor samples and normal breast tissues or peripheral blood samples from the same patients. No rearrangement or amplification of the ER gene was seen in either ER-positive or ER-negative breast tumors. One patient showed an apparent constitutional deletion of a non-allelic ("invariant") restriction fragment in DNAs from both normal leukocytes and bilateral breast tumors. Of 20 patients constitutionally heterozygous for an ER gene RFLP, only one showed tumor-specific loss of heterozygosity. This is consistent with the ER gene change we noted overall. At the c-myb locus on chromosome 6q adjacent to the ER gene, allele loss occurred in 1 out of 15 informative cases. In addition, tumor-specific allelic loss at the c-H-ras1 locus on chromosome 11p occurred in 4 of 22 informative cases, and at the D17S28 locus on chromosome 17p in 2 of 7 informative cases.