Loss of heterozygosity of the oestrogen receptor gene in breast cancer.

DNA from 67 primary breast carcinoma biopsies has been examined for loss of heterozygosity (LOH) using the microsatellite (TA)n repeat marker positioned 1 kb upstream of the oestrogen receptor (ER) gene. Forty-seven (70.1%) of the cases were informative; nine of these (19.1%) were positive for LOH. In three of the nine cases, there was total loss, and in the other six cases there was a marked reduction in the intensity of signal from one allele. LOH correlated weakly with histological grade and age, but not with ER status. This result suggests that LOH of the ER gene does not have an important role in the lack of ER function in breast cancer tissues.