Estrogen receptor variants in epithelial compartment of normal human breast.

Estrogen receptor (ER) splice variants have previously been identified in normal human breast. Normal breast, however, comprises many cell types including fat cells, fibroblasts, endothelial cells, and a variety of inflammatory cells besides breast epithelial cells. The objective of our study was to demonstrate the existence of several variants in the epithelial compartment of the normal human breast. To this end, highly enriched breast epithelial cells from reduction mammoplasty specimens were isolated using Percoll gradient centrifugation. We analyzed the presence of both wild-type (WT) and variant receptors in human breast epithelial cells using the seminested polymerase chain reaction and direct automated sequencing of the amplified products. We demonstrated that a number of spliced variants of the ER coexist with the WT receptor. Variants lacking exons 2, 4, 5, and 7 are detected in the breast epithelial compartment of the normal human breast.