INCREASED EXPRESSION OF ESTROGEN-RECEPTOR-BETA IN CHEMICALLY TRANSFORMED HUMAN BREAST EPITHELIAL-CELLS

Recent molecular cloning of estrogen receptor beta (ERR) suggests alte rnative pathways of estrogen signaling, but little is known concerning the role of ER beta in the development of human breast cancer. In the present study, expression of ER alpha and ER beta mRNA was determined in a series of chemically transformed human breast epithelial cells a s well as various normal and malignant breast cancer cell lines. We ob served a very low level of ER beta expression in the mortal S130 and t he spontaneously immortalized MCF10-F human breast epithelial cell lin es. As MCF-10F cells were treated with environmental chemical carcinog ens, an elevated level of ER beta expression was observed in the resul tant transformed BP1, D3 and BP1-ras cells. An even higher level of ER beta expression was detected in the more transformed BP1-E, D3-1 and D3-1-ras cell lines. Therefore, results from our study indicate that e xpression of ER beta can be induced in chemical carcinogen-transformed human breast epithelial cells, and the more transformed cells showed higher levels of ER beta expression, regardless of which chemical carc inogens were initially used for cell transformation. These results sug gest that expression of ER beta may contribute to the initiation and p rogression of chemical carcinogen-induced neoplastic transformation.