Transcriptional control of estrogen receptor in estrogen receptor-negative breast carcinoma

The mechanisms which control estrogen receptor (ER) expression in breast carcinoma have not been elucidated. The MCF-7 (ER-positive) and MDA-MB-231 (ER-negative) breast carcinoma cell lines have been used to examine ER gene expression. Northern blot analysis of mRNA isolated from these two cell lines demonstrates that MCF-7 cells express an expected 6.5-kilobase ER mRNA whereas MDA-MB-231 do not make detectable ER message. Reverse polymerase chain reaction, which offers greater sensitivity, confirms these Northern blot results. The nuclear run-on assay was used to examine directly transcription in these two cell lines. MCF-7 cells actively transcribe the ER gene whereas no ER transcription is detected in MDA-MB-231. Southern analysis of genomic DNA confirms that the ER gene is present in MDA-MB-231. We conclude that the ER gene is controlled transcriptionally in this ER-negative breast carcinoma line.