A reporter gene assay for evaluation of tissue-specific responses to estrogens based on the differential use of promoters A to F of the human estrogen receptor α gene

Introduction: Reporter gene assays are useful means for monitoring cellular responses. We report here a reporter gene assay for evaluating and monitoring estrogen activities by estrogen-like compounds and xenoestrogens, which is based on the promoters from the human estrogen receptor α (ERα) gene. Methods: The reporter gene constructs contained a proximal promoter region (containing promoters A and B: ProAB) or either of promoters C to F (ProC, ProD, ProE, and ProF) or fused minor promoters (ProCDEF). These constructs were first used to evaluate promoter activity in cell lines derived from breast (MCF-7 and T-47D cells), ovary (SK-OV-3 cells), endometrium (Ishikawa cells), and stomach (MKN-28 cells). Results: Besides very high levels of activity by ProAB in all of the cell lines tested, moderate levels were detected for ProD in the breast and endometrium cell lines and for ProF in the ovary and endometrium cell lines. A moderate level of activity by ProE was detected only in the stomach cells. Differences in estrogen-like activity between ProAB and ProD were observed for tamoxifen and bisphenol A (BPA) in MCF-7 cells. Discussion: The assay proposed here might provide expression profiles of cancer cells of various origins for evaluating the estrogen responsiveness and for identifying tissue- or cancer cell-specific transcription factors.