Identification of putative nonfunctional steroid receptors in breast and endometrial cancer

Determination of hormonal response in uterine cancer cell lines by the ATP bioluminescence assay and flow cytometry

Although progesterone receptor status has been shown to correlate with response to hormonal therapy, not all progesterone receptor-positive patients respond to this treatment and additional biologic assays are needed to help better predict clinical response to hormonal therapy. This study explored the potential of the ATP bioluminescence assay and flow cytometry as biological assays of hormonal response. Five uterine cancer cell lines were used: AE7, ECC-1, HEC1A, AN3, and SKUT1B. Cells were exposed to Provera or tamoxifen at 0.1, 0.2, 0.5, 1, 2, and 5X (X equal to peak plasma concentrations: 1.0 micrograms/ml Provera and 0.1 micrograms/ml tamoxifen). For correlation, estrogen and progesterone receptors were determined by the standard dextran-coated charcoal method. Only AE7 and ECC-1 were positive for progesterone receptors (501 fmol/mg AE7, 194 fmol/mg ECC-1) and the rest were negative (less than 8 fmol/mg). Tamoxifen exerted no inhibition to the above cell lines. Meanwhile, Provera exerted dose-response inhibition on both AE7 and ECC-1 cell lines. The effects of accumulation of G0-G1 phase and reduction of S, G2 cells (P less than 0.05), but not on the HEC1A cell line (P = 0.4). These changes confirmed the antiproliferative property of Provera. Further studies are needed to establish the role of the ATP bioluminescence assay and flow cytometry as biological assays of hormonal response.