Expression of estrogen receptor ß-isoforms in breast cancer cell lines with different potentials for mobility and invasiveness

Estrogen receptor (ER) β is involved in physiological and pathological processes in the mammary gland. Different ERβ-isoforms are described in the literature, without providing their exact function. In order to determine the biological function of distinct ERß-isoforms for breast cancer patients it is important to get detailed information about their expressional regulation. For this purpose we have established four classic multiplex- and six real-time RT-PCRs to quantify wild-type ERβ (ERßwt), ERβcx-, ERβδ5-, ERβ5-splice variants. Expression of ERβ-splice variants was examined in seven standard-cultured breast cancer cell lines: Tamoxifen-resistant MCF-7 (MCF-7TR) cell line, its parental MCF-7 cell line, MCF-10A, MDA-MB 231, AR, KS, and BM cells. Invasion- and mobilityassays were performed using cambers coated with matrigel or uncoated, respectively. RT-PCR data indicate that ERßwt is expressed in MCF-7TR cells compared to MCF-7 cells missing expression of ERβwt. On the other hand MCF-7 cells express ERβ5 which could not be detected in MCF-7TR cells. Comparing the ERß isoform expression patterns of all cell lines investigated it can be observed that the expression pattern of ERβ-isoforms is very similar in MCF-7TR, MDA-MB 231 and AR cells with strong signals for ERβcx. In mobility assays MCF-7TR and AR cells like MDA-MB 231 cells are highly mobile. However, in contrast to MCF-7TR and MDA-MB 231 cells, AR cells are not able to pass through matrigel. PCR analysis of two separate fractions of MCF-7TR cells which passed through matrigel and MCF-7TR cells which remained in or on top of it show a different expression pattern of ERβ-isoforms with a signal for ERβcx only in the invasive cells. MCF-7, MCF10A, KS, and BM cells having a different expression pattern of ERβ-isoforms are neither mobile nor invasive. These data suggest that the expression pattern of ERß-isoforms might be correlated with the mobility of cells in breast cancer.