GPR30 expression and function in breast cancer cells are induced through a cis‑acting element targeted by ETS factors

The capacity that G protein‑coupled receptor 30 (GPR30) has demonstrated for triggering estrogen‑dependent signaling pathways has attracted the interest of breast cancer researchers; however, the reported expression profiles and functions of GPR30 in breast cancer are inconsistent. The main purpose of the present investigation was to identify transcriptional mechanisms underlying the expression of GPR30 that allow a better understanding of its role in breast cancer progression. In the cell lines used as different polarity models in the present study, it was determined immunologically that GPR30 is expressed in normal mammary gland cells and that this expression decreased considerably during breast cancer development, where cell identity is lost. However, it was also determined that, in spite of low GPR30 expression levels in breast cancer cells with little differentiation, this membrane estrogen receptor (ER) is able to increase cell viability and suppress migration in cells that have acquired metastatic capacity. In addition, through transient expression assays in breast cancer cells, it was revealed that a transcriptional mechanism dependent on protein kinase A and susceptible to retinoic acid in ER‑positive cells induces GPR30 expression through a cis‑regulatory element for E26 transformation‑specific transcription factors, located between ‑631 and ‑625 bp from the GPR30 translation start codon. Overall, these results suggested that in vitro transcriptional regulation of GPR30 expression in breast cancer cells may serve a relevant role in the conservation of an epithelial phenotype, and also may be important to avoid the transition to metastasis.