G Protein-Coupled Oestrogen Receptor Actions Targeting the Hallmarks of Cancer in Human Prostate Cells: From Cell Fate to Metabolic Reprogramming

Background/Objectives: The G protein-coupled oestrogen receptor (GPER) has anti-tumorigenic effects in several human cancers. However, its role in prostate cancer (PCa) remains incompletely defined. The present study investigated GPER’s role in targeting the hallmarks of PCa. Methods: Tissue microarrays were used to analyse GPER immunoexpression in PCa samples. Non-neoplastic (PNT1A) and neoplastic (LNCaP, DU145 and PC3) prostate cells were treated with the GPER-specific agonist, G1. Cell viability, proliferation, cell cycle, apoptosis, migration and invasion were evaluated. Glucose consumption, lactate production, lactate dehydrogenase activity and oxidative status were determined spectrophotometrically. Results: GPER immunoreactivity was higher in PCa than in benign prostatic hyperplasia and inversely correlated with PSA serum levels. G1 modulated GPER subcellular location in prostate cells, being detected at the cell membrane, endoplasmic reticulum, and residually in the nucleus. GPER activation decreased cell viability and proliferation, induced cell cycle arrest at G2/M phase, and increased PCa cells apoptosis. Additionally, GPER activation inhibited the migration and invasion of DU145 cells, and long-term exposure to G1 reduced epithelial–mesenchymal transition, an effect not observed in PC3 cells, indicating the importance of cell-specific contexts. Our results also showed that G1 treatment modulated the metabolic profile of PCa cells, changing glucose, amino acids and lipid metabolism. Finally, G1 increased oxidative stress in PCa cells. Conclusions: Overall, this study demonstrated that GPER activation affects a broad range of PCa hallmarks. These findings support an anti-cancer role for GPER in PCa and encourage further exploration of its action in regulating metabolism and as a therapeutic target.