The G-protein-coupled estrogen receptor (GPER; G protein-coupled estrogen receptor 30, also known as GPR30) is a novel estrogen receptor and has emerged as a promising target for ovarian cancer. GPER, a seven-transmembrane receptor, suppresses cellular viability and migration in studied ovarian cancer cells. However, its impact on the fallopian tube, which is the potential origin of high-grade serous (HGSC) ovarian cancer, has not been addressed. This study was conducted to evaluate the relationship of GPER, ovarian cancer subtypes, i.e., high-grade serous cell lines (OV90 and OVCAR420), as well as potential HGSC ovarian cancer origin (i.e., the fallopian tube cell line FT190). The selective ligand assessed here is the agonist G-1, which was utilized in an in vitro study to characterize its effects on cellular viability and migration. As a result, this study has addressed the effect of a specific GPER antagonist in combination with an agonist on cell viability, providing a better understanding of the effects of these compounds on our diverse group of studied cell lines. Strikingly, attenuated cell proliferation and migration behaviors were observed in the presence of G-1. Thus, our in vitro study reveals the impact of the origin of HGSC ovarian cancers and highlights the GPER agonist G-1 as a potential therapy for ovarian cancer.

Piceatannol (PIC), a natural analog of resveratrol, has various biological functions. We previously reported that PIC had an anti-obesity effect only in ovariectomized mice. While ovariectomized mice have low phosphorylation levels of hormone-sensitive lipase (pHSL) at Ser563, we found that PIC increased those levels. Here, we investigated the effect of PIC using 3T3-L1 adipocytes to clarify the mechanism by which PIC activates HSL. First, PIC was confirmed to induce HSL phosphorylation at Ser563 in 3T3-L1 cells as in vivo experiments showed. pHSL (Ser563) is believed to be activated through the β-adrenergic receptor (β-AR) and protein kinase A (PKA) pathway; however, the addition of a selective inhibitor of β-AR did not inhibit the effect of PIC. The addition of PKA inhibitor with PIC blocked pHSL (Ser563), suggesting that PIC’s effects are mediated by PKA from a different pathway than β-AR. The addition of G15, a selective inhibitor of the G protein-coupled estrogen receptor (GPER), lowered HSL activation by PIC. Furthermore, PIC inhibited insulin signaling and did not induce pHSL (Ser565), which represents its inactive form. This study is the first to suggest that the GPER pathway might regulate HSL activation in adipocytes.