G Protein-Coupled Estrogen Receptor-Selective Ligands Modulate Endometrial Tumor Growth

Abstract

Endometrial carcinoma is the most common cancer of the female reproductive tract. GPER/GPR30 is a 7-transmembrane spanning G protein-coupled receptor that has been identified as the third estrogen receptor, in addition to ERα and ERβ. High GPER expression is predictive of poor survival in endometrial and ovarian cancer, but despite this, the estrogen-mediated signaling pathways and specific estrogen receptors involved in endometrial cancer remain unclear. Here, employing ERα-negative Hec50 endometrial cancer cells, we demonstrate that GPER mediates estrogen-stimulated activation of ERK and PI3K via matrix metalloproteinase activation and subsequent transactivation of the EGFR and that ER-targeted therapeutic agents (4-hydroxytamoxifen, ICI182,780/fulvestrant, and Raloxifene), the phytoestrogen genistein, and the “ERα-selective” agonist propylpyrazole triol also function as GPER agonists. Furthermore, xenograft tumors of Hec50 cells yield enhanced growth with G-1 and estrogen, the latter being inhibited by GPER-selective pharmacologic antagonism with G36. These results have important implications with respect to the use of putatively ER-selective ligands and particularly for the widespread long-term use of “ER-targeted” therapeutics. Moreover, our findings shed light on the potential mechanisms of SERM/SERD side effects reported in many clinical studies. Finally, our results provide the first demonstration that pharmacological inhibition of GPER activity in vivo prevents estrogen-mediated tumor growth.

International Union of Basic and Clinical Pharmacology. XCVII. G Protein–Coupled Estrogen Receptor and Its Pharmacologic Modulators

“…GPER (mRNA and protein) is expressed throughout the central and peripheral nervous system (although not universally) of both female and male rodents, including the cortex, hippocampus, hypothalamus, specific nuclei of the midbrain, the trigeminal nuclei and cerebellum Purkinje layer of the hindbrain, the anterior, intermediate and neural lobes of the pituitary, as well as the spinal cord and dorsal root ganglia (Brailoiu et al, 2007;Dun et al, 2009;Hazell et al, 2009). The activation of ERK1/2 in trigeminal ganglion neurons and the increased allodynia induced by PPT [4,49,-pyrazole-1,3,5-triyl) trisphenol] and G-1 has led to the conclusion of roles for both ERa and GPER in peripheral sensitization (Liverman et al, 2009); however, with the recent demonstration that PPT can also function as a GPER agonist (Petrie et al, 2013), it is possible that both responses, in fact, were mediated by GPER, because independent methods to assess receptor involvement were not employed. G-1 also depolarizes spinal cord neurons , stimulates mechanical hyperalgesia via protein kinase C« activation (Kuhn et al, 2008), and mediates visceral hypersensitivity in the absence of inflammation (Lu et al, 2009).…”

“…In addition to breast cancer cell lines and primary tumors of the breast (Carmeci et al, 1997;Filardo et al, 2000;Revankar et al, 2005;Albanito et al, 2008), GPER is also expressed in cancers and cell lines of the endometrium (Vivacqua et al, 2006a;Leblanc et al, 2007;Smith et al, 2007;He et al, 2009;Petrie et al, 2013;Dai et al, 2014), ovaries (Albanito et al, 2007(Albanito et al, , 2015Henic et al, 2009;Smith et al, 2009;Liu et al, 2014), thyroid (Vivacqua et al, 2006a), lung (Siegfried et al, 2009), prostate (Chan et al, 2010), and testes (Franco et al, 2011). In cell lines of thyroid, ovarian, endometrial, and breast cancers, stimulation of GPER with E2 (Vivacqua et al, 2006a,b;Albanito et al, 2007) or other estrogenic compounds, such as genistein (Vivacqua et al, 2006a), bisphenol A (Dong et al, 2011;Chevalier et al, 2012a), or tamoxifen (Vivacqua et al, 2006b) activates signaling mechanisms that typically promote proliferation.…”

“…This has led to development of drugs that target E2 binding to ERa and E2 synthesis, including the SERMs tamoxifen and raloxifene (Jordan, 2007;Sengupta and Jordan, 2008), SERDs (such as fulvestrant), and aromatase inhibitors (Orlando et al, 2010). Many of these agents, particularly SERMs such as tamoxifen (Revankar et al, 2005) and raloxifene (Petrie et al, 2013) and fulvestrant (Filardo et al, 2000), which also function as GPER agonists, produce complex physiologic and therapeutic actions. Multiple studies now reveal that long-term E2 deprivation of the E2-dependent human breast cancer cell line MCF-7, mimicking treatment of women with antiestrogens or aromatase inhibitors, increased expression of GPER (Craig Jordan et al, 2007), with tamoxifen treatment of such resistant cells stimulating proliferation via GPER (Ignatov et al, 2010).…”

Emerging roles for the novel estrogen-sensing receptor GPER1 in the CNS

“…Moreover the effects of ICI 182,780 were blocked by G15 and following knockdown of GPER1 (Ruiz-Palmero et al, 2013). Recent studies indicate that the "selective" ERα agonist, propylpyrazole triol (PPT), also has agonist actions at GPER1 (Petrie et al, 2013), which further complicates interpretation of data using this compound.…”

Protective Effect of 3, 3-Diindolylmethane on Bisphenol A Activated GPR30, RAS, PI3K/Akt Estrogenic Signaling Pathway in Female Sprague-Dawley Rats

“…Ligands binding to their respective receptor activate SRC which in turn leads to activation of matrix metalloproteinases (MMPs) which release the active form of heparin-binding epidermal growth factor (HB-EGF) [34,35]. This transactivates the epidermal growth factor receptor (EGFR), leading to the activation of Ras which ultimately activates Akt kinase through PI3K kinase [36]. Akt regulates the expression of estrogen responsive genes controlling cell proliferation, growth survival, and metastasis [37].…”