GPR30 Promotes Prostate Stromal Cell Activation via Suppression of ERα Expression and Its Downstream Signaling Pathway

Abstract

Cancer-associated fibroblasts (CAFs) play a vital role in malignant transformation and progression of prostate cancer (PCa), and accumulating evidence suggests an enhancing effect of estrogens on PCa. The present study aimed to investigate the possible origin of prostate CAFs and the effects of estrogen receptors, G protein-coupled receptor 30 (GPR30) and estrogen receptor (ER)-α, on stromal cell activation. High expression of fibroblast activation protein (FAP), CD44, and nonmuscle myosin heavy chain B (SMemb) accompanied by low expression of smooth muscle differentiation markers was found in the stromal cells of PCa tissues and in cultured human prostate CAFs. Additionally, SMemb expression, which is coupled to cell phenotype switching and proliferation, was coexpressed with FAP, a marker of activated stromal cells, and with the stem cell marker CD44 in the stromal cells of PCa tissue. Prostate CAFs showed high GPR30 and low ERα expression. Moreover, GPR30 was coexpressed with FAP, CD44, and SMemb. Furthermore, the study demonstrated that the overexpression of GPR30 or the knockdown of ERα in prostate stromal cells induced the up-regulation of FAP, CD44, Smemb, and the down-regulation of smooth muscle markers. The conditioned medium from these cells promoted the proliferation and migration of LNCaP and PC3 PCa cells. GPR30 knockdown or ERα overexpression showed opposite effects. Finally, we present a novel mechanism whereby GPR30 limits ERα expression via inhibition of the cAMP/protein kinase A signaling pathway. These results suggest that stem-like cells within the stroma are a possible source of prostate CAFs and that the negative regulation of ERα expression by GPR30 is centrally involved in prostate stromal cell activation.

Pro-tumorigenic roles of fibroblast activation protein in cancer: back to the basics

“…Less is known about what factors suppress FAP expression, either acutely or as part of basal regulation keeping FAP expression low in normal tissues ( Fig2 ). As mentioned above, estrogen signaling through ERα specifically was observed to inhibit FAP expression, and ERα levels are higher in normal fibroblasts than in CAFs( 65 ). Genistein—an isoflavone with multiple mechanisms of action on cells—was observed to reduce FAP expression on gastric cancer cell lines, through mechanisms unknown( 71 ).…”

“…investigated estrogen signaling in the context of prostate cancer and discovered opposing activity of the classic estrogen receptor alpha (ERα) and an alternate receptor, GPR30. They noted that CAFs expressed higher levels of GPR30 and lower ERα than normal fibroblasts, and using both receptor overexpression and silencing studies demonstrated that FAP expression is promoted by GPR30 but inhibited by ERα( 65 ).…”

The role of G-protein-coupled membrane estrogen receptor in mouse Leydig cell function—in vivo and in vitro evaluation

“…On a new but related point, tamoxifen acting through GPER is able to upregulate aromatase expression (Catalano et al 2014 ). In the male reproductive system, GPER suppression of ERα expression and its downstream signaling pathway was reported (Koong and Watson 2014 ; Jia et al 2016 ).…”

Ginsenoside Rg3 inhibits the senescence of prostate stromal cells through down-regulation of interleukin 8 expression

“…These results provide some clues about the phenotype of pro-carcinogenic stromal cells in the prostate. Our recent report also demonstrated the down-regulation of SM22 and SMMHC in carcinoma associated stromal cells [ 29 ]. Although the exact differentiation phenotype of senescent prostate stromal cells has not been fully identified, this research revealed an up-regulation of SM22 and SMMHC in ginsenoside Rg3-treated cells, indicating the compound may inhibit the pro-carcinogenic stromal phenotype.…”

“…A protocol for transwell assays was followed according to our previous report [ 29 ]. Results were obtained from 3 independent experiments and quantitative results expressed as mean ± SD.…”