Estrogen Activation of G-Protein–Coupled Estrogen Receptor 1 Regulates Phosphoinositide 3-Kinase and mTOR Signaling to Promote Liver Growth in Zebrafish and Proliferation of Human Hepatocytes

Abstract

BACKGROUND & AIMS: Patients with cirrhosis are at high risk for hepatocellular carcinoma (HCC) and often have increased serum levels of estrogen. It is not clear how estrogen promotes hepatic growth. We investigated the effects of estrogen on hepatocyte proliferation during zebrafish development, liver regeneration, and carcinogenesis. We also studied human hepatocytes and liver tissues. METHODS: Zebrafish were exposed to selective modifiers of estrogen signaling at larval and adult stages. Liver growth was assessed by gene expression, fluorescent imaging, and histologic analyses. We monitored liver regeneration after hepatocyte ablation and HCC development after administration of chemical carcinogens (dimethylbenzanthrazene). Proliferation of human hepatocytes was measured in a coculture system. We measured levels of G-protein–coupled estrogen receptor (GPER1) in HCC and nontumor liver tissues from 68 patients by immunohisto-chemistry. RESULTS: Exposure to 17β-estradiol (E2) increased proliferation of hepatocytes and liver volume and mass in larval and adult zebrafish. Chemical genetic and epistasis experiments showed that GPER1 mediates the effects of E2 via the phosphoinositide 3-kinase–protein kinase B–mechanistic target of rapamycin pathway:gper1-knockout and mtor-knockout zebrafish did not increase liver growth in response to E2. HCC samples from patients had increased levels of GPER1 compared with nontumor tissue samples; estrogen promoted proliferation of human primary hepatocytes. Estrogen accelerated hepatocarcinogenesis specifically in male zebrafish. Chemical inhibition or genetic loss of GPER1 significantly reduced tumor development in the zebrafish. CONCLUSIONS: In an analysis of zebrafish and human liver cells and tissues, we found GPER1 to be a hepatic estrogen sensor that regulates liver growth during development, regeneration, and tumorigenesis. Inhibitors of GPER1 might be developed for liver cancer prevention or treatment. TRANSCRIPT PROFILING: The accession number in the Gene Expression Omnibus is GSE92544.

Fetal alcohol spectrum disorder predisposes to metabolic abnormalities in adulthood

“…The AB strain was used for all population studies, diet challenges, and RNA-Seq experiments. Tg(fabp10a:mKate), Tg(tp1glob:eGFP), and Tg(fabp10a:NLS:mcherry) lines from a mixed TU/AB/TL background were used to examine liver and biliary development (78)(79)(80). For all studies, clutch-matched siblings were randomly assigned to each treatment group.…”

“…Confocal images of control and EAE embryos were obtained after overnight fixation in 4% PFA. To evaluate liver size, Tg(fabp10a:mKate) and Tg(fapb10a:N-LS-mcherry) lines were examined; for biliary tree structure and size, Tg(tp1glob:eGFP) lines were employed (78)(79)(80). Confocal stacks were uploaded and 3D reconstructions were generated using Imaris software.…”

MicroRNAs in Animal Models of HCC

“…Interestingly, as observed in humans, male fish developed HCC faster than females due to sex hormone imbalance via noncanonical estrogen signaling, including G protein-coupled estrogen receptor 1 (GPER) [203]. In line, fish treated with 17 β-estradiol developed more tumors than controls, and this effect was evident in particular in male cohorts [204]. Together with transgenic technology, several inducible expression systems are available for zebrafish.…”

Nomograms Predicting Long-Term Overall Survival and Cancer-Specific Survival in Metastatic Hepatocellular Carcinoma Patients

“…According to relevant statistics, from a global perspective, the ratio of smoking and drinking in women is signi cantly lower than that in men (31) . At the same time, smoking and drinking are important risk factors for the incidence of liver cancer (32) . Researchers pointed out that in liver cancer patients, the ratio of androgen and estrogen would change accordingly, and the rise of estrogen could promote the proliferation of human liver cells (33) .…”