Endocrine Abstracts

Oestrogenic effects on colorectal cancer (CRC) incidence, proliferation, and patient survival remains controversial. We have previously shown enzymic pathways favouring oestradiol (E₂) synthesis are upregulated in CRC, and stimulation of the G-protein coupled oestrogen receptor (GPER) by E₂ increases CRC proliferation. Here we interrogated The Cancer Genome Atlas (TCGA) Colon Adenocarcinoma (COAD) database to determine all oestrogen metabolism enzymes and oestrogen receptors, and how expression effected patient survival. Furthermore, we hypothesised that the Hippo signalling pathway, an evolutionary conserved proliferative pathway regulated by GPER action, is mediated by E₂ in CRC. Using in vitro (proliferation assays, immunocytochemistry, immunoblotting) and in vivo (xenograft tumour) models, we examined how E₂ through GPER alters Hippo signalling, with a particular focus on Yes-associated protein (YAP), transcription coactivator with PDZ-binding motif (TAZ), and connective tissue growth factor (CTGF). The TCGA COAD dataset (n=440) showed CRC favours E₂ synthesis, supporting our previous findings. Further analysis revealed ERalpha, ERbeta, and GPER are all significantly (P<0.0001) downregulated in CRC compared to normal colon. However, GPER remains the most abundantly expressed oestrogen receptor. CRC patients with high tumour GPER expression (n=110) had a significantly (P<0.05) worse survival. In HCT116 and HT-29 CRC cell lines, stimulation of GPER with E₂ or G1, a specific GPER agonist, altered Hippo signalling by increasing YAP phosphorylation, and TAZ and CTGF expression. G15, a specific GPER antagonist, blocked these responses. Furthermore, G15 significantly (P<0.01) inhibited the in vivo growth of HCT116 tumour xenografts. Further TCGA COAD analysis showed CRC patients with high TAZ expression had significantly worse survival outcomes. Our data suggests a novel pathway through which E2-GPER signalling can mediate the Hippo pathway in CRC resulting in increased proliferation. The TCGA COAD dataset supports this hypothesis and suggests targeting GPER and/or Hippo signalling may provide therapeutic benefit to patients with CRC.