Abstract
In normal colon tissue, oestrogen receptor alpha (ERα) is expressed at low levels, while oestrogen receptor beta (ERβ) is considered the dominant subtype. However, in colon carcinomas, the ERα/β ratio is often increased, an observation that prompted us to further investigate ERα's role in colorectal cancer (CRC). Here, we assessed ERα nuclear expression in 351 CRC patients. Among them, 119 exhibited positive ERα nuclear expression, which was significantly higher in cancer tissues than in matched normal tissues. Importantly, patients with positive nuclear ERα expression had a poor prognosis. Furthermore, positive ERα expression correlated with increased levels of the G-protein coupled cysteinyl leukotriene receptor 1 (CysLT1R) and nuclear β-catenin, both known tumour promoters. In mouse models, ERα expression was decreased in Cysltr1-/- CAC (colitis-associated colon cancer) mice but increased in ApcMin/+ mice with wild-type Cysltr1. In cell experiments, an ERα-specific agonist (PPT) increased cell survival via WNT/β-catenin signalling. ERα activation also promoted metastasis in a zebrafish xenograft model by affecting the tight junction proteins ZO-1 and Occludin. Pharmacological blockade or siRNA silencing of ERα limited cell survival and metastasis while restoring tight junction protein expression. In conclusion, these findings highlight the potential of ERα as a prognostic marker for CRC and its role in metastasis.