Estrogen receptor α suppresses hepatocellular carcinoma by restricting M2 macrophage infiltration through the YAP-CCL2 axis.

Purpose: Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide, with significant differences in incidence and outcomes between men and women. Estrogen receptor alpha (ERα) expression is associated with sex-based differences and poor prognostic outcomes in HCC. However, the detailed function of ERα in the tumor microenvironment of HCC remains unclear.

Methods: Bioinformatics analysis of differentially expressed genes in HCC samples was performed from publicly available databases, and ERα was selected. The function of ERα was examined in the cell experiments. A co-culture system was built to study function of ERα-treated liver cells on macrophages in vitro. The precise mechanism was determined using quantitative real-time PCR, western blotting, immunohistochemistry, mass spectrometry, co-immunoprecipitation, and dual-luciferase reporter assay.

Results: ERα played an important role in the pathogenesis of sexual dimorphism in HCC. ERα mainly acted on macrophages in the tumor microenvironment (TME) of HCC and reduced M2 macrophage infiltration through CCL2. By acting on NF2 and 14-3-3theta, ERα enhanced YAP phosphorylation and attenuated the nuclear translocation of YAP, thereby suppressing CCL2 expression. It also acted as a transcription factor that regulated CCL2 expression at the transcriptional level.

Conclusion: ERα/YAP/CCL2 signaling reduced M2 macrophages infiltration to inhibit HCC progression, revealing the effect of ERα in cancer cells on immune cells in HCC microenvironment.