Antagonism of estrogen-related receptor-α inhibits mitochondrial oxidative phosphorylation and reduces M2 macrophage infiltration in endometrial cancer.

OBJECTIVE: Endometrial cancer (EC) is a female malignancy closely linked to metabolic dysregulation. Most patients with EC exhibit poor responses to immunotherapy, underscoring the need to identify novel therapeutic targets at the intersection of metabolism and immune regulation. METHODS: In vitro: integrated proteomics, CUT&Tag (cleavage under targets and tag mentation) sequencing, dual-luciferase reporter assays, lipidomic profiling, and macrophage-tumor co-culture systems collectively demonstrated estrogen-related receptor (ERR) α's dual metabolic-immunomodulatory role in KLE and HEC-1A human cell lines. Patient-derived organoids were used to validate the therapeutic efficacy of ERRα targeting. In vivo, the KLE cell xenograft model was used to evaluate tumorigenicity and therapeutic efficacy in mice. In humans, a retrospective cohort of 166 patients with EC was analyzed by immunohistochemistry (IHC) to quantify ERRα expression and macrophage infiltration, establishing clinical correlations and therapeutic implications. Spatial analysis of M2 macrophages in EC progression was performed using multiplex IHC. RESULTS: In EC cells, ERRα transcriptionally upregulates protein tyrosine phosphatase mitochondrial 1 through direct promoter binding (-624 to -609 bp). This interaction promotes cardiolipin biosynthesis, thereby stabilizing mitochondrial inner membrane ultrastructure, enhancing oxidative phosphorylation activity, and elevating reactive oxygen species (ROS) levels. Subsequently, ROS activates the NF-κB signaling axis, inducing CCL2 secretion to recruit M2 macrophages into the tumor microenvironment. Importantly, combined inhibition of ERRα (using XCT790) and CCL2 (using carlumab) significantly enhanced antitumor efficacy in EC. Additionally, ERRα expression in EC tissues may serve as a clinical indicator for disease evaluation. CONCLUSIONS: This study uncovers a pivotal role of the ERRα metabolic axis in reshaping the EC immune microenvironment, providing the mechanistic evidence linking mitochondrial lipid metabolism to macrophage-driven immunosuppression. Our findings establish a theoretical foundation for developing combination therapies targeting metabolic-immune crosstalk, offering a strategy to overcome immunotherapy resistance in EC.