USP18-FTO axis activates PI3K-AKT signaling to drive endometrial carcinoma progression

Endometrial carcinoma lacks effective treatments for advanced cases. While the deubiquitinating enzyme ubiquitin-specific peptidase 18 is implicated in cancer, its role in EC remains unclear. This study aimed to investigate the expression, functional role, and molecular mechanisms of USP18 in EC, with a particular focus on its interaction with the fat mass and obesity-associated protein in regulating oncogenic signaling. Through comprehensive bioinformatics analysis of public datasets and rigorous validation in clinical patient cohorts, we discovered that USP18 is significantly upregulated in EC tissues and is intrinsically associated with poor clinical outcomes. Subsequent in vitro functional assays demonstrated that USP18 substantially promotes EC cell proliferation, inhibits apoptosis, and enhances migratory capacity. In vivo subcutaneous xenograft and tail-vein metastasis mouse models confirmed that USP18 overexpression significantly accelerates macroscopic tumor growth and extensive pulmonary metastasis. RNA-sequencing was performed on USP18-knockdown cell lines, which revealed a pronounced downregulation of the PI3K-AKT signaling pathway. Protein-protein interaction predictions coupled with co-immunoprecipitation and ubiquitination assays validated a direct physical interaction between USP18 and FTO. USP18 effectively stabilizes the FTO protein pool by suppressing its ubiquitin-mediated proteasomal degradation. Functional rescue experiments demonstrated that the targeted overexpression of FTO could effectively reverse the impaired PI3K-AKT activation and the associated tumor-suppressive phenotypes induced by USP18 knockdown both in vitro and in vivo. Our findings identify a novel USP18-FTO-PI3K/AKT regulatory axis driving endometrial carcinoma progression. This study highlights a previously unrecognized deubiquitination-dependent mechanism of epitranscriptomic regulation, offering a promising novel therapeutic target for precision intervention in EC.