Proteomic Identification of IL4I1 as a Therapeutic Target in P53-Mutant Endometrial Cancer.

Background: Endometrial cancer (EC) is one of the most common gynecologic malignancies, with a rising incidence worldwide. The Cancer Genome Atlas (TCGA) classifies EC into four molecular subtypes, among which the high-copy number subtype is characterized by TP53 mutations and associated with poor prognosis. However, this subtype remains understudied. IL4I1, an immunoregulatory enzyme implicated in various cancers, has emerged as a potential biomarker for tumor progression. This study aimed to explore IL4I1 as a prognostic marker in P53-mutant EC and to identify its potential as a therapeutic target. Methods: We retrospectively analyzed clinical data from 495 EC patients and selected 33 P53-mutant cases using Sanger sequencing and immunohistochemistry. Tumor tissues were collected via laser capture microdissection, stratified by five-year survival outcomes. IL4I1 expression was assessed through 4D label-free proteomics, immunohistochemistry, and Western blotting. TCGA data were used to validate expression patterns and prognostic significance. Functional analyses were performed using IL4I1-knockout P53-mutant EC cell lines generated via CRISPR/Cas9, followed by phenotypic assays and xenograft models. Results: IL4I1 was significantly upregulated in deceased patients and correlated with immune microenvironment alterations in TCGA data. Knockout of IL4I1 inhibited proliferation, migration, and invasion in vitro and tumor growth in vivo. Conclusions: IL4I1 is a key player in the aggressiveness of P53-mutant EC. It holds promise as a prognostic biomarker and may serve as a novel target for precision therapies in this high-risk EC subtype.