Prognostic value of IκB kinase-interacting protein (IKBIP) in stomach adenocarcinoma

Background: Stomach adenocarcinoma (STAD) remains a leading cause of cancer-related mortality worldwide, with frequent late-stage diagnosis necessitating the identification of reliable biomarkers. IκB kinase-interacting protein (IKBIP) has been implicated in tumor aggressiveness in other malignancies, but its role in STAD remains poorly understood.

Methods: We systematically evaluated IKBIP expression and its clinical significance using data from The Cancer Genome Atlas (TCGA)-STAD, TIMER 2.0, Gene Expression Omnibus (GEO) cohorts (GSE15459, GSE15460, GSE34942), and Kaplan-Meier plotter. Immunohistochemistry was performed on 45 STAD patients to validate protein expression and macrophage infiltration. Stable IKBIP knockdown and overexpression cell lines (SGC7901 and MGC803) were generated to assess proliferation [Cell Counting Kit-8 (CCK-8)], migration, and invasion (Transwell). Quantitative real-time polymerase chain reaction (qRT-PCR) examined epithelial-to-mesenchymal transition (EMT) markers (E-cadherin, N-cadherin, Snail, matrix metalloproteinase 9 (MMP9) and NF-κB pathway genes (p65, IL-6, TNF-α). Correlation analyses evaluated upstream regulators, immune checkpoints, chemoresistance genes, and immune checkpoint blockade (ICB) response prediction via Tumor Immune Dysfunction and Exclusion (TIDE) scores.

Results: IKBIP was significantly upregulated in STAD tissues versus normal controls at both mRNA and protein levels. High IKBIP expression correlated with age ≥65 years, advanced tumor (T) stage, higher grade, and independently predicted poor overall survival in both TCGA and institutional cohorts (P<0.05). IKBIP positively correlated with macrophage infiltration, particularly M2-polarized (CD163⁺/CD206⁺) macrophages (P=0.003), which were the predominant subset in poorly differentiated tumors and associated with reduced patient survival. Co-expression and pathway analyses linked IKBIP to EMT, extracellular matrix (ECM) receptor interactions, and Toll-like receptor signaling. In vitro, IKBIP knockdown impaired proliferation, migration, and invasion, upregulated E-cadherin, and downregulated N-cadherin, Snail, MMP9, p65, IL-6, and TNF-α; overexpression produced reciprocal changes (P<0.0001). Across multiple datasets, IKBIP consistently correlated positively with RELB, TIM-3, dysfunction/exclusion/TIDE scores, and several chemoresistance genes (P<0.05).

Conclusions: IKBIP may function as a novel oncogenic driver in STAD through dual mechanisms-remodeling the immune microenvironment via M2 macrophage polarization and immune checkpoint modulation, and promoting EMT and NF-κB signaling to enhance tumor invasion and metastasis. These findings position IKBIP as a potential prognostic biomarker and a potential therapeutic target, with utility in predicting ICB response and chemotherapy resistance.