Integrating Multi-Omics Mendelian Randomization and Functional Validation to Identify Novel Apoptosis Regulators in Follicular Lymphoma.

IntroductionDysregulation of apoptosis is a hallmark of follicular lymphoma (FL), yet the causal genetic drivers remain incompletely understood. This study aimed to identify causal apoptosis-related genes in FL and validate their functional roles.MethodsWe conducted a multi-omics Mendelian randomization (MR) study, integrating summary statistics from a large-scale FL genome-wide association study with data on methylation (mQTL), expression (eQTL), and protein (pQTL) quantitative trait loci. Summary data-based MR (SMR) and colocalization analyses were used to identify candidate causal genes. Independent external transcriptomic cohorts were utilized to validate the gene correlations, and evaluate the clinical prognostic relevance of the identified candidates. Key findings were then validated in FL patient tissues using RT-qPCR, and the functional role and downstream molecular mechanisms of the top candidate gene were systematically characterized through in vitro phenotypic characterization, drug sensitivity testing, and mechanistic signaling analyses.ResultsOur MR analysis identified several genes with causal links to FL risk, with integrative analysis highlighting IER3IP1, PRKCZ, and CD40. Notably, PRKCZ and CD40 exhibited significant correlation, whereas IER3IP1 displayed an independent regulatory pattern. Clinical tissue validation confirmed that IER3IP1 mRNA levels were significantly elevated in FL patient tissues. Functional studies in an FL cell line demonstrated that IER3IP1 acts as an oncogene, promoting proliferation, colony formation, and migration while inhibiting apoptosis. Mechanistically, IER3IP1 depletion promoted FOXO1-mediated transcriptional upregulation of CD20 via the XBP1/FOXO1 signaling axis, which concomitantly activated the intrinsic apoptotic pathway and significantly enhanced the sensitivity of FL cells to Rituximab-mediated cytotoxicity and apoptosis.Additionally, survival analysis revealed that CD40 serves as a strong prognostic indicator, with its low expression correlated with poorer progression-free survival and overall survival in FL patients.ConclusionsThis study provides the genetic and functional evidence establishing IER3IP1 as a novel causal oncogene in the pathogenesis of FL. Our findings elucidate the critical role of the IER3IP1-mediated XBP1/FOXO1/CD20 axis in targeted therapy resistance, highlighting IER3IP1 as a promising therapeutic target to restore apoptotic activity and improve Rituximab sensitivity.