IER5L is a Prognostic Biomarker in Pan-Cancer Analysis and Correlates with Immune Infiltration and Immune Molecules in Non-Small Cell Lung Cancer

Purpose: Non-small cell lung cancer (NSCLC) accounts for the majority of lung cancer cases. Immediate early response 5 like (IER5L) plays crucial roles in progression and prognosis for several tumors, but its role in NSCLC remains unclear. Patients and Methods: Gene expression and mutation profiles, DNA methylation data, and clinical information for cancers were downloaded from multiple databases. Relative expression, prognostic value, and correlation with disease progression of IER5L were analyzed in multiple cancers, including NSCLC. Upstream mechanisms were explored using a transcriptional network. Functional enrichment analysis, protein-protein interaction network, and gene set enrichment analysis were applied to study downstream mechanisms. Correlations of IER5L with immune infiltration, immune molecules, methylation status, and tumor mutation burden (TMB) were analyzed using R language. Finally, quantitative polymerase chain reaction (qPCR) and single-cell RNA sequencing (scRNA seq) analysis were performed to validate IER5L expression in NSCLC. Results: Pan-cancer analysis displayed that IER5L expression was upregulated in multiple cancers and was associated with disease prognosis and progression, including NSCLC, which was validated using qPCR. scRNA seq analysis showed that multiple cells had increased IER5L expression. An EGR1-hsa-miR-8075-IER5L network was constructed for NSCLC. A total of 191 DEGs were identified between the two IER5L groups, which were significantly enriched in biological process of action potential, sodium ion transport, and regulation of membrane potential. Increased IER5L expression was primarily enriched in cell cycle, NOTCH signaling pathway, and oxidative phosphorylation pathway, and was correlated with increased regulatory T cells and neutrophils, elevated levels of immune molecules, and higher TMB. Conclusion: Our findings show that increased IER5L expression was correlated with progression and prognosis in multiple cancers as well as with immune infiltration and immune molecules in NSCLC. Thus, IER5L is a prognostic biomarker in multiple cancers and may correlate with immunotherapeutic response in NSCLC.