Down-regulation of Interleukin-2 Predicts Poor Prognosis and Associated with Immune Escape in Lung Adenocarcinoma.

Background and Objective: Lung adenocarcinoma (LUAD) is the most common subtype of lung cancer and has a poor prognosis. Interleukin-2 (IL2) is a cytokine that stimulates lymphocyte proliferation. However, its role in LUAD remains unclear. Methods: The UALCAN, human protein atlas (HPA), and tumor immune estimation resource (TIMER) databases were used to investigate IL2 expression in samples from patients with LUAD. The HPA, PrognoScan, and Kaplan-Meier plotter databases were used to examine the prognostic value of IL2 in LUAD. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses were performed to analyze IL2-interacting genes identified through the GeneMANIA database. TIMER was used to analyze the correlation of IL2 expression with immune cell infiltration and immune checkpoint expression levels in LUAD. Results: Bioinformatic analysis using the TIMER, The University of Alabama at Birmingham Cancer data analysis Portal (UALCAN), and HPA public databases showed that IL2 expression was lower in patients with LUAD than in the normal control group. Moreover, patients with low IL2 expression exhibited poor overall survival. Furthermore, IL2 expression was significantly positively correlated with various immune cells, including B cells, CD8+ T cells, CD4+ T cells, macrophages, neutrophils, and dendritic cells, in patients with LUAD. Additionally, IL2 expression was markedly positively associated with the above-mentioned immune cells. Furthermore, IL2 expression was positively correlated with PD-1, PD-L1, and CTLA-4 expression. Conclusion: Our results indicate that down-regulation of IL2 predicts poor prognosis and is associated with immune escape in LUAD, and IL2 could serve as a potential novel prognostic biomarker of LUAD.