Abstract:

Objective To analyze the role of interleukin-33 （IL-33） in the occurrence and development of glioma and its related mechanism by bioinformatics technology， and to validate it through histopathological experiments， and to discuss the possibility of IL-33 as an auxiliary marker for the diagnosis and treatment of brain glioma. Methods The glioblastoma multiforme/lower grade glioma（GBMLGG） case data were downloaded from the UCSC XENA database， including data of 689 glioma samples， 5 paracancerous samples， and 1 152 normal brain tissue samples； Mann-Whitney U test was used to analyze the difference in the expression of IL-33 mRNA between the GBMLGG samples and the normal brain tissues； according to the expression level of IL-33 in GBMLGG tissue， the tumor samples were divided into IL-33 low expression group and IL-33 high expression group； the Human Protein Atlas （HPA） was used to validate the difference in the protein expression of IL-33 in the GBMLGG samples； the R language DESeq2 （v.1.36.0） package was used to screen the differentially expressed genes （DEGs） in the GBMLGG tumor case samples； Gene Ontology （GO） functional enrichment analysis and Kyoto Encyclopedia of Genes and Genomes （KEGG） signaling pathway enrichment analysis were used to perform pathway analysis on the DEGs； Gene Set Enrichment Analysis （GSEA） was used to discuss the pathways significantly enriched by IL-33 in the GBMLGG tissues； GSVA package was used to analyze the immune infiltration in the GBMLGG samples； survival package and survminer package were used to analyze the effect of IL-33 expression level on the survival of the patients in different clinical subgroups of GBMLGG； univariate and multivariate Cox proportional hazards regression models were used to analyze the relationship between IL-33 expression and the clinicopathological characteristics of the GBMLGG patients； the GBMLGG and control tissue samples were collected； immunohistochemical staining was used to detect the expression levels of IL-33 and its receptor suppression of tumorigenicity 2 （ST2） in the GBMLGG and normal brain tissue samples. Results The expression levels of IL-33 mRNA and protein in the GBMLGG tissues were significantly increased compared with those in normal brain tissues； there were 634 DEGs in total between the IL-33 low and high expression groups， including 283 up-regulated DEGs and 351 down-regulated DEGs； the GO functional enrichment analysis and KEGG signaling pathway enrichment analysis results showed that the DEGs were associated with biological behaviors such as activation of the classical pathway of complement， immunoglobulin complex formation， and mediated immunoglobulin receptor binding； in the course of GBMLGG development， high expression of IL-33 could degrade valine， leucine， and isoleucine， induce limonene and pinene degradation， promote propanoate metabolism， and simultaneously activate the Leishmania infection pathway， NOD-like receptor signaling pathway， and allograft rejection pathway； the infiltration levels of dendritic cell （DC） and mast cell in the IL-33 high expression group were higher than those in IL-33 low expression group； the infiltration levels of eosinophil， helper T cell， and central memory T cell （Tcm） were lower than those in IL-33 low expression group； the expression level of IL-33 was positively correlated with the infiltration of γδT cell （Tgd）， helper T cell， macrophage， eosinophil， Tcm， and effector memory T cell （Tem） （P<0.05）； it was negatively correlated with the infiltration levels of DC， natural killer cell （NK）， CD8+T cell， and CD56bright NK cell （P<0.05）. There were no significant differences in the overall survival （OS）， disease-specific survival （DSS）， and disease-free interval （DFI） of the GBMLGG patients between IL-33 high expression group and IL-33 low expression group （P>0.05）； the clinical subgroup analysis results showed that the expression level of IL-33 in oligodendrocytoma tissues was lower than those in astrocytoma and oligoastrocytoma tissues， and the expression level of IL-33 in glioblastoma tissues was higher than that in oligodendroglioma tissues. World Health Organization （WHO） stage and age were risk factors affecting the prognosis of the GBMLGG patients， and IDH mutation and primary treatment effect were protective factors affecting the prognosis； The immunohistochemical staining results showed that compared with normal brain tissues， the expression levels of IL-33 and its receptor ST2 proteins in the malignant glioma tissues were significantly increased （P<0.05）， and their expression levels were positively correlated in both normal brain tissues and malignant glioma tissues （P<0.05）. Conclusion The expression level of IL-33 in the glioma tissue is significantly increased， and high expression of IL-33 may be a potential factor for poor prognosis in the glioma patients.

Key words: Glioma, Interleukin-33, Immune microenvironment, Prognostic marker, Bioinformatics