IL-32-mediated caspase-43 induction: Shaping macrophage differentiation & immunomodulation in glioblastoma multiforme.

Abstract

Background & objectives Glioblastoma multiforme (GBM) is the most aggressive form of brain tumour, characterised by rapid progression, high recurrence, and poor prognosis. The immunosuppressive tumour microenvironment (TME) of GBM poses a major barrier to effective therapy. Interleukin (IL)-32, a pro-inflammatory cytokine, has been implicated in cancer progression, but its specific role in GBM remains unclear. This study aimed to investigate the immunoregulatory functions of IL-32 in GBM, particularly its impact on monocyte differentiation and macrophage polarisation. Methods Transcriptomic data from TCGA-GBM and GEO-GSE156902 were analysed to identify differentially expressed genes (DEGs), with a focus on IL-32. Functional enrichment analyses (GO and Kyoto Encyclopaedia of Genes and Genomes- KEGG) and protein-protein interaction (PPI) network construction were conducted using R software and Cytoscape. IL-32 expression was validated by qPCR and Western blot (WB) in GBM cell lines. Single-cell RNA sequencing data were integrated to determine IL-32 expression across brain cell types. Additionally, correlations between IL-32 and RNA modification genes (m6A, m5C, m1A) were analysed. Results IL-32 was significantly upregulated in GBM tissues and particularly enriched in microglial cells. Functional studies revealed that IL-32 promotes caspase-43-mediated monocyte differentiation into macrophages. Moreover, IL-32 induced a phenotypic shift from M1 to M2 macrophages via NF-κB pathway activation. PPI analysis confirmed IL-32 as a hub gene involved in immune regulation. RNA modification analysis showed positive correlations between IL-32 and METTL3, and a negative correlation with TET2, indicating epigenetic modulation of IL-32-related immune functions. Interpretation & conclusions IL-32 plays a pivotal immunoregulatory role in the GBM microenvironment by driving macrophage differentiation and M2 polarisation, contributing to tumour immune evasion. These findings highlight IL-32 as a potential therapeutic target for modulating immune responses in GBM and underscore its relevance in the design of future immunotherapeutic strategies.