Interferon regulatory factor 4 drives M2 macrophage polarization in lung adenocarcinoma via the absent in melanoma 2–mediated phosphoinositide 3-kinase/protein kinase B signaling pathway

Tumor-associated macrophages, predominant immunosuppressive components within the tumor microenvironment, critically regulate lung adenocarcinoma (LUAD) progression; however, their molecular regulatory mechanisms remain incompletely characterized. The Cancer Genome Atlas database analysis revealed absent in melanoma 2 (AIM2) expression in LUAD. The correlation between AIM2 expression and M2 macrophage infiltration levels was further evaluated. Putative transcriptional regulators upstream of AIM2 were predicted through bioinformatics screening, with JASPAR employed to identify potential binding sites between candidate factors and the AIM2 promoter. These predictions were experimentally validated using dual-luciferase reporter assays. Furthermore, we established a LUAD cell-macrophage coculture system. We performed flow cytometric analysis of macrophage surface CD206 expression, quantitative PCR quantification of mRNA levels, ELISA quantification of cytokine secretion profiles, and Western blot detection of proteins. Bioinformatics analysis revealed that AIM2 was highly expressed in LUAD tumor tissues and positively correlated with the marker genes of M2 macrophages. Overexpression of AIM2 in LUAD cells promoted the expression of CD206 on the macrophage surface, upregulated the mRNA expression levels of M2 macrophage marker genes such as CD163, ARG1, and MRC1, and enhanced the secretion of transforming growth factor-beta and interleukin-10 . These results indicated an increased level of macrophage polarization towards the M2 phenotype, and inhibiting the phosphoinositide 3-kinase/protein kinase B (PI3K/AKT) signaling pathway reversed the above phenomenon. Furthermore, the interferon regulatory factor 4 (IRF4) promoted the transcription of AIM2. IRF4 knockdown in LUAD cells suppressed M2 macrophage polarization, but simultaneous overexpression of AIM2 restored it to baseline levels. IRF4 drives M2 macrophage polarization in LUAD via the AIM2-mediated PI3K/AKT signaling pathway.