NEIL3 Upregulated by TFAP2A Promotes M2 Polarization of Macrophages in Liver Cancer via the Mediation of Glutamine Metabolism

INTRODUCTION: Tumor-associated macrophages, which are part of the tumor microenvironment, are a major factor in cancer progression. However, a complete understanding of the regulatory mechanism of M2 polarization of macrophages (Mø) in liver cancer is yet to be established. This study aimed to investigate the potential mechanism by which NEIL3 influenced M2 Mø polarization in liver cancer. METHODS: Bioinformatics analysis analyzed NEIL3 expression and its enriched pathways in liver cancer tissue, as well as its correlation with pathway genes. The upstream transcription factor of NEIL3, TFAP2A, was predicted and its expression in liver cancer tissue was analyzed. The binding relationship between the two was analyzed by dual-luciferase reporter and chromatin immunoprecipitation experiments. qRT-PCR assessed NEIL3 and TFAP2A levels in liver cancer cells. Cell viability was detected by CCK-8, while CD206 and CD86 expression was detected by immunofluorescence. IL-10 and CCR2 expressions were assessed using qRT-PCR, and M2 Mø quantity was detected using flow cytometry. Reagent kits tested glutamine (Gln) consumption, α-ketoglutarate, and glutamate content, as well as NADPH/NADP+ and GSH/GSSG ratios. Expression of Gln transport proteins was detected using Western blot. An animal model was established to investigate the influence of NEIL3 expression on liver cancer growth. RESULTS: NEIL3 was highly expressed in liver cancer and promoted Mø M2 polarization through Gln metabolism. TFAP2A was identified as the upstream transcription factor of NEIL3 and was highly expressed in liver cancer. Rescue experiments presented that overexpression of NEIL3 reversed the suppressive effect of TFAP2A knockdown on Mø M2 polarization in liver cancer. In vivo experiments demonstrated that the knockdown of NEIL3 could significantly repress the growth of xenograft tumors. CONCLUSION: This study suggested that the TFAP2A/NEIL3 axis promoted Mø M2 polarization through Gln metabolism, providing a theoretical basis for immune therapy targeting the liver cancer TME.