TOP2A, Stabilized by IGF2BP3 in an m6A-Dependent Manner, Drives Macrophage Recruitment and M2 Polarization in Hepatocellular Carcinoma by YAP1-Mediated CCL2 Activation.

M2-like tumor-associated macrophages (TAMs) exert immunosuppressive and protumorigenic functions in hepatocellular carcinoma (HCC). In this study, we explored the function and mechanism of Type IIA topoisomerase (TOP2A) in TAM recruitment and M2 polarization in the HCC microenvironment. The IGF2BP3-TOP2A relationship was confirmed by RIP, MeRIP, luciferase, and mRNA stability assays. Coculture experiments using a transwell system were performed to analyze the impact on the migration, CD206 cell population, and M2-related marker expression in THP-1-differentiated macrophages (THP-1-M0). Xenograft models were constructed to evaluate TOP2A's role in tumor growth. Expression analysis was performed by quantitative PCR (qPCR), immunoblotting, and immunohistochemical staining. Increased TOP2A expression was associated with advanced tumor stage and worse outcomes in HCC. IGF2BP3 was upregulated and positively correlated with TOP2A expression in HCC samples. TOP2A depletion reduced THP-1-M0 migration and M2 polarization in vitro and attenuated xenograft growth by suppressing TAM infiltration and M2 polarization in vivo. Mechanistically, IGF2BP3 recognized METTL3-catalyzed m6A sites to increase the stability and expression of TOP2A mRNA. TOP2A re-expression abolished IGF2BP3 knockdown-driven suppression of THP-1-M0 migration and M2 polarization. Moreover, TOP2A depletion decreased CCL2 production and YAP1 activation. CCL2 reconstruction or the Hippo pathway inhibitor XMU-MP-1 reversed TOP2A knockdown-driven suppression of THP-1-M0 migration and M2 polarization. Our findings identify the IGF2BP3/TOP2A axis as a master regulator of TAM recruitment and polarization in HCC via IGF2BP3-m6A-dependent TOP2A stabilization to facilitate YAP1-mediated CCL2 upregulation, providing novel strategies to overcome immunosuppression and combat HCC.