PFKFB4 promotes M2 polarization of tumor-associated macrophages through aerobic glycolysis-mediated modification of histone H3K18 lactylation in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) poses a substantial health burden globally. We explored the mechanism of PFKFB4 affecting M2 polarization of tumor-associated macrophages (TAMs) in HCC. The correlation between PFKFB4 expression and macrophage infiltration was analyzed by TIMER database. HCC and adjacent tissues from 30 HCC patients were collected to analyze the PFKFB4 positive expression rate, and the infiltration percentages of the M1- and M2-phenotype TAMs via immunohistochemistry and flow cytometry. PFKFB4 was knocked down or overexpressed in HCC cells, with cell glycolytic, proliferation, and migration assessed. M0 macrophages were co-cultured with HCC cells, with lactate level and TAM M2 polarization detected. H3K18 lactylation (H3K18la) level in TAMs, and its enrichment on the M2 polarization-related gene promoters (arginase 1 [Arg-1], CD206) were assessed by western blot and ChIP. Arg-1 and CD206 levels were tested by RT-qPCR and western blot. In vivo validations were performed in nude mice. PFKFB4 expression was increased in HCC, and was correlated with poor prognosis. The positive expression rate of PFKFB4 was positively correlated with M2-polarized TAM infiltration. PFKFB4 was up-regulated in HCC cells, which promoted the proliferation and migration of HCC cells via the glycolytic pathway and stimulated lactate production. Co-culture of TAMs with PFKFB4-overexpressing HCC cells promoted TAM M2 polarization. PFKFB4 stimulated tumor growth by promoting TAM M2 polarization via the glycolysis/lactate/H3K18la pathway in vivo. PFKFB4 promoted lactate accumulation in the tumor microenvironment via glycolysis, stimulated the H3K18la/M2 polarization regulatory axis in TAMs, thus regulating the immune microenvironment and promoting HCC growth.