Hepatocellular carcinoma (HCC) is the most frequently diagnosed primary liver tumor worldwide. Tumor-associated macrophages (TAMs) usually have a similar phenotype to M2-like macrophages and can participate in tumor progression by secreting cytokines to suppress the immune response and activity of tumor-infiltrating lymphocytes. We investigated the role of M2 macrophages in HCC progression and explored the effects of vascular endothelial growth factor receptor 2 inhibitor-apatinib. As a cellular model of HCC, Hepb3 cell line was used. M2 macrophages were obtained by differentiation of THP-1 cells. The Transwell chamber was used to co-culture M2 macrophages and Hepb3 cells. CCK-8 and EdU assays were conducted to measure cell viability and proliferation capacity. Transwell migration assay was performed to estimate cellular metastatic potential. Cytokine expression levels were assessed by ELISA. Western blotting was used to characterize activation of the VEGFR2/STAT3/PD-L1 axis. It has been shown that co-culture with M2 macrophages increased viability, cytokine production, promoted proliferation, invasion, and migration of Hepb3 cells. The secretion of TGF-β1, IL-6, MMP-9, and VEGF was significantly increased after co-culture. In contrast apatinib suppressed M2 macrophage-induced proliferation, cell viability, invasion, and migration of Hepb3 cells. Moreover, apatinib markedly decreased expression levels of p-VEGFR2, p-STAT3, and PD-L1 in Hepb3 cells under the co-culture conditions. In conclusion, apatinib treatment can suppress TAMs-mediated malignant behavior of HCC cells via modulation of the VEGFR2/STAT3/PD-L1 signaling pathway.
Keywords: VEGFR2; apatinib; hepatocellular carcinoma; malignant behavior; tumor-associated macrophages.