THBS4 Promotes the Metastasis of Hepatocellular Carcinoma Cells by Inducing M2 Polarization of Tumor-associated Macrophages / 中国生物化学与分子生物学报

ABSTRACT

Thrombospondin 4 (THBS4), a member of the THBS family, is a protein secreted by the extracellular matrix and is involved in regulating various physiological processes, such as cell proliferation, adhesion and angiogenesis. Recent studies have shown that the inflammation stimulates THBS4 production and induces the adhesion and accumulation of macrophages. Our previous study confirmed that THBS4 acts as an oncogene in hepatocellular carcinoma (HCC), the effect of THBS4 on the immune microenvironment of HCC remains unclear. This study aims to analyze the role of THBS4 in promoting the metastasis of HCC cells by inducing M2-type polarization of tumor-associated macrophages. We simulate the tumor microenvironment through HCC conditioned medium (HCM) and found that the expression of THBS4 in macrophages increased in a time-dependent manner under the action of HCM (P<0.05); THBS4 knockdown promotes the expression of M1 macrophages markers IL-1β and CD86 (P<0.01), while the expression of M2-type markers IL-10 and CD206 were decreased (P<0.01). Transwell co-culture assay was used to further detect the effect of THBS4-induced M2-type macrophages on HCC metastasis. Results from co-culture of THBS4-downregulated M2 macrophages with HepG2 cells showed that THBS4-downregulated M2-TAMs significantly inhibited the invasion and migration ability of HepG2 cells (all P < 0.01). In conclusion, the tumor microenvironment promotes the expression of THBS4 in macrophages, and THBS4 may promote the invasion and metastasis of HCC cells by inducing M2-type polarization of macrophages. This study provides some new experimental basis for exploring the establishment of THBS4-induced HCC immune microenvironment.