血小板反应蛋白4通过诱导肿瘤相关巨噬细胞M2型极化促进肝癌细胞转移

血小板反应蛋白4 (thrombospondin 4, THBS4) 属于THBS家族成员,是细胞外基质分泌的蛋白质,参与调控细胞增殖、黏附及血管生成等多种生理过程。近来研究表明,机体在炎症刺激下加速产生THBS4并诱导巨噬细胞粘附与积累。我们的前期研究证实,THBS4在肝癌(hepatocellular carcinoma,HCC)中发挥促癌作用,但THBS4对肝癌免疫微环境的影响尚不明确。本文旨在分析THBS4通过诱导肿瘤相关巨噬细胞M2型极化,促进肝癌细胞转移的作用。通过肝癌条件培养基(HCC conditioned medium,HCM)模拟肿瘤微环境,发现在HCM作用下巨噬细胞中THBS4表达呈时间依赖性升高(P＜0.05);下调THBS4促使M1型巨噬细胞标志物IL-1β、CD86的表达升高(P＜0.01),而M2型标志物 IL-10和CD206表达降低(P＜0.01)。进一步通过Transwell共培养实验检测THBS4诱导的M2型巨噬细胞对肝癌转移的影响。将下调THBS4的M2型巨噬细胞(M2-TAMs)与HepG2肝癌细胞进行共培养。结果显示,下调THBS4的M2-TAMs明显抑制了HepG2细胞的侵袭和迁移能力(P均＜0.01)。综上所述,肿瘤微环境促进巨噬细胞中THBS4表达,THBS4可能通过诱导巨噬细胞M2型极化促进肝癌细胞侵袭转移。本文为探究THBS4诱导肝癌免疫微环境的建立提供了一些新的实验依据。

THBS4 Promotes the Metastasis of Hepatocellular Carcinoma Cells by Inducing M2 Polarization of Tumor-associated Macrophages

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.