HLA-DR regulates macrophage phenotypic transformation and affects malignant behavior in esophageal squamous cell carcinoma

Abstract Background Tumor-associated macrophages (TAMs) are an important immune cell component of the tumor microenvironment. This study aimed to explore the molecular mechanism of TAMs phenotype transformation and the role in the development of esophageal squamous cell carcinoma (ESCC).Methods Co-culture conditions were employed to determine the phenotypic effects of TAMs on ESCC cell biological behavior. Tumor metastasis related molecules VEGF-C and MMP-9 produced by TAMs was evaluated by qRT-PCR and western blot. Expression of HLA-DR was knocked down in TAMs in vitro to determine the effects on macrophage polarization and the biological behavior of ESCC. We determined whether co-injection with M2 TAMs and macrophages depletion affected tumor growth in vivo tumor challenge model. Associations between HLA-DR, TAM density, and clinical outcomes were evaluated in patients with ESCC.Results TAMs in ESCC samples were found to closely reflect the M2 phenotype of TAMs, and exhibited low expression of HLA-DR. Which was involved in ESCC tumor invasion and metastasis. Low expression of HLA-DR positively correlated with high-density of M2 TAMs, indicating high invasiveness and poor prognosis in patients with ESCC. Downregulation of HLA-DR in TAMs led to additional M2-type TAM polarization and more VEGF-C and MMP-9 secretion, promoted the malignant transformation of ESCC.Conclusions These results demonstrate that downregulation of HLA-DR promote the transformation of M2 TAMs, and participate in the invasion and metastasis of ESCC.