ABSTRACT
CXC chemokine ligand 8 (CXCL8) is highly expressed in many human tumors including colorectal cancer, and it can promote the malignant progression of tumors. It was reported that M2 macrophages were abundant in colorectal cancer microenvironment, but whether CXCL8 affects the infiltration of M2 macrophages and its potential mechanism are not yet clear. The study aimed to investigate the effect of CXCL8 on M2 macrophage infiltration and chemotaxis in the colorectal cancer. Firstly, we analyzed the CXCL8 expression and immune cell infiltration in human colorectal cancer tissues from TCGA RNA-seq data. The expression of CXCL8 was verified by immunohistochemistry in tissues obtained from Shanxi Provincial Cancer Hospital. Then, Western blot and qRT-PCR were employed to detect CXCL8 expression in five colorectal cancer cell lines. THP-1 cells were allowed to differentiate into M2 macrophages via the phorbol myristate acetate (PMA) and IL-4 treatment, followed by detection of the chemotaxis of M2 macrophages towards HCT116, SW480 and CXCL8-HCT116, CXCL8-SW480 cell lines. HCT116 and SW480 cells were treated with interleukin 1β (IL-1β) to detect the expression of CXCL8, and co-cultured with M2 macrophages to analyze the chemotactic activity. The results revealed that the expression of CXCL8 was increased in pairs of CRC tissues versus normal adjacent tissues, and there were more M2 macrophage infiltration in cancer tissues with high expression of CXCL8. The mRNA and protein expression of CXCL8 in HCT116 and SW480 were increased after the IL-1β treatment (P < 0. 05). We confirmed that CXCL8 is a chemotactic factor for M2 macrophages by transwell assays (P<0. 05). In conclusion, CXCL8 in colorectal cancer cells can be induced by IL-1β in colorectal cancer cells and the upregulation of CXCL8 can promote the chemotaxis of M2 macrophages. The massive infiltration of M2 macrophages in colorectal cancer microenvironment may be related with the increased expression of CXCL8.
ABSTRACT
Sialic acid binding immunoglobulin type lectin-15 (Siglec-15), one of the Siglec gene family members, is a new immunosuppressive molecule. Siglec-15 is highly expressed in a variety of human tumor cells and tumor-associated macrophages, but the biological function of Siglec-15 in colorectal cancer (CRC) and its effect on the tumor immune microenvironment remains poorly understood. This study aimed to investigate the effects of aberrant expression of Siglec-15 on the biological behaviors of CRC cells and the infiltration of CD4