Tumour-associated Macrophages Mediate The Invasion And Metastasis Of Bladder Cancer Cells Through CXCL8

Objective: Bladder cancer is a common malignant tumor in China,and its development is closely related to the tumor microenvironment.Tumor-associated macrophages(TAMs)are associated with both the progression and poor prognosis of a variety of solid tumours,it is believed to play a key role in the progression of tumors.Tumor-associated macrophages can promote tumor invasion and metastasis by secreting cytokines and chemokines,and CXCL8 is the main chemokine secreted by them.The purpose of this study was to investigate and elucidate the correlation between infiltrating TAM and CXCL8 expression in bladder cancer tumor microenvironment and the effect of TAM-derived CXCL8 on bladder cancer cell invasion and metastasis.Methods: A total of 55 patients admitted to the second hospital of Lanzhou university from September 2017 to December 2018 and diagnosed with bladder urothelial carcinoma by pathological were collected.Immunohistochemistry was used to detect Chemokine(C-X-C motif)ligand 8(CXCL8),CD163(a TAM marker),Matrix metalloproteinase-9(MMP-9),vascular endothelial growth factor(VEGF),and E-cadherin in cancerous and adjacent tissues of bladder cancer patients.The correlation between CD163 and CXCL8 expression and the correlation between TAM of infiltration and the expression of MMP-9,VEGF and E-cadherin in bladder cancer cells were analyzed.Then,in vitro cell experiments,peripheral blood mononuclear cells(THP-1)were cultured,followed by the sequential induction of M2 macrophages by PMA and IL-4,namely TAM.Cell culture medium with THP-1-derived TAM was collected,that is conditioned medium(CM).CXCL8 in CM was determined by ELISA.Experimental intervention group was set up: conditioned medium was used;blank control group: serum-free 1640 medium was added;control group: both CM and antiCXCL8 neutralizing antibodies were added.Human bladder cancer cell lines T24,5637 and UM-UC-3 were cultured.In vitro,Transwell invasion assay,wound healing test and vascular endothelial cell tube formation assay were used to detect and analyze the effects of TAM-derived CXCL8 on the invasiveness,migration characteristics and angiogenesis promoting ability of bladder cancer cells.Results: The immunohistochemical study showed that the expression of CXCL8 was significantly upregulated as the number of infiltrating TAMs increased in the tumor tissues.A high expression of CXCL8 significantly correlated with an increase in the expression of MMP-9 and VEGF and a decrease in expression of E-cadherin in the microenvironment.This revealed that TAM-derived CXCL8 is highly associated with bladder cancer migration,invasion,and angiogenesis.The concentration of CXCL8 was significantly higher in CM collected from TAM-like PBM-derived macrophages than that from THP-1 cells.In subsequent in vitro experiments,we found that CM derived from TAM-like PBM-derived macrophages can also increase the migration rate,invasiveness,and pro-angiogenic properties of tumor cells.Additionally,the effect of CXCL8 was significantly diminished by the addition of an anti-CXCL8 neutralizing antibody to CM.Conclusion: The infiltration of TAM in the tumor microenvironment leads to the elevation of CXCL8,which in turn promotes the secretion of MMP-9,VEGF,and reduces the secretion of E-cadherin by bladder cancer cells.This alters the migration,invasion,and pro-angiogenic capacity of bladder cancer cells and accelerates cancer progression.