IL-8-induced CXCR2 down-regulation in circulating monocytes in hepatocellular carcinoma is partially dependent on MAGL.

BACKGROUND

CXC-chemokine receptor 2 (CXCR2) expression was found to be down-regulated on circulating monocytes of cancer patients. Here, we analyze the percentage of CD14CXCR2 monocyte subsets in hepatocellular carcinoma (HCC) patients, and investigate the mechanisms that regulate CXCR2 surface expression on monocytes and its biological function.

METHODS

Flow cytometry was used to analyze the proportion of the CD14CXCR2 subset from the total circulating monocytes of HCC patients. Interleukin 8 (IL-8) levels were measured from serum and ascites, and their correlation with the CD14CXCR2 monocyte subset proportion was calculated. THP-1 cells were cultured in vitro and treated with recombinant human IL-8 and CXCR2 surface expression was analyzed. CXCR2 was knocked down to examine how it affects the antitumor activity of monocytes. Finally, a monoacylglycerol lipase (MAGL) inhibitor was added to analyze its effect on CXCR2 expression.

RESULTS

A decrease in the proportion of the CD14CXCR2 monocyte subset was observed in HCC patients compared with healthy controls. CXCR2 monocyte subset proportion was associated with the AFP value, TNM stage, and liver function. Overexpression of IL-8 was observed in the serum and ascites of HCC patients, and negatively correlated with CXCR2 monocyte proportion. IL-8 decreased CXCR2 expression in THP-1 cells, contributing to decreased antitumor activity toward HCC cells. MAGL expression in THP-1 cells was up-regulated after IL-8 treatment, and the MAGL inhibitor partially reversed the effects of IL-8 on CXCR2 expression.

CONCLUSIONS

Overexpression of IL-8 drives CXCR2 down-regulation on circulating monocytes of HCC patients, which could be partially reversed by a MAGL inhibitor.