CCL2 and cancer: Among these genes, CCL2, also known as MCP-1, is a critical cytokine in recruiting monocytes to the tumor microenvironment, and it is correlated with the progression of several cancers, such as ESCC and colon cancer.31,32 We quantified CCL2 levels in the culture medium supernatants of CAFs stimulated with TGF-β, a cytokine secreted by tumor cells and implicated in fibroblast activation.