CAFs also contribute to M2 polarization by secreting multiple cytokines and stimuli including macrophage-colony stimulating factor, reactive oxygen species, IL-6, IL-8, CCL2, and CXCL6 as seen in multiple cancer model systems (e.g., PDAC, colorectal and esophageal squamous cell carcinoma) [136,138,140]. This evidence concerns the gene CCL2 and cancer.