SNAI1 and cancer: When activated by tumor‐derived factors in a Snail1‐dependent fashion, cancer‐activated fibroblasts secrete PGE2 and TGFβ and induce the polarization of macrophages to an alternative MHCII‐low state, preventing their cytotoxic activity on tumor cells and promoting immune evasion by the activation of regulatory T immune‐suppressive cells.