IL‐6, which was regulated by ZEB1 and ZEB2 in breast cancer cells, also induced the proliferation of fibroblasts in a context‐dependent manner, suggesting that ZEB1 and ZEB2 regulate the production and function of cancer‐associated fibroblasts, which are the main constituents of tumor microenvironments, thereby enhancing tumor growth (Kalluri and Zeisberg, 2006; Xing et al., 2010). The gene discussed is ZEB1; the disease is cancer.