The detailed mechanism of emodin involved in the regulation of CXC chemokine receptor-4 (CXCR4) gene expression, which affects cellular migration and invasion in lung cancer cells, was first studied by Ok et al. Emodin at a concentration of 100 μM considerably suppressed the expression of CXCR4 and also the expression of human epidermal growth factor receptor 2 (HER2) [69]. Here, CXCR4 is linked to lung cancer.