Our data also showed that plumbagin suppressed CXCR4 expression on various tumor cell lines including gastric cancer, lung adenocarcinoma, renal cell carcinoma, oral and hepatocellular carcinoma, thereby indicating that the effect of plumbagin on CXCR4 is not limited to a single tumor cell type. Here, CXCR4 is linked to renal cell carcinoma.