Shikonin and its analogues can kill cancer cells through a number of mechanisms, including inhibition of topoisom-erase-I (8), polo-like kinase 1 (PLK1) and protein tyrosine kinase (PTK) (9); regulation of phosphorylation-dependent activities of extracellular-regulated protein kinase (pERK), c-Jun N-terminal kinase (JNK), and protein kinase Cα PKCα (10); suppression of tumor necrosis factor receptor-associated protein 1 (TRAP1) expression (11); activation of caspases (12); and inhibition of proteasome activity (13). The gene discussed is PLK1; the disease is cancer.