CDK1 and neoplasm: To confirm the in vivo activity of shikonin was through inhibition of the Cdc25s, we also checked the phosphorylation state of CDK1 in tumour tissue from xenograph tumour model mice, and the results showed that shikonin could inhibit dephosphorylation of CDK1 in tumour tissue also, which suggested that shikonin could also participate in the Cdc25s-related cell cycle pathway in vivo.