Inhibitory effect of norcantharidin on K562 human myeloid leukemia cells in vitro

Mylabris, the dried body of the Chinese blister beetle, has been used as a Chinese medicinal for over 2000 years. Its active constituent, cantharidin, has antitumor properties and causes leukocytosis. Norcantharidin (NCTD), the demethylated form of cantharidin, is easier to synthesize and is less toxic. NCTD irreversibly reduced the clonogenic efficiency of parental and drug-resistant K562 sublines, with drug-resistant sublines showing greater susceptibility to NCTD than parental cells. NCTD inhibited DNA synthesis by blocking cells at the G2/M phase of the cell cycle. The data suggest that NCTD may be suitable in the treatment of drug-resistant leukemia.