Shikonin, an ingredient of Lithospermum erythrorhizon induced apoptosis inHL60 human premyelocytic leukemia cell line

Apoptosis is a new therapeutic target of cancer research. Shikonin isolated from Lithospermum erythrorhizon, a traditional oriental medicinal herb, wa s observed to induce apoptosis in HL60 human premyelocytic leukemia cell li ne. Shikonin induced DNA fragmentation into the multiples of 180 bp and inc reased the percentage of hypodiploid cells in flow cytometry after propidiu m iodide staining. The increase of apoptotic cells was preceded by the acti vation of caspase-3, which was reported to play a central role in apoptotic process. The DNA fragmentation induced by shikonin was completely inhibite d by the pretreatment of z-VAD-fmk, a specific inhibitor of caspase, clearl y showing that the mode of cell death is apoptotic.