Purpose: To test the effect of Cryptotanshinone (CPT), a natural compound isolated from the plant Salvia miltiorrhiza Bunge, on human leukemic cell lines (HL-60).

Methods: HL-60 cells were treated with CPT. Cell growth inhibition (%) was quantitated using MTT assay. Apoptosis detection with Annexin V-FITC/propidium iodide staining was followed by flow cytometry. Caspase-3, caspase-8, and caspase-9 colorimetric assay kit was used to determine caspase protease activity. Loss of mitochondrial membrane potential was examined by flow cytometry with JC-1 staining. Bax, PARP, p53, p21 and cytochrome C were determined using Western blot.

Results: Morphologic assessment, Annexin V-FITC/propidium iodide staining results and sub-G1 percentage indicate that the cytotoxic effect of CPT was mediated by induction of apoptosis. Furthermore, increased Bax expression, decreased Bcl-2 expression, loss of mitochondria membrane potential (MMP), release of cytochrome C, activation of caspase enzyme, cleavage of PARP and accumulation of p53 and p21 were detected during the apoptotic process. Caspase inhibitor partially abrogated CPT-induced apoptosis.

Conclusion: The results show that CPT induced apoptosis of HL-60 cell lines by mitochondria pathway, and suggest that CPT may serve as a potential therapy for leukemia.