[Molecular mechanism of norcantharidin inducing apoptosis in liver cancer cells].

Objective: To elucidate the molecular mechanism of norcantharidin (NCTD) in inducing apoptosis of liver cancer cells so as to provide basic rationales for its application in liver cancer treatment.

Methods: Liver cancer cell lines of SMMC-7721 and BEL-7402 were treated with NCTD. The cell growth inhibition was measured by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay, cell death detected by trypan blue exclusion assay and apoptosis examined by Annexin V/PI staining and flow cytometry. The cleavage of caspase-9, -3 and PARP, and the expression of the anti-apoptotic Bcl-2 proteins were analyzed by Western blot.

Results: The MTT results showed that, after a treatment with NCTD for 24, 48 and 72 h, the IC50 of NCTD in SMMC-7721 cell line was 12, 6 and 1.6 µg/ml respectively; in BEL-7402, the IC50 10, 4 and 2 µg/ml respectively. Trypan blue exclusion assay showed that NCTD mediated substantial cell death in two cancer cell lines. Apoptosis assay showed that, after a 12 h treatment with 10 µg/ml NCTD, 27% of SMMC-7721 cells were induced to undergo apoptosis, an increment of 20% over the untreated control cells (7%); 30% of BEL-7402 cells became apoptotic, an increment of 22% over the untreated control cells (8%). Western blot analysis showed that NCTD treatment potently induced the activation of caspase-9, -3 and the cleavage of PARP, and markedly down-regulated the expression of Bcl-2, Bcl-X(L) and Mcl-1.

Conclusion: NCTD strongly inhibits liver cancer cell growth and potently induces apoptotic cell death in two liver cancer cell lines. The strong anticancer activity of NCTD may be induced through targeting multiple Bcl-2 anti-apoptotic family members.