Abstract: BACKGROUND AND AIM: To investigate proliferation-inhibiting effects and mechanisms of shikonin on human choriocarcinoma JEG-3 cells. MATERIALS AND METHODS: 3-(4,5- dimethylthiazol-2-yl)-2,5- diphemyltetra-zolium Bromide (MTT) assay was used to determine the inhibitory rate of shikonin on the proliferation of JEG-3 cells. Apoptosis induced by shikonin was detected with Hoechst 33258 dye , flow cytometry (FCM) and Annexin V/PI assay. Western blot was used to evaluate the changes of pro-caspase-3, cleaved PARP, active MAPK in protein levels in JEG-3 cells. RESULTS: Shikonin induced JEG-3 apoptosis in a time- and dose-dependent manner. The IC50 of a 24 h time course for JEG-3 cells was 6.3±0.6 μmol/L. Typical morphological changes of apoptosis were observed in JEG-3 cells with Hoechst staining after induced by shikonin. The shikonin-treated JEG-3 cells with condensed and fragmented chromatin, apoptosis peak and hypo-diploid cells were revealed by proidum iodide (PI) staining. Furthermore, Annexin-V/PI staining showed the early apoptotic cells. To elucidate the apoptotic pathways induced by shikonin, we assessed the expression of active caspase-3, cleavages of poly(ADP-ribose) polymerase (PARP) and MAPK. Caspase-3 in JEG-3 cells was activated after 12 h treatment and PARP was cleaved subsequently. Phosphorylation of ERK and JNK was respectively blocked after 8 h and 12 h treatment. CONCLUSION: Shikonin could significantly inhibit the proliferation of JEG-3 cell and induce apoptosis. Activation and inhibition of MAPK pathway may affect apoptosis.

Key words: shikonin, human choriocarcinoma cells JEG-3, apoptosis, caspase-3