Shikonin Exerts Antitumor Activity In Burkitt's Lymphoma By Inhibiting C-MYC And PI3K/AKT/mTOR Pathway And Acts Synergistically With Doxorubicin

Objective To study the effect of shikonin on Burkitt's lymphoma(BL)cells in vitro and vivo.To explore the morphological changes and molecular mechanisms in BL cells after shikonin treatment.To find out the combined effects of treatment with Shikonin and doxorubicin in BL cells.Methods The growth inhibition of BL cell lines treated with drugs was determined by MTT assay.PI/Hoechst staining were applied for observing the changes of nuclear morphology by using fluorescence microscope after shikonin treatment.The apoptosis rate of BL cells was examined using Annexin V and 7-AAD staining assay followed by fow cytometry analysis.Furthermore,the pan-caspase inhibitor ZVAD-FMK was used to determine whether the apoptosis induced by SHK was caspase-dependent.The C-MYC and PI3K/AKT/m TOR pathways were evaluated by Western Blot.Q-PCR was performed to evaluate the effect of shikonin on expression of mi R-19 a in BL cells.The combination index isobologram method of Chou and Talalay was used to evaluate the synergistic efficacies of shikonin and doxorubicin.The xenograft mice models were established to investigate the function and mechanisms of shikonin in vivo by HE staining,immunohistochemistry,Western blotting and Q-PCR.Results Shikonin suppressed cellular proliferation in dose-dependent and time-dependent manners.Shikonin induced apoptosis in BL cells via caspase-dependent pathways,which was validated by nuclear fragmentation,apoptotic cell morphology and pan-caspase inhibitor ZVAD-FMK.Both in vitro and in vivo,Shikonin could significantly decrease the expression of C-MYC and PI3K/AKT/m TOR relevant pathways in protein level.Shikonin also down-regulated the expression of mi R-19 a in a dose-manner in BL cells.No significant difference in weight and liver function was observed between SHK-treated mice and control mice.Shikonin potentiated anti-proliferation activity of doxorubicin in BL cells.Conclusion Shikonin exhibits a strong antitumor activity against Burkitt's lymphoma cells.Inhibition of C-MYC and PI3K/AKT/m TOR pathway may contribute to Shikonin-induced cell death.Combination of shikonin with doxorubicin has potential for use in therapeutic interventions in BL.