Sanguinarine exhibits potent efficacy against cervical cancer cells through inhibiting the STAT3 pathway in vitro and in vivo

Background: Cervical cancer is the third most common malignancy among female cancer patients worldwide. Signal transducer and activator of transcription 3 (STAT3) is a transcription factor which regulates a variety of cancer cellular physiological activities including cervical cancer. Sanguinarine (SNG) is a natural plant-derived benzophenanthridine alkaloid that possesses antitumor activities in several cancer cells. However, its anticancer effect on human cervical cancer cells and the underlying mechanisms have not been fully defined. Methods: In this study, the inhibitory effect of SNG on the proliferation and growth of HeLa cell was detected by MTT assay. Next, cell cycle and apoptosis of HeLa cells was analyzed using Annexin-V/PI double staining and flow cytometry. Then, we measured intracellular ROS generation induced by SNG in HeLa cells by DCFH-DA (10 mu M) staining, and the expression level of p-STAT3 and STAT3 was detected by Western blot. Finally, in order to study the effect of SNG on tumor growth in vivo, athymic nude mice were used in the vivo experiments. Result: This study showed that SNG dose-dependently decreased the tumor cell proliferation and induced a marked increase in cell apoptosis in HeLa cells. Western blot analysis results revealed that SNG-induced antitumor effect might be mediated by STAT3 inhibition. SNG increased the expression of the proapoptotic protein Box and reduced the expression of the antiapoptotic protein Bcl-2. We further found that SNG dose-dependently increased ROS level in Hela cells. Moreover, pretreatment with N-acetyl-l-cysteine, a scavenger of ROS, almost reversed the SNG-induced anticancer effect. In addition, SNG inhibited human cervical cancer xenograft growth without exhibiting toxicity in vivo. Conclusion: Our findings highlight STAT3 as a promising therapeutic target. We also demonstrate that SNG is a novel anticancer drug for the treatment of cervical cancer.