Saikosaponin-d Inhibits the Hepatoma Cells and Enhances Chemosensitivity Through SENP5-Dependent Inhibition of Gli1 SUMOylation Under Hypoxia.

Chun-Yan Zhang,Li-Li Li,Yue Li,Tao Wang,Xiao-Fang Ma,Xiao-Zhi Liu,Zhong-Min Jiang,Wen-Han Wu

doi:10.3389/fphar.2019.01039

Abstract

Chemosensitivity is one of the key factors affecting the therapeutic effect on cancer, but the clinical application of corresponding drugs is rare. Hypoxia, a common feature of many solid tumors, including hepatocellular carcinoma (HCC), has been associated with resistance to chemotherapy in part through the activation of the Sonic Hedgehog (SHh) pathway. Hypoxia has also been associated with the increased SUMOylation of multiple proteins, including GLI family proteins, which are key mediators of SHh signaling, and has become a promising target to develop drug-resistant drugs for cancer treatment. However, there are few target drugs to abrogate chemotherapy resistance. Saikosaponin-d (Ssd), one of the main bioactive components of Radix bupleuri, has been reported to exert multiple biological effects, including anticancer activity. Here, we first found that Ssd inhibits the malignant phenotype of HCC cells while increasing their sensitivity to the herpes simplex virus thymidine kinase/ganciclovir (HSVtk/GCV) drug system under hypoxia in vitro and in vivo. Furthermore, we had explored that GLI family activation and extensive protein SUMOylation were characteristics of HCC cells, and hypoxia could activate the SHh pathway and promote epithelial-mesenchymal transition (EMT), invasion, and chemosensitivity in HCC cells. SUMOylation is required for hypoxia-dependent activation of GLI proteins. Finally, we found that Ssd could reverse the effects promoted by hypoxia, specifically active sentrin/small ubiquitin-like modifier (SUMO)-specific protease 5 (SENP5), a SUMO-specific protease, in a time- and dose-dependent manner while inhibiting the expression of SUMO1 and GLI proteins. Together, these findings confirm the important role of Ssd in the chemoresistance of liver cancer, provide some data support for further understanding the molecular mechanisms of Ssd inhibition of malignant transformation of HCC cells, and provide a new perspective for the application of traditional Chinese medicine in the chemical resistance of liver cancer.

Highlights

Hepatocellular carcinoma (HCC) is the leading cause of cancer-related deaths worldwide and is largely asymptomatic but a highly aggressive disease (Siegel et al, 2018; Marino et al, 2019)
We revealed that Ssd activates sentrin/small ubiquitin-like modifier (SUMO)-specific protease 5 (SENP5), strongly inhibiting SUMO1 and Gli1 and reversing the effects promoted by hypoxia
Western blotting analysis demonstrated that SUMO1 and Ubc9 were both highly expressed in HCC tissues (Figure 1A), and it can be seen that some bands bound to SUMO1, which may be a large amount of protein SUMOylation

Summary

Introduction

Hepatocellular carcinoma (HCC) is the leading cause of cancer-related deaths worldwide and is largely asymptomatic but a highly aggressive disease (Siegel et al, 2018; Marino et al, 2019). The drug resistance of tumor cells seriously affects the clinical chemotherapy effect of the drug (Liang and Aszalos, 2006). Some studies indicate that there are many reasons for drug resistance, including hypoxia, tumor suppressor gene mutation, and cell membrane transporter expression (Szakacs et al, 2006), which cause tumor cells to mutate, structure, and function to evolve and are not sensitive to drugs, lead to failure of chemotherapy. Researchers are devoting themselves to improving the sensitivity of chemotherapy drugs and overcoming the drug resistance of tumor cells. This problem has not been fundamentally solved, the clinical effects of some drugs are still not satisfactory

Methods

Results

Conclusion