Protodioscin Induces Mitochondrial Apoptosis of Human Hepatocellular Carcinoma Cells Through Eliciting ER Stress-Mediated IP3R Targeting Mfn1/Bak Expression

Abstract

Chen-Lin Yu,1,2,* Hsiang-Lin Lee,3,4,* Shun-Fa Yang,2,5 Shih-Wei Wang,1,6 Ching-Pin Lin,4,7 Yi-Hsien Hsieh,2,5 Hui-Ling Chiou8,9 1Institute of Biomedical Science, Mackay Medical College, New Taipei City, Taiwan; 2Institute of Medicine, Chung Shan Medical University, Taichung, Taiwan; 3Department of Surgery, Chung Shan Medical University Hospital, Taichung, Taiwan; 4School of Medicine, Chung Shan Medical University, Taichung, Taiwan; 5Department of Medical Research, Chung Shan Medical University Hospital, Taichung, Taiwan; 6Graduate Institute of Natural Products, College of Pharmacy, Kaohsiung Medical University, Kaohsiung, Taiwan; 7Division of Hepatology and Gastroenterology, Department of Internal Medicine, Chung Shan Medical University Hospital, Taichung, Taiwan; 8School of Medical Laboratory and Biotechnology, Chung Shan Medical University, Taichung, Taiwan; 9Department of Clinical Laboratory, Chung Shan Medical University Hospital, Taichung, Taiwan*These authors contributed equally to this workCorrespondence: Yi-Hsien Hsieh; Hui-Ling Chiou, Tel [phone], Fax [phone], Email [email protected]; [email protected]: Protodioscin (PD), a steroidal saponin, has a diverse pharmacological activity including neuroprotection, male fertility improvement, and cytotoxicity against various cancers cell lines of different origins. However, the effect of PD on hepatocellular carcinoma (HCC) is still unclear.Methods: Cell viability, colony formation and flow cytometry analysis for apoptosis profile, mitochondrial membrane potential endoplasmic reticulum (ER) expansion were employed to determine the effect of PD against HCC cells. Transient transfection of siRNA, immunofluorescent imaging and immunoprecipitation were used to elucidate the anti-cancer mechanism of PD. The in vivo toxicity and efficacy of PD were assessed by a xenograft mouse model.Results: PD induced apoptosis, loss of mitochondrial membrane potential and ER expansion in HCC cells. Either downregulation of Mfn1 or Bak reversed PD-induced apoptosis and loss of mitochondrial membrane potential. Further analysis revealed that Mfn1 and Bak will form a complex with IP3R to facilitate the transfer of Ca2+ from ER to mitochondria and apoptosis. In addition, our tumour xenograft model further verifies the in vivo anti-tumour effect of PD.Conclusion: Our study sheds light on the understanding of the anti-HCC effects of PD and may open new aspects for the development of novel treatment for human hepatocellular carcinoma.Graphical Abstract: Keywords: hepatocellular carcinoma, protodioscin, mitochondrial, apoptosis, endoplasmic reticulum

Keywords

• hepatocellular carcinoma
• protodioscin
• mitochondrial
• apoptosis
• endoplasmic reticulum