Ergosterol peroxide activates Foxo3-mediated cell death signaling by inhibiting AKT and c-Myc in human hepatocellular carcinoma cells

// Xiangmin Li 1, 2, 3, * , Qingping Wu 1, * , Ming Bu 4, * , Liming Hu 4 , William W. Du 2, 3 , Chunwei Jiao 1, 5 , Honghui Pan 1 , Mouna Sdiri 2, 3 , Nan Wu 2, 3 , Yizhen Xie 1, 5 , Burton B. Yang 2, 3, 6 1 State Key Laboratory of Applied Microbiology Southern China, Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Institute of Microbiology, Guangzhou, PR China 2 Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, Canada 3 Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada 4 College of Life Science and Bioengineering, Beijing University of Technology, Pingleyuan, Chaoyang, Beijing, China 5 Guangdong Yuewei Edible Fungi Technology Co. Ltd, Guangzhou, China 6 Institute of Medical Science, University of Toronto, Toronto, Canada * These authors contributed equally to this work Correspondence to: Yizhen Xie, email: 13622216490@126.com Burton B. Yang, email: byang@sri.utoronto.ca Keywords: ergosterol peroxide, pAKT, c-Myc, Foxo3, Puma Received: January 13, 2016      Accepted: March 14, 2016      Published: April 06, 2016 ABSTRACT Sterols are the important active ingredients of fungal secondary metabolites to induce death of tumor cells. In our previous study, we found that ergosterol peroxide (5α, 8α-epidioxiergosta-6, 22-dien-3β-ol), purified from Ganoderma lucidum , induced human cancer cell death. Since the amount of purified ergosterol peroxide is not sufficient to perform in vivo experiments or apply clinically, we developed an approach to synthesize ergosterol peroxide chemically. After confirming the production of ergosterol peroxide, we examined the biological functions of the synthetic ergosterol peroxide. The results showed that ergosterol peroxide induced cell death and inhibited cell migration, cell cycle progression, and colony growth of human hepatocellular carcinoma cells. We further examined the mechanism associated with this effect and found that treatment with ergosterol peroxide increased the expression of Foxo3 mRNA and protein in HepG2 cells. The upstream signal proteins pAKT and c-Myc, which can inhibit Foxo3 functions, were clearly decreased in HepG2 cells treated with ergosterol peroxide. The levels of Puma and Bax, pro-apoptotic proteins, were effectively enhanced. Our results suggest that ergosterol peroxide stimulated Foxo3 activity by inhibiting pAKT and c-Myc and activating pro-apoptotic protein Puma and Bax to induce cancer cell death.