title: Arenobufagin, a natural bufadienolide from toad venom, induces apoptosis and autophagy in human hepatocellular carcinoma cells through inhibition of PI3K/Akt/mTOR pathway.
abstract: Hepatocellular carcinoma (HCC) is a deadly form of cancer without effective chemotherapy so far. Currently, only sorafenib, a multitargeted tyrosine kinase inhibitor, slightly improves survival in HCC patients. In searching for natural anti-HCC components from toad venom, which is frequently used in the treatment of liver cancer in traditional Chinese medicine, we discovered that arenobufagin, a bufadienolide from toad venom, had potent antineoplastic activity against HCC HepG2 cells as well as corresponding multidrug-resistant HepG2/ADM cells. We found that arenobufagin induced mitochondria-mediated apoptosis in HCC cells, with decreasing mitochondrial potential, as well as increasing Bax/Bcl-2 expression ratio, Bax translocation from cytosol to mitochondria. Arenobufagin also induced autophagy in HepG2/ADM cells. Autophagy-specific inhibitors (3-methyladenine, chloroquine and bafilomycin A1) or Beclin1 and Atg 5 small interfering RNAs (siRNAs) enhanced arenobufagin-induced apoptosis, indicating that arenobufagin-mediated autophagy may protect HepG2/ADM cells from undergoing apoptotic cell death. In addition, we observed the inhibition of phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway by arenobufagin. Interestingly, inhibition of mTOR by rapamycin or siRNA duplexes augmented arenobufagin-induced apoptosis and autophagy. Finally, arenobufagin inhibited the growth of HepG2/ADM xenograft tumors, which were associated with poly (ADP-ribose) polymerase cleavage, light chain 3-II activation and mTOR inhibition. In summary, we first demonstrated the antineoplastic effect of arenobufagin on HCC cells both in vitro and in vivo. We elucidated the underlying antineoplastic mechanisms of arenobufagin that involve cross talk between apoptosis and autophagy via inhibition of the PI3K/Akt/mTOR pathway. This study may provide a rationale for future clinical application using arenobufagin as a chemotherapeutic agent for HCC.
authors: Institute of Traditional Chinese Medicine and Natural Products, College of Pharmacy, Jinan University, Guangzhou 510632, China.
authors: Dong-Mei
authors: DM
authors: Zhang
authors: Jun-Shan
authors: JS
authors: Liu
authors: Li-Juan
authors: LJ
authors: Deng
authors: Min-Feng
authors: MF
authors: Chen
authors: Anita
authors: A
authors: Yiu
authors: Hui-Hui
authors: HH
authors: Cao
authors: Hai-Yan
authors: HY
authors: Tian
authors: Kwok-Pui
authors: KP
authors: Fung
authors: Hiroshi
authors: H
authors: Kurihara
authors: Jing-Xuan
authors: JX
authors: Pan
authors: Wen-Cai
authors: WC
authors: Ye
mesh_terms: D000664:Amphibian Venoms / Q000378:metabolism; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D051017:Apoptosis Regulatory Proteins / Q000235:genetics; D000071187:Autophagy-Related Protein 5; D000071186:Beclin-1; D002018:Bufanolides / Q000494:pharmacology*; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy / Q000378:metabolism; D045744:Cell Line, Tumor; D056945:Hep G2 Cells; D006801:Humans; D008113:Liver Neoplasms / Q000188:drug therapy / Q000378:metabolism; D008297:Male; D008516:Medicine, Chinese Traditional; D008565:Membrane Proteins / Q000235:genetics; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D008869:Microtubule-Associated Proteins / Q000235:genetics; D009368:Neoplasm Transplantation; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors* / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis; D034622:RNA Interference; D034741:RNA, Small Interfering; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays; D051028:bcl-2-Associated X Protein / Q000096:biosynthesis
chemical_list: D000664:Amphibian Venoms; D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; D000071187:Autophagy-Related Protein 5; D000071186:Beclin-1; D002018:Bufanolides; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; D058570:TOR Serine-Threonine Kinases; D051028:bcl-2-Associated X Protein; C502778:ATG5 protein, human; C491997:BECN1 protein, human; C055393:arenobufagin; C546842:MTOR protein, human