title: Oleanolic acid induces protective autophagy in cancer cells through the JNK and mTOR pathways.
abstract: Autophagy is a biological process that eliminates damaged or excessive proteins and is utilized by various types of cells to maintain cellular homeostasis. Autophagy also occurs in cancer cells and exerts anti-survival or pro-survival effects depending on stimuli, nutrient and context. Oleanolic acid (OA), a widely spread natural compound, induces apoptosis in a range of cancer cells. However, some tumor cell lines are resistant to the pro-apoptotic effect of OA, and the mechanism remains unknown. In the present study, we found that OA induced autophagic event in cancer cells in a dose- and time-dependent manner, evidenced by an increased ratio between LC3-II and LC3-I and frequent granulation of LC3 proteins in OA-stimulated tumor cell lines. Inhibition of autophagy potentiated the pro-apoptotic activity of OA on cancer cells. Furthermore, the JNK and mTOR signaling pathways were found to be affected by OA treatment. Interfering with JNK and mTOR abolished OA-induced autophagy and sensitized cancer cells to apoptosis. Collectively, we showed that OA was able to initiate protective autophagy, which compromised the antitumor activity of OA on cancer cells. Blocking autophagy may be a promising strategy to enhance the tumor suppressor activity of OA.
authors.affiliation: Institutes of Oceanology, Chinese Academy of Sciences, Qingdao, Shandong 266071, P.R. China.
authors.forename: Jia
authors.initials: J
authors.lastname: Liu
authors.affiliation: Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao, Shandong 266071, P.R. China.
authors.forename: Lanhong
authors.initials: L
authors.lastname: Zheng
authors.affiliation: Department of Pathophysiology, Norman Bethune College of Medicine, Jilin University, Changchun, Jilin 130021, P.R. China.
authors.forename: Jiateng
authors.initials: J
authors.lastname: Zhong
authors.affiliation: Institutes of Oceanology, Chinese Academy of Sciences, Qingdao, Shandong 266071, P.R. China.
authors.forename: Ning
authors.initials: N
authors.lastname: Wu
authors.affiliation: Institutes of Oceanology, Chinese Academy of Sciences, Qingdao, Shandong 266071, P.R. China.
authors.forename: Ge
authors.initials: G
authors.lastname: Liu
authors.affiliation: Institutes of Oceanology, Chinese Academy of Sciences, Qingdao, Shandong 266071, P.R. China.
authors.forename: Xiukun
authors.initials: X
authors.lastname: Lin
mesh_terms: D001343:Autophagy / Q000187:drug effects; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D061986:MCF-7 Cells; D009369:Neoplasms / Q000473:pathology*; D009828:Oleanolic Acid / Q000494:pharmacology*; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*; D013997:Time Factors
chemical_list: D009828:Oleanolic Acid; D058570:TOR Serine-Threonine Kinases