title: Longikaurin A, a natural ent-kaurane, induces G2/M phase arrest via downregulation of Skp2 and apoptosis induction through ROS/JNK/c-Jun pathway in hepatocellular carcinoma cells.
abstract: Hepatocellular carcinoma (HCC) is the most common form of primary liver cancer, and is also highly resistant to conventional chemotherapy treatments. In this study, we report that Longikaurin A (LK-A), an ent-kaurane diterpenoid isolated from the plant Isodon ternifolius, induced cell cycle arrest and apoptosis in human HCC cell lines. LK-A also suppressed tumor growth in SMMC-7721 xenograft models, without inducing any notable major organ-related toxicity. LK-A treatment led to reduced expression of the proto-oncogene S phase kinase-associated protein 2 (Skp2) in SMMC-7721 cells. Lower Skp2 levels correlated with increased expression of p21 and p-cdc2 (Try15), and a corresponding decrease in protein levels of Cyclin B1 and cdc2. Overexpression of Skp2 significantly inhibited LK-A-induced cell cycle arrest in SMMC-7721 cells, suggesting that LK-A may target Skp2 to arrest cells at the G2/M phase. LK-A also induced reactive oxygen species (ROS) production and apoptosis in SMMC-7721 cells. LK-A induced phosphorylation of c-Jun N-terminal kinase (JNK), but not extracellular signal-regulated kinase and P38 MAP kinase. Treatment with, the JNK inhibitor SP600125 prevented LK-A-induced apoptosis in SMMC-7721 cells. Moreover, the antioxidant N-acetylcysteine prevented phosphorylation of both JNK and c-Jun. Taken together, these data indicate that LK-A induces cell cycle arrest and apoptosis in cancer cells by dampening Skp2 expression, and thereby activating the ROS/JNK/c-Jun signaling pathways. LK-A is therefore a potential lead compound for development of antitumor drugs targeting HCC.
authors.affiliation: Sun Yat-Sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, China.
authors.forename: Y-J
authors.initials: YJ
authors.lastname: Liao
authors.affiliation: 1] Sun Yat-Sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, China [2] Department of Forensic Medicine, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China.
authors.forename: H-Y
authors.initials: HY
authors.lastname: Bai
authors.affiliation: Department of Forensic Medicine, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China.
authors.forename: Z-H
authors.initials: ZH
authors.lastname: Li
authors.affiliation: State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China.
authors.forename: J
authors.initials: J
authors.lastname: Zou
authors.affiliation: Sun Yat-Sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, China.
authors.forename: J-W
authors.initials: JW
authors.lastname: Chen
authors.affiliation: Medical Research Center, Sun Yat-Sen Memorial Hospital, Guangzhou, China.
authors.forename: F
authors.initials: F
authors.lastname: Zheng
authors.affiliation: Sun Yat-Sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, China.
authors.forename: J-X
authors.initials: JX
authors.lastname: Zhang
authors.affiliation: Sun Yat-Sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, China.
authors.forename: S-J
authors.initials: SJ
authors.lastname: Mai
authors.affiliation: Sun Yat-Sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, China.
authors.forename: M-S
authors.initials: MS
authors.lastname: Zeng
authors.affiliation: State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China.
authors.forename: H-D
authors.initials: HD
authors.lastname: Sun
authors.affiliation: State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China.
authors.forename: J-X
authors.initials: JX
authors.lastname: Pu
authors.affiliation: Sun Yat-Sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, China.
authors.forename: D
authors.initials: D
authors.lastname: Xie
mesh_terms: D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D016203:CDC2 Protein Kinase; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D019926:Cyclin B / Q000378:metabolism; D056744:Cyclin B1 / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D018844:Cyclin-Dependent Kinases; D045786:Diterpenes, Kaurane / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D059565:G2 Phase Cell Cycle Checkpoints / Q000187:drug effects*; D056945:Hep G2 Cells; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D000090063:Proto-Oncogene Mas; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D044786:S-Phase Kinase-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D013997:Time Factors; D014162:Transfection; D047368:Tumor Burden / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays
chemical_list: D000972:Antineoplastic Agents, Phytogenic; C534699:CCNB1 protein, human; C493956:CDKN1A protein, human; D019926:Cyclin B; D056744:Cyclin B1; D050759:Cyclin-Dependent Kinase Inhibitor p21; D045786:Diterpenes, Kaurane; C000715470:MAS1 protein, human; D047428:Protein Kinase Inhibitors; D000090063:Proto-Oncogene Mas; D016755:Proto-Oncogene Proteins c-jun; D017382:Reactive Oxygen Species; D044786:S-Phase Kinase-Associated Proteins; C581034:longikaurin A; D016203:CDC2 Protein Kinase; C528899:CDK1 protein, human; D018844:Cyclin-Dependent Kinases; D048031:JNK Mitogen-Activated Protein Kinases