title: Activation of NAG-1 via JNK signaling revealed an isochaihulactone-triggered cell death in human LNCaP prostate cancer cells.
abstract: BACKGROUND
  We explored the mechanisms of cell death induced by isochaihulactone treatment in LNCaP cells.
  
  
  METHODS
  LNCaP cells were treated with isochaihulactone and growth inhibition was assessed. Cell cycle profiles after isochaihulactone treatment were determined by flow cytometry. Expression levels of cell cycle regulatory proteins, caspase 9, caspase 3, and PARP were determined after isochaihulactone treatment. Signaling pathway was verified by inhibitors pre-treatment. Expression levels of early growth response gene 1 (EGR-1) and nonsteroidal anti-inflammatory drug-activated gene 1 (NAG-1) were determined to investigate their role in LNCaP cell death. NAG-1 expression was knocked down by si-NAG-1 siRNA transfection. Rate of cell death and proliferation were obtained by MTT assay.
  
  
  RESULTS
  Isochaihulactone caused cell cycle arrest at G2/M phase in LNCaP cells, which was correlated with an increase of p53 and p21 levels and downregulation of the checkpoint proteins cdc25c, cyclin B1, and cdc2. Bcl-2 phosphorylation and caspase activation were also observed. Isochaihulactone induced phosphorylation of c-Jun-N-terminal kinase (JNK), and JNK inhibitor partially reduced isochaihulactone-induced cell death. Isochaihulactone also induced the expressions of EGR-1 and NAG-1. Expression of NAG-1 was reduced by JNK inhibitor, and knocking down of NAG-1 inhibited isochaihulactone-induced cell death.
  
  
  CONCLUSIONS
  Isochaihulactone apparently induces G2/M cell cycle arrest via downregulation of cyclin B1 and cdc2, and induces cellular death by upregulation of NAG-1 via JNK activation in LNCaP cells.
authors.affiliation: Institute of Medical Sciences, Tzu-Chi University, and Department of Medical Research, Buddhist Tzu-Chi General Hospital, Hualien, Taiwan.
authors.forename: Sheng-Chun
authors.initials: SC
authors.lastname: Chiu
authors.forename: Mei-Jen
authors.initials: MJ
authors.lastname: Wang
authors.forename: Hsueh-Hui
authors.initials: HH
authors.lastname: Yang
authors.forename: Shee-Ping
authors.initials: SP
authors.lastname: Chen
authors.forename: Sung-Ying
authors.initials: SY
authors.lastname: Huang
authors.forename: Yi-Lin
authors.initials: YL
authors.lastname: Chen
authors.forename: Shinn-Zong
authors.initials: SZ
authors.lastname: Lin
authors.forename: Horng-Jyh
authors.initials: HJ
authors.lastname: Harn
authors.forename: Cheng-Yoong
authors.initials: CY
authors.lastname: Pang
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000494:pharmacology; D000873:Anthracenes / Q000494:pharmacology; D052117:Benzodioxoles / Q000494:pharmacology*; D015153:Blotting, Western; D016203:CDC2 Protein Kinase / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D056744:Cyclin B1 / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D051766:Early Growth Response Protein 1 / Q000378:metabolism; D055436:Growth Differentiation Factor 15 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008297:Male; D048055:Mitogen-Activated Protein Kinase 8 / Q000037:antagonists & inhibitors / Q000378:metabolism; D048056:Mitogen-Activated Protein Kinase 9 / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D034622:RNA Interference; D015398:Signal Transduction / Q000187:drug effects*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D020687:cdc25 Phosphatases / Q000378:metabolism
chemical_list: D000873:Anthracenes; D052117:Benzodioxoles; C493956:CDKN1A protein, human; D056744:Cyclin B1; D050759:Cyclin-Dependent Kinase Inhibitor p21; D051766:Early Growth Response Protein 1; C526140:GDF15 protein, human; D055436:Growth Differentiation Factor 15; D019253:Proto-Oncogene Proteins c-bcl-2; D016159:Tumor Suppressor Protein p53; C512868:isochaihulactone; C432165:pyrazolanthrone; D048056:Mitogen-Activated Protein Kinase 9; D016203:CDC2 Protein Kinase; D048031:JNK Mitogen-Activated Protein Kinases; D048055:Mitogen-Activated Protein Kinase 8; C517009:CDC25C protein, human; D020687:cdc25 Phosphatases; D015107:4-Butyrolactone