N-acetylcysteine conjugate of phenethyl isothiocyanate enhances apoptosis in growth-stimulated human lung cells.
We previously showed that dietary treatment with the N-acetylcysteine conjugate of phenethyl isothiocyanate (PEITC-NAC) inhibited benzo(a)pyrene-induced lung tumorigenesis in A/J mice, and that tumor inhibition was associated with induction of activator protein-1 (AP-1) activity and stimulation of apoptosis in the lungs of mice. In the present study, we show that PEITC-NAC also induces apoptosis and AP-1 activity in human lung adenocarcinoma A549 cells, and that activation of AP-1 is important in PEITC-NAC induced apoptosis in these cells. PEITC-NAC induced AP-1 binding activity in A549 cells in a dose- and time-dependent manner; peak activity appeared at 10 micromol/L after 24 hours. At that time, flow cytometric analysis showed a sub-G1 peak, indicating that approximately 4.5% of the cells had undergone apoptosis. When wild-type c-jun cDNA was transfected into A549 cells, PEITC-NAC-mediated apoptosis was greatly increased in the c-jun-transfected cells compared with the control vector-transfected cells, based on cell morphology and analysis of DNA fragmentation. Furthermore, cells that were pretreated with 100 nmol/L 12-O-tetradecanoyl phorbol-13-acetate, and then treated with 25 micromol/L PEITC-NAC, underwent enhanced apoptosis compared with cells that were treated with PEITC-NAC alone; cells treated with 12-O-tetradecanoyl phorbol-13-acetate alone showed active cell growth without apoptosis. Bivariate flow cytometric analysis of DNA strand breaks versus DNA content showed that apoptosis induced by PEITC-NAC occurred predominantly in the G2-M phase. These findings suggest that growth-stimulated cells with an elevated basal AP-1 activity, i.e., A549 cells transfected with wild-type c-jun or treated with a tumor promoter, were more sensitive to PEITC-NAC-mediated apoptosis. The observation that PEITC-NAC induces apoptosis predominantly in growth-promoted cells, such as neoplastic cells, suggests a selective mechanism by which PEITC-NAC inhibits lung carcinogenesis.
Yang
Yang-Ming
YM
Division of Carcinogenesis, American Health Foundation Cancer Center, Institute for Cancer Prevention, Valhalla, New York, USA. yang-ming_yang@nymc.edu
Jhanwar-Uniyal
Meena
M
Schwartz
Joel
J
Conaway
C Clifford
CC
Halicka
H Dorota
HD
Traganos
Frank
F
Chung
Fung-Lung
FL
D000230:Adenocarcinoma / Q000139:chemically induced / Q000188:drug therapy* / Q000473:pathology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D045744:Cell Line, Tumor; D003545:Cysteine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D008168:Lung / Q000187:drug effects; D008175:Lung Neoplasms / Q000139:chemically induced / Q000188:drug therapy* / Q000473:pathology; D051379:Mice; D008805:Mice, Inbred A; D013755:Tetradecanoylphorbol Acetate; D013859:Thiocarbamates / Q000494:pharmacology*; D018808:Transcription Factor AP-1 / Q000502:physiology; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis / Q000235:genetics
C465294:N-acetyl-S-(N-2-phenethylthiocarbamoyl)-L-cysteine; C495901:TP53 protein, human; D013859:Thiocarbamates; D018808:Transcription Factor AP-1; D016159:Tumor Suppressor Protein p53; D048031:JNK Mitogen-Activated Protein Kinases; D003545:Cysteine; D013755:Tetradecanoylphorbol Acetate