On the mechanisms of 12-O-tetradecanoylphorbol-13-acetate-induced growth arrest in pancreatic cancer cells.
OBJECTIVE
Protein kinase C (PKC) is involved in cell growth, differentiation, and apoptosis. We investigated the effects of the PKC activator, the tetradecanylphorbol acetate (TPA), in human pancreatic cancer cells.


METHODS
Cell proliferation was measured by thymidine incorporation. Expression of cell cycle proteins was investigated by Western blot. Real-time reverse transcriptase-polymerase chain reaction was used to measure p21 messenger RNA expression, whereas knockdown of its expression was accomplished with a specific small interferring RNA. Cell cycle phases were determined by flow cytometry.


RESULTS
TPA time and concentration dependently inhibited thymidine incorporation in Panc-1 and CD18 cells and induced G2/M cell cycle arrest. The TPA decreased cyclin A and B expression, increased cyclin E, and markedly increased the expression of p21 at both the messenger RNA and protein levels. TPA-induced p21 expression and growth inhibition were blocked by the PKC inhibitor, bisindoylmaleimide. TPA induced extracellular signal-regulated kinase1/2 phosphorylation, whereas the MEK inhibitor, PD98059, blocked the TPA-induced p21 expression. Small interferring RNA targeted to p21 blocked TPA-induced p21 protein expression but not TPA-induced cell growth arrest.


CONCLUSIONS
TPA-induced p21 expression is mediated by the MEK/ERK pathway but is not involved in TPA-induced growth inhibition. In contrast, cyclin A and cyclin B are likely involved in TPA-induced G2/M arrest because both proteins are involved in S phase and G2/M transition during cell proliferation.
Salabat
Mohammad R
MR
Department of Surgery and Robert H Lurie Cancer Center, Northwestern University, Feinberg School of Medicine, Chicago, IL 60611, USA.
Ding
Xian Z
XZ
Flesche
Jan B
JB
Ujiki
Micheal B
MB
Robin
Tyler P
TP
Talamonti
Mark S
MS
Bell
Richard H
RH
Adrian
Thomas E
TE
D002455:Cell Division; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D019925:Cyclin A / Q000378:metabolism; D019926:Cyclin B / Q000378:metabolism; D056744:Cyclin B1; D019927:Cyclin E / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D005419:Flavonoids / Q000494:pharmacology; D016195:G2 Phase; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D020930:MAP Kinase Kinase Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D008301:Maleimides / Q000494:pharmacology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D010190:Pancreatic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
C534699:CCNB1 protein, human; C493956:CDKN1A protein, human; D019925:Cyclin A; D019926:Cyclin B; D056744:Cyclin B1; D019927:Cyclin E; D050759:Cyclin-Dependent Kinase Inhibitor p21; D005419:Flavonoids; D007211:Indoles; D008301:Maleimides; D047428:Protein Kinase Inhibitors; D012333:RNA, Messenger; D011493:Protein Kinase C; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020930:MAP Kinase Kinase Kinases; C070515:bisindolylmaleimide I; D013755:Tetradecanoylphorbol Acetate; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one