Abstract
OBJECTIVES: 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 WAF1 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 p21WAF1 at both the messenger RNA and protein levels. TPA-induced p21WAF1 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 p21WAF1 expression. Small interferring RNA targeted to p21WAF1 blocked TPA-induced p21WAF1 protein expression but not TPA-induced cell growth arrest. CONCLUSIONS: TPA-induced p21WAF1 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.
Original language | English |
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Pages (from-to) | 148-155 |
Number of pages | 8 |
Journal | Pancreas |
Volume | 33 |
Issue number | 2 |
DOIs | |
Publication status | Published - Aug 2006 |
Externally published | Yes |
Keywords
- Cyclin A
- Cyclin B
- G2/M phase arrest
- Pancreatic cancer
- Protein kinase C
- TPA
- Tumor-promoting phorbol ester
- p21
ASJC Scopus subject areas
- Internal Medicine
- Endocrinology, Diabetes and Metabolism
- Hepatology
- Endocrinology