PI-3' kinase and NF-kappaB cross-signaling in human pancreatic cancer cells

J Gastrointest Surg. Nov-Dec 2001;5(6):603-12; discussion 612-3. doi: 10.1016/s1091-255x(01)80102-5.

Abstract

Because tumor necrosis factor-alpha (TNF-alpha) and some chemotherapeutic agents activate both apoptosis and NF-kappaB-dependent antiapoptotic genes, they may neutralize their own antitumor effects. The cell-signaling mechanisms for such chemoresistance are not clear but may involve phosphotidylinositol-3' kinase (PI3K). To clarify this we examined whether cross-signaling between PI3K and NF-kappaB enhances the antitumor effect of TNF-alpha in human pancreatic cancer cells. Quiescent pancreatic cancer cells (Panc-1, MiaPaCa-2) with TNF-alpha, Ly294002 (PI3K inhibitor), alone or combined, were restimulated with mitogen (10% fetal calf serum [FCS] to induce cell cycle entry). Proliferation (monotetrazolium), cell cycle progression (ApoBrDU and fluorescence-activated cell sorter analysis), and apoptosis (PARP cleavage; caspase-3 activation) were measured. Akt activation (Akt kinase assay) and IkappaBalpha degradation were determined by Western blot analysis. Translocation of NF-kappaB into the nucleus was examined by EMSA, whereas an NF-kappaB/luciferase reporter gene was used to quantify NF-kappaB-dependent gene expression. Statistical analysis was carried out by means of two-tailed t test (P <0.05). PI3K inhibition significantly enhanced the antiproliferative and proapoptotic effects of TNF-alpha in both cell lines, Ly294002 also blocked TNF-alpha-induced Akt activation but failed to alter cytoplasmic IkappaBalpha degradation or subsequent NF-kappaB nuclear translocation. NF-kappaB-dependent gene expression, however, was ultimately suppressed by Ly294002, suggesting that PI3k-dependent activation of NF-kappaB is IkappaBalpha independent. PI3K inhibition can block NF-kappaB-dependent gene expression regardless of cytoplasmic IkappaBalpha/NF-kappaB activation. Because it also regulates the antitumor effects of TNF-alpha, PI3K may in part determine NF-kappaB-induced chemoresistance in human pancreatic cancer.

Publication types

  • Comparative Study

MeSH terms

  • Adenocarcinoma / pathology
  • Analysis of Variance
  • Apoptosis / drug effects*
  • Humans
  • NF-kappa B / metabolism*
  • Pancreas / cytology
  • Pancreatic Neoplasms / pathology
  • Phosphatidylinositol 3-Kinases / metabolism*
  • Probability
  • Sensitivity and Specificity
  • Signal Transduction
  • Tumor Cells, Cultured
  • Tumor Necrosis Factor-alpha / pharmacology*

Substances

  • NF-kappa B
  • Tumor Necrosis Factor-alpha
  • Phosphatidylinositol 3-Kinases