Abstract
The persistent activation of signaling cascades results in dramatic consequences that include loss of cellular growth control and neoplastic transformation. We show here that phosphoinositide 3-kinase (PI 3-kinase) and its mediator Akt were constitutively activated in pancreatic cancer and that this might be due to the aberrant expression of their natural antagonist MMAC/PTEN. Indeed, our results show that MMAC/PTEN expression was either lost or significantly reduced in five of eight cell lines and in twelve of seventeen tumor specimens examined. That the poor expression of MMAC/PTEN in pancreatic cancer cells could be due to promoter methylation was indicated by methylation-specific PCR analysis. Our studies also indicated that PI 3-kinase targeted two important transcription factors in pancreatic cancer cells. The ability of constitutively activated NF-κB to induce gene expression and the stabilization of c-MYC protein by decreased phosphorylation of Thr58 were both dependent on PI 3-kinase activity. When pancreatic cancer cells were treated with a peptide antagonist of NF-κB nuclear translocation, or stably transfected with a dominant-negative mutant of MYC, their proliferation was markedly inhibited. Taken together, these data indicate that the aberrant expression of MMAC/PTEN contributes to the activation of the PI 3-kinase/Akt pathway and its transcription factor mediators in pancreatic cancer.
Original language | English (US) |
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Pages (from-to) | 8571-8580 |
Number of pages | 10 |
Journal | Oncogene |
Volume | 23 |
Issue number | 53 |
DOIs | |
State | Published - Nov 11 2004 |
Keywords
- Akt
- NF-κB
- PI 3-kinase
- PTEN
- Pancreatic cancer
- c-Myc
ASJC Scopus subject areas
- Molecular Biology
- Genetics
- Cancer Research