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Mol Cells. 2011 Jul;32(1):107-11. doi: 10.1007/s10059-011-0074-y. Epub 2011 May 11.

PI3-kinase/p38 kinase-dependent E2F1 activation is critical for Pin1 induction in tamoxifen-resistant breast cancer cells.

Author information

1
College of Pharmacy, Chonnam National University, Gwangju, 500-757, Korea.

Abstract

Acquired resistance to tamoxifen (TAM) is a serious therapeutic problem in breast cancer patients. We have shown that Pin1, a peptidyl prolyl isomerase, is consistently overexpressed in TAM-resistant MCF-7 cells (TAMR-MCF-7 cells) and plays a key role in the enhanced angiogenic potential of TAMR-MCF-7 cells. In the present study, we focused on signaling pathways for Pin1 up-regulation in TAMR-MCF-7 cells. Relative to MCF-7 cells, Pin1 gene transcription and E2 transcription factor1 (E2F1) expression were enhanced in TAMR-MCF-7 cells. E2F1 siRNA significantly reduced both the protein expression and the promoter transcriptional activity of Pin1. Activities of phosphatidylinositol 3-kinase (PI3K), extracellular signal-regulated kinase (ERK) and p38 kinase were all higher in TAMR-MCF-7 cells than in control MCF-7 cells and the enhanced Pin1 and E2F1 expression in TAMR-MCF-7 cells was reversed by inhibition of PI3K or p38 kinase. Moreover, the higher production of vascular endothelial growth factor (VEGF) in TAMR-MCF-7 cells was significantly diminished by suppression of PI3K or p38 kinase. These results suggest that Pin1 overexpression and subsequent VEGF production in TAMR-MCF-7 cells are mediated through PI3-kinase or p38 kinase-dependent E2F1 activation.

PMID:
21573702
PMCID:
PMC3887657
DOI:
10.1007/s10059-011-0074-y
[Indexed for MEDLINE]
Free PMC Article

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