Inhibition of p38-MAPK alters SRC coactivation and estrogen receptor phosphorylation

Cancer Biol Ther. 2012 Sep;13(11):1026-33. doi: 10.4161/cbt.20992. Epub 2012 Jul 24.

Abstract

The p38 mitogen activated protein kinase pathway (MAPK) is known to promote cell survival, endocrine therapy resistance and hormone independent breast cancer cell proliferation. Therefore, we utilized the novel p38 inhibitor RWJ67657 to investigate the relevance of targeting this pathway in the ER (+) breast cancer cell line MCF-7. Our results show that RWJ67657 inhibits both basal and estrogen stimulated phosphorylation of p38α, resulting in decreased activation of the downstream p38α targets hsp27 and MAPAPK. Furthermore, inhibition of p38α by RWJ67657 blocks clonogenic survival of MCF-7 cells with little effect on non-cancerous breast epithelial cells. Even though p38α is known to phosphorylate ERα at residue within ER's hinge region at Thr311, resulting in increased ERα transcriptional activation, our results suggest RWJ67657 inhibits the p38α-induced activation of ER by targeting both the AF-1 and AF-2 activation domains within ERα. We further show that RWJ67657 decreases the transcriptional activity of the ER coactivators SRC-1, SRC-2 and SRC-3. Taken together, our results strongly suggest that in addition to phosphorylating Thr311 within ERα, p38α indirectly activates the ER by phosphorylation and stimulation of the known ERα coactivators, SRC-1, -2 and-3. Overall, our data underscore the therapeutic potential of targeting the p38 MAPK pathway in the treatment of ER (+) breast cancer.

MeSH terms

  • Breast Neoplasms / genetics
  • Breast Neoplasms / metabolism*
  • Cell Line, Tumor
  • Enzyme Activation
  • Estrogen Receptor alpha / genetics
  • Estrogen Receptor alpha / metabolism*
  • Female
  • HEK293 Cells
  • Humans
  • Imidazoles / pharmacology
  • MAP Kinase Signaling System / drug effects
  • MCF-7 Cells
  • Mitogen-Activated Protein Kinase 14 / antagonists & inhibitors*
  • Mitogen-Activated Protein Kinase 14 / genetics
  • Mitogen-Activated Protein Kinase 14 / metabolism
  • Mitogen-Activated Protein Kinases / antagonists & inhibitors*
  • Mitogen-Activated Protein Kinases / metabolism
  • Phosphorylation
  • Protein Kinase Inhibitors / pharmacology
  • Pyridines / pharmacology
  • Signal Transduction
  • Transcriptional Activation
  • Transfection
  • src-Family Kinases / metabolism*

Substances

  • Estrogen Receptor alpha
  • Imidazoles
  • Protein Kinase Inhibitors
  • Pyridines
  • RWJ 67657
  • estrogen receptor alpha, human
  • src-Family Kinases
  • Mitogen-Activated Protein Kinase 14
  • Mitogen-Activated Protein Kinases