Soluble factors derived from stroma activated androgen receptor phosphorylation in human prostate LNCaP cells: roles of ERK/MAP kinase

Prostate. 2009 Jun 15;69(9):949-55. doi: 10.1002/pros.20944.


Background: Accumulated evidence suggests stromal-epithelial interactions are critical to the progression of prostate cancer. In this study, we characterized AR phosphorylation in LNCaP cells co-cultured with the conditioned medium (CM) from human prostate stromal fibroblasts.

Methods: CM harvested from prostate stromal fibroblasts was added to LNCaP cells, and both anchorage-dependent and -independent growth was determined. Status of AR phosphorylation at Ser-81 and Ser-213 was assessed by immunoblot analysis. ERK kinase activity was measured using MBP-2 protein as the substrate.

Results: The growth of LNCaP cells on plastic dishes increased by 1.7-fold upon exposure to stromal CM or androgen, and their combination resulted in additive growth (2.4-fold). Anchorage-independent growth of LNCaP cells in soft agar, however, was induced synergistically at 80-fold by both stromal CM and androgen. Stromal CM or androgen alone induced LNCaP cell growth by 10- and 26-fold, respectively. We observed ERK kinase inhibitor, U0126, but not phosphatidylinositol 3-kinase (PI-3K), LY294002, or protein kinase A (PKA) inhibitor, H-89, inhibited stromal CM or androgen-induced PSA promoter luciferase activities, and anchorage-independent growth of LNCaP cells. Our results demonstrated for the first time how stromal CM acts in synergy with androgen by activation of ERK kinase and AR phosphorylation at Ser-81 but not Ser-213, for AR-regulated PSA promoter and anchorage-independent growth of human prostate cancer cells.

Conclusions: A stromal factor-activated ERK pathway mediated by AR phosphorylation at Ser-81 could be responsible for stimulating the growth of human prostate cancer cells.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Androgens / metabolism
  • Cell Communication / physiology
  • Cell Division / physiology
  • Coculture Techniques
  • Culture Media, Conditioned / pharmacology
  • Epithelial Cells / cytology
  • Epithelial Cells / metabolism*
  • Extracellular Signal-Regulated MAP Kinases / metabolism
  • Fibroblasts / cytology
  • Fibroblasts / metabolism
  • Humans
  • Luciferases / metabolism
  • MAP Kinase Signaling System / physiology*
  • Male
  • Phosphorylation / physiology
  • Prostate-Specific Antigen / metabolism
  • Prostatic Neoplasms / metabolism*
  • Prostatic Neoplasms / pathology*
  • Receptors, Androgen / metabolism*
  • Serine / metabolism
  • Solubility
  • Stem Cells
  • Stromal Cells / cytology
  • Stromal Cells / metabolism*
  • Tumor Cells, Cultured


  • AR protein, human
  • Androgens
  • Culture Media, Conditioned
  • Receptors, Androgen
  • Serine
  • Luciferases
  • Extracellular Signal-Regulated MAP Kinases
  • Prostate-Specific Antigen