A novel interplay between Rap1 and PKA regulates induction of angiogenesis in prostate cancer

PLoS One. 2012;7(11):e49893. doi: 10.1371/journal.pone.0049893. Epub 2012 Nov 15.


Angiogenesis inhibition is an important therapeutic strategy for advanced stage prostate cancer. Previous work from our laboratory showed that sustained stimulation of Rap1 by 8-pCPT-2'-O-Me-cAMP (8CPT) via activation of Epac, a Rap1 GEF, or by expression of a constitutively active Rap1 mutant (cRap1) suppresses endothelial cell chemotaxis and subsequent angiogenesis. When we tested this model in the context of a prostate tumor xenograft, we found that 8CPT had no significant effect on prostate tumor growth alone. However, in cells harboring cRap1, 8CPT dramatically inhibited not only prostate tumor growth but also VEGF expression and angiogenesis within the tumor microenvironment. Subsequent analysis of the mechanism revealed that, in prostate tumor epithelial cells, 8CPT acted via stimulation of PKA rather than Epac/Rap1. PKA antagonizes Rap1 and hypoxic induction of 1α protein expression, VEGF production and, ultimately, angiogenesis. Together these findings provide evidence for a novel interplay between Rap1, Epac, and PKA that regulates tumor-stromal induction of angiogenesis.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Analysis of Variance
  • Animals
  • Blotting, Western
  • Cell Line, Tumor
  • Cyclic AMP / analogs & derivatives*
  • Cyclic AMP / pharmacology
  • Cyclic AMP-Dependent Protein Kinases / metabolism*
  • Enzyme-Linked Immunosorbent Assay
  • Guanine Nucleotide Exchange Factors / metabolism
  • Humans
  • Immunohistochemistry
  • Male
  • Mice
  • Neovascularization, Pathologic / drug therapy
  • Neovascularization, Pathologic / metabolism*
  • Neovascularization, Pathologic / physiopathology
  • Prostatic Neoplasms / drug therapy
  • Prostatic Neoplasms / physiopathology*
  • Real-Time Polymerase Chain Reaction
  • Reverse Transcriptase Polymerase Chain Reaction
  • Vascular Endothelial Growth Factor A / metabolism
  • rap1 GTP-Binding Proteins / antagonists & inhibitors
  • rap1 GTP-Binding Proteins / metabolism*


  • 8-(4-chloro-phenylthio)-2'-O-methyladenosine-3'-5'-cyclic monophosphate
  • Epac protein, mouse
  • Guanine Nucleotide Exchange Factors
  • Vascular Endothelial Growth Factor A
  • Cyclic AMP
  • Cyclic AMP-Dependent Protein Kinases
  • rap1 GTP-Binding Proteins