Epac1-induced cellular proliferation in prostate cancer cells is mediated by B-Raf/ERK and mTOR signaling cascades

• Published in: Journal of cellular biochemistry 2009-11, Vol.108 (4), p.998-1011
• Main Authors: Misra, Uma Kant, Pizzo, Salvatore Vincent
• Format: Article
• Language: English
• Subjects: 8-CPT-2-O-Me-cAMP and cancer cell proliferation; cAMP-dependent; cAMP-mediated cellular proliferation; Cell Line, Tumor; Cell Proliferation; Cyclic AMP - metabolism; Cyclic AMP-Dependent Protein Kinases - metabolism; Enzyme Inhibitors - pharmacology; Epac and B-Raf/ERK signaling; Epac and mTOR signaling; Epac and prostate cancer; Extracellular Signal-Regulated MAP Kinases - metabolism; Guanine Nucleotide Exchange Factors - metabolism; Humans; Intracellular Signaling Peptides and Proteins - metabolism; Male; Phosphorylation; PKA-independent cellular proliferation; Prostatic Neoplasms - metabolism; Protein-Serine-Threonine Kinases - metabolism; Proto-Oncogene Proteins B-raf - metabolism; Signal Transduction; Theophylline - analogs & derivatives; Theophylline - pharmacology; TOR Serine-Threonine Kinases
• ISSN: 0730-2312; 1097-4644
• DOI: 10.1002/jcb.22333

cAMP‐dependent, PKA‐independent effects on cell proliferation are mediated by cAMP binding to EPAC and activation of Rap signaling. In this report, we employed the analogue 8‐CPT‐2‐O‐Me‐cAMP to study binding to EPAC and subsequent activation of B‐Raf/ERK and mTOR signaling in human cancer cells. This compound significantly stimulated DNA synthesis, protein synthesis, and cellular proliferation of human 1‐LN prostate cancer cells. By study of phosphorylation‐dependent activation, we demonstrate that EPAC‐mediated cellular effects require activation of the B‐Raf/ERK and mTOR signaling cascades. RNAi directed against EPAC gene expression as well as inhibitors of ERK, PI 3‐kinase, and mTOR were employed to further demonstrate the role of these pathways in regulating prostate cancer cell proliferation. These studies were then extended to several other human prostate cancer cell lines and melanoma cells with comparable results. We conclude that B‐Raf/ERK and mTOR signaling play an essential role in cAMP‐dependent, but PKA‐independent, proliferation of cancer cells. J. Cell. Biochem. 108: 998–1011, 2009. © 2009 Wiley‐Liss, Inc.