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Mol Cancer. 2011 Dec 15;10:149. doi: 10.1186/1476-4598-10-149.

Protein kinase A antagonist inhibits β-catenin nuclear translocation, c-Myc and COX-2 expression and tumor promotion in Apc(Min/+) mice.

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Centre for Molecular Medicine Norway, Nordic EMBL Partnership and Biotechnology Centre, University of Oslo, Oslo, Norway.



The adenomatous polyposis coli (APC) protein is part of the destruction complex controlling proteosomal degradation of β-catenin and limiting its nuclear translocation, which is thought to play a gate-keeping role in colorectal cancer. The destruction complex is inhibited by Wnt-Frz and prostaglandin E(2) (PGE(2)) - PI-3 kinase pathways. Recent reports show that PGE(2)-induced phosphorylation of β-catenin by protein kinase A (PKA) increases nuclear translocation indicating two mechanisms of action of PGE(2) on β-catenin homeostasis.


Treatment of Apc(Min/+) mice that spontaneously develop intestinal adenomas with a PKA antagonist (Rp-8-Br-cAMPS) selectively targeting only the latter pathway reduced tumor load, but not the number of adenomas. Immunohistochemical characterization of intestines from treated and control animals revealed that expression of β-catenin, β-catenin nuclear translocation and expression of the β-catenin target genes c-Myc and COX-2 were significantly down-regulated upon Rp-8-Br-cAMPS treatment. Parallel experiments in a human colon cancer cell line (HCT116) revealed that Rp-8-Br-cAMPS blocked PGE(2)-induced β-catenin phosphorylation and c-Myc upregulation.


Based on our findings we suggest that PGE(2) act through PKA to promote β-catenin nuclear translocation and tumor development in Apc(Min/+) mice in vivo, indicating that the direct regulatory effect of PKA on β-catenin nuclear translocation is operative in intestinal cancer.

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