Stimulation of protein kinase C-alpha suppresses colon cancer cell proliferation by down-regulation of beta-catenin

Gwak, J.; Jung, S.-J.; Kang, D.-I.; Kim, E.-Y.; Kim, D.-E.; Chung, Y.-H.; Shin, J.-G.; Oh, S.

Journal of Cellular and Molecular Medicine 13(8b): 2171-2180

2009


ISSN/ISBN: 1582-4934
PMID: 20141613
DOI: 10.1111/j.1582-4934.2008.00683.x
Accession: 055927680

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Abstract
We reported previously that protein kinase C-alpha (PKC-alpha) negatively regulates Wnt/beta-catenin signalling pathway. The current study explores the role of PKC-alpha in the regulation of proliferation of colon cancer cells, which contain aberrant up-regulation of intracellular beta-catenin. In colon tissue and cells, an inverse correlation was observed between the expression levels of PKC-alpha and intracellular beta-catenin. Activation of PKC-alpha inhibited beta-catenin response transcription by down-regulation of intracellular beta-catenin and induced phosphorylation of the N-terminal serine and threonine residues (Ser33/Ser37/Thr41) of beta-catenin, marking it for proteasomal degradation, in colon cancer cells. Pharmacological inhibition or depletion of PKC-alpha-abrogated PKC-alpha-mediated beta-catenin down-regulation and phosphorylation in colon cancer cells. Notably, the Ser45 residue of beta-catenin was essential for PKC-alpha-induced beta-catenin down-regulation in colon cancer cells. Moreover, PKC-alpha activation repressed the expression of cyclin D1 and c-myc, which are known beta-catenin target genes, and thus inhibited the growth of colon cancer cells. These findings suggest that PKC-alpha negatively regulates colon cancer cell proliferation viabeta-catenin phosphorylation/down-regulation and may facilitate the development of new strategies to treatment of colon cancer.