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Title: Demonstration and biological significance of a gastrin-P21-activated kinase 1 feedback loop in colorectal cancer cells.
Austin Authors: Huynh, Nhi;Liu, Kevin H;Yim, Mildred;Shulkes, Arthur;Baldwin, Graham S;He, Hong 
Affiliation: Department of Surgery, University of Melbourne, Austin Health, Heidelberg, Victoria, Australia
Issue Date: 24-Jun-2014
Publication information: Physiological Reports 2014; 2(6):
Abstract: Gastrins, including amidated gastrin17 and glycine-extended gastrin17, are important growth factors in colorectal cancer (CRC). The p21-activated kinase 1 (PAK1) plays key roles in cellular processes including proliferation, survival, and motility, and in cell transformation and tumor progression. PAK1 expression increases with the progression of CRC, and knockdown of PAK1 blocks CRC cell growth and metastasis both in vitro and in vivo. The aim of this study was to determine the interaction between PAK1 and gastrins in CRC cells. PAK1 expression and activation were assayed by Western blots, and concentrations of gastrin mRNA and peptides by real-time PCR and radioimmunoassay, respectively. Proliferation of CRC cells was measured by (3)H-thymidine incorporation, and vascular endothelial growth factor : VEGF) secretion was measured by ELISA. Gastrins activated PAK1 via PI3K-dependent pathways. Activated PAK1 in turn mediated gastrin-stimulated activation of β-catenin and VEGF secretion in CRC cells, as knockdown of PAK1 blocked stimulation of these cellular processes by gastrins. Downregulation of gastrin reduced the expression and activity of PAK1, but in contrast there was a compensatory increase in gastrins either when PAK1 was downregulated, or after treatment with a PAK inhibitor. Our results indicate that PAK1 is required for the stimulation of CRC cells by gastrins, and suggest the existence of an inhibitory feedback loop by which PAK1 downregulates gastrin production in CRC cells.
Gov't Doc #: 24963032
DOI: 10.14814/phy2.12048
Journal: Physiological reports
Type: Journal Article
Subjects: Colon cancer
glycine extended
p21‐activated kinase 1
Appears in Collections:Journal articles

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