Journal Article

The oncogenic kinase Pim-1 is modulated by K-Ras signaling and mediates transformed growth and radioresistance in human pancreatic ductal adenocarcinoma cells

Dapeng Xu, Stephen A. Allsop, Sam M. Witherspoon, Jared L. Snider, Jen Jen Yeh, James J. Fiordalisi, Catherine D. White, Daniel Williams, Adrienne D. Cox and Antonio T. Baines

in Carcinogenesis

Volume 32, issue 4, pages 488-495
Published in print April 2011 | ISSN: 0143-3334
Published online January 2011 | e-ISSN: 1460-2180 | DOI: http://dx.doi.org/10.1093/carcin/bgr007
The oncogenic kinase Pim-1 is modulated by K-Ras signaling and mediates transformed growth and radioresistance in human pancreatic ductal adenocarcinoma cells

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Oncogenic Pim-1 kinase is upregulated in multiple solid cancers, including human pancreatic ductal adenocarcinoma (PDAC), a highly lethal disease with few useful treatment options. Pim-1 is also transcriptionally induced upon oncogenic K-Ras-mediated transformation of the human pancreatic ductal epithelial (HPDE) cell model of PDAC. Given the near ubiquitous presence of mutant K-Ras in PDAC and its critical role in this disease, we wished to study the effects of oncogenic K-Ras signaling on Pim-1 expression, as well as the role of Pim-1 in growth transformation of PDAC cells. Pim-1 protein levels were upregulated in both PDAC cell lines and patient tumor tissues. Furthermore, ectopic oncogenic K-Ras increased Pim-1 expression in human pancreatic nestin-expressing (HPNE) cells, a distinct immortalized cell model of PDAC. Conversely, shRNA-mediated suppression of oncogenic K-Ras decreased Pim-1 protein in PDAC cell lines. These results indicate that oncogenic K-Ras regulates Pim-1 expression. The kinase activity of Pim-1 is constitutively active. Accordingly, shRNA-mediated suppression of Pim-1 in K-Ras-dependent PDAC cell lines decreased Pim-1 activity, as measured by decreased phosphorylation of the pro-apoptotic protein Bad and increased expression of the cyclin-dependent kinase inhibitor p27Kip1. Biological consequences of inhibiting Pim-1 expression included decreases in both anchorage-dependent and -independent cell growth, invasion through Matrigel and radioresistance as measured by standard clonogenic assays. These results indicate that Pim-1 is required for PDAC cell growth, invasion and radioresistance downstream of oncogenic K-Ras. Overall, our studies help to elucidate the role of Pim-1 in PDAC growth transformation and validate Pim-1 kinase as a potential molecular marker for mutated K-Ras activity.

Journal Article.  5278 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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