The oncogenic kinase Pim-1 is modulated by K-Ras signaling and mediates transformed growth and radioresistance in human pancreatic ductal adenocarcinoma cells.
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.
Department of Biology, Cancer Research Program, JLC-Biomedical/Biotechnology Research Institute, North Carolina Central University, Durham, NC 27707, USA.
Dapeng
D
Xu
Stephen A
SA
Allsop
Sam M
SM
Witherspoon
Jared L
JL
Snider
Jen Jen
JJ
Yeh
James J
JJ
Fiordalisi
Catherine D
CD
White
Daniel
D
Williams
Adrienne D
AD
Cox
Antonio T
AT
Baines
D000230:Adenocarcinoma / Q000473:pathology* / Q000532:radiotherapy; D021441:Carcinoma, Pancreatic Ductal / Q000473:pathology* / Q000532:radiotherapy; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000032:analysis; D006801:Humans; D009361:Neoplasm Invasiveness; D010190:Pancreatic Neoplasms / Q000473:pathology* / Q000532:radiotherapy; D010766:Phosphorylation; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D051573:Proto-Oncogene Proteins c-pim-1 / Q000032:analysis / Q000502:physiology*; D016283:Proto-Oncogene Proteins p21(ras); D011836:Radiation Tolerance; D015398:Signal Transduction / Q000502:physiology*; D051025:bcl-Associated Death Protein / Q000378:metabolism; D018631:ras Proteins / Q000502:physiology*
C494819:BAD protein, human; C436291:CDKN1B protein, human; C117307:KRAS protein, human; D011518:Proto-Oncogene Proteins; D051025:bcl-Associated Death Protein; D050760:Cyclin-Dependent Kinase Inhibitor p27; C496634:PIM1 protein, human; D051573:Proto-Oncogene Proteins c-pim-1; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins
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