Protein kinase Cα suppresses Kras-mediated lung tumor formation through activation of a p38 MAPK-TGFβ signaling axis

K. S. Hill, E. Erdogan, Andras Khoor, M. P. Walsh, M. Leitges, Nicole R Murray, Alan P Fields

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

Protein kinase C alpha (PKCα) can activate both pro- and anti-tumorigenic signaling depending upon cellular context. Here, we investigated the role of PKCα in lung tumorigenesis in vivo. Gene expression data sets revealed that primary human non-small lung cancers (NSCLC) express significantly decreased PKCα levels, indicating that loss of PKCα expression is a recurrent event in NSCLC. We evaluated the functional relevance of PKCα loss during lung tumorigenesis in three murine lung adenocarcinoma models (LSL-Kras, LA2-Kras and urethane exposure). Genetic deletion of PKCα resulted in a significant increase in lung tumor number, size, burden and grade, bypass of oncogene-induced senescence, progression from adenoma to carcinoma and a significant decrease in survival in vivo. The tumor promoting effect of PKCα loss was reflected in enhanced Kras-mediated expansion of bronchio-alveolar stem cells (BASCs), putative tumor-initiating cells, both in vitro and in vivo. LSL-Kras/Prkca -/- mice exhibited a decrease in phospho-p38 MAPK in BASCs in vitro and in tumors in vivo, and treatment of LSL-Kras BASCs with a p38 inhibitor resulted in increased colony size indistinguishable from that observed in LSL-Kras/Prkca -/- BASCs. In addition, LSL-Kras/Prkca -/- BASCs exhibited a modest but reproducible increase in TGFβ1 mRNA, and addition of exogenous TGFβ1 to LSL-Kras BASCs results in enhanced growth similar to untreated BASCs from LSL-Kras/Prkca -/- mice. Conversely, a TGFβR1 inhibitor reversed the effects of PKCα loss in LSL-Kras/Prkca -/- BASCs. Finally, we identified the inhibitors of DNA binding (Id) Id1-3 and the Wilm's Tumor 1 as potential downstream targets of PKCα-dependent tumor suppressor activity in vitro and in vivo. We conclude that PKCα suppresses tumor initiation and progression, at least in part, through a PKCα-p38MAPK-TGFβ signaling axis that regulates tumor cell proliferation and Kras-induced senescence. Our results provide the first direct evidence that PKCα exhibits tumor suppressor activity in the lung in vivo.

Original languageEnglish (US)
Pages (from-to)2134-2144
Number of pages11
JournalOncogene
Volume33
Issue number16
DOIs
StatePublished - Apr 17 2014

Fingerprint

Protein Kinase C-alpha
p38 Mitogen-Activated Protein Kinases
Protein Kinase C
Alveolar Epithelial Cells
Lung
Stem Cells
Neoplasms
Carcinogenesis
Neoplastic Stem Cells
Urethane
Oncogenes
Adenoma
Lung Neoplasms

Keywords

  • bronchio-alveolar stem cells
  • inhibitors of DNA Binding (Id)
  • lung adenocarcinoma
  • p38 MAPK
  • tumor suppressor
  • Wilm's Tumor 1 gene

ASJC Scopus subject areas

  • Molecular Biology
  • Cancer Research
  • Genetics

Cite this

Protein kinase Cα suppresses Kras-mediated lung tumor formation through activation of a p38 MAPK-TGFβ signaling axis. / Hill, K. S.; Erdogan, E.; Khoor, Andras; Walsh, M. P.; Leitges, M.; Murray, Nicole R; Fields, Alan P.

In: Oncogene, Vol. 33, No. 16, 17.04.2014, p. 2134-2144.

Research output: Contribution to journalArticle

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AU - Leitges, M.

AU - Murray, Nicole R

AU - Fields, Alan P

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AB - Protein kinase C alpha (PKCα) can activate both pro- and anti-tumorigenic signaling depending upon cellular context. Here, we investigated the role of PKCα in lung tumorigenesis in vivo. Gene expression data sets revealed that primary human non-small lung cancers (NSCLC) express significantly decreased PKCα levels, indicating that loss of PKCα expression is a recurrent event in NSCLC. We evaluated the functional relevance of PKCα loss during lung tumorigenesis in three murine lung adenocarcinoma models (LSL-Kras, LA2-Kras and urethane exposure). Genetic deletion of PKCα resulted in a significant increase in lung tumor number, size, burden and grade, bypass of oncogene-induced senescence, progression from adenoma to carcinoma and a significant decrease in survival in vivo. The tumor promoting effect of PKCα loss was reflected in enhanced Kras-mediated expansion of bronchio-alveolar stem cells (BASCs), putative tumor-initiating cells, both in vitro and in vivo. LSL-Kras/Prkca -/- mice exhibited a decrease in phospho-p38 MAPK in BASCs in vitro and in tumors in vivo, and treatment of LSL-Kras BASCs with a p38 inhibitor resulted in increased colony size indistinguishable from that observed in LSL-Kras/Prkca -/- BASCs. In addition, LSL-Kras/Prkca -/- BASCs exhibited a modest but reproducible increase in TGFβ1 mRNA, and addition of exogenous TGFβ1 to LSL-Kras BASCs results in enhanced growth similar to untreated BASCs from LSL-Kras/Prkca -/- mice. Conversely, a TGFβR1 inhibitor reversed the effects of PKCα loss in LSL-Kras/Prkca -/- BASCs. Finally, we identified the inhibitors of DNA binding (Id) Id1-3 and the Wilm's Tumor 1 as potential downstream targets of PKCα-dependent tumor suppressor activity in vitro and in vivo. We conclude that PKCα suppresses tumor initiation and progression, at least in part, through a PKCα-p38MAPK-TGFβ signaling axis that regulates tumor cell proliferation and Kras-induced senescence. Our results provide the first direct evidence that PKCα exhibits tumor suppressor activity in the lung in vivo.

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