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Autocrine IL-1α mediates NF-κB activation by oncogenic ras in keratinocytes

ABSTRACT: Constitutively active RAS plays a central role in the development of skin cancer in the classical two stage skin carcinogenesis in mice and in a number of human cancers. Ras-mediated tumor formation is commonly associated with upregulation of cytokines and chemokines that mediate an inflammatory response considered relevant to oncogenesis. MyD88 is a crucial intermediate in the expression of multiple innate immune responders through signaling from the Toll-like/IL-1R family. We report that mice ablated for MyD88 or the IL-1R are resistant to topical skin carcinogenesis, and cultured MyD88-/- keratinocytes transduced with an oncogenic ras vector form only a few small tumors in orthotopic grafts. Initiated keratinocytes arising from oncogenic activation of ras are hyperproliferative but also resist signals for induced differentiation and upregulate a host of pro-inflammatory genes. Ras-transduced MyD88-/- keratinocytes are also hyperproliferative but the differentiation response is intact and pro-inflammatory genes are not upregulated. Using both genetic and pharmacological approaches, we find that in keratinocytes, the differentiation and immune regulation functions mediated by oncogenic ras require the establishment of an autocrine loop through IL-1α and its receptor leading to NF-κB activation. In the absence of MyD88 or IL-1R, this loop cannot be established. Further, blocking the IL-1a mediated NF-κB activation in ras-transduced wildtype keratinocytes corrects the defect in both differentiation response and proinflammatory gene expression. Collectively, these results demonstrate that ras activation converts normal keratinocytes to an initiated phenotype through a series of potentially reversible feedback signals that provide therapeutic opportunities through inhibition of IL-1 signaling.

ORGANISM(S): Mus musculus

PROVIDER: GSE22777 | GEO | 2011/08/29

SECONDARY ACCESSION(S): PRJNA128083

REPOSITORIES: GEO

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Project description:We have compared the response to TGFbeta1 in normal and v-rasHa transduced primary mouse keratinocytes using NCI cDNA microarrays. This analysis reveals that Ha-ras alters global TGFbeta1 mediated gene expression in a gene specific manner. The expression pattern of TGFbeta1 immediate early response genes and down regulation of cell cycle control genes is not altered by Ha-ras but the induction of most extracellular matrix genes is blocked. Using Smad3 null keratinocytes, we find that the majority of TGFbeta1 responsive genes in primary keratinocytes are Smad3 dependent, but patterns of transcriptional responses suggest that the ability of Ha-ras to block TGFbeta1 mediated gene expression is not dependent on Smad3. However, the combination of oncogenic ras and loss of Smad3 prevents the TGFbeta1 dependent suppression of genes associated with cell cycle progression and apoptosis observed with either genotype alone. In addition several extracellular matrix genes are super-repressed by TGFbeta1 in the Ha-ras Smad3 null keratinocytes. These data provide a genomic framework for understanding how disruptions of TGFbeta signaling and oncogenic ras cooperate to promote premalignant progression of primary keratinocytes. Keywords: time series design RNA from Balb/c primary and ras keratinocytes treated for 1, 6, 24, and 48 hours with TGFbeta1 at 1ng/ml was compared to RNA from the corresponding untreated controls. For each timepoint sample from primary and ras cells, multiple arrays (including dye swaps) were analyzed. There are 6, 7, 6, and 5 arrays analyzed for RNA from primary keratinocytes treated for 1, 6, 24, and 48 hours as compared to RNA from untreated primary cells, respectively. There are 6, 8, 7, and 5 arrays analyzed for RNA from ras keratinocytes treated for 1, 6, 24, and 48 hours as compared to RNA from untreated ras cells, respectively. There are 50 arrays analyzed for the Balb/c time-course dataset. RNA from Smad3 WT and KO primary and ras keratinocytes treated 48 hours with TGFbeta1 were compared to RNA from its untreated corresponding controls. There are 6 arrays analyzed for the Smad3 WT/KO data set. There are 56 arrays in this series.

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Autocrine IL-1α mediates NF-κB activation by oncogenic ras in keratinocytes

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