RESUMO
Pancreatic ductal adenocarcinoma (PDAC), a poor prognostic cancer, commonly develops following activating mutations in the KRAS oncogene. Activation of WNT signaling is also commonly observed in PDAC. To ascertain the impact of postnatal activation of WNT-stimulated signaling pathways in PDAC development, we combined the Elastase-tva-based RCAS-TVA pancreatic cancer model with the established LSL-KrasG12D, Ptf1a-cre model. Delivery of RCAS viruses encoding ß-cateninS37A and WNT1 stimulated the progression of premalignant pancreatic intraepithelial neoplasias (PanIN) and PDAC development. Moreover, mice injected with RCAS-ß-cateninS37A or RCAS-Wnt1 had reduced survival relative to RCAS-GFP-injected controls (P<.05). Ectopic expression of active ß-catenin, or its DNA-binding partner TCF4, enhanced transformation associated phenotypes in PDAC cells. In contrast, these phenotypes were significantly impaired by the introduction of ICAT, an inhibitor of the ß-catenin/TCF4 interaction. By gene expression profiling, we identified Cyr61 as a target molecule of the WNT/ß-catenin signaling pathway in pancreatic cancer cells. Nuclear ß-catenin and CYR61 expression were predominantly detected in moderately to poorly differentiated murine and human PDAC. Indeed, nuclear ß-catenin- and CYR61-positive PDAC patients demonstrated poor prognosis (P<.01). Knockdown of CYR61 in a ß-catenin-activated pancreatic cancer cell line reduced soft agar, migration and invasion activity. Together, these data suggest that the WNT/ß-catenin signaling pathway enhances pancreatic cancer development and malignancy in part via up-regulation of CYR61.
Assuntos
Proteína Rica em Cisteína 61/metabolismo , Neoplasias Pancreáticas/metabolismo , Neoplasias Pancreáticas/patologia , Proteínas Wnt/metabolismo , Via de Sinalização Wnt , beta Catenina/metabolismo , Animais , Linhagem Celular Tumoral , Proteína Rica em Cisteína 61/genética , Modelos Animais de Doenças , Expressão Gênica , Humanos , Imuno-Histoquímica , Camundongos , Camundongos Transgênicos , Neoplasias Pancreáticas/genética , Esferoides Celulares , Transcriptoma , Células Tumorais Cultivadas , Proteínas Wnt/genética , beta Catenina/genéticaRESUMO
Mutation of KRAS is a common initiating event in pancreatic ductal adenocarcinoma (PDAC). Yet, the specific roles of KRAS-stimulated signaling pathways in the transformation of pancreatic ductal epithelial cells (PDEC), putative cells of origin for PDAC, remain unclear. Here, we show that KRAS(G12D) and BRAF(V600E) enhance PDEC proliferation and increase survival after exposure to apoptotic stimuli in a manner dependent on MEK/ERK and PI3K/AKT signaling. Interestingly, we find that activation of PI3K/AKT signaling occurs downstream of MAP-ERK kinase (MEK), and is dependent on the autocrine activation of the insulin-like growth factor (IGF) receptor (IGF1R) by IGF2. Importantly, IGF1R inhibition impairs KRAS(G12D)- and BRAF(V600E)-induced survival, whereas ectopic IGF2 expression rescues KRAS(G12D)- and BRAF(V600E)-mediated survival downstream of MEK inhibition. Moreover, we show that KRAS(G12D)- and BRAF(V600E)-induced tumor formation in an orthotopic model requires IGF1R. Interestingly, we show that while individual inhibition of MEK or IGF1R does not sensitize PDAC cells to apoptosis, their concomitant inhibition reduces survival. Our findings identify a novel mechanism of PI3K/AKT activation downstream of activated KRAS, illustrate the importance of MEK/ERK, PI3K/AKT, and IGF1R signaling in pancreatic tumor initiation, and suggest potential therapeutic strategies for this malignancy.
Assuntos
Carcinoma Ductal Pancreático/metabolismo , Quinases de Proteína Quinase Ativadas por Mitógeno/metabolismo , Neoplasias Pancreáticas/metabolismo , Proteínas Proto-Oncogênicas B-raf/genética , Proteínas Proto-Oncogênicas p21(ras)/genética , Receptor IGF Tipo 1/antagonistas & inibidores , Animais , Carcinogênese , Carcinoma Ductal Pancreático/genética , Proliferação de Células , Sobrevivência Celular , Modelos Animais de Doenças , Células Epiteliais/metabolismo , Regulação Neoplásica da Expressão Gênica , Técnicas de Silenciamento de Genes , Humanos , Sistema de Sinalização das MAP Quinases , Camundongos , Camundongos Nus , Camundongos Transgênicos , Mutação de Sentido Incorreto , Pâncreas/metabolismo , Neoplasias Pancreáticas/genética , Fosfatidilinositol 3-Quinases/metabolismo , Fosforilação , Proteínas Proto-Oncogênicas B-raf/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Proteínas Proto-Oncogênicas p21(ras)/metabolismo , Receptor IGF Tipo 1/metabolismo , Proteínas Recombinantes de FusãoRESUMO
Pancreatic ductal adenocarcinoma (PDAC), one of the most aggressive human malignancies, is thought to be initiated by KRAS activation. Here we find that transcriptional activation mediated by the Gli family of transcription factors, although dispensable for pancreatic development, is required for Kras-induced proliferation and survival in primary pancreatic epithelial cells in culture and for Kras-driven pancreatic intraepithelial neoplasia and PDAC formation in vivo. Further, ectopic Gli1 activation in the mouse pancreas accelerates Kras-driven tumor formation, underscoring the importance of Gli transcription factors in pancreatic tumorigenesis. Interestingly, we demonstrate Gli-regulated I-kappa-B kinase epsilon (IKBKE) and NF-κB activity in pancreatic cancer cells and show that this activity is a critical downstream mediator for Gli-dependent PDAC cell transformation and survival. Together, these studies demonstrate the requirement for Gli in Kras-dependent pancreatic epithelial transformation, suggest a mechanism of Gli-NF-κB oncogenic activation, and provide genetic evidence supporting the therapeutic targeting of Gli activity in pancreatic cancer.
