Zebrafish reporter lines reveal in vivo signaling pathway activities involved in pancreatic cancer (original) (raw)
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Zebrafish, 2013
Experimental studies in the zebrafish have greatly facilitated understanding of genetic regulation of the early developmental events in the pancreas. Various approaches using forward and reverse genetics, chemical genetics, and transgenesis in zebrafish have demonstrated generally conserved regulatory roles of mammalian genes and discovered novel genetic pathways in exocrine pancreatic development. Accumulating evidence has supported the use of zebrafish as a model of human malignant diseases, including pancreatic cancer. Studies have shown that the genetic regulators of exocrine pancreatic development in zebrafish can be translated into potential clinical biomarkers and therapeutic targets in human pancreatic adenocarcinoma. Transgenic zebrafish expressing oncogenic K-ras and zebrafish tumor xenograft model have emerged as valuable tools for dissecting the pathogenetic mechanisms of pancreatic cancer and for drug discovery and toxicology. Future analysis of the pancreas in zebrafish will continue to advance understanding of the genetic regulation and biological mechanisms during organogenesis. Results of those studies are expected to provide new insights into how aberrant developmental pathways contribute to formation and growth of pancreatic neoplasia, and hopefully generate valid biomarkers and targets as well as effective and safe therapeutics in pancreatic cancer.
Zebrafish as a Model for Pancreatic Cancer Research
Pancreatic Cancer, 2004
Elucidation of basic mechanisms that regulate pancreatic organogenesis may help define molecular pathways involved in the development of exocrine pancreas cancer. The zebrafish has emerged as a powerful model for genetic dissection of the mechanisms underlying vertebrate organogenesis including formation of the pancreas. Unique properties of zebrafish enable genetic and embryological analyses not feasible using other vertebrate model organisms. The optical clarity of the zebrafish embryos allows visual detection of markers for pancreatic morphogenesis and cytodifferentiation by whole mount immunohistochemistry and RNA in situ hybridization. This feature, coupled with the accessibility of the externally fertilized zebrafish embryo and the small size and fecundity of adult zebrafish, facilitates large-scale forward genetic screens using chemical or insertional mutagenesis techniques. Furthermore, these properties allow high throughput studies that target functions of known genes via antisense or enforced expression studies. Together, such studies are predicted to identify novel genes, or known genes essential for pancreas development. Work in zebrafish is predicted to complement research performed using other vertebrate model organisms, and may help identify markers that define early stages of pancreatic tumorigenesis as well as potential targets for therapy.
Cancer Cell Article EGF Receptor Is Required for KRAS-Induced Pancreatic Tumorigenesis
Initiation of pancreatic ductal adenocarcinoma (PDA) is definitively linked to activating mutations in the KRAS oncogene. However, PDA mouse models show that mutant Kras expression early in development gives rise to a normal pancreas, with tumors forming only after a long latency or pancreatitis induction. Here, we show that oncogenic KRAS upregulates endogenous EGFR expression and activation, the latter being dependent on the EGFR ligand sheddase, ADAM17. Genetic ablation or pharmacological inhibition of EGFR or ADAM17 effectively eliminates KRAS-driven tumorigenesis in vivo. Without EGFR activity, active RAS levels are not sufficient to induce robust MEK/ERK activity, a requirement for epithelial transformation.
Clinical evidence indicates that mutation/activation of EGF receptors (EGFRs) is mutually exclusive with the presence of K-RAS oncogenes in lung and colon tumors. We have validated these observations using genetically engineered mouse models. However, development of pancreatic ductal adenocarcinomas driven by K-Ras oncogenes are totally dependent on EGFR signaling. Similar results were obtained using human pancreatic tumor cell lines. EGFRs were also essential even in the context of pancreatic injury and absence of p16Ink4a/p19Arf. Only loss of p53 made pancreatic tumors independent of EGFR signaling. Additional inhibition of PI3K and STAT3 effectively prevented proliferation of explants derived from these p53-defective pancreatic tumors. These findings may provide the bases for more rational approaches to treat pancreatic tumors in the clinic.
EGF Receptor Signaling Is Essential for K-Ras Oncogene-Driven Pancreatic Ductal Adenocarcinoma
Cancer Cell, 2012
Clinical evidence indicates that mutation/activation of EGF receptors (EGFRs) is mutually exclusive with the presence of K-RAS oncogenes in lung and colon tumors. We have validated these observations using genetically engineered mouse models. However, development of pancreatic ductal adenocarcinomas driven by K-Ras oncogenes are totally dependent on EGFR signaling. Similar results were obtained using human pancreatic tumor cell lines. EGFRs were also essential even in the context of pancreatic injury and absence of p16Ink4a/p19Arf. Only loss of p53 made pancreatic tumors independent of EGFR signaling. Additional inhibition of PI3K and STAT3 effectively prevented proliferation of explants derived from these p53-defective pancreatic tumors. These findings may provide the bases for more rational approaches to treat pancreatic tumors in the clinic.
Oncogenic KRAS and the EGFR loop in pancreatic carcinogenesis—A connection to licensing nodes
Small GTPases, 2016
EGFR signaling has a critical role in oncogenic KRAS-driven tumorigenesis of the pancreas, whereas it is dispensable in other organs. The complex signaling network engaged by oncogenic KRAS and its modulation by EGFR signaling, remains incompletely understood. In order to study early signaling events activated by oncogenic KRAS in the pancreas, we recently developed a novel model system based on murine primary pancreatic epithelial cells enabling the time-specific expression of mutant Kras G12D from its endogenous promoter. Here, we discuss our findings of a Kras G12D-induced autocrine EGFR loop, how this loop is integrated by the MYC oncogene, and point to possible translational implications.
Cancers, 2021
Simple Summary Treating the PDAC (pancreatic ductal adenocarcinoma) zPDXs (zebrafish patient-derived xenografts) with chemotherapy regimens commonly used, we performed a co-clinical trial testing the predictiveness of the model. We found that zPDX may predict patient outcomes, classifying them into responders (R) and non-responders (NR), reporting a statistically significant higher cancer recurrence rate at 1 year after surgery in the NR group: 66.7 versus 14.3%. Our zPDX model seems to be a promising tool for the stratification of PDAC patients. This is a crucial starting point for future study involving more patients to obtain a method to really personalize the oncological treatment of PDAC patients. Abstract It is increasingly evident the necessity of new predictive tools for the treatment of pancreatic ductal adenocarcinoma in a personalized manner. We present a co-clinical trial testing the predictiveness of zPDX (zebrafish patient-derived xenograft) for assessing if patients c...
Oncogenic Kras is required for both the initiation and maintenance of pancreatic cancer in mice
Journal of Clinical Investigation, 2012
Pancreatic cancer is almost invariably associated with mutations in the KRAS gene, most commonly KRAS G12D , that result in a dominant-active form of the KRAS GTPase. However, how KRAS mutations promote pancreatic carcinogenesis is not fully understood, and whether oncogenic KRAS is required for the maintenance of pancreatic cancer has not been established. To address these questions, we generated two mouse models of pancreatic tumorigenesis: mice transgenic for inducible Kras G12D , which allows for inducible, pancreas-specific, and reversible expression of the oncogenic Kras G12D , with or without inactivation of one allele of the tumor suppressor gene p53. Here, we report that, early in tumorigenesis, induction of oncogenic Kras G12D reversibly altered normal epithelial differentiation following tissue damage, leading to precancerous lesions. Inactivation of Kras G12D in established precursor lesions and during progression to cancer led to regression of the lesions, indicating that Kras G12D was required for tumor cell survival. Strikingly, during all stages of carcinogenesis, Kras G12D upregulated Hedgehog signaling, inflammatory pathways, and several pathways known to mediate paracrine interactions between epithelial cells and their surrounding microenvironment, thus promoting formation and maintenance of the fibroinflammatory stroma that plays a pivotal role in pancreatic cancer. Our data establish that epithelial Kras G12D influences multiple cell types to drive pancreatic tumorigenesis and is essential for tumor maintenance. They also strongly support the notion that inhibiting Kras G12D , or its downstream […]
Metastatic Pancreatic Cancer Is Dependent on Oncogenic Kras in Mice
PLoS ONE, 2012
Pancreatic cancer is one of the deadliest human malignancies, and its prognosis has not improved over the past 40 years. Mouse models that spontaneously develop pancreatic adenocarcinoma and mimic the progression of the human disease are emerging as a new tool to investigate the basic biology of this disease and identify potential therapeutic targets. Here, we describe a new model of metastatic pancreatic adenocarcinoma based on pancreas-specific, inducible and reversible expression of an oncogenic form of Kras, together with pancreas-specific expression of a mutant form of the tumor suppressor p53. Using high-resolution magnetic resonance imaging to follow individual animals in longitudinal studies, we show that both primary and metastatic lesions depend on continuous Kras activity for their maintenance. However, reactivation of Kras* following prolonged inactivation leads to rapid tumor relapse, raising the concern that Kras*-resistance might eventually be acquired. Thus, our data identifies Kras* as a key oncogene in pancreatic cancer maintenance, but raises the possibility of acquired resistance should Kras inhibitors become available for use in pancreatic cancer.