Dataset Information

Notch1 is not required for acinar-to-ductal metaplasia in a model of Kras-induced pancreatic ductal adenocarcinoma.

ABSTRACT: Pancreatic ductal adenocarcinoma is believed to arise from precursor lesions termed pancreatic intraepithelial neoplasia (PanIN). Mouse models have demonstrated that targeted expression of activated K-ras to mature acinar cells in the pancreas induces the spontaneous development of PanIN lesions; implying acinar-to-ductal metaplasia (ADM) is a key event in this process. Recent studies suggest Notch signaling is a key regulator of ADM. To assess if Notch1 is required for K-ras driven ADM we employed both an in vivo mouse model and in vitro explant culture system, in which an oncogenic allele of K-ras is activated and Notch1 is deleted simultaneously in acinar cells. Our results demonstrate that oncogenic K-ras is sufficient to drive ADM both in vitro and in vivo but that loss of Notch1 has a minimal effect on this process. Interestingly, while loss of Notch1 in vivo does not affect the severity of PanIN lesions observed, the overall numbers of lesions were greater in mice with deleted Notch1. This suggests Notch1 deletion renders acinar cells more susceptible to formation of K-ras-induced PanINs.

SUBMITTER: Avila JL

PROVIDER: S-EPMC3526595 | biostudies-other | 2012

REPOSITORIES: biostudies-other

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Notch1 is not required for acinar-to-ductal metaplasia in a model of Kras-induced pancreatic ductal adenocarcinoma.

Avila Jacqueline L JL Troutman Scott S Durham Amy A Kissil Joseph L JL

PloS one 20121219 12

Pancreatic ductal adenocarcinoma is believed to arise from precursor lesions termed pancreatic intraepithelial neoplasia (PanIN). Mouse models have demonstrated that targeted expression of activated K-ras to mature acinar cells in the pancreas induces the spontaneous development of PanIN lesions; implying acinar-to-ductal metaplasia (ADM) is a key event in this process. Recent studies suggest Notch signaling is a key regulator of ADM. To assess if Notch1 is required for K-ras driven ADM we emplo ...[more]

PMID: 23284900

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Project description:BACKGROUND & AIMS:Activating mutations in KRAS are detected in most pancreatic ductal adenocarcinomas (PDACs). Expression of an activated form of KRAS (KrasG12D) in pancreata of mice is sufficient to induce formation of pancreatic intraepithelial neoplasia (PanINs)-a precursor of PDAC. Pancreatitis increases formation of PanINs in mice that express KrasG12D by promoting acinar-to-ductal metaplasia (ADM). We investigated the role of the transcription factor Krüppel-like factor 5 (KLF5) in ADM and KRAS-mediated formation of PanINs. METHODS:We performed studies in adult mice with conditional disruption of Klf5 (Klf5fl/fl) and/or expression of KrasG12D (LSL-KrasG12D) via CreERTM recombinase regulated by an acinar cell-specific promoter (Ptf1a). Activation of KrasG12D and loss of KLF5 was achieved by administration of tamoxifen. Pancreatitis was induced in mice by administration of cerulein; pancreatic tissues were collected, analyzed by histology and immunohistochemistry, and transcriptomes were compared between mice that did or did not express KLF5. We performed immunohistochemical analyses of human tissue microarrays, comparing levels of KLF5 among 96 human samples of PDAC. UN-KC-6141 cells (pancreatic cancer cells derived from Pdx1-Cre;LSL-KrasG12D mice) were incubated with inhibitors of different kinases and analyzed in proliferation assays and by immunoblots. Expression of KLF5 was knocked down with small hairpin RNAs or CRISPR/Cas9 strategies; cells were analyzed in proliferation and gene expression assays, and compared with cells expressing control vectors. Cells were subcutaneously injected into flanks of syngeneic mice and tumor growth was assessed. RESULTS:Of the 96 PDAC samples analyzed, 73% were positive for KLF5 (defined as nuclear staining in more than 5% of tumor cells). Pancreata from Ptf1a-CreERTM;LSL-KrasG12D mice contained ADM and PanIN lesions, which contained high levels of nuclear KLF5 within these structures. In contrast, Ptf1a-CreERTM;LSL-KrasG12D;Klf5fl/fl mice formed fewer PanINs. After cerulein administration, Ptf1a-CreERTM;LSL-KrasG12D mice formed more extensive ADM than Ptf1a-CreERTM;LSL-KrasG12D;Klf5fl/fl mice. Pancreata from Ptf1a-CreERTM;LSL-KrasG12D;Klf5fl/fl mice had increased expression of the tumor suppressor NDRG2 and reduced phosphorylation (activation) of STAT3, compared with Ptf1a-CreERTM;LSL-KrasG12D mice. In UN-KC-6141 cells, PI3K and MEK signaling increased expression of KLF5; a high level of KLF5 increased proliferation. Cells with knockdown of Klf5 had reduced proliferation, compared with control cells, had reduced expression of ductal markers, and formed smaller tumors (71.61 ± 30.79 mm3 vs 121.44 ± 34.90 mm3 from control cells) in flanks of mice. CONCLUSION:Levels of KLF5 are increased in human PDAC samples and in PanINs of Ptf1a-CreERTM;LSL-KrasG12D mice, compared with controls. KLF5 disruption increases expression of NDRG2 and reduces activation of STAT3 and reduces ADM and PanINs formation in mice. Strategies to reduce KLF5 activity might reduce progression of acinar cells from ADM to PanIN and pancreatic tumorigenesis.

Dataset Information

Notch1 is not required for acinar-to-ductal metaplasia in a model of Kras-induced pancreatic ductal adenocarcinoma.

Publications

Notch1 is not required for acinar-to-ductal metaplasia in a model of Kras-induced pancreatic ductal adenocarcinoma.

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