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Wild-Type Hras Suppresses the Earliest Stages of Tumorigenesis in a Genetically Engineered Mouse Model of Pancreatic Cancer.

ABSTRACT: Oncogenic, activating mutations in KRAS initiate pancreatic cancer. There are, however, two other Ras family members, Nras and Hras, which can be activated in the presence of oncogenic Kras. The role of these wild-type Ras proteins in cancer remains unclear, as their disruption has been shown to enhance or inhibit tumorigenesis depending upon the context. As pancreatic cancer is critically dependent upon Ras signaling, we tested and now report that loss of Hras increases tumor load and reduces survival in an oncogenic Kras-driven pancreatic adenocarcinoma mouse model. These effects were traced to the earliest stages of pancreatic cancer, suggesting that wild-type Hras may suppress tumor initiation. In normal cells, activated Ras can suppress proliferation through p53-dependent mechanisms. We find that the tumor suppressive effects of Hras are nullified in a homozygous mutant p53 background. As such, loss of wild-type Hras fosters the earliest stages of pancreatic cancer in a p53-dependent manner.

SUBMITTER: Weyandt JD

PROVIDER: S-EPMC4599940 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Wild-Type Hras Suppresses the Earliest Stages of Tumorigenesis in a Genetically Engineered Mouse Model of Pancreatic Cancer.

Weyandt Jamie D JD Lampson Benjamin L BL Tang Sherry S Mastrodomenico Matthew M Cardona Diana M DM Counter Christopher M CM

PloS one 20151009 10

Oncogenic, activating mutations in KRAS initiate pancreatic cancer. There are, however, two other Ras family members, Nras and Hras, which can be activated in the presence of oncogenic Kras. The role of these wild-type Ras proteins in cancer remains unclear, as their disruption has been shown to enhance or inhibit tumorigenesis depending upon the context. As pancreatic cancer is critically dependent upon Ras signaling, we tested and now report that loss of Hras increases tumor load and reduces s ...[more]

PMID: 26452271

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Project description:BACKGROUND: Pancreatic cancer remains one of the deadliest cancers due to lack of early detection and absence of effective treatments. Gemcitabine, the current standard-of-care chemotherapy for pancreatic cancer, has limited clinical benefit. Treatment of pancreatic cancer cells with gemcitabine has been shown to induce the activity of the transcription factor nuclear factor-kappaB (NF-?B) which regulates the expression of genes involved in the inflammatory response and tumorigenesis. It has therefore been proposed that gemcitabine-induced NF-?B activation may result in chemoresistance. We hypothesize that NF-?B suppression by the novel inhibitor dimethylaminoparthenolide (DMAPT) may enhance the effect of gemcitabine in pancreatic cancer. METHODS: The efficacy of DMAPT and gemcitabine was evaluated in a chemoprevention trial using the mutant Kras and p53-expressing LSL-KrasG12D/+; LSL-Trp53R172H; Pdx-1-Cre mouse model of pancreatic cancer. Mice were randomized to treatment groups (placebo, DMAPT [40 mg/kg/day], gemcitabine [50 mg/kg twice weekly], and the combination DMAPT/gemcitabine). Treatment was continued until mice showed signs of ill health at which time they were sacrificed. Plasma cytokine levels were determined using a Bio-Plex immunoassay. Statistical tests used included log-rank test, ANOVA with Dunnett's post-test, Student's t-test, and Fisher exact test. RESULTS: Gemcitabine or the combination DMAPT/gemcitabine significantly increased median survival and decreased the incidence and multiplicity of pancreatic adenocarcinomas. The DMAPT/gemcitabine combination also significantly decreased tumor size and the incidence of metastasis to the liver. No significant differences in the percentages of normal pancreatic ducts or premalignant pancreatic lesions were observed between the treatment groups. Pancreata in which no tumors formed were analyzed to determine the extent of pre-neoplasia; mostly normal ducts or low grade pancreatic lesions were observed, suggesting prevention of higher grade lesions in these animals. While gemcitabine treatment increased the levels of the inflammatory cytokines interleukin 1? (IL-1?), IL-1?, and IL-17 in mouse plasma, DMAPT and DMAPT/gemcitabine reduced the levels of the inflammatory cytokines IL-12p40, monocyte chemotactic protein-1 (MCP-1), macrophage inflammatory protein-1 beta (MIP-1?), eotaxin, and tumor necrosis factor-alpha (TNF-?), all of which are NF-?B target genes. CONCLUSION: In summary, these findings provide preclinical evidence supporting further evaluation of agents such as DMAPT and gemcitabine for the prevention and treatment of pancreatic cancer.

Dataset Information

Wild-Type Hras Suppresses the Earliest Stages of Tumorigenesis in a Genetically Engineered Mouse Model of Pancreatic Cancer.

Publications

Wild-Type Hras Suppresses the Earliest Stages of Tumorigenesis in a Genetically Engineered Mouse Model of Pancreatic Cancer.

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