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Decreased tumorigenesis in mice with a Kras point mutation at C118.

ABSTRACT: KRAS, NRAS or HRAS genes are mutated to encode an active oncogenic protein in a quarter of human cancers. Redox-dependent reactions can also lead to Ras activation in a manner dependent upon the thiol residue of cysteine 118 (C118). Here, to investigate the effect of mutating this residue on tumorigenesis, we introduce a C118S mutation into the endogenous murine Kras allele and expose the resultant mice to the carcinogen urethane, which induces Kras mutation-positive lung tumours. We report that Kras(+/C118S) and Kras(C118S/C118S) mice develop fewer lung tumours. Although the Kras(C118S) allele does not appear to affect tumorigenesis when the remaining Kras allele is conditionally oncogenic, there is a moderate imbalance of oncogenic mutations favouring the native Kras allele in tumours from Kras(+/C118S) mice treated with urethane. We conclude that the Kras(C118S) allele impedes urethane-induced lung tumorigenesis.

SUBMITTER: Huang L

PROVIDER: S-EPMC4234187 | biostudies-literature | 2014 Nov

REPOSITORIES: biostudies-literature

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Decreased tumorigenesis in mice with a Kras point mutation at C118.

Huang Lu L Carney John J Cardona Diana M DM Counter Christopher M CM

Nature communications 20141114

KRAS, NRAS or HRAS genes are mutated to encode an active oncogenic protein in a quarter of human cancers. Redox-dependent reactions can also lead to Ras activation in a manner dependent upon the thiol residue of cysteine 118 (C118). Here, to investigate the effect of mutating this residue on tumorigenesis, we introduce a C118S mutation into the endogenous murine Kras allele and expose the resultant mice to the carcinogen urethane, which induces Kras mutation-positive lung tumours. We report that ...[more]

PMID: 25394415

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Project description:Background & aimsNew drug targets are urgently needed for the treatment of patients with pancreatic ductal adenocarcinoma (PDA). Nearly all PDAs contain oncogenic mutations in the KRAS gene. Pharmacological inhibition of KRAS has been unsuccessful, leading to a focus on downstream effectors that are more easily targeted with small molecule inhibitors. We investigated the contributions of phosphoinositide 3-kinase (PI3K) to KRAS-initiated tumorigenesis.MethodsTumorigenesis was measured in the Kras(G12D/+);Ptf1a(Cre/+) mouse model of PDA; these mice were crossed with mice with pancreas-specific disruption of genes encoding PI3K p110α (Pik3ca), p110β (Pik3cb), or RAC1 (Rac1). Pancreatitis was induced with 5 daily intraperitoneal injections of cerulein. Pancreata and primary acinar cells were isolated; acinar cells were incubated with an inhibitor of p110α (PIK75) followed by a broad-spectrum PI3K inhibitor (GDC0941). PDA cell lines (NB490 and MiaPaCa2) were incubated with PIK75 followed by GDC0941. Tissues and cells were analyzed by histology, immunohistochemistry, quantitative reverse-transcription polymerase chain reaction, and immunofluorescence analyses for factors involved in the PI3K signaling pathway. We also examined human pancreas tissue microarrays for levels of p110α and other PI3K pathway components.ResultsPancreas-specific disruption of Pik3ca or Rac1, but not Pik3cb, prevented the development of pancreatic tumors in Kras(G12D/+);Ptf1a(Cre/+) mice. Loss of transformation was independent of AKT regulation. Preneoplastic ductal metaplasia developed in mice lacking pancreatic p110α but regressed. Levels of activated and total RAC1 were higher in pancreatic tissues from Kras(G12D/+);Ptf1a(Cre/+) mice compared with controls. Loss of p110α reduced RAC1 activity and expression in these tissues. p110α was required for the up-regulation and activity of RAC guanine exchange factors during tumorigenesis. Levels of p110α and RAC1 were increased in human pancreatic intraepithelial neoplasias and PDAs compared with healthy pancreata.ConclusionsKRAS signaling, via p110α to activate RAC1, is required for transformation in Kras(G12D/+);Ptf1a(Cre/+) mice.

Dataset Information

Decreased tumorigenesis in mice with a Kras point mutation at C118.

Publications

Decreased tumorigenesis in mice with a Kras point mutation at C118.

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