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Oncogenic Kras cells override homeostatic cell elimination mechanisms in adult pancreas via Wnt signalling and cell dormancy.

ABSTRACT: Epithelial tissues use homeostatic defence mechanisms to actively remove aberrant or poorly functioning cells and maintain tissue health. We show that when present in tissues in low numbers, cells expressing KrasG12D or p53R172H mutations compete with normal cells for survival and are often eliminated. This implies that tumour initiation would require mechanisms whereby mutant cells override tissue homeostasis and remain in a tissue; however, the biology of these initial events is poorly understood. Here, we use an in vivo model of sporadic tumorigenesis in the adult pancreas to show that cell elimination processes are inefficient and a proportion of KrasG12D or p53R172H expressing cells are never eliminated from the epithelium. Using RNA sequencing of non-eliminated mutant populations, we reveal a general activation of the non-canonical Wnt pathway. We demonstrate that non-eliminated KrasG12D cells express cell dormancy and diapause gene signatures, suggesting non-eliminated KRasG12D cells adopt a dormant cell state in vivo. Using cell competition assays in vitro, we show that active Wnt or cell cycle arrest blocks elimination of RasV12 mutant cells from normal epithelial cell sheets. Importantly, we demonstrate that Wnt signalling is a general mechanism required to promote retention of KrasG12D and p53R172H cells in tissues in vivo . Our results suggest that mutant cells activate Wnt and/or a dormant cell state to avoid homeostatic tissue defence mechanisms and survive in the adult pancreas.

ORGANISM(S): Mus musculus

PROVIDER: GSE255283 | GEO | 2025/10/02

REPOSITORIES: GEO

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Project description:Although mutations in Kras are present in 21% of lung tumors, there is a high level of heterogeneity in phenotype and outcomes amongst lung cancer patients suggesting the importance of other pathways. Wnt/β-catenin signaling is a known oncogenic pathway that plays a well defined role in colon and skin cancer but its role in lung cancer remains unclear. We show that activation of Wnt/β-catenin in the bronchiolar epithelium of the adult lung does not promote tumor development by itself. However, activation of Wnt/β- catenin signaling leads to a dramatic increase in tumor formation both in overall tumor number and size compared to KrasG12D alone. We show that activation of Wnt/β- catenin signaling significantly alters the KrasG12D tumor phenotype resulting in a phenotypic switch from bronchiolar epithelium to the highly proliferative distal progenitors found in the embryonic lung. This is associated with a decrease in E- cadherin expression at the cell surface which may increase metastasis in Wnt/β-catenin signaling positive tumors. Together, these data suggest that activation of Wnt/β-catenin signaling in combination with other oncogenic pathways in lung epithelium may lead to a more aggressive phenotype due to the imposition of an embryonic distal progenitor phenotype accompanied by decreased E-cadherin expression. We performed microarray analysis of control murine lung, CC10-cre:KrasG12D, and CC10-cre:Ctnnb1ex3flox:LSL-KrasG12D double mutant micro-dissected murine lung tumors to determine their transcriptional phenotype. Lungs of five-month-old mice were PBS inflated and all the tumors in each lobe were dissected. The total number of tumors obtained from three out of the 5 pulmonar lobes of each animal was called a sample the other two lobes were saved in case there were problems and the array needed to be repeated. Trizol was used to isolate RNA for microarray analysis. Samples & Genotypes: control murine lung n=2 animals, CC10-cre:KrasG12D n=2 animals, and CC10-cre:Ctnnb1ex3flox:LSL-KrasG12D n=2 animals.

Project description:The small G-protein KRAS is crucial for mediating gonadotropin-induced events associated with ovulation. However, constitutive expression of KrasG12D in granulosa cells disrupted normal follicle development leading to the persistence of abnormal follicle-like structures containing non-mitotic cells. To determine what factors mediate this potent effect of KrasG12D, gene profiling analyses were done. We also analyzed KrasG12D;Cyp19-Cre and KrasG12D;Pgr-Cre mutant mouse models that express Cre prior to or after the initiation of granulosa cell differentiation, respectively. KrasG12D induced cell cycle arrest in granulosa cells of the KrasG12D;Cyp19-Cre mice but not in the KrasG12D;Pgr-Cre mice, documenting the cell context specific effect of KrasG12D. Expression of KrasG12D silenced the Kras gene, reduced cell cycle activator genes and impaired expression of granulosa cell and oocyte specific genes. Conversely, levels of PTEN and phosphorylated p38MAPK increased markedly in the mutant granulosa cells. Because disrupting Pten in granulosa cells leads to increased proliferation and survival, Pten was disrupted in the KrasG12D mutant mice. The Pten/Kras mutant mice were infertile but lacked GCTs. By contrast, the Ptenfl/fl;KrasG12D;Amhr2-Cre mice developed aggressive ovarian surface epithelial (OSE) cell tumors that did not occur in the Ptenfl/fl;KrasG12D;Cyp19-Cre or Ptenfl/fl;KrasG12D;Pgr-Cre mouse strains. These data document unequivocally that Amhr2-Cre is expressed in and mediates allelic recombination of oncogenic genes in OSE cells. That KrasG12D/Pten mutant granulosa cells do not transform but rather undergo cell cycle arrest indicates that they resist the oncogenic insults of Kras/Pten by robust self-protecting mechanisms that silence the Kras gene and elevate PTEN and phospho-p38MAPK. Experiment Overall Design: Whole ovaries were collected from 26-day-old wild type mice, 26-day-old K-ras conditional mutant mice and 3-month-old K-ras conditional mutant mice. The gene expression profiles of these samples were compared using microarray method.

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Oncogenic Kras cells override homeostatic cell elimination mechanisms in adult pancreas via Wnt signalling and cell dormancy.

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