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Expression profiles of Rb-deficient islet cells in mouse

ABSTRACT: Pancreatic neuroendocrine tumors (PanNET) were classified into grades (G) 1-3 by the World Health Organization in 2017, but the precise mechanisms of PanNET initiation and progression have remained unclear. In this study, we used a genetically engineered mouse model to investigate the mechanisms of PanNET formation. Although pancreas-specific deletion of the Rb gene (Pdx1-Cre;Rbf/f) in mice did not affect pancreatic exocrine cells, the α-cell/β-cell ratio of islet cells was decreased at 8 months of age. During long-term observation (18-20 months), mice formed well-differentiated PanNET with a Ki67-labeling index of 2.7%. In contrast, pancreas-specific induction of a p53 mutation (Pdx1-Cre;Trp53R172H) had no effect on pancreatic exocrine and endocrine tissues, but simultaneous induction of a p53 mutation with Rb gene deletion (Pdx1-Cre;Trp53R172H;Rb f/f) resulted in the formation of aggressive PanNET with a Ki67-labeling index of 24.7% over the short-term (4 months). In Pdx1-Cre;Trp53R172H;Rb f/f mice, mRNA expression of Pten and Tsc2, negative regulators of the mTOR pathway, significantly decreased in the islet cells, and activation of the mTOR pathway was confirmed in subsequently formed PanNET. Thus, by manipulating Rb and p53 genes, we established a multistep progression model from dysplastic islet to indolent PanNET and aggressive metastatic PanNET in mice. These observations suggest that Rb and p53 have distinct roles in the development of PanNET.

ORGANISM(S): Mus musculus

PROVIDER: GSE152582 | GEO | 2020/06/17

REPOSITORIES: GEO

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Project description:We have previously reported that the deficiency of p53 alone or in combination with Rb (Rb-/- p53-/-) in adipose-derived MSCs (ASCs) promotes leiomyosarcoma-like tumors in vivo. Here, we hypothesized that the source of MSCs and/or the cell differentiation stage could determine the phenotype of sarcoma development. To investigate whether there is a link between the source of MSCs and sarcoma phenotype, we generated p53-/- and Rb-/-p53-/- MSCs from bone marrow (BM-MSCs). Both genotypes of BM-MSCs initiated leiomyosarcoma formation similar to p53-/- and Rb-/-p53-/- ASCs. In addition, gene expression profiling revealed a link between p53- or Rb-p53-deficient BM-MSCs and ASCs and muscle-associated sarcomagenesis. These data suggest that the tissue source of MSC does not seem a crucial factor in the development of a particular sarcoma phenotype. To analyze whether the differentiation stage defines the sarcoma phenotype, BM-MSCs and ASCs were induced to differentiate towards the osteogenic lineage, and both p53 and Rb were excised using Cre-expressing adenovectors at different stages along osteogenic differentiation. Regardless of the level of osteogenic commitment, the inactivation of Rb and p53 in BM-MSC-derived, but not in ASC-derived, osteogenic progenitors gave rise to osteosarcoma-like tumors which could be serially transplanted. This indicates that the osteogenic differentiation stage of BM-MSCs imposes the phenotype of in vivo sarcoma development, and that BM-MSC-derived osteogenic progenitors rather than undifferentiated BM-MSCs, undifferentiated ASCs or ASC-derived osteogenic progenitors, represent the cell of origin for osteosarcoma development. To analyse whether the BM-MSC and Fat-MSC (ASC) differentiation stage may define the sarcoma phenotype, RbloxP/loxPp53loxP/loxP BM-MSCs and ASCs were induced to differentiate towards the osteogenic lineage and both Rb and p53 were excised with adenoviral vectors expressing the Cre-recombinase gene (Ad-CMV-Cre) at different stages (day 0 and 10) along osteogenic differentiation. NSG mice were inoculated subcutaneously with 5M-CM-^W10^6 mutant cells. Animals were killed when tumors reached 1 cm3 or 150 days after infusion. Some of the obtained tumors were mechanically disaggregated to establish ex vivo MSC-transformed cell lines. Gene expression analysis was performed using: WT BM-MSCs and ASCs, Rb-/-p53-/- BM-MSCs and ASCs previously differentiated to the osteogenic lineage for 10 days and a tumor cell line derived from p53-/-Rb-/- BM-MSC differentiated to the osteogenic lineage for 10 days.

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Expression profiles of Rb-deficient islet cells in mouse

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