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Hyperinsulinemia acts via acinar INSR to drive obesity-associated PDAC initiation by promoting digestive enzyme production and inflammation

ABSTRACT: The rising incidence of pancreatic cancer is largely driven by the skyrocketing prevalence of obesity and type 2 diabetes (T2D). Hyperinsulinemia is a cardinal feature of both conditions, and is independently associated with increased cancer incidence and mortality. Our previous studies demonstrated that genetically reducing insulin production suppressed formation of pancreatic intraepithelial neoplasia (PanIN) pre-cancerous lesions in mice with mutant Kras. However, we found that hyperinsulinemia affected many cell types in the pancreatic microenvironment. Thus, it remained unclear whether hyperinsulinemia exerted its effects directly on the cells that give rise to PanINs or indirectly on the tumor microenvironment, and molecular mechanisms involved were unknown. Here, we tested whether insulin receptors (Insr) in KrasG12D-expressing pancreatic acinar cells are necessary for the effects of hyperinsulinemia on obesity-associated pancreatic cancer development. Loss of Insr in KrasG12D-expressing acinar cells did not prevent hyperinsulinemia or weight gain associated with high fat diet (HFD) consumption in mice. However, solely reducing Insr in KrasG12D-expressing acinar cells significantly reduced formation of PanIN and tumors, in a gene dose-dependent manner. Mechanistically, proteomic analyses showed that hyperinsulinemia acts through Insr to drive the excess production of digestive enzymes in acinar cells by modulating the activity of the spliceosome, ribosome, and secretory machinery. This resulted in increased inflammation, which was abrogated by acinar-specific Insr knockout. We confirmed that insulin increased the conversion of wild-type acinar cells into acinar-to-ductal metaplasia (ADM) in a trypsin-dependent manner. Collectively, these data demonstrate that hyperinsulinemia acting via acinar cells insulin receptors promotes inflammatory conditions that cooperate with Kras signaling to increase the risk of developing pancreatic cancer, mechanistically linking obesity and pancreatic cancer.

ORGANISM(S): Mus musculus

PROVIDER: GSE229053 | GEO | 2023/08/01

REPOSITORIES: GEO

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Project description:The objective of this study was to elucidate the role of Nupr1 in pancreatic tumorigenesis. Using the Pdx-1-cre;LSL-KrasG12D mouse as model we discovered that, in contrast to KrasG12D pancreas that develop multiple foci of pancreatic intraepithelial neoplasia (PanIN), KrasG12D;Nupr1KO pancreas were free from such lesions, indicating that Nupr1 is pivotal for PanIN formation. In vitro, MiaPaCa2 cells activated Nupr1 expression in response to nutrient deprivation and this expression was necessary for cell survival. Mechanistically, Nupr1 protected cells from stress-induced death by inhibiting apoptosis through an alternative RelBàIER3-dependent pathway and independent from activation of the classical RelA-based NF-kB pathway. In agreement with these findings, Nupr1, RelB and IER3 proteins were found co-expressed in PanINs from KrasG12D pancreas. Moreover, pancreas-specific KrasG12D;RelbDpanc mice displayed a delay in PanIN development associated with a lack of IER3 expression, further emphasizing the relevance of this pathway in vivo. Efficient PanIN formation was therefore dependent on the expression of Nupr1 and RelB, with the probable involvement of IER3. Finally, a significant correlation between expression of Nupr1, RelB and IER3 and a poor prognosis of patients with PDAC was found. Altogether, our results reveal a novel stress-related pathway that requires the functional interaction of Nupr1àRelBàIER3 in KrasG12D-dependent transformation of the pancreas and expand our understanding of the molecular machinery that mediates the early steps of pancreatic carcinogenesis. Since Nupr1 belongs to the HMG family of chromatin remodelers with transcriptional co-factor activity, Nupr1 could increase cell survival in a nutrient-deprived microenvironment by activating the expression of pro-survival genes. Moreover, considering that RelB, and not RelA/p65, is essential to the Nupr1-mediated survival mechanism that takes place upon nutrient deprivation-induced stress, we made the hypothesis that the two NF-kB transcription factors should activate different sets of genes among which a pivotal pro-survival gene would be exclusively dependent on RelB. In order to test this two hypothesis, an Affymetrix microarray analysis was performed using pancreatic cancer cells transfected with siCtrl or siNupr1 and cultured for 3, 6 or 9 hrs in EBSS; or transfected with siRelB, siRelA/p65 or siCtrl and cultured for 9 hrs in EBSS or Mock.

Project description:Insulin receptor (Insr) protein can be found at higher levels in pancreatic b-cells than in most other cell types, but the consequences of b-cell insulin resistance remain enigmatic. Ins1cre allele was used to delete Insr specifically in b-cells of both female and male mice which were compared to Ins1cre-containing littermate controls at multiple ages and on multiple diets. RNA-seq of recombined b-cells revealed significant differences in multiple pathways previously implicated in insulin secretion and cellular fate, including rewired Ras and NFkB signaling. Male, but not female, bInsrKO mice had reduced oxygen consumption rate, while action potential and calcium oscillation frequencies were increased in Insr knockout b-cells from female, but not male mice. Female bInsrKO and bInsrHET mice exhibited elevated insulin release in perifusion experiments, during hyperglycemic clamps, and following i.p. glucose challenge. Deletion of Insr did not reduce b-cell mass up to 9 months of age, nor did it impair hyperglycemia-induced proliferation. Based on our data, we adapted a mathematical model to include b-cell insulin resistance, which predicted that b-cell Insr knockout would improve glucose tolerance depending on the degree of whole-body insulin resistance. Indeed, glucose tolerance was significantly improved in female bInsrKO and bInsrHET mice when compared to controls at 9, 21 and 39 weeks. We did not observe improved glucose tolerance in adult male mice or in high fat diet-fed mice, corroborating the prediction that global insulin resistance obscures the effects of b-cell specific insulin resistance. We further validated our in vivo findings using the Ins1-CreERT transgenic line and found improved glucose tolerance 4 weeks after tamoxifen-mediated Insr deletion. Collectively, our data show that loss of b-cell Insr alone is sufficient to drive glucose-induced hyperinsulinemia, thereby improving glucose homeostasis in otherwise insulin sensitive dietary and age contexts.

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Hyperinsulinemia acts via acinar INSR to drive obesity-associated PDAC initiation by promoting digestive enzyme production and inflammation

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