Hyperinsulinemia acts via acinar INSR to drive obesity-associated PDAC initiation by promoting digestive enzyme production and inflammation
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. Overall design: Total RNA of a piece of the tail of pancreata were collected from 12-week old female mice for the following 3 genotypes: Insr WT (Ptf1aCreER;KrasLSL-G12D;Insrw/w;nTnG), Insr Het (Ptf1aCreER;KrasLSL-G12D;Insrw/f;nTnG), Insr KO(Ptf1aCreER;KrasLSL-G12D;Insrf/f;nTnG).