Glycemic Variability Promotes Both Local Invasion and Metastatic Colonization by Pancreatic Ductal Adenocarcinoma

Background & Aims: Although nearly half of pancreatic ductal adenocarcinoma (PDAC) patients have diabetes mellitus with episodes of hyperglycemia, its tumor microenvironment is hypoglycemic. Thus, it is crucial for PDAC cells to develop adaptive mechanisms dealing with oscillating glucose levels. So far, the biological impact of such glycemic variability on PDAC biology remains unknown. Methods: Murine PDAC cells were cultured in low- and high-glucose medium to investigate the molecular, biochemical, and metabolic influence of glycemic variability on tumor behavior. A set of in vivo functional assays including orthotopic implantation and portal and tail vein injection were used. Results were further confirmed on tissues from PDAC patients. Results: Glycemic variability has no significant effect on PDAC cell proliferation. Hypoglycemia is associated with local invasion and angiogenesis, whereas hyperglycemia promotes metastatic colonization. Increased metastatic colonization under hyperglycemia is due to increased expression of runt related transcription factor 3 (Runx3), which further activates expression of collagen, type VI, alpha 1 (Col6a1), forming a glycemic pro-metastatic pathway. Through epigenetic machinery, retinoic acid receptor beta (Rarb) expression fluctuates according to glycemic variability, acting as a critical sensor relaying the glycemic signal to Runx3/Col6a1. Moreover, the signal axis of Rarb/Runx3/Col6a1 is pharmaceutically accessible to a widely used antidiabetic substance, metformin, and Rar modulator. Finally, PDAC tissues from patients with diabetes show an increased expression of COL6A1. Conclusions: Glycemic variability promotes both local invasion and metastatic colonization of PDAC. A pro-metastatic signal axis Rarb/Runx3/Col6a1 whose activity is controlled by glycemic variability is identified. The therapeutic relevance of this pathway needs to be explored in PDAC patients, especially in those with diabetes

Sca-1 is a marker for cell plasticity in murine pancreatic epithelial cells and induced by IFN-β in vitro

BACKGROUND & AIMS: Sca-1 is a surface marker for murine hematopoietic stem cells (HSCs) and type-I interferon is a key regulator for Lin$^{-}$Sca-1$^{+}$ HSCs expansion through Ifnar/Stat-1/Sca-1-signaling. In this study we aimed to characterize the role and regulation of Sca-1$^{+}$ cells in pancreatic regeneration. METHODS: To characterize Sca-1 in vivo, immunohistochemistry and immunofluorescence staining of Sca-1 was conducted in normal pancreas, in cerulein-mediated acute pancreatitis, and in Kras-triggered cancerous lesions. Ifnar/Stat-1/Sca-1-signaling was studied in type-I IFN-treated epithelial explants of adult wildtype, Ifnar$^{-}$$^{/-}$, and Stat-1$^{-}$$^{/}$$^{-}$ mice. Sca-1 induction was analyzed by gene expression and FACS analysis. After isolation of pancreatic epithelial Lin$^{-}$Sca-1$^{+}$cells, pancreatosphere-formation and immunofluorescence-assays were carried out to investigate self-renewal and differentiation capabilities. RESULTS: Sca-1$^{+}$ cells were located in periacinar and periductal spaces and showed an enrichment during cerulein-induced acute pancreatitis (23.2/100 μm$^{2}$ ± 4.9 SEM) and in early inflammation-mediated carcinogenic lesions of the pancreas of Kras$^{G12D}$ mice (35.8/100 μm$^{2}$ ± SEM 1.9) compared to controls (3.6/100 μm$^{2}$ ± 1.3 SEM). Pancreatic Lin$^{-}$Sca-1$^{+}$ cells displayed a small population of 1.46% ± 0.12 SEM in FACS. In IFN-β treated pancreatic epithelial explants, Sca-1 expression was increased, and Lin$^{-}$Sca-1$^{+}$ cells were enriched in vitro (from 1.49% ± 0.36 SEM to 3.85% ± 0.78 SEM). Lin$^{-}$Sca-1$^{+}$ cells showed a 12 to 51-fold higher capacity for clonal self-renewal compared to Lin$^{-}$Sca-1$^{-}$ cells and generated cells express markers of the acinar and ductal compartment. CONCLUSIONS: Pancreatic Sca-1$^{+}$ cells enriched during parenchymal damage showed a significant capacity for cell renewal and in vitro plasticity, suggesting that corresponding to the type I interferon-dependent regulation of Lin$^{-}$Sca-1$^{+}$ hematopoietic stem cells, pancreatic Sca-1$^{+}$ cells also employ type-I-interferon for regulating progenitor-cell-homeostasis