Pancreatic ductal adenocarcinoma is one of the most intractable and fatal cancer. The decreased blood vessel density displayed by this tumor not only favors its resistance to chemotherapy but also participates in its aggressiveness due to the consequent high degree of hypoxia. It is indeed clear that hypoxia promotes selective pressure on malignant cells that must develop adaptive metabolic responses to reach their energetic and biosynthetic demands. Here, using a well-defined mouse model of pancreatic cancer, we report that hypoxic areas from pancreatic ductal adenocarcinoma are mainly composed of epithelial cells harboring epithelial-mesenchymal transition features and expressing glycolytic markers, two characteristics associated with tumor aggressiveness. We also show that hypoxia increases the "glycolytic" switch of pancreatic cancer cells from oxydative phosphorylation to lactate production and we demonstrate that increased lactate efflux from hypoxic cancer cells favors the growth of normoxic cancer cells. In addition, we show that glutamine metabolization by hypoxic pancreatic tumor cells is necessary for their survival. Metabolized glucose and glutamine converge toward a common pathway, termed hexosamine biosynthetic pathway, which allows O-linked N-acetylglucosamine modifications of proteins. Here, we report that hypoxia increases transcription of hexosamine biosynthetic pathway genes as well as levels of O-glycosylated proteins and that O-linked N-acetylglucosaminylation of proteins is a process required for hypoxic pancreatic cancer cell survival. Our results demonstrate that hypoxia-driven metabolic adaptive processes, such as high glycolytic rate and hexosamine biosynthetic pathway activation, favor hypoxic and normoxic cancer cell survival and correlate with pancreatic ductal adenocarcinoma aggressiveness.pancreas | malignancy | metabolism | glutamate N inety-five percent of patients with pancreatic cancer harbor tumors classified as pancreatic ductal adenocarcinoma (PDAC). Commonly described as a silent killer regarding its late diagnosis, PDAC is noted for its aggressiveness and its intrinsic resistance to standard chemotherapy. This specificity is probably due to a low vascular density and a prominent nontumoral cell compartment (stroma), which impact on intratumoral perfusion, therapeutic delivery, and patient outcome (1). Indeed, PDAC is characterized by numerous and severe hypoxic regions (2), a feature that has been proven to be correlated with tumor aggressiveness and poor prognosis compared with well-oxygenated tumors (3). Moreover, combined with hypoxia, the subsequent nutrient-devoid environment provides physiological selective pressure promoting expansion of the most aggressive malignant cells, particularly those acquiring mutations in genes encoding tumor suppressor protein p53 (TP53) and v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog protein (KRAS) (4, 5), two of the main mutations present in PDAC patients. Regarding such statements, it appears relevant to deeply explore consequ...