Abstract 117: Therapeutic targeting of hypoxia tolerance and oxygen consumption in pancreatic cancer
Authors: Zhang Ji , Cojocari Dan , Boasquevisque Pedro , Zaidi Mark , McKee Trevor , Radulovich Nikolina , Tsao Ming-Sound , Hedley David , Koritzinsky Marianne , Wouters Bradley 
Published: June 2022

Hypoxia is present in most solid tumours and has been clinically correlated with poor prognosis, aggressive disease, and resistance to therapy in multiple cancer including pancreatic ductal adenocarcinoma (PDAC). It has been shown PDAC hypoxia levels are highly heterogeneous and that patient-derived-xenografts (PDXs) of PDAC have similar histological phenotypes including hypoxia to their matching primary tumours. This suggests a strong genetic determinant may underlie variations in tumour hypoxia and it is not simply the result of random events of angiogenesis. We hypothesize the steady state levels of hypoxia across patient tumours is also influenced by tumour specific differences in oxygen metabolism and tolerance to hypoxia. Genetic driven changes in cellular metabolism influence the demand for oxygen, which defines the levels and steepness of hypoxia gradients around perfused vessels. Tolerance to hypoxia determines the time cells can survive in oxygen depleted microenvironments. Adaptive hypoxia stress responses such as the activation of HIF, UPR, and autophagy pathways can affect both these factors. To investigate relationship of the two factors to hypoxia, we established a matched panel of primary PDAC, PDX, and patient-derived-organoid (PDO) models covering the clinical spectrum of hypoxia. We characterized oxygen consumption and glycolytic rates of PDOs using Seahorse XF96. Hypoxia tolerance was measured by assessing PDO regrowth characteristics under defined levels of oxygenation. We then analyzed hypoxia gradients in matching PDXs by measuring the staining of the hypoxia marker, pimonidazole, as a function of distance to the nearest perfused blood vessels with an immunofluorescence image analysis pipeline. These data allow for characterizing the degree which tumour perfusion, oxygen consumption, and hypoxia tolerance correlates with and drives hypoxia levels. As a proof of concept in targeting the two proposed factors, we investigated in PDOs the effect of inhibiting ULK1, a kinase critical to autophagy initiation downstream of the PERK/UPR pathway. The upregulation of ULK1 under hypoxia promotes survival through mitophagy and ER-phagy. This reduces cellular stress and severity of hypoxia by lowering oxygen consumption and ROS levels. Inhibition of ULK1 sensitized our panel of PDOs to severe hypoxia but at varying degrees. This is correlated with differences in their functional characteristics and genomic features. Understanding the impact of oxygen consumption and hypoxia tolerance on the individual tumour hypoxia levels sets the stage for identifying genetic drivers of tumour hypoxia and development of hypoxia-targeted therapies.

Citation Format: Ji Zhang, Dan Cojocari, Pedro Boasquevisque, Mark Zaidi, Trevor McKee, Nikolina Radulovich, Ming-Sound Tsao, David Hedley, Marianne Koritzinsky, Bradley Wouters. Therapeutic targeting of hypoxia tolerance and oxygen consumption in pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 117.