Organoid Models of Pancreatic Cancer
Organoids are 3-dimensional primary epithelial cell cultures formed from benign and malignant murine and human pancreatic tissues (Boj et al, 2014). Organoids can be generated from small human tissue samples such as endoscopic needle biopsies, providing a feasible route to influence patient management. With our panel of organoids, we can perform any type of molecular evaluation including transcriptomic, genomic, metabolomic and proteomic analyses. These studies have identified new pathways that are altered in pancreatic cancer, including lipid metabolism. Additionally, there is marked inter-patient genetic diversity in the human pancreatic cancer organoids, and strikingly also intra-patient subclonal diversity uncovered by single cell assessment. To determine the extent of inter-patient and intra-patient heterogeneity, we have initiated a project with multiple sites internationally to collect and characterize 300 human organoids. Single cell analyses will be performed on some of these specimens to determine the pattern of co-occurrent mutations that define distinct genetic subtypes and likely represent unique therapeutic vulnerabilities. Isolation of the individual clones can be achieved as single cells can give rise to organoids.
Intriguingly, organoids recapitulated tumor progression following orthotopic transplantation, representing the first robust transplantable model of human pancreatic cancer progression. Remarkably, both the neoplastic and tumor microenvironment composition evolved simultaneously, and we are currently determining whether these orthotopically engrafted organoids (OGO) models accurately reflect therapeutic responses. We expect that the OGO models will be a rich resource for fundamental biology and biomarker discovery during the earliest stages of human cancer, including the identification of new therapeutic strategies.
NRF2, Redox and Pancreatic Cancer
Reduction-oxidation (Redox) chemical reactions in which the oxidation states of atoms are changed, represent a principle constituent of all life. Despite this, our current understanding of redox biochemistry inside living cells remains surprisingly elusive in both physiological and pathological settings. In the context of tumorigenesis, there is much excitement over the possibility of harnessing differences in cellular redox states to develop novel therapeutic strategies. To date, most effort has been invested in defining the role of reactive oxygen species (ROS) as a tumor promoting or a tumor-suppressing agent, with abundant evidence supporting either argument. ROS on the one hand, can suppress cell growth through genotoxic stress and protein translational arrest; and on the other hand, can promote cell growth through activation of mitogenic signaling cascades. The role of ROS in cellular outcome is clearly more diverse than anticipated. Cellular responses to ROS reflect a complex integration of ROS type, location and levels. This presents a conundrum on how we should approach ROS therapy in cancer.
Our laboratory focuses on studying the regulation of ROS by a transcriptional factor called NRF2. In our recent work, we demonstrated that genetic ablation of NRF2 led to elevated levels of H2O2 and consequently oxidative inactivation of various components of the translation machinery. This presents a therapeutically actionable vulnerability in pancreatic cancer cells.