Pancreatic inflammation is the major cause of gastrointestinal-related clinical morbidity and mortality, and effective therapeutic strategies against pancreatic inflammatory diseases remain an unmet medical need. Inflammation is a common feature in the pathogenesis of pancreatitis and associated acinar-to-ductal metaplasia (ADM), pancreatic intraepithelial neoplasia (PanIN) lesions, and pancreatic ductal adenocarcinoma (PDAC). Given the prominent role of inflammation in the spectrum of pancreatic pathologies, understanding pancreas- specific inflammatory mechanisms is critical for the prevention and treatment of the associated diseases. Inflammation is known to induce reactive oxygen species (ROS). Among known causal factors, ROS act as both a signaling molecule and a mediator of inflammation. Wild-type KRAS is subject to ROS modification on cysteine of the redox-sensitive NKC118D motif leading to a transient hyperactivation. KRAS mutants are observed in ~30% of patients with chronic pancreatitis, suggesting the critical role of KRAS mutations in pancreatic inflammation. In the past thirty years, mutant KRAS has been viewed as being locked in a constitutively active state. However, recent studies have found that mutant KRAS, at an endogenous level, is not constitutively active but can be hyper-activated by inflammatory insults leading to sustained inflammation, irreversible ADM, and PanIN lesions. However, the molecular mediator and mechanism linking inflammation to mutant KRAS hyperactivation and associated pathologies remain elusive. Studies have shown that NADPH oxidases (NOXs) are a major mediator of pancreatitis-induced inflammation and major enzymes activated by mutant KRAS for the generation of ROS. However, whether mutant KRAS is subject to the same ROS modification as wild-type KRAS leading to the observed hyperactivity in the context of inflammation is unknown. The objective of this proposal is to identify the molecular mediator and unravel the underlying mechanism on how inflammation promotes mutant KRAS hyperactivation and associated pancreatic pathologies. Notably, by ablating the NOX-docking subunit p22phox in mice expressing an endogenous level of KRASG12D/+ in pancreatic acinar cells, we demonstrate that NOX inhibition considerably curbs KRASG12D/+ hyperactivation, suggesting that NOX is not only a downstream effector but also a potential upstream regulator of KRASG12D. Thus, NOX and KRASG12D potentially form a co-activation feed-forward loop necessary to induce chronic inflammation, irreversible ADM, and PanIN lesions. We hypothesize that under inflammation, NOX generates ROS to modify the redox-sensitive motif of KRASG12D, leading to KRASG12D hyperactivation and associated pathologies. Our hypothesis will be tested with three specific aims in mouse models in the context of inflammatory insults.
Aim 1 is to determine the role of NOX in pancreatic inflammation.
Aim 2 is to determine if NOX is necessary for KRASG12D hyperactivation, sustained inflammation, irreversible ADM, and PanIN lesions.
Aim 3 is to determine if the redox-sensitive NKC118D motif is required for KRASG12D hyperactivation and associated pathologies. Information gained in our studies will fill the outstanding knowledge gap on how inflammatory insults promote mutant KRAS hyperactivation and associated pathologies and guide the design of novel preventive and therapeutic strategies against these diseases in humans.
Our studies support the role of inflammatory stimulants in promoting mutant KRAS hyperactivation leading to a long-sustained pancreatic inflammation, irreversible acinar-to-ductal metaplasia, and pancreatic intraepithelial neoplasia. The objective of this proposal is to unravel the role of NADPH oxidases as a critical mediator linking inflammation to mutant KRAS hyperactivation and associated pathologic consequences. Knowledge gained from the current proposal will guide the design of new targets for prevention and treatment in humans of inflammation- associated pancreatic diseases.
