Unraveling the Role of NADPH Oxidase in Inflammation-associated Pancreatic Diseases - Abstract
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.
