A major effort in cancer research is focused on identifying genes directly responsible for promoting cancer progression (referred to here as ?drivers?). Perhaps nowhere is this need more acute than for pancreatic ductal adenocarcinoma (PDAC), a notoriously aggressive disease without durable treatment options. Identifying PDAC drivers and understanding their mechanism-of-action is critically important, as this information could inform new PDAC diagnostics and therapeutics. To identify such PDAC drivers, we developed novel genetic screening technologies to identify genes found mutated in PDAC that functionally cooperate with KRAS, the major driver gene found in pancreatic cancer, to promote PDAC tumor development in mice. Our approach identified the NAD Kinase (NADK), which is known in other organisms to influence redox metabolic pathways that regulate cell growth and resistance to growth-related oxidative stress. Our preliminary results indicate that NADK activation robustly drives PDAC initiation and growth, and NADK depletion significantly decreases PDAC growth concomitant with high oxidative stress owning to changes in redox state. Recent work by others has demonstrated the importance of redox pathways such as the glutamine reprogramming pathway (GRP) in promoting and maintaining PDAC growth. We hypothesize that interplay between the GRP and NADK activity centrally influences redox state and PDAC growth. We further hypothesize that NADK represents a redox vulnerability, as inhibiting NADK in patient tumors would serve as a means to selectively kill PDAC cells or sensitize them to cancer chemotherapeutics.
In Aim1 we will use a large panel of PDAC cell lines and tumors genetically modified to inducibly express or deplete NADK and GRP expression to evaluate their relative roles in influencing redox state, oxidative stress and PDAC growth in culture assays and mice. In addition, we will examine the combined effect of NADK depletion and gemcitabine, a first-line PDAC chemotherapy agent and inducer of oxidative stress, to determine whether adjuvant use of NADK inhibitors would synergize with gemcitabine to kill PDAC cells. Finally, we will measure relative levels of NADK protein and oxidative stress on clinically- and genomically-annotated PDAC patient tumors, work intended to correlate these markers with gemcitabine response to provide insight on NADK inhibitor responder (patient) identification.
In Aim 2 we will evaluate the in vivo role of NADK and therapeutic potential of NADK inhibitors by employing a novel electroporation model that allows rapid and cost-effective NADK expression and depletion in the context of activated KRAS in the mouse pancreas. In addition, we will examine NADK?s role in PDAC development and maintenance of tumor redox state using a genetically engineered mouse model of PDAC harboring a NADK conditional knockout allele. In the future, these models will also serve as a platform for testing additional chemotherapeutic agents (e.g., gemcitabine) in the context of targeted NADK depletion.

Public Health Relevance

There is a great need to identify genetic ?drivers? of pancreatic ductal adenocarcinoma (PDAC), a notoriously aggressive cancer, since understanding driver activity can reveal new ways to treat this deadly disease. We employed a novel in vivo functional screening platform that revealed robust driver activity for the NAD Kinase (NADK), which when highly expressed or mutationally-activated in PDAC influences metabolic pathways that regulate cell growth and resistance to growth-related cell stress. This proposal seeks to elucidate how NADK influences PDAC progression and will examine the hypothesis that increasing oxidative stress through NADK depletion would selectively kill PDAC cells and/or sensitize them to stress-inducing chemotherapeutics.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
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Tumor Cell Biology Study Section (TCB)
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Salnikow, Konstantin
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Baylor College of Medicine
Schools of Medicine
United States
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