Researchers at the University of Michigan have uncovered metabolic pathways that explain how pancreatic cells transition from acinar-to-ductal metaplasia to pancreatic ductal adenocarcinoma (PDAC). The study, published in Nature Metabolism, detailed on how reduced production of a molecule central to biosynthesis and oxidative stress control called NADPH alters cellular conditions to favor cancer progression. By examining precancerous pancreatic lesions, the team found that disruptions in enzymes responsible for NADPH production increase oxidative stress, accelerating the formation of lesions and, in some cases, the progression to PDAC.
“We know a lot about how pancreatic tumors behave and look, but we don’t know how they become cancerous,” said lead author Megan Radyk, PhD, a former postdoc in the lab of Costas Lyssiotis, PhD, at the University of Michigan and now an assistant professor at Roswell Park Comprehensive Cancer Center. “We wanted to learn about what metabolic changes happen before you get an established tumor.”
PDAC is the most common form of pancreatic cancer and has a low five-year survival rate. The disease develops through a stepwise process that begins with acinar-to-ductal metaplasia (ADM), a reversible state in which pancreatic cells respond to injury or inflammation by adopting a duct-like phenotype. Under normal conditions, these cells can revert to their original state. However, in the presence of oncogenic KRAS mutations, this process is disrupted, leading to persistent ADM and progression to pancreatic intraepithelial neoplasia (PanIN), which can ultimately become PDAC.
NADPH’s normal role is in maintaining cellular homeostasis. It supports the synthesis of lipids, cholesterol, and nucleotides, and it aids antioxidant systems that regulate reactive oxygen species (ROS). Under normal conditions, NADPH helps neutralize ROS, preventing cellular damage. The current study, however, demonstrated that lower levels of NADPH impair antioxidant defenses, leading to increased ROS and lipid peroxidation, which in turn promote the formation of precancerous lesions.
The researchers identified two NADPH-producing enzymes for their work: glucose-6-phosphate dehydrogenase (G6PD) and malic enzyme 1 (ME1). Both enzymes support the production of the appropriate levels of NADPH needed for biosynthesis and ROS regulation.
Using a multimodal approach involving RNA sequencing, metabolomics, and mouse models with oncogenic KRAS mutations, the Michigan team studied how the loss of these two enzymes affects pancreatic tissue. They observed that deficiency in either G6PD or ME1 increased ROS levels and accelerated the formation of ADM and pancreatic intraepithelial neoplasia (PanIN) lesions. Antioxidant treatments, including glutathione and N-acetyl cysteine, reduced lesion formation, further bolstering the current understanding of the role of oxidative stress in early tumorigenesis. The team achieved similar results when these methods were applied to human pancreatic tissue samples.
But results from later in the study showed that the two enzymes played distinct roles in the later stages of PDAC. While they both contributed to early lesion formation, only the loss of ME1 promoted progression to PDAC. This suggests that although both enzymes regulate NADPH and oxidative stress, they have distinct roles in later metabolic demands of cancer cells.
The study builds on prior research showing that KRAS mutations drive metabolic reprogramming and ROS production in pancreatic cells. Previous work has also indicated that antioxidant pathways, including those regulated by NRF2, are activated during tumor initiation.
Clinically, these findings suggest that targeting metabolic pathways involved in NADPH production could provide a strategy to intercept pancreatic cancer before it fully develops. Measuring levels of G6PD, ME1, or related metabolites could also serve as biomarkers to identify patients at higher risk of lesions progressing to cancer.
“Our study can help the search for new biomarkers that can intercept pancreatic cancer before it progresses,” the researchers wrote.
Future research will focus on identifying additional enzymes that regulate NADPH levels and determining how these pathways can be targeted safely. The researchers also plan to study whether patients with mutations in G6PD, ME1, or related pathways have an increased risk of pancreatic disease.
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