A research team at Duke Health has identified a set of biomarkers that could help to distinguish whether cysts on the pancreas are likely to develop into cancer or remain benign. The team carried out digital spatial RNA profiling of intraductal papillary mucinous neoplasms (IPMNs)—a type of pancreatic cyst that can be a precursor to pancreatic cancer—to determine biomarkers associated with a high risk of progression to cancer, and identify biological processes linked to that malignant progression.
The team, headed by Peter Allen, MD, chief of the Division of Surgical Oncology at in the Department of Surgery at Duke University School of Medicine, suggests that their findings represent an important first step toward a clinical approach for classifying lesions on the pancreas that are at highest risk of becoming cancerous, potentially enabling their removal before they begin to spread.
Allen and colleagues reported on their findings in Science Advances, in a paper titled “Digital spatial profiling of intraductal papillary mucinous neoplasms: Toward a molecular framework for risk stratification,” in which they concluded “the incorporation of subtype-specific and high-risk marker genes nominated by this study may facilitate the development of an accurate risk stratification assay in IPMN.”
“Pancreatic ductal adenocarcinoma (PDAC) remains a leading cause of cancer death, predominantly because of the lack of early detection strategies that enable identification of patients at a potentially curable stage,” the authors noted. “Even when pancreas cancer is detected at its earliest stage, it almost always has shed cells throughout the body, and the cancer returns,” said Allen. “That’s why we shifted our focus to these precancerous cysts, known as intraductal papillary mucinous neoplasms, or IPMNs.”
IPMNs are cystic lesions of the pancreas that can be detected radiographically, and which represent a potential precursor to pancreatic cancer. But while most IPMNs don’t progress to cancer, the ability to accurately differentiate those that are low risk for progression (low-grade dysplasia; LGD)—from those that are high risk (high-grade dysplasia; HGD and early cancer), “remains elusive,” the investigators stated. Allen further pointed out, “Most IPMNs will never progress to pancreas cancer, but by distinguishing which ones will progress, we are creating an opportunity to prevent an incurable disease from developing. It is also generally accepted that while that HGD will require surgery, patients with LGD should be monitored by radiographic surveillance.”
Allen explained that current diagnostic strategies—including clinical, radiographic, laboratory, endoscopic, and cytologic analysis—have an overall accuracy of approximately 60%. “Pancreatic cancer is on the rise,” he added, “and, if the current trajectory continues, it will become the second-leading cause of cancer death in the United States in the next few years.”
Pathologic characterization of IPMN has shown that there are multiple dysplastic histologic epithelial subtypes, and these can often be found together, within individual specimens, the team continued. “Epithelial subtypes observed histologically include pancreaticobiliary (PB), intestinal (INT), gastric foveolar (GF), and an oncocytic variant. The PB and INT subtypes comprise the overwhelming majority of IPMN with propensity for invasive cancer, and GF represents an indolent subtype associated with favorable prognosis.” But while techniques such as microdissection can allow scientists to isolate and compare different regions of dysplastic epithelium, they are also technically challenging and disrupt tissue quality. And as the team pointed out, while “numerous studies have proposed possible mRNA, microRNA, and protein biomarkers for high-risk IPMN, to date, none has been incorporated into clinical use because of prognostic inaccuracies.”
In contrast with previous, less precise methods for characterizing IPMNs that have not been able to identify particularly accurate markers of cancer risk, digital spatial profiling allows researchers to choose individual groups of cells for analysis. “This technology offers precise comparison of gene expression among user-defined disease regions without the need for cumbersome microdissection,” the scientists explained.
For their newly reported study, Allen and colleagues used digital spatial RNA profiling to home in on these specific areas of the cyst with high- and low-grade areas of abnormal cell growth. They profiled dysplastic epithelium (83 regions) from IPMN tissues that had been surgically resected from 12 patients, to differentiate subtypes and predict genes associated with malignancy. “In the current study, we leveraged digital spatial RNA profiling using a targeted gene panel to characterize precise regions of IPMN histopathology across tissue slides and produce robust gene expression patterns by epithelial subtype and grade,” they explained. Their analyses identified a host of genetic mutations that appear to both fuel and potentially suppress pancreatic cancer development.
The team also identified markers for discriminating between the two leading variants of IPMN and found distinct markers for defining a third common variant that generally results in less aggressive disease. “In summary, our findings offer several refinements to our understanding of IPMN,” they wrote. “First, GF epithelium likely represents a precursor to PB rather than a common progenitor to either PB or INT. Second, the activation of inflammatory signaling associates with high-risk IPMN and occurs predominantly in PB lesions. This finding lends credence to ongoing clinical trials of anti-inflammatory therapies in the prevention of IPMN progression.”
“We found very distinct markers for high-grade cell abnormalities, as well as for slow-growing subtypes,” Allen said. “Our work now is focusing on finding it in the cyst fluid. If we can identify these unique markers in cyst fluid, it could provide the basis for a protein biopsy that would guide whether we should remove the cyst before cancer develops and spreads.” Allen further noted that some studies suggest a role for inflammation. A clinical trial at Duke, led by Allen, is testing whether an anti-inflammatory therapy could reduce the development of cancer in patients with IPMN.