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Oral Microbiota Mouth Off in Cystic Pancreatic Tumors

Article reposted from Genetic Engineering & Biotechnology News March 15, 2019.

Scientists at the Karolinska Institutet report that the presence of oral bacteria in cystic pancreatic tumors is associated with the severity of the tumor. The team, whose study (“Enrichment of oral microbiota in early cystic precursors to invasive pancreatic cancer”) appears in Gut, hopes the results can help to improve the diagnosis and treatment of pancreatic cancer.

“Intraductal papillary mucinous neoplasms (IPMNs) are pancreatic cysts that can progress to invasive pancreatic cancer. Associations between oncogenesis and oral microbiome alterations have been reported. This study aims to investigate a potential intracystic pancreatic microbiome in a pancreatic cystic neoplasm (PCN) surgery patient cohort.

“Paired cyst fluid and plasma were collected at pancreatic surgery from patients with suspected PCN (n=105). Quantitative and qualitative assessment of bacterial DNA by qPCR, PacBio sequencing (n=35), and interleukin (IL)-1β quantification was performed. The data were correlated to diagnosis, lesion severity, and clinical and laboratory profile, including proton-pump inhibitor (PPI) usage and history of invasive endoscopy procedures,” the investigators wrote.

“Intracystic bacterial 16S DNA copy number and IL-1β protein quantity were significantly higher in IPMN with high-grade dysplasia and IPMN with cancer compared with non-IPMN PCNs. Despite high interpersonal variation of intracystic microbiota composition, bacterial network and linear discriminant analysis effect size analyses demonstrated co-occurrence and enrichment of oral bacterial taxa including Fusobacterium nucleatum and Granulicatella adiacens in cyst fluid from IPMN with high-grade dysplasia. The elevated intracystic bacterial DNA is associated with, but not limited to, prior exposure to invasive endoscopic procedures, and is independent from the use of PPI and antibiotics.

“Collectively, these findings warrant further investigation into the role of oral bacteria in cystic precursors to pancreatic cancer and have added values on the etiopathology as well as the management of pancreatic cysts.”

Pancreatic cancer is one of the most lethal cancers in the west. The disease is often discovered late, which means that in most cases the prognosis is poor. But not all pancreatic tumors are cancerous. For instance, there are cystic pancreatic tumors (pancreatic cysts), many of which are benign. A few can, however, become cancerous.

It is currently difficult to differentiate between these tumors. To rule out cancer, many patients therefore undergo surgery, which puts a strain both on the patient and on the healthcare services. Now, however, researchers at Karolinska Institutet have found that the presence of bacteria inside the cystic tumors is linked to how severe the tumor is.

“We find most bacteria at the stage where the cysts are starting to show signs of cancer,” said corresponding author Margaret Sällberg Chen, DDS, PhD, docent and senior lecturer at the department of dental medicine, Karolinska Institutet. “What we hope is that this can be used as a biomarker for the early identification of the cancerous cysts that need to be surgically removed to cure cancer, this will in turn also reduce the amount of unnecessary surgery of benignant tumors. But first, studies will be needed to corroborate our findings.”

The researchers examined the presence of bacterial DNA in fluid from pancreatic cysts in 105 patients and compared the type and severity of the tumors. Doing this they found that the fluid from the cysts with high-grade dysplasia and cancer contained much more bacterial DNA than that from benign cysts.

To identify the bacteria, the researchers sequenced the DNA of 35 of the samples that had high amounts of bacterial DNA. They found large variations in the bacterial composition between different individuals, but also a greater presence of certain oral bacteria in fluid and tissue from cysts with high-grade dysplasia and cancer.

“We were surprised to find oral bacteria in the pancreas, but it wasn’t totally unexpected,” said Sällberg Chen. “The bacteria we identified has already been shown in an earlier, smaller study to be higher in the saliva of patients with pancreatic cancer.”

The results can help to reappraise the role of bacteria in the development of pancreatic cysts, she noted. If further studies show that the bacteria actually affect the pathological process it could lead to new therapeutic strategies using antibacterial agents.

The researchers also studied different factors that could conceivably affect the amount of bacterial DNA in the tumor fluid. They found that the presence of bacterial DNA was higher in patients who had undergone invasive pancreas endoscopy, a procedure that involves the insertion of a flexible tube into the mouth to examine and treat pancreatic conditions thus the possible transfer of oral bacteria into the pancreas.

“The results were not completely unequivocal, so the endoscopy can’t be the whole answer to why the bacteria is there,” Sällberg Chen continued. “But maybe we can reduce the risk of transferring oral bacteria to the pancreas by rinsing the mouth with an antibacterial agent and ensuring good oral hygiene prior to examination. That would be an interesting clinical study.”

Light scattering spectroscopy helps doctors identify early pancreatic cancer

Image from WebMD

Image from WebMD

Pancreatic cancer has the lowest survival rate among all major cancers, largely because physicians lack diagnostic tools to detect the disease in its early, treatable stages. Now, a team of investigators led by Lev T. Perelman, PhD, Director of the Center for Advanced Biomedical Imaging and Photonics at Beth Israel Deaconess Medical Center (BIDMC), has developed a promising new tool capable of distinguishing between harmless pancreatic cysts and those with malignant potential with an overall accuracy of 95 percent. The team’s preliminary data was published online in the journal Nature Biomedical Engineering.

The new device uses light scattering spectroscopy (LSS) to detect the structural changes that occur in cancerous or pre-cancerous cells by bouncing light off tissues and analyzing the reflected spectrum. The results could help guide physicians’ decision making when considering whether the presence of pancreatic cysts requires surgery, a high-risk procedure. Today, because of the lack of less-invasive diagnostic methods, more than half of these procedures turn out to have been unnecessary.

“About one-fifth of pancreatic cancers develop from cysts, but not all lesions are cancerous,” said Perelman, who is also Professor of Medicine and Professor of Obstetrics, Gynecology and Reproductive Biology at Harvard Medical School. “Considering the high risk of pancreatic surgeries and the even higher mortality from untreated pancreatic cancers, there’s an obvious need for new diagnostic methods to accurately identify the pancreatic cysts that need surgical intervention and those that do not.”

In Perelman and colleagues’ series of experiments, the LSS technique achieved 95 percent accuracy for identifying malignancy. Cytology — the only pre-operative test currently availably — is accurate only 58 percent of the time. While the new technique requires further testing, LSS could represent a major advance against pancreatic cancer.

“This tool is a technology that is transformative in the evaluation of pancreatic cysts,” said co-lead author Douglas K. Pleskow, MD, Clinical Chief of the Division of Gastroenterology and Director of the Colon and Rectal Cancer Program at the Cancer Center at BIDMC. “It provides a high level of precision in the detection of potential malignant transformation of these cysts.”

Pancreatic cysts are common, and today’s high-definition scanning technologies like MRI and CT imaging are detecting them with increasing frequency. Despite their high resolution, these scanners provide doctors with limited information about cysts’ malignant potential.

Currently, physicians rely on minimally-invasive fine needle aspiration (FNA) biopsies to test pancreatic cysts for malignancy. The biopsy removes fluid from the cysts, which is then analyzed for cancer cells and other telltale signs of the disease, a process called cytology. However, the test fails to detect cancer about half the time, leaving high-risk surgery as the current gold-standard means of diagnosing pancreatic cysts.

To test the accuracy of the LSS system, Perelman and colleagues collected and analyzed the reflected light from 13 cysts taken from recent surgeries. Next, they compared their findings with the results from pre-operative imaging, FNA biopsies and post-operative tissues analysis. In all cases, the LSS diagnosis agreed with the post-operative analysis.

In a second experiment, the LSS tool was tested in 14 patients with pancreatic cysts who were undergoing the standard FNA biopsy. Measuring less than half a millimeter in diameter, the miniature experimental LSS fiber-optic probe was inserted in the FNA needle. Physicians spent two minutes or less measuring optical spectra from the internal cyst surface before collecting fluid from the cysts as part of the traditional biopsy. Out of nine patients whose cysts had been definitely diagnosed as either cancerous or benign, all were correctly identified by LSS.

Next, the researchers will assess the LSS system’s accuracy by continuing to analyze post-operative tissues as they become available.

Article from Science Daily, Story source: Beth Israel Deaconess Medical Center