Studies have analyzed the differences in the microbiome of patients with pancreatic cancer and healthy controls. However, the results have been inconsistent, and studies focusing on blood samples are limited. The current study compared the microbiome profiles of patients with pancreatic cancer and healthy controls based on 16S rRNA sequencing of saliva, fecal, and blood samples. This study identified features that differentiated the microbial composition of patients with pancreatic cancer from that of healthy controls.
Previous studies on saliva samples have shown inconsistent findings regarding alpha diversity in patients with pancreatic cancer [22–25]. However, alpha diversity showed no significant difference between patients with pancreatic cancer and healthy controls in the current study, consistent with the findings of a few studies [8, 20]. Fecal samples of patients with pancreatic cancer exhibited decreased alpha diversity and a significant difference in beta diversity, consistent with the findings of other studies [19, 30, 31].
Network analysis of the blood microbiome revealed a higher clustering coefficient and lower average path length in healthy controls than in patients with pancreatic cancer, indicating greater complexity and strength of microbial interactions. Therefore, in patients with pancreatic cancer, the complexity and compactness of microbial interactions are reduced. This result is consistent with that of other studies reporting similar patterns in microbial interaction network in other cancer types [32].
This study found distinctive microbiomes, such as Lactobacillus, Enterobacter, and Prevotella in saliva, fecal, and blood samples of patients with pancreatic cancer, respectively. Lactobacillus was consistently elevated in the saliva of patients with pancreatic cancer, which is consistent with the findings of other studies [25]. In contrast, an increased abundance of Lactobacillus was reported in the fecal samples of patients with pancreatic cancer [27]. In a mouse model of pancreatic cancer, Lactobacillus influenced macrophage activity, potentially contributing to rapid disease progression and mortality [33]. In a comparison of saliva samples between patients with precancerous lesions and squamous cell carcinoma, Lactobacillus was more abundant in patients with cancer [34]. The abundance of Enterobacter in the fecal samples of patients with pancreatic cancer was consistent with that reported in other studies [9, 35]. Enterobacter was more abundant in tumor [31, 35] and bile samples of patients with pancreatic cancer [35]. In a mouse study, Enterobacter induced chronic pancreatitis, elevating the risk of pancreatic cancer development [36]. Consistently, Enterobacteriaceae was abundant in pancreatic cancer [37]. Prevotella was more abundant in the saliva samples of healthy controls than in those of patients with pancreatic cancer [25]. In contrast, Prevotella had a higher prevalence in the tumors [35] and feces [9] of patients with pancreatic cancer. These findings underscore the complex interplay between Lactobacillus, Enterobacter, and Prevotella, and cancer, warranting further investigation.
This study had several limitations. First, the study population was small, although it was comparable to other studies. Second, as this is a single center study, studies from several institutions are needed for generalizing the findings. Third, because this study conducted a cross-sectional microbiome analysis, additional experimental models must establish causality between microbial taxa and pancreatic cancer.
In conclusion, this study identified significant microbial taxa such as Lactobacillus, Enterobacter, and Prevotella in patients with pancreatic cancer. Network analysis revealed reduced complexity, strength, and compactness of microbial interaction patterns in the blood samples of patients with pancreatic cancer. Our findings can serve as a guide for future research on the complex connection between the microbiome and pancreatic cancer.