3.1.1 Characteristics of participants
A total of 38 feces samples were included in this study, including 9 from healthy controls (HC) and 29 from pancreatic cancer patients. The average age of HC group was (30.54 ± 6.75) years, and the average age of PC group was (67.55 ± 10.78) years, the difference was statistically significant (P < 0.0001). The BMI of HC group was (20.84 ± 1.46) (kg/m2) and the BMI of PC group was (22.40 ± 2.90) (kg/m2), the difference was not statistically significant (P = 0.1134). There was no significant difference in gender between HC group and PC group(P = 0.3450)(Table.1).
Table 1
Basic Information of Participants
Groups
Items
|
HC
|
PC
|
Statistical value
|
P
|
Age (year)
|
30.54 ± 6.75
|
67.55 ± 10.78
|
t = 10.142
|
0.0000
|
BMI (kg/m2)
|
20.84 ± 1.46
|
22.40 ± 2.90
|
t = 1.622
|
0.1134
|
Gender
|
male
|
3
|
17
|
χ2 = 0.893
|
0.3450
|
female
|
6
|
12
|
3.1.2 Abnormal changes in gut microbes in pancreatic cancer patients
In 29 fecal samples, we detected a total of 104,082 valid sequences. After removing redundant sequences, the sequences are clustered by OTU with a similarity of 0.97. Venn diagram is drawn to visually show the common and unique numbers of two groups of OTUs. The number of unique OTUs in the HC group is 38, that in the PC group is 700, and that in the two groups is 338 (Supplementary Fig. 1A). On the PCoA analysis chart based on OTU distribution (Fig. 1G), the fecal microbial community was separated between PC1 and PC2, the main components of PC group and HC group (P = 0.006), which indicated that the intestinal microbial community of pancreatic cancer had unique microbial structure characteristics.
Analysis of alpha diversity results showed that the Sobs index of gut microbes in PC group was significantly higher than that of HC group(P = 0.0227) (Fig. 1A); The Ace and Chao indices in PC were significantly higher than those in HC (P = 0.0128; P = 0.0185) (Fig. 1B,C); Meanwhile, the Shannon index in PC was higher than that of HC (P = 0.0143) (Fig. 1D), while the Simpson index in PC was lower than that of HC (P = 0.0297) (Fig. 1E); Convergence index showed that there was no difference in species converge between PC and HC (P = 0.0596) (Fig. 1F). The above results indicate that PC can significantly increase the species richness and diversity of gut microbes in patients.
We further performed a species composition analysis of the gut microbes that in the Heatmap diagram at genus level, the results show that the dominant species of GM in HC and PC are Bacteroides, Lachnospira, Lachnospiraceae_NK4A136_group(Supplementary Fig. 1B). Next, based on the abundance of species, At the genus level, the results showed that the main species of difference in intestinal microorganisms between the HC group and PC group were Bacteroides (P = 0.0004), Lachnospira(P = 0.0001), Lachnospiraceae_NK4A136_group (P = 0.0034), Streptococcus (P = 0.0456) (Fig. 1H). At that specie level, The results showed that the species were mainly Bacteroides_vulgatus (P = 0.0264), Bacteroides_plebeius (P = 0.0120), unclassified_g__Lachnospira (P = 0.0001), Lachnospiraceae_bacterium_GAM79 (P = 0.0025) (Supplementary Fig. 1C). The above results indicated that pancreatic cancer significantly changed the species composition of intestinal microbiota.