3.1. ARMC10 expression in Pan-cancers and PAAD
We analyzed the expression data of pan-cancer tissues and normal controls based on TCGA and Genotype-Tissue Expression (GTEx) datasets. ARMC10 expression was significantly elevated in adrenocortical carcinoma (ACC), bladder urothelial carcinoma (BLCA), breast filtrating carcinoma (BRCA), cholangiocarcinoma (CHOL), colon adenocarcinoma (COAD), diffuse large B cell lymphoma (DLBCL), esophageal carcinoma (ESCA), pleomorphic glioma (GBM), Head and Neck squamous cell carcinoma (HNSC), renal clear cell carcinoma (KIRC), renal papillary cell carcinoma (KIRP), brain low grade glioma (LGG), liver hepatocellular carcinoma (LIHC), lung adenocarcinoma (LUAD), lung squamous cell carcinoma (LUSC), ovarian serous cystadenocarcinoma (OV), PAAD, prostate cancer (PRAD), rectum adenocarcinoma (READ), skin melanoma (SKCM), gastric cancer (STAD), testicular germ cell tumors (TGCT), thyroid cancer (THCA), thymic cancer (THYM), endometrial cancer (UCEC) and down-regulated in acute myeloid leukemia (LAML) based on the Wilcoxon test (P<0.05; Figure 1A). Besides, to detect the diagnostic effects of ARMC10, which was found to be higher expressed in tumor tissues than that in normal controls in three different datasets (P < 0.05; Figure 1B-D), the ROC curves were plotted. As shown in Figure 1E, the area under the curve (AUC) of ARMC10 is 0.957, indicating it may be a potential diagnostic biomarker for PAAD.
3.2. Recognition of DEGs in PAAD
We compared 90 ARMC10-high PAAD samples with 89 ARMC10-low PAAD samples and found a total of 668 DEGs with statistical significance (adjusted p-value < 0.05, absolute log2-FC> 1.5) (Figure 1F; Supplementary Table 2). Using DESeq2 package, we analyzed DEGs in HTSeq-Counts. The top 10 DEGs ranked by relative expression were shown in Figure 1G.
3.3. Functional Enrichment Analysis of ARMC10-associated Genes in PAAD
To further study the biological functions of ARMC10-associated genes, the DEGs were subjected to the GO analysis using Metascape and classified into Biological Processes (BPs), Cellular Components (CCs), and Molecular Functions (MFs) categories. The results showed that cellular potassium ion transport, regulation of membrane potential, glutamate receptor signaling pathway, cation channel complex, transmembrane transporter complex, glutamate receptor activity and growth factor activity were related to modulation of ARMC10-associated genes (Figure 2A; Supplementary Table 3).
3.4. Protein-Protein Interaction (PPI) Network Analysis
A PPI network was framed grounded on the STRING dataset to identify the association among the 1033 DEGs in PAAD group with the high confidence of interaction score was set as 0.70. We found that 311 proteins and 566 edges presented significant disease associations and 16 clusters of hub genes were picked from the PPI network with scores ≥ 5000 (Supplementary Figure1A-Q; Supplementary Table 4). Thereinto, the top 10 hub genes were CBX3, USP39, TMEM41A, RPE, RALB, BRSK2, AMY1B, TMEM72, LINC01625 and CCKBR.
3.5. Potential Mechanism of ARMC10 in the progression of PAAD
Using GSEA, we compared the expression data between ARMC10-high and -low samples to excavate ARMC10-related signaling pathways and significant differences (nominal, NOM p value < 0.05; false discovery rate, FDR q value < 0.25) in enrichment of the Molecular Signatures Database (MSigDB) Collection (c2.cp.reactome/biocarta/kegg.v6.2.symbols.gmt). The top significantly enriched pathways were selected according to their normalized enrichment score (NES). Enrichment plots of GSEA showed that Genes with high-CpG-density promoters (HCP) bearing histone H3 dimethylation mark at K4 (H3K4me2) in neural precursor cells (NPC), G alpha (i) signaling events, APC targets, integration of energy metabolism, potassium channels, FCGR3A mediated IL10 synthesis, were significantly enriched in ARMC10-high patients (Figure 2B-G; Supplementary Table 5).
3.6. Relevance Between ARMC10 Expression Level and Immune Infiltration
The ssGSEA was performed in PAAD samples and relevance between ARMC10 expression level and immune infiltration was demonstrated using Spearman correlation. As shown in Figure 3, the expression level of ARMC10 was positively relevant to the abundance of T helper 2 (Th2) cells (R=0.530, P<0.001), T helper cells (R=0.220, P=0.003) and negatively related to the abundance of plasmacytoid dendritic cells (pDC) (R=-0.380, P<0.001).
3.7. Relevance Between ARMC10 Expression Level and Clinicopathological Variables
To better seize the potential mechanisms of ARMC10 expression in PAAD, we explored its association with clinical characteristics of PAAD patients from TCGA. As the results showed, higher ARMC10 expression was relevant to clinical T stage (T3&4 vs. T1&2, P=0.003), clinical M stage (M1 vs. M0, P=0.043), pathologic stage (Stage II-IV vs. Stage I, P=0.029), residual tumor (R1&2 vs. R0, p=0.03), histologic grade (G3/G4 vs. G1, P<0.001; G2 vs. G1, P<0.001), primary therapy endpoint (PR&CR vs. PD&SD, P=0.018), OS event (Dead vs. Alive, P<0.001), DSS event (Dead vs. Alive, P<0.001) and PFI event (Dead vs. Alive, P<0.001) (Table1, Figure4). Using univariate logistic regression, we found that ARMC10 expression level in PAAD was positively associated with T stage (T3&4 vs. T1&2, OR=5.122, P=0.003), pathologic stage (Stage II-IV vs. Stage I, OR=4.609, P=0.011), primary therapy outcome (PR&CR vs. PD&SD, OR=0.353, P=0.040), Residual tumor (R1&2 vs. R0, OR=2.757, P=0.034) (Table2). The results above indicated that PAAD patients with higher ARMC10 expression were more likely to develop into advanced stage.
3.8. Relevance Between ARMC10 Expression Level and prognosis of PAAD patients
As shown in Figure5A-C, patients with higher expression of ARMC10 have lower OS (HR=2.45, P<0.001), DSS (HR=2.57, P<0.001), and PFI (HR=2.12, P<0.001) compared to those with lower expression. Furthermore, we performed subgroup analysis and found that higher ARMC10 expression had prognostic value for lower OS in PAAD patients of T1-T4 stage, N0& N1, pathologic stage I& II, G1& G2 histologic grade, head of pancreas neoplasm and male (Figure5D-K). We also performed subgroup analysis of DSS and PFI in PAAD patients with high ARMC10 expression (Seen in Supplementary Table8, 9). Besides, we did univariate Cox regression and discovered that higher ARMC10 expression was correlated to lower OS (HR: 2.424; CI: 1.567-3.750; P <0.001; Table3), DSS (HR: 2.560; CI: 1.555-4.216; P <0.001; Supplementary Table6) and PFI (HR: 2.246; CI: 1.506-3.349; P <0.001; Supplementary Table7). Then using multivariate Cox regression, we excavated factors correlated to prognosis including ARMC10 expression, anatomic neoplasm subdivision, histology grade, residual tumor, T, N and pathologic stage, radiation therapy and primary therapy outcome. It showed that high ARMC10 was also relevant to poor OS (HR: 2.797; CI: 1.581-4.950; P <0.001; Table3), DSS (HR: 2.681; CI: 1.432-5.018; P =0.002; Supplementary Table6) and PFI (HR: 2.063; CI: 1.227-3.468; P =0.006; Supplementary Table7). Selected from Cox regression results, multiple subgroups of PAAD patients with higher ARMC10 expression had lower OS, DSS and PFI (Seen in Table4, Supplementary Table8, 9).
Table 1: Relevance Between ARMC10 Expression Level and Clinicopathological Variables
Characteristic
|
levels
|
Low expression of ARMC10
|
High expression of ARMC10
|
p
|
n
|
|
89
|
89
|
|
T stage, n (%)
|
T1
|
4 (2.3%)
|
3 (1.7%)
|
0.024
|
|
T2
|
18 (10.2%)
|
6 (3.4%)
|
|
|
T3
|
63 (35.8%)
|
79 (44.9%)
|
|
|
T4
|
2 (1.1%)
|
1 (0.6%)
|
|
N stage, n (%)
|
N0
|
26 (15%)
|
24 (13.9%)
|
0.829
|
|
N1
|
60 (34.7%)
|
63 (36.4%)
|
|
M stage, n (%)
|
M0
|
35 (41.7%)
|
44 (52.4%)
|
0.386
|
|
M1
|
1 (1.2%)
|
4 (4.8%)
|
|
Pathologic stage, n (%)
|
Stage I
|
15 (8.6%)
|
6 (3.4%)
|
0.069
|
|
Stage II
|
68 (38.9%)
|
78 (44.6%)
|
|
|
Stage III
|
2 (1.1%)
|
1 (0.6%)
|
|
|
Stage IV
|
1 (0.6%)
|
4 (2.3%)
|
|
Radiation therapy, n (%)
|
No
|
55 (33.7%)
|
63 (38.7%)
|
0.398
|
|
Yes
|
25 (15.3%)
|
20 (12.3%)
|
|
Primary therapy outcome, n (%)
|
PD
|
19 (13.7%)
|
30 (21.6%)
|
0.261
|
|
SD
|
3 (2.2%)
|
6 (4.3%)
|
|
|
PR
|
4 (2.9%)
|
6 (4.3%)
|
|
|
CR
|
39 (28.1%)
|
32 (23%)
|
|
Age, n (%)
|
<=65
|
48 (27%)
|
45 (25.3%)
|
0.764
|
|
>65
|
41 (23%)
|
44 (24.7%)
|
|
Race, n (%)
|
Asian
|
5 (2.9%)
|
6 (3.4%)
|
0.285
|
|
Black or African American
|
1 (0.6%)
|
5 (2.9%)
|
|
|
White
|
81 (46.6%)
|
76 (43.7%)
|
|
Gender, n (%)
|
Female
|
43 (24.2%)
|
37 (20.8%)
|
0.451
|
|
Male
|
46 (25.8%)
|
52 (29.2%)
|
|
Histologic grade, n (%)
|
G1
|
24 (13.6%)
|
7 (4%)
|
0.001
|
|
G2
|
44 (25%)
|
51 (29%)
|
|
|
G3
|
18 (10.2%)
|
30 (17%)
|
|
|
G4
|
2 (1.1%)
|
0 (0%)
|
|
Residual tumor, n (%)
|
R0
|
61 (37.2%)
|
46 (28%)
|
0.020
|
|
R1
|
18 (11%)
|
34 (20.7%)
|
|
|
R2
|
3 (1.8%)
|
2 (1.2%)
|
|
Anatomic neoplasm subdivision, n (%)
|
Head of Pancreas
|
70 (39.3%)
|
68 (38.2%)
|
0.857
|
|
Other
|
19 (10.7%)
|
21 (11.8%)
|
|
Alcohol history, n (%)
|
No
|
34 (20.5%)
|
31 (18.7%)
|
0.658
|
|
Yes
|
48 (28.9%)
|
53 (31.9%)
|
|
Smoker, n (%)
|
No
|
36 (25%)
|
29 (20.1%)
|
0.482
|
|
Yes
|
38 (26.4%)
|
41 (28.5%)
|
|
History of chronic pancreatitis, n (%)
|
No
|
68 (48.2%)
|
60 (42.6%)
|
0.076
|
|
Yes
|
3 (2.1%)
|
10 (7.1%)
|
|
History of diabetes, n (%)
|
No
|
52 (35.6%)
|
56 (38.4%)
|
0.774
|
|
Yes
|
20 (13.7%)
|
18 (12.3%)
|
|
Table 2: Univariate logistic regression between ARMC10 expression level and clinical characteristics
Characteristics
|
Total(N)
|
Odds Ratio(OR)
|
P value
|
T stage (T3&T4 vs. T1&T2)
|
176
|
5.122 (1.804-15.704)
|
0.003
|
N stage (N1 vs. N0)
|
173
|
1.208 (0.480-3.010)
|
0.685
|
M stage (M1 vs. M0)
|
84
|
15.330 (0.839-469.031)
|
0.080
|
Pathologic stage (Stage II&Stage III&Stage IV vs. Stage I)
|
175
|
4.609 (1.432-15.426)
|
0.011
|
Radiation therapy (Yes vs. No)
|
163
|
0.928 (0.378-2.330)
|
0.872
|
Primary therapy outcome (PR&CR vs. PD&SD)
|
139
|
0.353 (0.124-0.913)
|
0.040
|
Gender (Male vs. Female)
|
178
|
1.520 (0.684-3.459)
|
0.307
|
Race (White vs. Asian&Black or African American)
|
174
|
0.422 (0.096-1.673)
|
0.236
|
Age (>65 vs. <=65)
|
178
|
1.047 (0.472-2.335)
|
0.910
|
Residual tumor (R1&R2 vs. R0)
|
164
|
2.757 (1.120-7.370)
|
0.034
|
Histologic grade (G3&G4 vs. G1&G2)
|
176
|
1.788 (0.730-4.636)
|
0.215
|
Anatomic neoplasm subdivision (Other vs. Head of Pancreas)
|
178
|
0.836 (0.328-2.180)
|
0.708
|
Smoker (Yes vs. No)
|
144
|
1.249 (0.524-3.020)
|
0.615
|
Alcohol history (Yes vs. No)
|
166
|
1.124 (0.481-2.620)
|
0.784
|
History of diabetes (Yes vs. No)
|
146
|
0.564 (0.211-1.493)
|
0.246
|
History of chronic pancreatitis (Yes vs. No)
|
141
|
3.447 (0.708-19.167)
|
0.141
|
Table 3: Univariate and multivariate survival results (Overall Survival) of prognostic covariates in PAAD patients.
Characteristics
|
Total(N)
|
Univariate analysis
|
|
Multivariate analysis
|
Hazard ratio (95% CI)
|
P value
|
Hazard ratio (95% CI)
|
P value
|
T stage (T3&T4 vs. T1&T2)
|
176
|
2.023 (1.072-3.816)
|
0.030
|
|
1.099 (0.385-3.139)
|
0.860
|
N stage (N1 vs. N0)
|
173
|
2.154 (1.282-3.618)
|
0.004
|
|
2.355 (1.086-5.107)
|
0.030
|
M stage (M1 vs. M0)
|
84
|
0.756 (0.181-3.157)
|
0.701
|
|
|
|
Pathologic stage (Stage II&Stage III&Stage IV vs. Stage I)
|
175
|
2.291 (1.051-4.997)
|
0.037
|
|
0.391 (0.084-1.824)
|
0.232
|
Radiation therapy (Yes vs. No)
|
163
|
0.508 (0.298-0.866)
|
0.013
|
|
0.381 (0.196-0.742)
|
0.005
|
Primary therapy outcome (CR&PR vs. PD&SD)
|
139
|
0.425 (0.267-0.677)
|
<0.001
|
|
0.489 (0.289-0.826)
|
0.007
|
Gender (Male vs. Female)
|
178
|
0.809 (0.537-1.219)
|
0.311
|
|
|
|
Race (White vs. Asian&Black or African American)
|
174
|
1.161 (0.582-2.318)
|
0.672
|
|
|
|
Age (>65 vs. <=65)
|
178
|
1.290 (0.854-1.948)
|
0.227
|
|
|
|
Residual tumor (R1&R2 vs. R0)
|
164
|
1.645 (1.056-2.561)
|
0.028
|
|
1.438 (0.841-2.458)
|
0.184
|
Histologic grade (G3&G4 vs. G1&G2)
|
176
|
1.538 (0.996-2.376)
|
0.052
|
|
1.709 (0.974-2.997)
|
0.062
|
Anatomic neoplasm subdivision (Other vs. Head of Pancreas)
|
178
|
0.417 (0.231-0.754)
|
0.004
|
|
0.418 (0.194-0.900)
|
0.026
|
ARMC10 (High vs. Low)
|
178
|
2.424 (1.567-3.750)
|
<0.001
|
|
2.797 (1.581-4.950)
|
<0.001
|
Table 4: The prognostic value of ARMC10 (Overall Survival) in multiple PAAD subgroups.
Characteristics
|
N (%)
|
HR (95% CI)
|
P value
|
T stage
|
|
|
|
T1&T2
|
31 (17.6%)
|
5.35 (1.13-25.25)
|
0.034
|
T3&T4
|
145 (82.4%)
|
1.71 (1.09-2.70)
|
0.021
|
N stage
|
|
|
|
N0
|
50 (28.9%)
|
4.18 (1.36-12.83)
|
0.013
|
N1
|
123 (71.1%)
|
1.73 (1.07-2.80)
|
0.026
|
M stage
|
|
|
|
M0
|
79 (94%)
|
1.64 (0.85-3.16)
|
0.140
|
M1
|
5 (6%)
|
-
|
-
|
Pathologic stage
|
|
|
|
Stage I-Stage II
|
167 (95.4%)
|
2.23 (1.44-3.47)
|
0.000
|
Stage III-Stage IV
|
8 (4.6%)
|
-
|
-
|
Histologic grade
|
|
|
|
G1& G2
|
126 (71.6%)
|
3.75 (2.12-6.64)
|
0.000
|
G4&G3
|
131 (37)
|
1.05 (0.52-2.13)
|
0.886
|
3.9. A Nomogram Constructed to Predict Survival Rates of PAAD Patients
We further constructed a nomogram based on ARMC10 expression and some related clinicopathologic variables to predict the survival rates of PAAD patients (Figure6A). The point scale of nomogram was set as 0-100 assigned to the variables according to the multivariate Cox regression and the total scores were calculated. The predictive value of each variable for prognosis was defined as vertical dimension from the total score axis to the outcome axis. For instance, a PAAD patient with high ARMC10 expression (97.5 points), N1 stage (62 points), R0 residual (0 points), G3 histologic grade (55 points) tumor located on head of pancreas (80 points), radiation therapy YES (0 points), PD (77.5 points) has a total point of 372. Correspondingly, the 1-, 3- and 5-year survival probability are 65%, 14% and 6%, respectively. Then using Hosmer test of the calibration curve, we evaluated the predictive validity of the nomogram in the TCGA-PAAD cohort. The C-index was 0.727 (95% CI 0.696-0.758), indicating a moderate predictive accuracy of this nomogram model (Figure6B).
3.10. Knockdown of ARMC10 Alleviated Malignant Phenotype of PAAD in vitro
To better recognize the role of ARMC10 in PAAD, we observed the expression of ARMC10 in some PAAD cell lines (HPNE, CFPAC-1, Aspc-1, Bxpc-3, Panc-1, PATU8988, Mia). As shown in Figure7A, the expression level of ARMC10 was higher in Bxpc-3 and Aspc1 than in other cell lines. Thus, further analysis was performed in Bxpc-3 and Aspc1 cell lines. Using western blotting, the transfection efficiency of si-ARMC10 was identified (Figure7B). We performed colony formation and CCK8 experiments and the results showed that inhibition of ARMC10 could lead to lower proliferation and colony formation rate in Bxpc-3 and Aspc1 cells (Figure7C-E). Besides, the result of wound healing assay showed that lower expression of ARMC10 could restrain the migration ability of Bxpc-3 and Aspc1 cells (Figure7F, G). Then using transwell experiment, we found that cells after ARMC10 knockdown had lower invasion ability (Figure7H, I). These results demonstrated that ARMC10 played an important role in PAAD progression. Further studies are required to excavate the underlying mechanisms.