Differentially expressed ARGs
A total 4 downregulated ARGs (DIRAS3, FOS, FOXO1, NRG1) and 58 upregulated ARGs (ATG10, ATG16L2, ATG4B, ATG9B, ATIC, BAK1, BAX, BIRC5, CANX, CAPN10, CAPN2, CAPNS1, CASP3, CASP8, CD46, CDKN2A, CLN3, DAPK2, DDIT3, DRAM1, FKBP1A, GAPDH, HDAC1, HGS, HSP90AB1, HSPA5, HSPB8, IKBKE, IRGM, ITGA3, ITGA6, ITGB4, MAPK3, MLST8, NKX2−3, NPC1, NRG2, PARP1, PEA15, PELP1, PRKCD, RAB24, RB1CC1, RGS19, RHEB, RPTOR, RUBCN, SPHK1, SPNS1, SQSTM1, TMEM74, TP63, TP73, TSC1, TSC2, ULK3, VMP1, WDR45B) were obtained from data analysis (Figure 1 A). We visualize the expression pattern of the differentially expressed ARGs by volcano plot and box plot (Figure 1 B, C).
Functional and pathway enrichment analysis
The GO and KEGG enrichment analysis showed the differentially expressed ARGs were mainly associated with the BP terms autophagy, process utilizing autophagic mechanism, macro-autophagy, and regulation of autophagy. In addition, CC terms showed that the ARGs were associated with vacuolar membrane, membrane region, lysosomal membrane, and lytic vacuole membrane. Moreover, MF terms were mainly protein kinase regulator activity, kinase regulator activity, and ubiquitin−like protein ligase binding (Figure 2 A). We also performed KEGG pathway enrichment analysis to determine the pathways most enriched, which included Autophagy − animal, Human papillomavirus infection, and Apoptosis (Figure 2 B, C).
Identification of prognosis‑related ARGs survival model
A total of 48 ARGs were identified closely related to HCC patient survival by the univariate Cox regression analysis. Then, we exclude genes that may be highly correlated with other genes by the Lasso regression analysis (Figure 3 A, B). Finally, seven survival-related ARGs were submitted to multivariate Cox proportional hazards model, generate 5 candidate ARGs (SQSTM1, ATIC, CAPN10, RHEB, EIF2S1) were identified to construct the survival model (Table 1). Our survival model was formed using the following formula: risk score = (the means expression of SQSTM1*0.002097) + (the means expression of ATIC * 0.021484) + (the means expression of CAPN10 * 0.229976) + (the means expression of RHEB * 0.032636) + (the means expression of EIF2S1 * 0.108674).
Table 1
The regression coefficient of five candidate ARGs genes.
Gene
|
Coef
|
HR
|
HR.95L
|
HR.95H
|
pvalue
|
SQSTM1
|
0.00209656
|
1.00209876
|
1.000964733
|
1.003234071
|
0.000284431
|
ATIC
|
0.021484244
|
1.021716692
|
0.999648782
|
1.044271767
|
0.053801295
|
CAPN10
|
0.22997623
|
1.258570093
|
0.949114099
|
1.668923348
|
0.110212197
|
RHEB
|
0.032636098
|
1.033174496
|
1.002195687
|
1.065110889
|
0.035625927
|
EIF2S1
|
0.1086743
|
1.114799201
|
1.05082418
|
1.182669073
|
0.000313294
|
The HCC patients divided into low- and high-risk groups base on the median of the risk score. The low-risk group had a higher survival rate than high-risk group (HR = 1.202, 95% CI = 1.141– 1.268, P < 0.001) according Kaplan–Meier survival curves (Figure 4A). In addition, we assess the accuracy of the OS-related survival model by constructed the ROC curve, and the AUC of risk score was significant than other clinicopathological parameters (Figure 4B). Finally, we ranked the HCC patients by survival model to analyses the survival distribution. We could identify the mortality rate of HCC patients with their risk scores. Moreover, with the increase of risk score, the mortality rate of patients rose (Figure 4 C, D). We described the expression of ARGs between low- and high-risk groups by heat maps (Figure 4 E).
The relationships between prognosis‑related survival model, Tumor-infiltrating immune cells and clinicopathological parameters
The univariate and multivariate Cox regression analysis showed that the survival model can be used as an independent prognostic factor for HCC patients (Figure 5 A, B). The survival model was significantly related to clinicopathological features mainly including survival state, stage, and tumor T status (Figure 5 C-E).
We next evaluated the association of prognosis‑related survival model and tumor-infiltrating immune cells in HCC microenvironment using CIBERSORT algorithm. The CIBERSORT analysis showed that the composition of 22 immune cell types in High-risk group and low-risk group of HCC varied significantly (Figure 6 A, B). Moreover, Dendritic cell resting were more enriched in High-risk group (Figure 6 C).
Validation of the survival model
We calculated the risk score of each HCC patients in the ICGC data portal project Liver Cancer - RIKEN, JP (LIRI-JP) as an independent external validation by the same formula. And HCC patients divided into high- and low-risk groups based on the median of risk score. The Kaplan–Meier survival curves showed the prognostic value of our survival model (HR = 1.215, 95% CI = 1.160– 1.271, P < 0.001) (Figure. 7 A). In addition, the ROC curve also showed a good ability of the OS-related survival model to predict prognosis of HCC patients (Figure. 7 B). And with the increase of risk score, the mortality rate of patients rose (Figure. 7 C, D). Heat maps described the expression level of ARGs with the different risk scores of samples (Figure. 7 E). Therefore, these validation results confirmed the predict prognosis ability of our survival model.
The expression of ARGs in Oncomine database, Human Protein Atlas, and Kaplan-Meier plotter
We analyze the SQSTM1, ATIC, CAPN10, RHEB, and EIF2S1 in liver cancer by Oncomine database. The expression level of SQSTM1, ATIC, CAPN10, RHEB, and EIF2S1 in different hepatocellular carcinoma was higher than the normal group in the Wurmbach Liver (201471_s_at), Roessler Liver 2 (208758_at), Roessler Liver (219333_s_at), Roessler Liver 2 (201453_x_at), and Roessler Liver 2 (201144_s_at) studies (Figure 8 A-E).
In addition, we verify the histological level of SQSTM1, ATIC, CAPN10, RHEB, and EIF2S1 by the Human Protein Atlas database, and the results showed that SQSTM1, ATIC, CAPN10, RHEB, and EIF2S1 is upregulated in HCC tissues and downregulated in normal tissue (Figure.8 F-J).
The prognostic significance of SQSTM1, ATIC, CAPN10, RHEB, and EIF2S1 was identified using the Kaplan-Meier plotter server. The results showed that the 5 RBPs were closely related to OS of HCC patients (Figure 8 K-O).
ARGs nomogram
We tried to establish nomograms to connect survival model with 1-,2-,3- year survival. We analyze the ARGs that affecting the prognosis of HCC patients and establish an ARGs nomogram using the Cox multivariate analysis. Ultimately, the prognosis‑related ARGs nomogram included 5 prognostic ARGs (SQSTM1, ATIC, CAPN10, RHEB, EIF2S1) (Figure 9 A). Moreover, we validation the ARGs nomogram by ICGC cohort. The C-index for OS prediction was 0.683 (95% confidence interval (CI): 0.672-0.713) in TCGA cohort, 0.747 (95%CI: 0.71-0.77) in ICGC cohort. The calibration curve for predicting 3-years survival and 5-years survival in the TCGA cohort (Figure 9 B, C) and at 3-years survival in the ICGC cohort (Figure 9 D). The 3-year and 5-year survival AUC of ARGs nomogram also explained that nomogram suitable for clinical application (Figure 9 E, F). In summary, these results showed that our ARGs nomogram had great value for application in clinical practice.