Genetic Mutation Landscape of AAGs in KIRC
We first identified the expression levels of the 36 AAGs in tumor specimens and normal specimens with the TCGA-KIRC dataset. A total of 31 DEGs were found, and most of the DEGs were abundant in the tumor samples (Fig. 1A). A protein-protein interaction (PPI) analysis through the STRING website was established to reveal the interactivity of AAGs, which indicated that VEGFA, SPP1, POSTN, COL3A1, VCAN, ITGAV, UTN and TIMP1 were hub genes (Fig. 1B). Next, we determined the incidence of CNVs and somatic mutations of 36 AAGs in KIRC by cBioPortal website (https://www.cbioportal.org/). As depicted in Fig. 1C, 92 of 448 (21%) ccRCC samples presented genetic mutations, and the findings suggested ITGAV as the gene with the highest mutation incidence, followed by FGFR1 and COL5A2, among the 36 AAGs. Furthermore, we explored OS in the Altered and Unaltered groups (Fig. 1D). The findings indicated a substantial difference in the genomic background and expression levels of AAGs between ccRCC and normal specimens, suggesting the potential role of AAGs in ccRCC tumorigenesis.
Construction of Angiogenesis Subgroups in ccRCC
Figure S1 shows the detailed flowchart for this work. A total of 530 ccRCC patients from TCGA-KIRC were enrolled in this study to reveal the relationship between angiogenesis and tumorigenesis. Full details of these patients were listed in Table S2. uniCox and Kaplan–Meier analysis were performed in Table S3 to identify the prognostic values of 36 AAGs in patients with ccRCC. The correlation network of the AAG interactions in the KIRC patients was then presented in Fig. 2A and Table S4. We performed a consensus cluster analysis to determine the relationship between the AAG and ccRCC subtypes. Patients with ccRCC were classified based on these AAG expression levels.
We found that the optimal clustering variable was 2 (Fig. 2B), and the ccRCC patients in the full cohort were well dispersed across both cluster 1 (n = 23) and cluster 2 (n = 507). The results of the PCA analysis also supported the excellent inter-group distribution (Fig. 2C). In addition, OS time for both clusters was discussed, and a significant difference in survival was observed (Fig. 2D).
Characteristics of the TME in Different Subgroups
According to the findings of GSVA analysis, cluster 2 was abundant in cancer-associated pathways (RCC, pancreatic cancer, bladder cancer), and metabolism-associated pathways (NOTCH signaling pathway, mTOR signaling pathway) (Fig. 3A and Table S5). To identify the relationship between AAGs and the TME of ccRCC, we explore the infiltrating levels of 28 subpopulations of human immune cell subpopulations in the two clusters with the ssGSEA algorithm (Table S6). Figure 3B shows that the levels of activated B cell, activated CD8 T cell, CD56dim NK cell, Central memory CD4 T cell, NK T cell, T follicular helper cell, and type 1 T helper cell enrichment were clearly higher in cluster2 than in cluster1. However, there was no difference in the expression of 3 critical ICPs (PD-1, PD-L1, and CTLA-4) (Figs. 3C–E). The abundance of immune and stromal elements in the TME could be assessed by TME scores, in addition, we ran the ESTIMATE algorithm to obtain the TME scores in the different clusters, including the stromal score, the immune score, and the estimation score. The findings indicated patients in cluster2 had higher stromal score (Fig. 3F).
Identification of Subgroups Based on DEGs
To investigate the underlying biological activity of angiogenesis subgroups, we obtained 329 angiogenesis clusters-associated DEGs with the “DSEeq2” package and conducted functional enrichment analysis (Table S7). DEGs associated with these angiogenesis subgroups were primarily enriched in immune-associated biological processes (Fig. 4A). KEGG analysis demonstrated the abundance of cancer-associated pathways (Fig. 4B). Then, we performed uniCox analysis to determine the survival significance of 234 coding genes, and 161 coding genes were extracted with a criterion of p < 0.05 (Table S8).
Construction and Evaluation of the Prognostic AAG_Score
The AAG_score was created based on cluster-associated DEGs. The LASSO regression analysis and multiCox analysis for 161 angiogenesis cluster-associated prognostic DEGs were conducted to establish an optimal predictive model. The LASSO regression analysis and partial likelihood deviance on the prognostic genes were shown in Fig. 4C and D. Ultimately, we acquired nine genes (HS3ST1, CFH, SRPX2, TFPI2, ITGB8, GALNT15, CLEC18A, GRIK3, and SLC23A3), and the AAG_score was listed in TableS9. TableS10 show the specific coefficients. Patients' distributions in the two angiogenesis clusters and two AAG_score groups were displayed in Fig. 5A. We found a substantial difference in AAG_score between angiogenesis clusters (Figs. 5B). AAG_scores in cluster 1 were higher than AAG_scores in cluster 2. Using the aforementioned survival analysis, we identified that patients with higher risk scores were correlated with worse survival outcomes. Furthermore, Kaplan-Meier analysis indicated that low-risk patients had a better OS over high-risk patients (Fig. 5C), and the AUCs of 1-, 3-, and 5-years OS were 0.679, 0.665, and 0.678, respectively (Fig. 5D). The risk plot indicated that as AAG_score increased, OS time decreased while mortality increased (Figs. 5E).
Clinical Correlation Analysis of the Prognostic AAG_Score
We discussed the interplay between AAG_score and various clinical parameters in order to determine the relationship between AAG_score and clinicopathological characteristics (age, gender, stage, grade). We found increased risk scores in the higher stage, grade, and male patients (Fig. 6A-D). In addition, the independent prognostic value of the AAG_score for ccRCC patients was assessed. To explore the prognostic independence of multiple clinical factors, we conducted both uniCox and multiCox analyses. As presented in Fig. 6E-F. age, stage, grade, gender, and risk score in the cohort demonstrated significant differences.
Constructing Nomogram Based on AAG_score and Clinical Features
Due to the high correlation between risk scores and patient outcomes, we combined clinical parameters to create a nomogram. This nomogram was used to estimate OS at 1, 3, and 5 years for ccRCC patients (Fig. 7A). Furthermore, we estimated the AUC values of the nomogram for predicting 1-, 3-, and 5-year OS, respectively (Fig. 7B). As shown in Figs. 7C–E, the calibration curves of this established nomogram presented moderate accuracy between actual observations and predicted values. In addition, we found that this prognostic model with diverse clinical factors had a greater net benefit in predicting prognosis (Figs. 7F- H).
Assessment of TME and Checkpoints in Each Groups
We used the ssGSEA algorithm to assess the correlation between AAG_score and immune cell infiltration. As depicted in Fig. 8A, Activated B cell, Activated CD4 T cell, Activated CD8 T cell, Effector memory CD4 T cell, Effector memory CD8 T cell, Gamma delta T cell, Macrophage, Mast cell, MDSC, Type 1 T helper cell was higher in high- riskscore group, while the opposite performance was observed in relationship with AAG_score and CD56 bright natural killer cell, CD56 dim natural killer cell, Central memory CD4 T cell, Immature dendritic cell, Memory B cell, Natural killer cell, Neutrophil, Plasmacytoid dendritic cell, Regulatory T cell. Moreover, the AAG_score was positively linked to stromal score, and immune score (Fig. 8B). Additionally, we assessed the relationship between ICPs and this prognostic signature. Figure 8C demonstrates that 4 ICPs were discrepantly represented in the two risk subgroups, such as SIGLEC15, CD274, HAVCR2 and PDCD1LG2.
Association of AAG_Score With TMB, MSI, and NEO
Several studies found TMB and MSI to be valuable predictive indicators of tumor immune response, and patients with elevated TMB or MSI may benefit from ICP inhibitors[21–23]. However, we found that TMB, MSI, and NEO did not differ between the low-and high-risk groups (Fig. 8D-F).