CDC42 is enriched in human pan-cancer. Pan-cancer analysis was accomplished through the TCGA and GTEx databases, including mRNA and protein expression distinction between tumor and adjacent normal tissues in different organs. And the CDC42 expression levels in various clinical and molecular biological characteristics in gliomas was explored. The functional enrichment of differential genes was analyzed, subsequently the correlation between CDC42 and relevant immune checkpoint inhibitors and cell markers were investigated. GSEA was applied to the correlation study of CDC42 and related signaling pathways. The specific flow chart is as follows (Figure 1)
TIMER2.0 was applied to study the mRNA expression levels of CDC42 for the entire 32 tumors in the TCGA database in order to explore the difference in CDC42 expression between tumors and adjacent tumor-free tissues. The outcome demonstrated that the expression rates is relatively high in BRCA (breast invasive carcinoma), CHOL (cholangiocarcinoma), ESCA (esophageal carcinoma), HNSC (head and neck squamous cell carcinoma), LIHC (liver hepatocellular carcinoma), STAD (stomach adenocarcinoma) compared with the corresponding tumor-free tissues (Figure 2A).
In addition,we considered that TIMER 2.0 lacked certain normal tissues as controls, we supplemented GTEx database normal tissues as controls, and found that CDC42 was highly expressed in CHOL (cholangiocarcinoma), GBM (glioblastoma multiforme), PAAD (pancreatic adenocarcinoma), STAD (stomach adenocarcinoma) and TGCT (testicular germ cell tumors) than normal tissues (Figure 2B).
The normal metabolism of tissues and various life activities are closely related to protein functions. The CTPAC analysis implied that CDC42 protein was enriched in UCEC (uterine corpus endometrial carcinoma), KIRC (kidney renal clear cell carcinoma), HNSC (head and neck squamous cell carcinoma) and HCC (hepatocellular carcinoma) than normal tissues (Figrue2C). All evidence suggested that CDC42 was enriched in multiple tumors, it manifested that this molecule may be a promising pan-cancer marker.
CDC42 is associated with glioma clinicopathological characteristics. CDC42 with different expression levels of showed diverse clinicopathological characteristics, showing an asymmetric distribution in IDH mutation status, MGMT promoter methylation status, 1p/19q codeletion status and WHO grade (Figure 3), which were analyzed in the TCGA database and validated in the CGGA database. We found that CDC42 was highly enriched in high-grade gliomas, IDH wild-type patients (Figure3 C, G), non-methylated patients (Figure3 D, I) and non-codel patients (Figure3 E, J). Glioma transcriptional subtyping is a widely used molecular diagnostic technique17. CDC42 expression was higher in the mesenchymal categorization (Figure 4 A, C), which may predict that CDC42 was the molecule with prediction in transcriptional subtyping. The ROC prediction curve (Figure4 B, D) was established and the effectiveness of this model was confirmed by
CDC42 highly expressed tumors have a significantly poor prognosis. According to an analysis of the KM curve and the cox proportional hazard model based on the TCGA and CGGA databases (Figure 5A), patients with high CDC42 expression (median survival 639 days) in the TCGA database had considerably shorter overall survival compared to patients with low CDC42 expression (median survival 3519 days), this conclusion was verified in the CGGA database (Figure 5B). CDC42 expression was a predictive predictor in univariate and multivariate cox regression studies, independent of other known prognostic markers, such as WHO grade, age at diagnosis, IDH mutation, deletion of 1p/19q coding, and MGMT promoter methylation. These results imply that CDC42 in the TCGA and CGGA datasets is an independent predictive factor (Tables 1 and 2).
|
Univariate analysis
|
|
Multivariate analysis
|
Variable
|
HR(95%CI)
|
P-value
|
|
HR(95%CI)
|
P-value
|
CDC42 expression
|
4.518(3.417-5.881)
|
3.49E-29
|
|
1.721(1.141-2.596)
|
9.65E-03
|
WHO grade(III-II)
|
3.269(1.996-5.356)
|
2.56E-06
|
|
2.186 (1.299-3.680)
|
0.003
|
WHO grade(VI-III)
|
20.067(12.149-33.145)
|
1.09E-31
|
|
2.714(1.343-5.488)
|
0.005
|
Age
|
1.075(1.063-1.088)
|
5.10E-34
|
|
1.058(1.041-1.074)
|
1.39E-12
|
IDH status
|
0.091(0.064-0.129)
|
2.56E-40
|
|
0.353(0.202-0.618
|
2.64E-04
|
MGMT status
|
0.309(0.223-0.429)
|
1.94E-12
|
|
0.910(0.619-1.339)
|
0.632
|
1p/19q Codel
|
0.268(0.193-0.372)
|
2.11E-08
|
|
|
|
Table 1. Prognostic factors in the TCGA database: a multivariate and univariate analysis of overall survival (OS).Abbreviations: CI, confidence interval; HR, hazard ratio; IDH, isocitrate dehydrogenase; WHO, world health organization
|
Univariate analysis
|
|
Multivariate analysis
|
Variable
|
HR(95%CI)
|
P-value
|
|
HR(95%CI)
|
P-value
|
CDC42 expression
|
1.733(1.514-1.984)
|
1.59E-15
|
|
1.409(1.135-1.748)
|
0.002
|
WHO grade(III-II)
|
2.545(1.846-3.508)
|
1.18E-08
|
|
2.745(1.835-4.107)
|
9.01E-07
|
WHO grade(VI-III)
|
6.968(5.081-9.554)
|
1.90E-33
|
|
4.356(2.813-6.747)
|
4.28E-11
|
Age
|
1.026(1.018-1.035)
|
1.37E-09
|
|
1.008(0.999-1.017)
|
0.083
|
IDH status
|
0.323(0.262-0.399)
|
3.38E-26
|
|
0.676(0.496-0.923)
|
0.014
|
MGMT status
|
0.795(0.639-0.990)
|
0.041
|
|
0.912(0.716-1.161)
|
0.454
|
1p/19q Codel
|
0.268(0.193-0.372)
|
3.02E-15
|
|
0.551(0.358-0.850)
|
0.007
|
Table 2. Prognostic factors in the TCGA database: a multivariate and univariate analysis of overall survival (OS). Abbreviations: CI, confidence interval; HR, hazard ratio; IDH, isocitrate dehydrogenase; WHO, world health organization
CDC42 is significantly associated with cellular immune activities. 20 CDC42 binding proteins were screened using for PPI network analysis (Figure6A) and the binding protein-related annotations (Table s1) were downloaded. In order to investigate the biological functions and molecular mechanism connection between CDC42 and tumors, differential analysis of genes associated with CDC42 expression was performed using the “limma” package, the genes most relevant to CDC42 were screened in the TCGA database and the CGGA database (p<0.05, log Fc>0.5), a differential gene expression heatmap was drawn (Figure S1,S2), and R packages were used to screen the genes for GO and KEGG analysis. Bioinformatics was applied to observe the enrichment results using the Gene Ontology bar and bubble plots. GO analysis of TCGA and CGGA databases manifested that CDC42 high-expression genes were intimately related to leukocyte migration and leukocyte migration regulation (Figure 6B). KEGG enrichment analysis showed that CDC42 was associated with signaling pathways such as Neuroactive ligand receptor interaction, MAPK signaling pathway, and CAMP signaling pathway 18 and was involved in tumorigenesis and development (Figure 6C). These results indicate that CDC42 on glioma cells may be crucial for immune response and disease regulation.
CDC42 is highly correlated with tumor immune infiltration. The association between CDC42 and immune cells in LGG and GBM was examined using the online program TIMMER2,0 to investigate the interaction between CDC42 and the tumor microenvironment, and the results (Figrue7) showed that B cells (0.682, p=1.26e-66), CD8+ T cells (0.52, p=1.91e-34), CD4+T cells (r=0.422, p=4.96e-22), Macrophage (r=0.473, p=1.06e-27), Neutrophil (r=0.62, p=8.42e-52) and Dendritic cell (r=0.604, p=1.32e-48) cells were positively correlated with CDC42 expression in LGG, and B cells (r=0.03, p=5.35e-01), CD8+ T cells (r=0.165, p=6.82e-04), Macrophage (r=0.054, p=2.75e-01) and Neutrophil (r=0.242, p=5.77e-07) were positively correlated in CDC42 expression in GBM. Immune cells express a class of immunosuppressive molecules known as immune checkpoint inhibitors, which can control the level of immunological activation. Immune evasion of tumors can be accomplished by upregulating immune checkpoint inhibitors 19. The relationship between the expression of CDC42 and the pertinent immune checkpoint inhibitors was investigated (Figrue8). The TCGA database showed that CDC42 expression was positively correlated with TIM-3(HAVCR2), HVEM(TNFRSF14), IDO(IDO1), CD27L(CD70), CD200R1, PD-L1(CD274), PD-1(PDCD1), CTLA4, BTLA, LAG3 and CD47 immune checkpoint inhibitors 20 in gliomas, and this result was verified in the CGGA database.
CDC42 is associated with the development of Treg cells in the tumor microenvironment. According to the literature, Treg cells play an indispensable role in tumor immune evasion, The correlation between CDC42 expression in glioma and three markers of Treg cells (CD4, IL2RA (CD25), IL7R (CD127)) 21 (Figrue9) was explored by person correlation analysis using Stata software, the results showed that CDC42 expression correlated with CD4 (r=0.552, p<0.001), IL2RA (r=0.560, p<0.001) in the TCGA database. The expression results of CD4 (r=0.326, p<0.001), IL2RA (r=244, p<0.001), IL7R (r=447, p<0.001) were demonstrated in the CGGA database, and the level of CDC42 expression may be related to the effectiveness of immunotherapy.
CDC42 is positively correlated with Treg cell development-related pathways. PI3K/AKT signaling pathway occupies a critical role in Treg cell development, functional implementation and cell stability, it has been reported that PI3K-AKT signaling pathway is involved in the migration, proliferation, metabolism and other processes of Treg cells 22. In order to further explore the role of CDC42 expression in PI3K/AKT pathway in the tumor microenvironment Treg cell migration and proliferation, GSEA analysis was performed. The results of GSEA provide a clearer explanation of the critical role played by CDC42 in the migration and proliferation of Treg cells in gliomas by demonstrating a positive correlation between CDC42 expression and the PI3K/AKT signaling pathway (Figure 10).