3.1 Acquisition of immune DEGs and differentially expressed transcription factors.
The research team downloaded clinical data and gene expression data of 385 COAD patients from the TCGA database, and obtained differentially expressed genes (DEGs) through screening (screening conditions: LogFC>| 2 |, FDR <0.05) (Figure 2A,B). The IMMPORT database contains the names of a large number of immune genes. We obtain the differentially expressed immune genes through the intersection of the immune gene names and DEGs (Figure 2C,D). The transcription factor names were obtained from the Cistrome database, and the differentially expressed transcription factors were obtained by intersecting with the DEGs. the screening conditions for transcription factors are: LogFC> |1|; P <0.05. The volcano and heat maps were drawn (Figure 2E,F).
3.2 Construction of prognostic related immune gene model and interaction network of prognostic related immune genes and transcription factors.
Univariate Cox regression analysis was used to study the differentially expressed immune genes related to survival prognosis. The results showed that there are 12 immune genes that are closely related to the prognosis of gastric adenocarcinoma in Asian yellow people. (Figure 3A). Cor = 0.4, P = 0.01 screening criteria were used to establish the interaction between immune genes and transcription factors, and network diagrams were made (Figure 3B). Details of the regulatory relationship between transcription factors and the immune genes associated with COAD prognosis are shown in Table 1. The results showed that 8 immune genes are closely related to the regulation of transcription factors and belong to positive regulation.
3.3 Calculation of immune gene riskScore and construction of survival prognosis model.
We calculated the Coef coefficient of immune genes related to survival prognosis by multivariate Cox regression, and then calculated the riskScore of immune genes by the product of Coef coefficient and gene expression. Among the immune genes related to survival prognosis, 7 immune genes are closely related to the composition of risk scores, which are SLC10A2, CXCL3, IGHV5-51, INHBA, STC1, UCN and OXTR (Table 2), this is also the key immune gene that we will study later. According to the median riskScore, the riskScore is divided into two groups. Survival and survminer packages in R were used to correlate risk scores with survival prognosis and draw the Kaplan-Meier survival curves. The results showed that P = 8.876e-04. The survival prognosis of the high-risk group was significantly worse than that of the low-expression group(Figure 4A), The survivalROC package of R language is used to draw the ROC curve. The results show that the AUC of the ROC curve = 0.749(Figure 4B). Detailed data on the survival rates of high- and low-risk patients are shown in Table 3 and Table 4.
3.4 Immune gene risk curve mapping and independent prognostic analysis.
Use R language related codes to draw related pictures of risk curve. The results showed that with the gradual increase of the immune gene risk value, the survival time of patients gradually decreased (Figure 5A,B). Heat map of related immune gene expression(Figure 5C). Univariate independent prognostic analysis showed that the Hazard ratio of riskScore was 1.033 (1.018-1.049), and P <0.001. Multivariate independent prognostic analysis showed that Hazard ration of riskScore was 1.023 (1.008-1.038), P=0.003 (Figure 6A,B). RiskSore is clinically and statistically significant.
3.5 Correlation analysis of immune genes and clinical data.
We analyzed the correlation between the 7 immune genes that make up the immune score and clinical data, using the R language beeswarm package. The results showed that there were statistically significant correlations between seven immune genes and clinical data, namely CXCL3, OXTR and STC1 (Figure 7). Among them, the expressions of CXCL3 was statistically significant in correlation with stage, while the expressions of OXTR and STC1 were statistically significant in correlation with T. CXCL3 also has significant differences in N and M.
3.6 Correlation Analysis of Risk Score and Tumor Microenvironment Cells.
Correlation analysis was performed between the risk scores assessed by our research and immune microenvironment genes, and the results showed that in CD4, CD8, Dendritic, Macrophage, and Neutrophil cells, as the risk scores increased, the expression levels of these genes became upward. And It has statistical significance P <0.05. Correlation analysis of our risk value model with some widely recognized genes that constitute the immune microenvironment showed that CD4, CD8, Dendritic, Macrophage, and Neutrophil cells were positively correlated with the riskScore model. As the riskScore increases, so does the expression of these genes.