TME cell infiltrating patterns and DEGs associated with TME
We calculated the proportion of immune cells in 477 PCa samples, according to the previous findings that immune cells, especially tumor infiltering lymphocytes, are more related to the prognosis and immunotherapy effect of patients than the stromal cells in the TME[6, 17]. We depicted a comprehensive profile of the immune cell interactions, lineages and their effects on the OS of PCa patients, and obtained four distinct patterns of TME cell infiltration (Fig. 1A). The cell cluster A was characterized by the infiltration of the macrophages (M0), B cells (naïve), mast cells (resting) and so on. The cell cluster B was characterized by the infiltration of mast cells (activated), neutrophils, NK cells (activated) and so on. The cell cluster C and cluster D was characterized by the infiltration of the CD4+ T cells (memory resting) and the macrophages (M2), respectively. According to the proportion of immune cells, the PCa samples can be divided into three TME clusters through consensus clustering analysis (Figure S1A-C). Interestingly, by mapping the TME clusters to the proportion of immune cells, we found significant differences in the distribution of immune cells among different TMEcluster samples, and TMEcluster 1 and 2 were quite different from TMEcluster 3 (Fig. 1B). The survival analysis showed that the survival was not significantly different among the three TME clusters (Fig. 1C). Unexpectedly, the TME clusters directly classified by the proportion of immune cells cannot distinguish the prognosis of PCa. It is probably due to the redundant information caused by LM22 gene. In order to reduce redundant information interference, we used an unsupervised clustering method to re-cluster 477 PCa samples based on the expression profile of TME-infiltrating phenotype related differential genes, and a total of 3637 DEGs were obtained. After dimensionality reduction by random forest algorism, the most relevant signature genes (n = 104) were used to classify the 477 samples into two clusters (Fig. 1D). These genes are mainly enriched in the pathways involved in immune activation, such as neutrophil chemotaxis, positive regulation of alpha-beta T cell activation, regulation of alpha-beta T cell differentiation, neutrophil migration and so on (Fig. 1E).
Construction of the TMEscore model for PCa samples
Based on the re-clustering model, we evaluated the correlation between DEGs and prognosis. The Cox regression model was used to evaluate the relationship between the DEGs and OS of PCa samples. According to the coefficient value of genes, the 477 samples were classified into two groups with the TMEscore high (n = 308) and TMEscore low (n = 169) phenotype (x=-0.31).
As shown in Fig. 2A, the prognosis of the TMEscore high group was significantly better than that of the TMEscore low group. A comprehensive comparison of different TME clusters (Fig. 2B) showed that cluster samples based on immune cell components and proportions were notably correlated with the DEGs and TMEscore. Consistent with these findings, the TMEscore of the 111 PCa samples from the GEO can also reflect the prognosis of samples (Fig. 2C and 2D).
Correlation of the mutational signatures with the TMEScore phenotypes in PCa
The common genomic mutations, such as SNPs, have been reported to be used as predictors of aggressive prostate cancer. The exploration of characteristic SNPs would enable more accurate risk stratification, allowing for tailored management of individual prostate cancer [18]. Therefore, we further explored the relationship between the genomic mutations and TMEScore. The somatic mutation analysis showed that the most common mutation in PCa is the missense mutation, mainly caused by SNP, and C > T is the most common type of SNP mutations (Figure S2).The frequently mutated genes in TMEscore high group and TMEscore low group were presented in Fig. 3A and 3B, respectively, and their variant allele fractions (VAFs) were different between two groups (Fig. 3C). The contribution of 96 base substitution types was presented in Figure S3A and B. The mutational signature analysis showed that TMEscore high group was mainly related to signature1, signature3 and signature5 (Fig. 3E), and TMEscore low group was mainly related to signature1, signature5 and signature6 (Fig. 3F). It can be seen that there are significant differences in mutation characteristics between TMEscore high group and TMEscore low group.
MSI is an emerging biomarker used to predict the outcome of cancer treatment, and patients with MSI-H usually have better prognosis than those with MSI-L/MSS. The correlation analysis between TMEScore and MSI showed that the high TMEscore was significantly associated with MSI-H (Fig. 3D), and was associated with a good prognosis.
Correlation of copy number variants with the TMEScore phenotypes in PCa
We analyzed the correlation between the TMEscore and the characteristic of the chromosome CNV in PCa. The results showed that there were significant differences in chromosome copy number amplifications or deletions between the two TMEscore related phenotypes. The CNVs analysis by GISTIC showed that amplifications of chromosomal arms 8p, 8q, 7p and 7q, and deletions of chromosomal arms 8p, 18p, 18q and 16q frequently occurred in TMEscore-high subtype (Fig. 4A, C); amplifications of chromosomal arms 8p, 8q, 7p and 7q, and deletions of chromosomal arms 8p and 18q frequently occurred in TMEscore-low subtype (Fig. 4B, D). There were significant differences in MCRs between TMEscore high group and TMEscore low group. In the TMEscore high group, 14 amplifications and 30 deletions were detected, in which 3q26.2 amplification and 8p21.3 deletion were most significant (Fig. 4E); while in the TMEscore low group, 22 amplifications and 24 deletions were detected, in which 8q24.21, 8q21.13 amplifications and 6q14.3, 13q14.13 deletions were most significant (Fig. 4F). We also analyzed the correlation of tumor purity and tumor ploidy with the TMEScore related phenotypes, and the results showed no significant correlations (Figure S3C, D).
Comprehensive analysis of genomic signatures associated with the TMEscore in PCa
Based on the TMEscore phenotypes, we conducted a comprehensive analysis of the genomic signatures associated with the prognosis of PCa. DEG analysis obtained 5 differentially expressed miRNAs and 127 differentially expressed mRNAs between TMEscore-high and TMEscore-low subtypes, with the threshold P < 0.05 and |logFC|>1 for miRNA, and |logFC|>1 and P < 0.05 for mRNA, respectively. Among them, has-mir-133b (Fig. 5A) and FMOD (Fig. 5B) were most significantly correlated with survival of PCa. As DNA methylation status is closely related to tumor progression and prognosis, we performed differential methylation analysis between the TMEscore high and TMEscore low groups, and 38 significantly differential methylation sites were obtained, among which cg03804126 was most significantly correlated with OS (Fig. 5C). Moreover, a comprehensive genomic landscape of PCa was presented in Fig. 5D. We found 12 survival-related genes, including CD38, PROK1, SRD5A2, TMEM35, DPT,FAM107A, SPOCK3, MT1G, SLC22A3, ANO7, MYLK and PTN.