SRD5A1 Expression Profiles in Human Normal Tissues and Cancers
The design of this study as significant in Figure 1. To determine the expression profiles of SRD5A1 in human normal tissues, we investigated the mRNA expression patterns of SRD5A1 in various non-tumor tissues and single-cell types based on publicly available genome-wide expression data. As presented in Figure 2A, among all detected tissues and cell types, the highest PHF19 expression was observed in the liver, followed by the skin and breast, based on the Consensus dataset. RNA tissue specificity was enhanced in the liver. Concerning RNA blood cell-type specificity, interestingly, the PHF19 mRNA expression was enriched in basophil, when analyzed in the HPA datasets (Figure 2B). To further evaluate the expression status of SRD5A1 spanning various cancer types, we analyzed the TCGA RNA sequencing data by applying the TIMER2.0 approach, As showed in Figure 2C, SRD5A1 expression was significantly elevated in multiple cancer types, including Bladder Urothelial Carcinoma (BLCA, p=7.9e-8), Breast invasive carcinoma (BRCA, p=3.5e-52), Cervical squamous cell carcinoma and endocervical adenocarcinoma (CESC, p=8.5e-5), Cholangiocarcinoma (CHOL, p=3.8e-3), Colon adenocarcinoma (COAD, p=2.4e- 89), Esophageal carcinoma (ESCA, p=8.2e-15), GBM (Glioblastoma multiforme ,p=1.5e-21), Head and Neck squamous cell carcinoma (HNSC, p=1.1e-3), HNSC-HPV+, Kidney renal papillary cell carcinoma (KIRP, p=4.7e-7), Liver hepatocellular carcinoma (LIHC, p=1.2e-11), Lung adenocarcinoma (LUAD, p=2.2e-118), Lung squamous cell carcinoma (LUSC, p=1.6e-137), Pheochromocytoma and Paraganglioma (PCPG, p=3.8e-3), Prostate adenocarcinoma (PRAD, p=4.5e-28), Rectum adenocarcinoma (READ, p=1.4e-5), Stomach adenocarcinoma (STAD, p=2.8e-62), Thyroid carcinoma (THCA, p=2.8e-25) and Uterine Corpus Endometrial Carcinoma (UCEC, p=2.8e-3) than in their respective normal samples. By integrating data from the GTEx database as normal controls, we further performed a differential-expression analysis of SRD5A1 between tumor and normal samples. We observed significant upregulation in 30 tumors such as Glioma (GBMLGG, p=5.7 e-54), Brain Lower Grade Glioma (LGG, p=2.7e-43), Stomach and Esophageal carcinoma (STES, p=1.6e-38), Pan-kidney cohort (KIPAN (KICH+KIRC+KIRP), p=9.6e-4), Colon adenocarcinoma/Rectum adenocarcinoma Esophageal carcinoma (COADREAD, p=1.5e-102)), KIRC (Kidney renal clear cell carcinoma , p=4.7e-7), High-Risk Wilms Tumor (WT, p =4.6e-15), Ovarian serous cystadenocarcinoma (OV, p=2.7e-27), Pancreatic adenocarcinoma (PAAD, p=1.1e-48), Testicular Germ Cell Tumors (TGCT, p=1.2e-19), Uterine Carcinosarcoma (UCS, p=1.1e-12), Acute Lymphoblastic Leukemia (ALL, p=5.7e-8), Acute Myeloid Leukemia (LAML, p=1.2e -42), Adrenocortical carcinoma (ACC, p=2.1e-6), Kidney Chromophobe (KICH, p=7.3e-11).And significant down-regulation in 3 tumors such as LIHC, Skin Cutaneous Melanoma (SKCM, p=5.3 e-42), and CHOL (Figure 2D). Besides, we further evaluated the correlation of SRD5A1 expression with cancer pathological stages, including ACC, BLCA, BRCA, CHOL, COAD, ESCA, HNSC, KICH, KIRC, KIRP, LIHC, LUAD, LUSC, MESO, PAAD, READ, SKCM, STAD, TGCT, THCA, UVM (Uveal Melanoma) (Figure 2E). We observed significant differences among 3 tumors such as GBMLGG(Stage I=143,II=139,III=150,IV=58)(p=0.01)、SARC(Stage I=50,II=54,III=64,IV=24)(p=0.04)、THCA(Stage I=98,II=119,III=94,IV=50)(p=0.02).The results determined a positive relationship between SRD5A1 level and advanced tumor stages.
Multifaceted Prognostic Analysis of SRD5A1 in Cancers
To investigate the clinical significance of SRD5A1 in cancer patients, we downloaded the TCGA mRNA sequencing and clinical information of 44 cancer types from the UCSC Xena platform and calculated the correlations of SRD5A1 expression with overall survival (OS), disease-specific survival (DSS), Disease-free interval (DFS) and Progression-free interval(PFS) of patients using the univariate Cox survival analysis. As shown in Figure 3A, the forest plots suggested that elevated SRD5A1 expression was significantly associated with worse OS in 6 tumor types (TCGA-GBMLGG (N=619, p=0.04, HR=1.22 (1.01, 1.48)), TCGA-SARC (N=254, p=0.03, HR=1.25 (1.02, 1.53) )), TCGA-GBM(N=144,p=3.1e-3,HR=1.50(1.15,1.96)), TCGA-THYM(N=117,p=0.03,HR=1.83(1.05,3.17)), TCGA-MESO (N=84, p=0.01, HR=1.48 (1.09, 2.01)), TCGA-LAML (N=209, p=1.4e-3, HR=1.31 (1.11, 1.54))) showed that high expression of SRD5A1 were strongly associated with poor patient outcomes, in 2 tumor types (TCGA-KIRC (N=515, p=0.04, HR=0.83 (0.69, 0.99)), TARGET-NB (N=151, p=0.02, HR=0.68 (0.49, 0.95) )) showed that medium and low expression have poor OS. While 6 tumor types ( TCGA-BRCA(N=1025,p=0.03,HR=1.21(1.02,1.43))、TCGA-SARC(N=248,p=0.03,HR=1.28(1.02,1.60))、TCGA-KIRP(N=272,p=0.03,HR=1.66(1.06,2.59))、TCGA-PRAD(N=490,p=0.02,HR=5.58(1.41,22.06))、TCGA-GBM(N=131,p=3.6e-3,HR=1.54(1.15,2.06))、TCGA-MESO(N=64,p=0.01,HR=1.72(1.14,2.61) were significantly associated with worse DSS(Figure 3B). High expression in 1 tumor type (TCGA-READ (N=29, p=0.01, HR=10.95 (1.36, 87.83))) was associated with poor DFS, and low expression in 2 tumor types (TCGA-LGG (N=126, p=0.03, HR=0.48 (0.25, 0.94)), TCGA-GBMLGG (N=127, p=0.04, HR=0.50 (0.26, 0.96))) were significantly associated with worse DFS(Figure 3C).Finally observed in 3 tumor types (TCGA-GBM (N=143, p=0.02, HR=1.43 (1.06, 1.93)), TCGA-THYM (N=117, p=0.04, HR=1.41 (1.02, 1.95)), high expression in TCGA-BLCA (N=397, p=0.03, HR=1.15 (1.02, 1.31))) poor prognosis with worse PFS (Figure 3D).
Kaplan-Meier (KM) survival curves comparing SRD5A1 high and low expressing patients were also constructed to further evaluate the prognostic potential of SRD5A1 via the Kaplan-Meier plotter database. The results revealed that high SRD5A1 mRNA expression predicted worse OS in ACC, BRCA, CESC, COAD, GBM, LUAD, MESO, PAAD, SARC, THCA, THYM, and UCEC, nevertheless, patients with lower SRD5A1 mRNA expression showed remarkably improved OS in KIRP, and STAD(all log-rank P values < 0.05) (Figure 4A). However, high methylation of SRD5A1 predicted worse OS in ACC, CHOL, LUAD, and THCA, and lower methylation of SRD5A1 showed remarkably improved OS in KIRP, LGG, LIHC, SKCM, and THYM(all log-rank P values < 0.05) (Figure 4B).
We next compared the survival contribution of SRD5A1 in multiple cancer types, estimated using the Mantel-Cox test through the GEPIA2 database, and the survival maps accompanied with OS curves in Figure 5A and DFS curves in Figure 5B are presented. High transcriptional levels of SRD5A1 were linked to unfavorable prognosis in OS of BRAC, GMB, and PAAD, while low transcriptional levels of SRD5A1 were linked to unfavorable prognosis in OS of KIRC, and DFS analysis data showed that elevated SRD5A1 level was related to unfavorable prognosis for GMB and SARC (all log-rank P values < 0.05). Overall, the above data indicated that SRD5A1 expression was significantly correlated with patient prognosis in various cancers, especially in UCEC, and the relevance of SRD5A1 to clinical outcomes may shed new light on the underlying pathogenesis of different tumors.
Mutation Landscape of SRD5A1 in Cancers
We inspected the genomic alterations and mutation profiles of SRD5A1 in the TCGA cancer cohorts by employing the cBioPortal database. As presented in Figure 6A, the highest alteration frequency of SRD5A1 appeared in LUSC patients with “amplification” mutation" as the predominant type, while the type of “deep deletion” copy number alteration (CNA) was primary in UCS. We also analyzed the general mutation count of SRD5A1 in 10953 patients / 10967 samples from TCGA datasets (Figure 6B). Besides, for SRD5A1, the most common mutation in cancers was missense mutation, and not less than 2.0% of patients with SKCM and 0.7% GBM had observed mutations (Figure 6C).To investigate whether these distinct characteristics of SRD5A1 mutation could translate into cancer prognosis, we compared the OS (P = 3.684e-4), DFS (P = 4.471e-3), disease-specific survival (P = 1.70 e-3), and PFS (P = 6.214e-4) between patients with SRD5A1 mutant cancer and patients with SRD5A1 nonmutant cancer(Figure 6D).Spearman correlation analysis of TMB and MSI with SRD5A1 gene expression. The abscissa represents the correlation coefficient between genes and TMB and MSI, the ordinate represents different tumors. The size of the dots represents the size of the correlation coefficient, and different colors represent the significance of the p-value. The bluer the color, the smaller the p-value (Figure 6E).
SRD5A1 Expression Correlates To Tumor Immune Infiltration
Tumor-infiltrating immune cells, as principal compositions of the TME, are frequently involved in tumor behaviors including cancer initiation, progression, or metastasis, and are deemed as independent predictors of sentinel lymph node status and cancer prognosis. Given that SRD5A1 expression correlates with TMB and MSI which affect response to cancer immunotherapy, we next explored the correlations between SRD5A1 expression level and the abundance of immune cell infiltrates. By adopting the ESTIMATE method, we first computed the immune and stromal scores of cancer tissues. As Figure 7A indicated, the top three correlations between SRD5A1 expression with the immune and stromal scores in STES, SKCM-M, and LAML (all data P-values < 0.001). Since immune checkpoint-associated genes participate in the immunosuppressive mechanism that allows tumor cells to escape anti-tumor immunity, we next investigated the correlations between SRD5A1 expression and immune checkpoint-related genes, SRD5A1 expression is associated with 60 genes of two types of immune checkpoint pathways, 24 are inhibitory, of which 36 are stimulatory (Figure 7B). The heatmap exhibited that SRD5A1 expression was positively and statistically significantly correlated with the immune infiltration of myeloid-derived suppressor cells (MDSCs) in 18 cancer types, and negatively relevant to that in 4 cancer types. Intriguingly, SRD5A1 expression was also positively relevant to the infiltration abundance of CD4+ Th1 cells, CD4+ Th2 cells in 4 cancer types and 18 cancer types, respectively, and negatively relevant to that in 9 cancer types and 4 cancer types, respectively (Figure 7C). in Figure 7D, using the TIDE algorithm (with the correlation coefficient > 0.5). The results indicated that SRD5A1 expression was obviously positively correlated with the infiltration abundance of MDSCs in MESO (Cor = 0.510, P = 2.46E-06), UCEC (Cor =0.487, P = 1.54E-17). As shown in Figure 7E, SRD5A1 expression was also significantly associated with the infiltration levels of CD4+ Th2 cells in BLAC (Cor = 0.488, P = 4.26E-21), BRAC (Cor = 0.480, P = 1.04E-55), MESO (Cor = 0.473, P = 9.86E-05),with all correlation coefficients >0.45.The profiles illustrated that SRD5A1, to a certain extent, was engaged in the immune infiltration-related pathways and served a critical role in the immuno-oncological interactions.
Enrichment Analysis of SRD5A1-Related Partners
To further decipher the underlying molecular mechanisms by which SRD5A1 contributes to carcinogenesis, we next investigated the available experimentally confirmed SRD5A1-binding proteins and SRD5A1 expression-associated genes for pathway enrichment analyses. In total, 52 SRD5A1-interacted proteins were retrieved from the STRING database by experimental evidence, and the PPI network of proteins with a confidence level > 0.400 was presented in Figure 8A. Besides, we discovered functionally similar genes in GeneMANIA, the GeneMANIA results also revealed the functions of the differentially expressed SRD5A1 and their associated molecules (such as HSD17B3, and SRD5A2) were primarily related to Physical Interactions (Figure 8B). We next acquired the top 100 genes associated with SRD5A1 expression based on TCGA and GTEx datasets by utilizing the GEPIA2 database. As seen in Figure 8C, the SRD5A1 expression was significantly positively correlated with the expression of LAD1(Ladinin 1, R=0.52), PKP3(Plakophilin 3, R=0.51), PVRL1(Poliovirus receptor-related protein 1, R=0.50), and PERP (P53 apoptosis effector related to PMP22, R=0.50). The correlation heatmap showed that SRD5A1 was positively related to the above genes in the majority of TCGA cancers (Figure 8D). Further, these two datasets were combined to perform KEGG pathway and GO molecular function (MF) enrichment analyses. As presented in Figure 8E, several pathways including “Steroid hormone biosynthesis”, "Ovarian steroidogenesis”, “Metabolic pathways”, “Cortisol synthesis and secretion”, and “Cushing syndrome” were revealed as the most significantly enriched KEGG pathways. Next, we characterized what kinds of proteins were enriched in SRD5A1. For this purpose, we collected the Gene Ontology annotations of all the human proteins and used them as the background (Figure 8F). The Cellular response to Steroid dehydrogenase activity (0034754) and Steroid metabolic process (0008202) were the two main and related categories of biological process terms. The largest category of molecular function terms was Steroid dehydrogenase activity (0016229) and Oxidoreductase activity (0016491), while Endoplasmic reticulum membrane (0005789) was the largest category of molecular function terms. We also performed a single-cell analysis by using the CancerSEA database and determined that SRD5A1 stimulated a multitude of carcinogenic processes, including the promotion of angiogenesis and stemness in different cancer cell types (Figure 8G).
In light of the significant positive association between SRD5A1 expression and the number of immune neoantigens, TMB levels, and MSI in LUSC, we investigated the potential effect of SRD5A1 on LUSC progression, then GSEA analysis was used to explore the signaling pathways between low expression and high expression group of SRD5A1 in LUSC to identify the relevant pathways and underlying mechanisms, and the top one terms of KEGG(Non−homologous end−joining), Reactome(Type I hemidesmosome assembly), GO−BP(hemidesmosome assembly), GO−CC(juxtaparanode region of the axon) and GO−MF(arachidonic acid epoxygenase activity )analysis and transcription factor targets were exhibited(Figure 8H).
Data analysis of patients with immunotherapy
Next, we investigated the correlations between SRD5A1 mutation and various immune signatures, including 28 TIL types, 24 immune inhibitors, 45 immunostimulators, 21 major histocompatibility complex molecules, 40 chemokines, and 18 chemokine receptors, in 30 tumors in the TCGA cohort (Figure 9). Most immune-related genes were increased in SRD5A1 mutant samples compared to nonmutant samples, and many of them were statistically significant. These findings revealed that the immune system was more active in SRD5A1 mutant cancer, which may be classified as a "hot" tumor immunologically. Moreover, our data provided strong evidence that cancer epigenetic driver mutations could shape tumor immune phenotype.
SRD5A1 is prognostic, high expression is unfavorable in UCEC
The distribution of risk scores, survival statuses, and signature gene expression patterns for UCEC patients in training were visualized in Figure 10A. We first calculated and plotted the prognostic Kaplan-Meier survival curves (Figure 10B), the results showed that a high level of SRD5A1 expression was related to a poor prognosis in UCEC. Additionally, we also ran a time-dependent ROC curve study to confirm the risk-score model's predictive classification efficiency in UCEC, and the area under the curve (AUC) values for 1-, 3-, and 5-year overall survival are shown in Figure 10C. DEGs analysis shows up-regulated 262 genes and down-regulated 800 genes(Figure 10D)and the top 4 GSEA as shown in Figure 10E. Furthermore, a total of 180 samples were included in which mutations were detected, of which the plotted samples included a total of 59 (32.8%) (Figure 10F). Immune cell infiltration landscapes between high SRD5A1expression and low SRD5A1 expression groups in UCEC analyzed by CIBERSORT shown activated memory CD4+ T cells, T follicular helper cells, regulatory T cells (Tregs), resting natural killer (NK) cells, M1 macrophages, resting dendritic cells and activated dendritic cells significantly different(Figure 10G). In addition, as demonstrated in Figure 10H, the risk score was capable of independently predicting the prognosis of UCEC after controlling for SRD5A1 expression and age in both univariate COX regression model and multivariate COX regression model analyses. These findings indicated that the eleven-gene prognostic signature was effective in predicting the prognosis of UCEC patients and that it may be used to enhance the gold standard for clinical diagnosis.
Immunohistochemical staining of SRD5A1 in cancers
To ensure positive confirmation of the pathophysiological roles of SRD5A1, we applied experimental validation to investigate its clinicopathological characteristics. We performed immunohistochemically (IHC) analyses in 78 cancer samples across BLAC, CESC, COAD, LUAD, LUSC, PAAD, SKCM, and STAD(Figure 11A–H). Adjacent or distant noncancerous tissues from the surgical margin were used as the control tissues. We found that the SRD5A1 protein expressions were significantly higher in tumor tissues in comparison with the control tissues, Most cancers displayed moderate to strong cytoplasmic immunoreactivity with a granular pattern. Lymphomas and testicular cancers along with most gliomas and the results were quantitated in Figure 11I, which indicated the extensive carcinogenic effects of SRD5A1.