Expression analysis of S100A2
In our study, we analyze the expression of S100A2 in different cancers. As shown in Fig. 1A, the expression level of S100A2 was higher in the tumor tissues of CHOL, COAD, ESCA, HNSC, LUAD, LUSC, READ, STAD, THCA and UCEC than in the adjacent normal tissues. It was significantly lower expressed in the tumor tissues of KICH KIRC KIRP and PRAD. Then, in the TCGA tumors with the data of the GTEx database, the S100A2 gene showed a high expression in BLCA, CESC, CHOL, COAD, DLBC, ESCA, GBM, HNSC, LGG, LUAD, LUSC, OV, PAAD, STAD, THCA, THYM, UCEC and UCS (Fig. 1B). For TCGA tumors and adjacent normal tissues, S100A2 expression was upregulated in BRCA, CHOL, COAD, LUAD, LUSC, THCA and UCEC, while lower expressed in KICH, KIRC, KIRP and PRAD (Fig. 1C).
Correlations between S100A2 Expression and Molecular Subtypes and Immune Subtypes of Different Cancers
Violin plots demonstrated that S100A2 expression was statistically associated with different molecular and immune subtypes of different caner types including UCEC, HNSC, STAD, BRCA, PRAD, OV, LIHC, LUSC, COAD, ESCA, KIRP and GBM (Fig. 2A-L, Fig. 3A-L). For molecular subtypes, S100A2 was highly expressed in the Atypical subtype and expressed at a low level in the Basal subtype of HNSC. S100A2 was highly expressed in the immunoreactive subtype of OV, the basal subtype of LUSC, and the ESCC subtype of ESCA. Immune subtypes were classified into six types including C1 (wound healing), C2 (IFN-γ dominant), C3 (inflammation), C4(lymphocytopenia depleted), C5 (immune silencing) and C6 (TGF-β dominant). S100A2 was highly expressed in wound healing of MESO and BRAC. For CESC, PRAD, OV and PAAD, the highest expression of S100A2 was found in IFN-γ dominant. The lowest levels expression of S100A2 in LUAD, KIRC, OV and STAD was found in the inflammation subtype. S100A2 had lowest levels expression in the TGF-β dominant subtype of SARC.
PPI Network and GO and KEGG Enrichment Analyses
We identified 50 targeted proteins interacting with S100A2 by the STRING database in Fig. 4A. The Cytoscape was performed for the obtained network visualization in Fig. 4B. Then we explored the functional mechanism of S100A2 expression by GO and KEGG enrichment analysis in Fig. 4C, D. GO analysis suggested that the enriched terms in the biological process (BP) were skin development, epidermal cell differentiation, keratinocyte differ entiation, peptide cross-linking. The cellular component (CC) was mainly involved in cornified envelope, collagen-containing extracellular matrix, cell cortex and azurophil granule lumen. For the molecular function ontology, the terms were S100 protein binding calcium-dependent protein binding, structural constituent of epidermis and RAGE receptor binding. In addition, the KEGG analysis showed that S100A2 expression were enriched in cellular senescence, wnt signaling pathway, cell cycle, colorectal cancer and chronic myeloid leukemia.
Diagnostic Value of S100A6 in Pan-Cancer
We performed the ROC curve to evaluate the prognostic predictive ability of S100A2 in pan-cancer. ROC curves analysis revealed that S100A2 gene had a high diagnostic value (AUC > 0.7) in COAD (AUC = 0.983) (Fig. 5A), GBMLGG (AUC = 0.852) (Fig. 5B), KICH (AUC = 0.922) (Fig. 5C), KIRP (AUC = 0.901) (Fig. 5D), LGG (AUC = 0.818) (Fig. 5E), LIHC (AUC = 0.723) (Fig. 5F), LUAD (AUC = 0.855) (Fig. 5G), LUSC (AUC = 0.962) (Fig. 5H), OSCC (AUC = 0.748) (Fig. 5I), PAAD (AUC = 0.968) (Fig. 5J), STAD (0.823) (Fig. 5K), UCEC (AUC = 0.920) (Fig. 5L)
Kaplan-Meier analysis demonstrated a relationship between S100A2 expression and prognosis significance in the patients with GBMLGG, LGG, PAAD and OV. For GBMLGG, Cox regression results revealed that upregulated S100A2 expression was associated with low OS (HR = 3.57, 95% CI: 2.74–4.64, p < 0.001) DSS (HR = 3.66, 95% CI: 2.77–4.83, p < 0.001), AND PFI (HR = 2.84, 95% CI: 2.27–3.55, p < 0.001). For LGG, Cox regression results showed that upregulated S100A2 expression was associated with worse prognosis, including OS (HR = 2.05, 95% CI: 1.44–2.90, p < 0.001) (Fig. 6A), DSS (HR = 2.10, 95% CI: 1.46–3.04, p < 0.001) (Fig. 6B), AND PFI (HR = 1.79, 95% CI:1.35–2.36, p < 0.001) (Fig. 6C). For PAAD, the results showed that S100A2 was significantly associated with poor OS (HR = 1.62, 95% CI: 1.07–2.46, p = 0.023) (Fig. 6D), DSS (HR = 1.80, 95% CI: 1.12–2.89, p = 0.015) (Fig. 6E), AND PFI (HR = 1.81, 95% CI:1.22–2.69, p = 0.003) (Fig. 6F). For OV, the results showed that S100A2 was significantly associated with poor OS (HR = 1.36, 95% CI: 1.05–1.77, p = 0.002) (Fig. 6G), DSS (HR = 1.33, 95% CI: 1.00-1.76, p = 0.048) (Fig. 6H), AND PFI (HR = 1.28, 95% CI:1.01–1.63, p = 0.039) (Fig. 6I).
Clinical Characteristics S100A2 GBMLGG
Baseline characteristics of S100A2 patients from TVGA are shown in Table 1. Results showed that S100A2 expression in patients was related to WHO grade, IDH status, gender, age, and histological type of GBMLGG. In additional, S100A2 was expressed higher in patients with age > 60 (Fig. 7A), WHO grade 3(Fig. 7B), 1p/19q codeletion non-codel (Fig. 7C) and male (Fig. 7D), while it was lower in patients with Glioblastoma (Fig. 7E) and IDH status Mut (Fig. 7F).
Table 1
Clinical characteristics of GBMLGG patients
Characteristic | Low expression of S100A2 | High expression of S100A2 | p |
n | 348 | 348 | |
WHO grade, n (%) | | | < 0.001 |
G2 | 165 (26%) | 59 (9.3%) | |
G3 | 129 (20.3%) | 114 (18%) | |
G4 | 19 (3%) | 149 (23.5%) | |
IDH status, n (%) | | | < 0.001 |
WT | 45 (6.6%) | 201 (29.3%) | |
Mut | 301 (43.9%) | 139 (20.3%) | |
1p/19q codeletion, n (%) | | | < 0.001 |
codel | 143 (20.8%) | 28 (4.1%) | |
non-codel | 204 (29.6%) | 314 (45.6%) | |
Gender, n (%) | | | 0.007 |
Female | 167 (24%) | 131 (18.8%) | |
Male | 181 (26%) | 217 (31.2%) | |
Age, n (%) | | | < 0.001 |
<=60 | 306 (44%) | 247 (35.5%) | |
> 60 | 42 (6%) | 101 (14.5%) | |
Histological type, n (%) | | | < 0.001 |
Astrocytoma | 92 (13.2%) | 103 (14.8%) | |
Glioblastoma | 19 (2.7%) | 149 (21.4%) | |
Oligoastrocytoma | 84 (12.1%) | 50 (7.2%) | |
Oligodendroglioma | 153 (22%) | 46 (6.6%) | |
Age, median (IQR) | 39.5 (32, 51) | 52.5 (38, 62) | < 0.001 |
Prognostic Value of S100A2 in Pan-Cancer
We explored the correlations between S100A2 and prognosis value for OS, DSS, and PFI in different subgroups of MGBLGG. According to Kaplan-Meier, we found that the higher expression S100A2 had a worse OS in some clinical subgroups, subgroup of age < = 60 (Fig. 8A), subgroup of white (Fig. 8B), subgroup of female (Fig. 8C), subgroup of WHO grade G2 (Fig. 8D) and subgroup of 1p/19q codeletion non-codel (Fig. 8E). For DSS, it was found that the high S100A2 gene expression correlated with worse DSS in subgroup of age < = 60 (Fig. 9A), subgroup of white (Fig. 9B), subgroup of female (Fig. 9C), subgroup of WHO grade G2 (Fig. 9D) and subgroup of 1p/19q codeletion non-codel (Fig. 9E). For PFI, it was found that the high S100A2 gene expression correlated with worse PFI in subgroup of age < = 60 (Fig. 10A), subgroup of white (Fig. 10B), subgroup of female (Fig. 10C), subgroup of WHO grade G2 (Fig. 10D), subgroup of 1p/19q codeletion non-codel (Fig. 10E), and subgroup of IDH status Mut (Fig. 10F).
Univariate and Multivariate Cox Regression Analyses in GBMLGG
In our study, we performed univariate and multivariate cox regression analyses for the S100A2 and clinical characteristics in GBMLGG. In the univariate and multivariate Cox regression analyses, WHO grade, 1p/19q codeletion, primary therapy outcome, IDH status and age were associated with OS, DSS and PFI (Table 2–4).
Table 2
Univariate and multivariate Cox regression analyses of clinical characteristics associated with OS of MGBLGG
Characteristics | Total(N) | Univariate analysis | | Multivariate analysis |
Hazard ratio (95% CI) | P value | Hazard ratio (95% CI) | P value |
WHO grade(G3&G4 VS. G2) | 634 | 0.177 (0.123–0.255) | < 0.001 | | 0.496 (0.314–0.783) | 0.003 |
1p/19q codeletion (codel VS. non-codel ) | 688 | 4.428 (2.885–6.799) | < 0.001 | | 1.596 (0.928–2.747) | 0.091 |
Primary therapy outcome (PD VS. SD&PR&CR) | 461 | 0.282 (0.196–0.407) | < 0.001 | | 0.314 (0.203–0.486) | < 0.001 |
IDH status (WT VS. Mut) | 685 | 0.117 (0.090–0.152) | < 0.001 | | 0.535 (0.322–0.887) | 0.015 |
Age ( < = 60 VS. >60) | 695 | 4.668 (3.598–6.056) | < 0.001 | | 5.049 (3.085–8.266) | < 0.001 |
Table 3
Univariate and multivariate Cox regression analyses of clinical characteristics associated with DSS of MGBLGG
Characteristics | Total(N) | Univariate analysis | | Multivariate analysis |
Hazard ratio (95% CI) | P value | Hazard ratio (95% CI) | P value |
WHO grade (G3&G4 vs. G2 ) | 614 | 0.172 (0.117–0.253) | < 0.001 | | 0.510 (0.314–0.828) | 0.006 |
1p/19q codeletion (codel vs. non-codel) | 668 | 4.987 (3.117–7.978) | < 0.001 | | 1.759 (0.979–3.160) | 0.059 |
Primary therapy outcome (PD vs. SD&PR&CR) | 457 | 0.236 (0.160–0.347) | < 0.001 | | 0.261 (0.164–0.417) | < 0.001 |
IDH status (WT vs. Mut) | 664 | 0.110 (0.083–0.146) | < 0.001 | | 0.526 (0.309–0.894) | 0.018 |
Age ( < = 60vs. >60) | 674 | 4.500 (3.409–5.940) | < 0.001 | | 4.522 (2.688–7.606) | < 0.001 |
Table 4
Univariate and multivariate Cox regression analyses of clinical characteristics associated with PFI of MGBLGG
Characteristics | Total(N) | Univariate analysis | | Multivariate analysis |
Hazard ratio (95% CI) | P value | Hazard ratio (95% CI) | P value |
WHO grade (G3&G4 vs. G2 ) | 634 | 0.363 (0.279–0.473) | < 0.001 | | 0.843 (0.600-1.184) | 0.324 |
1p/19q codeletion(codel vs non-codel) | 688 | 3.373 (2.438–4.666) | < 0.001 | | 1.476 (0.988–2.207) | 0.057 |
Primary therapy outcome (PD vs. SD&PR&CR) | 461 | 0.212 (0.160–0.282) | < 0.001 | | 0.241 (0.175–0.332) | < 0.001 |
IDH status (WT vs. Mut) | 685 | 0.151 (0.119–0.191) | < 0.001 | | 0.399 (0.266-0.600) | < 0.001 |
Age ( < = 60 vs. >60 ) | 695 | 2.873 (2.268–3.640) | < 0.001 | | 2.214 (1.477–3.320) | < 0.001 |
ACC Adrenocortical carcinoma |
APOBEC3B Apolipoprotein B mRNA editing enzyme catalytic subunit 3B |
BLCA Bladder urothelial carcinomas |
BP Biological process |
CC Cellular component |
CEP55 Centrosomal protein |
CESE Cervical squamous cell carcinomas and endocervical adenocarcinomas |
CHOL Cholangiocarcinomas |
CNA Copy number alteration |
COAD Colon adenocarcinomas |
CPTAC Clinical proteomic tumor analysis consortium |
DBLC Lymphoid neoplasm diffuse large B-cell lymphomas |
DFS Disease-free survival |
ESCA Esophageal carcinomas |
GBM Glioblastoma multiforme |
GEPIA Gene expression profiling interactive analysis |
GO Gene ontology |
GTE Genotype-tissue expression |
HNSC Head and neck squamous carcinomas |
HPV Human papilloma virus |
KEGG Kyoto encyclopedia of genes and genomes |
KICH Kidney chromophobes |
KIRC Kidney renal clear cell carcinomas |
KIRP Kidney renal papillary cell carcinomas |
KPNA2 Karyopherin subunit alpha 2 |
LAML Acute myeloid leukemia |
LGG Brain lower grade gliomas |
LIHC Liver hepatocellular carcinomas |
LUAD Lung adenocarcinomas |
LUSC Lung squamous cell carcinomas |
MCM2 Minichromosome maintenance complex component 2 |
MELK Maternal embryonic leucine zipper kinase |
MESO Mesotheliomas |
MF Molecular function |
MSI Microsatellite instability |
NCAPH Non-SMC condensin I complex subunit H |
OV Ovarian cancers |
PAAD Pancreatic adenocarcinomas |
PCPG Pheochromocytomas and paragangliomas |
PFS Progression-free survival |
PRAD Prostate adenocarcinomas |
READ Rectum adenocarcinoma |
SKCM Skin cutaneous melanomas |
STAD Stomach adenocarcinomas |
TCGA The cancer genome atlas |
TGCT Testicular germ cell tumors |
THCA Thyroid carcinomas |
THYM Thymomas |
TIMER Tumor immune estimation resource |
TK1 Thymidine kinase 1 |
TMB Tumor mutational burden. TPM: transcripts per million reads |
UCEC Uterine corpus endometrial carcinomas |
UCS Uterine carcinosarcomas |
UVM Uveal melanomas |
Co-expression Gene Analysis of S100A2 in GBMLGG
To find out the role of S100A2 in GBMLGG, we analyzed the first 50 important genes that positively correlated with S100A2 expression in GBMLGG as shown in the heat map (Fig. 11A). We selected the top 10 genes, including S100A6 (r = 0.752) (Fig. 11B), VAMP5 (r = 0.697) (Fig. 11C), RHOC (r = 0.667) (Fig. 11D), TRIP6 (r = 0.663) (Fig. 11E), GNG5 (r = 0.662) (Fig. 11F), HSPB1 (r = 0.659) (Fig. 11G), S100A16 (r = 0.656) (Fig. 11H), BCL2L12 (r = 0.667) (Fig. 11I), LAMTOR2 (r = 0.667) (Fig. 11J) and AGTRAP(r = 0.667) (Fig. 11K).
Differentially Expressed Genes Between S100A2 High Expression and Low Expression Groups in GBMLGG
There were 2750 DEGs obtained with the threshold values of |log2 fold-change (FC)| > 1.0 and adjusted p-value < 0.05, including 1741 upregulated genes and 1009 downregulated genes in Fig. 12A. Among them, 392 DEGs were obtained with the threshold values of |log2 fold-change (FC)| > 2.0 and adjusted p-value < 0.05, including 312 upregulated genes and 80 downregulated genes. Then we conducted GO and KEGG functional enrichment analyses of DEGs in Fig. 12B, C. It was found that the primary BP was involved in regulation of ion transmembrane transport, regulation of membrane potential and regulation of trans-synaptic signaling. CC analysis showed that S100A2 may be associated with synaptic membrane, transmembrane transporter complex and ion channel complex. MF analysis revealed that S100A2-realted genes were enriched in passive transmembrane transporter activity, channel activity and substrate-specific channel activity. The KEGG analysis confirmed the enrichment of neuroactive ligand-receptor interaction, systemic lupus erythematosus and staphylococcus aureus infection.
Immune Cell Infiltration Analyses
The TIMER2 was used to assess the relationship between S100A2 expression and the infiltration of different immune cells. The results showed that S100A2 expression was positively correlated with CD8+ T cells, CD4+ T cells and Tregs cells in most cancer types (Fig. 13A, B, C). We found that macrophages, eosinophils, neutrophils and aDC were positively correlated with S100A2, and tcm, tgd, pDC and TFH were negatively correlated with S100A2 (Fig. 13D).