3.1 Technology Roadmap
3.2 Data gathering
We standardized the two glioma data sets, and there are 284 samples in the GSE16011 data set, including 8 normal samples (control) and 276 glioma samples (GBMLGG) (Supplementary Figs. S1A-B). GSE50161 data set has 230 samples, including 13 cases of normal samples (control) and 117 cases of glioma samples (GBMLGG) (Supplementary Figs. S1C–D).
3.3 Nicotinamide metabolism score (NAMS) construction and clinical prognosis analysis
We initially intersected 50 NAM metabolism-related genes (NAMRGs) with genes in datasets TCGA-GBMLGG, GSE16011, and GSE50161 and obtained 39 NAMRGs for subsequent analysis (Fig. 2A). We obtained the NAMS of each sample in the three data sets through the single-sample GSEA (ssGSEA) algorithm, then we divided the glioma samples into high and low groups based on the median of NAMs (high score group: high, low score group: low). Stacked histograms (Figs. 2B–D) show the the differences between the two groups in patient age, overall survival, and gender (age, OS, gender). And OS Kaplan–Meier (KM) curve (Fig. 2E) show that low group exhibited a better prognosis than high group, with statistically significant (P < 0.001).Finally, we performed differential analysis on the counts data of the TCGA-GBMLGG dataset datasets GSE16011 and GSE50161, and plotted the volcano map (Figs. 2F–H) and the heat map of NAMRGs (Fig. 2I) to show the results.
3.4 WGCNA
In order to analyze the difference in gene expression between the high and low groups of NAMS, we performed WGCNA to screen for co-expression modules. We obtained the correlation between six modules (MEyellow, MEbrown, MEturquoise, MEblue, MEgreen, and MEgrey) and two groups (Fig. 3A-E). We intersected the 39 NAMRGs with the module genes contained in the MEbrown (Fig. 3F), MEgrey (Fig. 3G), and MEturquoise (Fig. 3H) modules and drew a Venn diagram to obtain the module NAMRGs (Figs. 3F–H). We obtained 11 module NAMRGs, PARP10, PARP14, PARP9, CDKN1A, NT5E, NAPRT, PTGIS, PTGS2, NNMT, NT5C1A, and PNP. These 11 genes were used as hub genes for subsequent analysis.
3.5 Mutation analysis and copy number variation of hub genes
The results of the genetic variation analysis of hub genes showed that the main mutation types were missense mutations, nonsense mutations, and frameshift mutations (Frame Shift Ins). Among them, missense mutations account for the main part. Additionally, the mutation types in the hub genes were mainly single nucleotide polymorphisms, and C > T was the most common single nucleotide variant, followed by C > A (Supplementary Fig. S2A). By analyzing the copy number variation of hub genes (Supplementary Fig. S2B), we found that most of the genes exhibited copy number changes (Altered group), among which the gene NT5C1A exhibited a higher frequency of copy number alterations. Furthermore, the copy number changes of half of the genes are concentrated in the deep deletion (Supplementary Fig. S2C). For example, the gene NT5C1A has a high frequency of copy number deep deletion (> 30%) and a low frequency (< 10%) of significant amplification.
3.6 Expression difference analysis of hub genes
The results of difference analysis showed that the ten hub genes in the TCGA-GBMLGG exhibited higher expression in the high group than in the low group, with statistically significant. (Supplementary Fig. S3A): CDKN1A, NNMT, NT5C1A, NT5E, PARP10, PARP14, PARP9, PNP, PTGIS, and PTGS2. And the same is true in GSE16011. (Supplementary Fig. S3B). In GSE50161, compared to low group, 8 hub genes were higher expressed in the high group, with statistical significance (Supplementary Fig. S3C): CDKN1A, NNMT, NT5E, PARP10, PARP14, PARP9, PNP, and PTGS2. According to the results of the group comparison chart, 8 hub genes were higher expressed in the high group in TCGA-GBMLGG, GSE16011, and GSE50161, with statistical significance: CDKN1A, NNMT, NT5E, PARP10, PARP14, PARP9, PNP, and PTGS2. And we plotted the receiver operating characteristic (ROC) curves displayed the results (Supplementary Figs. S3D–O). The ROC curve results are as follows: CDKN1A, NNMT, PARP10, PARP14, PARP9, PNP, PTGS2 (The AUC values were 0.705, 0.765, 0.701, 0.793, 0.827, 0.761 and 0.700, respectively) have certain diagnostic value in TCGA-GBMLGG, but NT5E is distinctive (AUC = 0.649) ; CDKN1A, NNMT, NT5E, PARP14, PARP9, PNP, and PTGS2 (The AUC values were 0.721, 0.810, 0.716, 0.758, 0.770, 0.779 and 0.759, respectively) have certain diagnostic value in GSE16011, but PARP10 is distinctive (AUC = 0.584); CDKN1A, NT5E, PARP10, PARP14, PARP9, PNP, and PTGS2 (The AUC values were 0.715, 0.787, 0.762, 0.825, 0.871, 0.715 and 0.761, respectively) have certain diagnostic value in GSE50161; but NNMT is distinctive (AUC = 0.665).
3.7 Construction of related subtypes of GBMLGG
To explore the heterogeneity of NAMRGs in GBMLGG, based on the expression levels of 11 hub genes, GBMLGG was divided into two subtypes (clusters 1 and 2) by consensus clustering (Supplementary Fig. S4A). Additionally, cluster 1 contained 249 samples, and cluster 2 contained 94 samples. We performed principal component analysis (PCA) on the dataset expression matrix of the two subtype, and the PCA clustering results showed that there were significant differences between the two subtype (Supplementary Fig. S4B). We showed the consistent clustering cumulative distribution function (CDF) graph and delta graph (Supplementary Fig. S4C-D) for different cluster numbers. The figure shows that clustering results for the TCGA-GBMLGG are best. We draw a heat map to show the expression difference of 11 hub genes in the two subtype. The results showed that in the TCGA-GBMLGG, the expression levels of 11 hub genes in the two subtype mostly showed a significant negative correlation (Supplementary Fig. S4E). The KM curve showed that two subtype have statistical heterogeneity between the outcomes of the patients (P < 0.0001, Supplementary Fig. S4F).
Subsequently, we analyzed the expression differences of 11 hub genes between the two subtypes. Supplementary Fig. S4G shows that the ten hub genes expression in the two subtypes has statistical significance (P < 0.05): PARP10, PARP14, PARP9, CDKN1A, NT5E, PTGIS, PTGS2, NNMT, NT5C1A, and PNP. NT5C1A has a higher expression level in cluster 1 than in cluster 2, while the opposite is true for the rest of the genes. (Supplementary Fig. S4G).
3.8 Construction of key genes prognostic model (NMRS)
To determine the prognostic value of the 11 hub genes, we perform a single-factor Cox regression analysis on them and screened out 8 genes significantly associated with OS time ( P < 0.001) that were used as the key genes (PARP10, PARP14, PARP9, CDKN1A, PTGS2, NNMT, NT5C1A, and PNP) for our follow-up research (Fig. 4A). Afterwards; we built a prognostic LASSO regression model based on the key genes (Fig. 4B). According to the minimum partial likelihood deviation, we kept all eight key genes. Additionally, we obtained the LASSO variable trajectory map by visualizing the results (Fig. 4C). To further verify the impact of the 8 key genes on the prognosis of glioma, a multivariate Cox model was constructed by performing multivariate Cox regression analysis on the multivariate Cox regression analysis. A risk factor map showed grouping in the multivariate Cox model ,and its included Risk score, SO, and Heat map (Fig. 4D). ( Risk score = PARP14 * -0.45538137 + PARP9 * 0.660476921 + CDKN1A * 0.034173338 + PTGS2 * 0.2545473 + NNMT * 0.150412959 + NT5C1A * − 0.66393584 + PNP * 0.143448889 )
Then, a time-dependent ROC curve (Fig. 4E) show the impact of the risk score on survival outcomes, and KM curve showed that risk score exhibited a statistical significance in predicting the survival outcome of glioma (P < 0.001, Fig. 4F). Finally, the boxplot showed the similarity between different key genes(Fig. 4G). To verify further the value of the multivariate Cox model, We drew the ROC curve based on the risk score and NAMs. The result showed that the diagnostic results of risk score in both the high and low groups are relatively accurate (AUC = 0.765, Fig. 4H).
3.9 Difference analysis of NMRS
The TCGA-GBMLGG patients had their individual risk scores determined, and they were assigned to different risk groups by the median. We perform differential analysis on the counts data of the TCGA-GBMLGG dataset, and drew the volcano map and the heat map of the eight key genes to show the results(Fig. 5A-B).The results of difference analysis of 8 key genes in the high and low risk groups showed that all key genes have higher expression in the high-risk group, with statistical significance (P < 0.001) (Fig. 5C).In addition, the heatmap shows the correlation between the eight key genes in the glioma sample group (Fig. 5D). Then We drawed correlation scatter plots of four most correlated gene immune cell pairs (Figs. 5E–H), and the results are as follows: PARP9 and NNMT ( R = 0.681, P < 0.001); PARP9 and PARP10 ( R = 0.602, P < 0.001); PARP14 and PARP10 ( R = 0.634, P < 0.001); PNP and PARP9 ( R = 0.569, P < 0.001) (Figs. 5E–H).
3.10 Functional enrichment analysis (GO) and pathway enrichment (KEGG) analysis of key genes
To investigate biological processes of eight key genes, We first performed GO analysis and KEGG enrichment analysis. GO analysis enriched key genes from two categories: biological processes (BPs), and molecular functions (MFs). BPs were primarily enriched in the pyridine-containing compound metabolic process, NAD biosynthesis via the NAM riboside salvage pathway, protein mono-ADP-ribosylation, NAM nucleotide biosynthetic process, and NAM nucleotide metabolic process. MFs were mainly enriched in pentosyl transferase activity, NAD+-protein ADP-ribosyl transferase activity, NAD + ADP-ribosyl transferase activity, glycosyl transferase activity, and transcription corepressor activity. The result of KEGG enrichment analysis showed that these genes were significantly enriched in nicotinate and NAM metabolism, nucleotide metabolism, small cell lung cancer, purine metabolism, and the oxytocin signaling pathway (Table S1, Supplementary Materials) (Figs. 6A–D). Additionally, we draw pathway diagrams to show the basic situation of the five main enriched pathways in the KEGG enrichment analysisc(Supplementary Figs. S5A–E). Finally, we performed the GO/KEGG enrichment analysis of the combined logFC of the eight key genes, the bubble diagram indicates that the eight key genes are mainly enriched in the BPs.
3.11 GSEA between high- and low-risk groups in NMRS
GSEA was conducted to complement and validate the functional annotation of GO analysis and KEGG enrichment analysis. The results show that the high- risk groups are significantly enriched in apoptosis, oxidative phosphorylation, TGF-beta receptor signaling, and JAK-STAT signaling pathway, and low-risk groups are mainly enriched in NO2IL12 pathway and interleukin-10 signaling pathway (Supplementary Figs. S6A–G; Table S2, Supplementary Materials).
3.12 Construction of PPI network, mRNA-miRNA, mRNA-binding protein (RBP), and mRNA-TF interaction network
We conducted a PPI analysis of the eight key genes and the PPI network composed of these eight key genes was visualized (Supplementary Fig. S7A).We predicted miRNAs interacting with eight key genes and drew the mRNA-miRNA interaction network (Supplementary Fig. S7B). The mRNA-miRNA interaction network consists of 6 key genes (CDKN1A, NNMT, PARP14, PARP9, PNP, and PTGS2) and 98 miRNA molecules, forming 196 pairs of mRNA-miRNA interaction relationships (specifically as reported in Table S3 (Supplementary Materials) ).We predicted the RBP interacting with eight key genes and draw the mRNA-RBP interaction network for visualization (Supplementary Fig. S7C). The mRNA-RBP interaction network consists of seven essential genes (CDKN1A, NNMT, PARP10, PARP14, PARP9, PNP, and PTGS2) and 92 RBP molecules, forming 204 pairs of mRNA-RBP interaction relationships (specifically as reported in Table S4 (Supplementary Materials) ). Finally, we searched for transcription factors (TF) that bind to eight key genes. The interaction relationship data of six key genes (PARP10, NT5C1A, PARP14, PARP9, PNP, and PTGS2) and 97 TF were obtained and visualized (Supplementary Fig. S7D). Table S5 (Supplementary Materials) shows the specific mRNA-TF interaction relationship.
3.13 The impact of NMRS on immune assessment
We calculated the immune score, stroma score, and ESTIMA score based on the expression matrix of each glioma using the ESTIMATE algorithm. The results disclosed that the stromal score, immune score, and ESTIMATE score in high-risk group significantly higher than those in low-risk group (P < 0.05) (Fig. 7A-C). This suggests that the high-risk group has stronger invasion and immune escape capabilities. Additionally, We also found that the stromal score, immune score, and ESTIMATE score were all significantly positively correlated with the NMRS. This implies that the higher the score, the more unfavorable the patient's prognosis may be.
3.14 Difference analysis of ssGSEA immune signature
We calculated and displayed the infiltration abundance of 28 types of immune cells in high- and low-risk groups through the ssGSEA algorithm and Mann–Whitney U. The findings indicated that high-risk groups exhibited greater infiltration abundance of immune cells with pro-tumor effects, when compared to the Low-risk group. This difference was statistically significant, with myeloid-derived suppressor cells (MDSC) being the most prominent (P < 0.05) (Fig. 8A) We further calculated the correlation between the abundance of 27 kinds of immune cell infiltration in high- and low-risk groups. The results show that The positive correlation between MDSCs in the high-risk group is stronger, suggesting a more potent mutual promotion effect and closer crosstalk communication.(Figs. 8B–C). Ultimately, we examined the correlation between the 27 kinds of immune cell infiltration abundance and eight key gene expression levels. The results showed that in low-risk groups, PARP14 and PARP9 have a significant positive correlation with immune cells, And in high-risk groups, NT5C1A negatively correlates with immune cells, and other key genes have a positive correlation.(Figs. 8D–E)
3.15 NMRS mutation analysis of high- and low-risk groups
We analyzed the differences in tumor mutation burden (TMB) and microsatellite instability (MSI) between two groups, and also evaluated the sensitivity of both groups of patients to immunotherapy using the tumor immune dysfunction and exclusion (TIDE) algorithm. The findings revealed that low-risk groups exhibit higher levels of MSI and lower TMB (P < 0.001), suggesting a better immune response. there was no statistical significance in TIDE between two groups ( Supplementary Fig. S8A-C). (Supplementary Figs. S8D–E). The results of the copy number variation (CNV) show that in the low-risk groups, PARP10 exhibited the most CNV amplification and the least CNV deletion; while NT5C1A exhibited the opposite pattern. In the high-risk groups (Supplementary Fig. S8E), PARP10 exhibited the most CNV amplification and the least CNV deletion; While PNP displayed the inverse pattern.
3.16 Nomogram establishment based on the multivariable Cox regression model
The clinical information of glioma patients in TCGA was statistically analyzed (Table S6, Supplementary Materials). We performed univariate Cox regression analysis on the expression levels of eight key genes and clinical variables (age, gender). Based on the outcomes of univariate analysis(Supplementary Fig. S9A), we incorporated these indicators into the multivariate Cox analysis in order to construct a multivariate Cox prognostic model (Table 1). Subsequently, based on the results of multivariate Cox analysis, we constructed nomogram and drew calibration curves. The nomogram showed better accuracy in predicting both short- and long-term survival, and was consistent with the results of the calibration curve.(Supplementary Figs.S9B–E) The decision curves demonstrated that the risk score was superior to other factors in forecasting the prognosis of glioma.(Supplementary Figs. S9F–H).
Table 1
COX regression analysis to key genes associated with OS in TCGA-GBMLGG.
Characteristics
|
Total(N)
|
Univariate analysis
|
|
Multivariate analysis
|
Hazard ratio (95% CI)
|
P value
|
Hazard ratio (95% CI)
|
P value
|
age
|
343
|
|
< 0.001
|
|
|
|
<=50
|
201
|
Reference
|
|
|
Reference
|
|
> 50
|
142
|
5.029 (3.422–7.391)
|
< 0.001
|
|
3.430 (2.211–5.320)
|
< 0.001
|
gender
|
343
|
|
0.214
|
|
|
|
MALE
|
210
|
Reference
|
|
|
|
|
FEMALE
|
133
|
0.796 (0.553–1.145)
|
0.219
|
|
|
|
PARP10
|
343
|
1.911 (1.574–2.320)
|
< 0.001
|
|
1.309 (0.966–1.774)
|
0.082
|
PARP14
|
343
|
1.859 (1.513–2.284)
|
< 0.001
|
|
0.830 (0.517–1.333)
|
0.441
|
PARP9
|
343
|
2.637 (2.156–3.225)
|
< 0.001
|
|
1.366 (0.816–2.285)
|
0.235
|
CDKN1A
|
343
|
1.397 (1.223–1.596)
|
< 0.001
|
|
0.976 (0.818–1.165)
|
0.789
|
PTGS2
|
343
|
1.612 (1.361–1.910)
|
< 0.001
|
|
1.200 (0.997–1.445)
|
0.054
|
NNMT
|
343
|
1.486 (1.388–1.591)
|
< 0.001
|
|
1.203 (1.063–1.362)
|
0.003
|
NT5C1A
|
343
|
0.229 (0.155–0.339)
|
< 0.001
|
|
0.528 (0.355–0.785)
|
0.002
|
PNP
|
343
|
2.428 (1.875–3.143)
|
< 0.001
|
|
1.196 (0.846–1.691)
|
0.311
|
OS, Overall Survival;TCGA, The cancer genome atlas༛GBMLGG, Glioma。
3.17 PARP9 promotes glioma cell proliferation in vivo and in vitro
PARP9 expression was detected in glioma tissue and normal brain tissue, which showed that PARP9 was significantly upregulated in glioma tissue. We detected PARP9 expression in HA, U87, U251, A172, SHY5Y, and SHG44 cells, and it showed that PARP9 was highly expressed in glioma cells, especially in U251 cells (Figs. 9A–E). The lentivirus was used to construct U251 cell lines with stably silenced PARP9-expression. The CCK-8 assay, Edu assay, and plate colony formation assay demonstrated that knocking down PARP9 expression level could inhibit the proliferation of U251 cells in vitro (Figs. 9F–I and L). In previous bioinformatic analysis, we found that PARP9 might be correlated with the JAK2-STAT3 signaling pathway. Subsequent cell experiments revealed that the phosphorylation levels of JAK2 (p-JAK2) and STAT3 (p-STAT3) in the shPARP9 group were significantly reduced compared to the scramble group. Therefore, PARP9 in U251 cells could activate JAK2–STAT3 signaling (Figs. 9J–K). Orthotopic homograft tumor models were constructed in nude mice to verify the change in the proliferation ability of glioma after the knockdown of PARP9 to determine the function of PARP9 in tumor propagation in vivo. The mice exhibited prolonged survival and decreased tumor volumes compared to those of the scramble group, suggesting the importance of PARP9 for the proliferation of U251 cells and tumorigenicity (Figs. 9M–O).