3.1. Clinical characteristics information
After censoring some invalid information in 1018 samples, the sample data of 748 glioma patients can be obtained from the CGGA database. It includes general clinical information, such as gender, age, pathological type, and WHO classification of glioma, in addition to PRS (primary, recurring, secondary) type, IDH (isocitrate dehydrogenase) mutation and some data on the missing status of the 1p19q codon. Detailed clinical information is shown in Table 1.
3.2. DRAXIN is highly expressed in glioma tissues and cell lines relative to normal control
Through the GEPIA database, the DRAXIN gene is highly expressed(it was found that) in glioblastoma (Fig 1A). It was verified in GSE50161 that the expression of DRAXIN in glioma tissue was much higher than normal brain tissue. At the same time, at the nucleic acid level, the high expression of DRAXIN was proved by the IVY-GAP database using ISH images (Fig 2). The results showed that the expression level of tumor cells in the same glioma tissue is higher than that of normal brain adjacent tissue. In order to verify the results of previous studies, we performed RT-qPCR at the tissue and cell levels. The results show that DRAXIN is highly expressed in glioma tissues and cells compared with normal brain tissues and human brain astrocytes, especially the expression level of A172 cell line is 1569 times of that in normal cells (Figure 1D, E). In summary, the high expression of DRAXIN has been proven on multiple levels.
3.3. Relationship between the expression of DRAXIN and the clinical features and prognosis of patients with glioma
To further explore whether the high expression of DRAXIN has a certain clinical significance, such as a certain impact on the prognosis, OS curve was drawn and it was found that the survival time of the high expression group was lower than the low expression group in these queues, indicating a poor prognosis (Fig 3 A). In addition, combined with the conditions such as WHO classification, IDH mutation, and 1p19q co-deletion status, OS diagrams were further obtained (Fig 3 B-D). Moreover, ROC curves were drawn with above categories, we discovered that expression of DRAXIN, accompanied with 1p19q deletion status, and IDH mutation with 1p19q co-deletion status is statistical significance (AUC>0.7). In the end, univariate and multivariate logistic regression analysis exhibited three independent risk factors (HR>1, p<0.001) for glioma, the expression of DRAXIN, PRS grade and high-grade glioma leading to poor prognosis (Fig 3I, J). IDH mutation type and 1p19q co-deletion status were present as protective factors (HR<1, p<0.001). Based on the above data, high expression of DRAXIN could be used to indicate a poor prognosis for patients, and it had a certain clinical diagnostic value.
3.4. The relationship between the expression of DRAXIN and clinical features in patients with glioma
Not only of overall survival, the relationship between various clinical characteristics and expression of DRAXIN was also estimated via correlation analysis. The data of glioma was screened for the complete information including gender, age, pathological type, and WHO grade of glioma, PRS (primary, recurring, secondary) type, IDH (isocitrate dehydrogenase) mutation and the status of the 1p19q codon. After Wilcox and Kruskal tests, it was concluded that the increased expression of DRAXIN was positively correlated with higher WHO classification and recurrent and secondary glioma (p<0.001; Fig 4A-B). In the primary glioma, the wild-type expression of DRAXIN was higher than that of the mutant (p<0.001, Fig 4C). Compared with the 1p19q co-deletion status, the gene expression level of DRAXIN was lower than that with non-co-deletion state (p<0.001, Fig 4D). In addition, histocytology showed that the expression level of DRAXIN in the GBM group and the relapsed GBM group was significantly increased. In summary, expression of DRAXIN was significantly related to the malignant features of glioma.
3.5. GSEA reveals DRAXIN-related cell signaling pathways
To further study the specific mechanism of DRAXIN in glioma, GSEA was used to explain the cancer-related cell signaling pathways that DRAXIN involved in. Several items were obtained by screening with p<0.05, FDR q-value<0.25, which turned out that focal adhesion, cell cycle, DNA replication, pyrimidine metabolism, Toll-like receptor signaling pathway, VEGF signaling pathway, the DRAXIN high expression group showed significant differential enrichment (Fig 5).
3.6. Co-expression analysis and drug analysis
Furthermore, to explain the role of gene itself in glioma, individual top ten most related genes were obtained after screening the p value and correlation coefficient value of co-expressed genes (Fig 6). Through co-expression analysis, it was found that ten genes were positively correlated with DRAXIN, including CDCA8, KIF2C, DLGAP5, KIFA4, CCNB1, MELK, KIF23, GTSE1, ASPM and GAS2L3, and other ten genes, AKR1C3, RASL10A, SLC25A18, CYP17A1-AS1, ETNPPL, FBXW4, LDHD, SLC22A6, SLC25A48 and MRVI1, were negatively correlated. Finally, Cmap drug analysis using these 20 genes found that there were 4 drugs, as camptothecin, doxorubicin, etoposide and lomustine, that might have therapeutic effects. Drug-related information such as chemical formula and PubChem CID were obtained on PubChem and shown in Fig 7.