In recent years, cancer research on energy metabolism has attracted attention. Moreover, a large number of researchers have supported tumour metabolism as a critical determinant of glioma progression. In addition to TME-related factors, oncogenic mutations also modulate glioma metabolism to promote tumour cell proliferation and evasion of drug therapy [20, 21]. It has been demonstrated that the cancer genotype and the TME shape the metabolic reprogramming of GBM and are thus potential therapeutic targets. Moreover, regulators of GBM metabolism can be useful tools for prognostication, diagnosis and therapy [20]. The Warburg effect is a phenomenon in which metabolism shifts to aerobic glycolysis rather than mitochondrial oxidative phosphorylation, which is a typical biochemical adaptation in GBM. Targeting glycolysis-related regulatory genes is an ideal therapeutic strategy for GBM. Several glycolysis regulatory genes have been reported, including hexokinase 2 (HK2) and PTEN-induced kinase 1 (PINK1), where the inhibition of HK2 and activation of PINK1 in preclinical GBM models have shown therapeutic benefit [22, 23].
However, due to the high heterogeneity of GBM, targeting a single gene is often unable to effectively control tumour progression; moreover, single gene expression is easily interfered with by many external factors, and it is difficult for these biomarkers to independently and accurately predict the survival rate of patients. Therefore, in the present study, we constructed a statistical model containing multiple glycolysis-related genes and combined the function of each gene to improve the prediction efficiency. This kind of model has been confirmed in many other solid tumours and is superior to a single biomarker in predicting tumour prognosis [24–26].
Ten glycolysis-related biomarker genes (B4GALT7, CHST12, G6PC2, GALE, IL13RA1, LDHB, SPAG4, STC1, TGFBI and TPBG) were found to be statistically and biologically significant in the discrimination of LGGs from GBM in the present study, and six genes (CHST12, G6PC2, IL13RA1, LDHB, TGFBI and TPBG) were demonstrated to be significantly correlated with the prognosis of GBM patients (Table 2). Among these biomarker genes, LDHB is a dehydrogenase and a critical switch that regulates glycolysis and OXPHOS. It has been demonstrated that the expression of LDHB alone was not able to predict a difference in OS, but the concomitant expression of LDHB and CCNB1 was able to identify medulloblastoma patients with a significantly worse prognosis [27]. Transforming growth factor-beta-induced (TGFBI) is an exocrine protein that has been found to be able to promote the development of glioma, nasopharyngeal carcinoma, bladder cancer and other tumours [28, 29]. In a recent study, Guo Sk and colleagues showed that TGFBI was upregulated in glioma cells and played a promoting role in the growth and motility of U87 and U251 cells. Their results suggested that TGFBI has the potential to be a diagnostic marker and to serve as a target for the treatment of gliomas [30]. IL-13 receptor subunits α1 and α2 of the IL-13R complex are overexpressed in GBM. Jing Han and his colleagues showed that high IL13Rα1 with or without IL13Rα2 expression was associated with poor prognosis in patients with high-grade gliomas, but there was no correlation between IL-13Rα1 mRNA and IL-13Rα2 mRNA expression. Their findings have important implications in understanding the role of IL-13R in the pathogenesis of GBM and potentially other cancers [31]. Although these genes can independently predict tumour prognosis to some extent, our results demonstrated that the ten-mRNA signature has better prognostic significance than the corresponding single biomarkers. Moreover, by using KM and ROC curve analyses of GBM, we verified our statistical results in the CGGA and REMBRANDT data sets and confirmed that the risk signature performed well in predicting the survival of GBM patients (Fig. 4). Therefore, this glycolysis-related gene signature can predict tumour prognosis more accurately and guide treatment more comprehensively.
We also constructed a heatmap to present the associations between the risk signature and clinical characteristics in the TCGA database. Our results indicated that elderly age, the mesenchymal subtype and wild-type IDH1 were significantly correlated with higher risk scores (Table 4) (Fig. 5). Consistent with mainstream views, elderly patients, the mesenchymal subtype and wild-type IDH1 usually predict an unfavourable prognosis [32, 33]. Moreover, by using GSVA to explore the biological processes and KEGG pathways associated with the risk signature, we noticed that the risk signature was correlated with almost every step of oncogenesis and tumour progression, including adverse biological processes and signal transduction pathways (Fig. 6). Currently, many studies have elucidated the aggressive behaviours associated with GBM glycolysis and attempted to find ways to target GBM glycolysis, such as through Myc, PGK1, SIRT3 and HK1 [34–37]. Therefore, our results once again confirm the reliability of the risk score in predicting the prognosis of GBM and provide new potential targets for targeting glycolysis.