Metabolic reprogramming has been shown to play important roles in tumor cell growth, proliferation, and survival [5]. Recent research has focused on glycolytic processes in cell invasion, autophagy, and treatment resistance [6–9]. Despite extensive research on prognostic signatures in LUAD, studies involving GRG with a predictive significance are insufficient.
In the present study, we initially revealed the transcriptional expression patterns of GRGs, and the prognosis was further analyzed. Two distinct molecular patterns were identified based on 18 prognostic GRGs. By comparing with patients with pattern A, patients with pattern B had better OS. According to GSVA enrichment analysis, pattern A was significantly enriched in base repair and metabolism related pathways. The level of immune cell infiltration and immune function also different greatly between the two patterns. Subsequently, a novel glycolysis-related signature based on 5 prognostic related DEGs, including ALDOA, FOSL2, PDE6D, PPARD, and RASAL2, was generated using Lasso Cox hazards regression analysis in the testing cohort and internal validation cohort, then calculated the risk score based on the signature formula.
Most of these genes have been studied in a variety of tumors. GRG ALDOA encodes glycolytic enzyme aldolase A. It is reported that the established effect of ALDOA including epithelial–mesenchymal transition [23] and multiple growth factor signaling pathways crosslink with alternative metabolism, such as the EGFR/MAPK and PI3K/AKT-mTOR pathways [24, 25]. Moreover, ALDOA phosphorylation was validated to promote glycolysis and cell proliferation in the hepatocellular carcinoma [26]. Recent studies have shown that ALDOA is a key enzyme involved in lung cancer metabolic reprogramming and metastasis. Overexpression of ALDOA is related to various clinical parameters and increase migration and invasion of lung cancer cell lines in vitro and formation of metastatic lung cancer foci in vivo.
Fos-like antigen 2 (FOSL2/FRA-2) is a member of the activator protein 1 transcription factor family. As a transcriptional switch in the lung tumor microenvironment, the activation of Wnt/β-catenin pathway-mediated FOSL2 drive transformation of gene regulatory from M1-like tumor-associated macrophages (TAMs) to M2-like TAMs, thereby promoting lung cancer progression and metastasis [27]. Furthermore, Wan et al., reported that the enhancement of FOSL2 in breast cancer-associated fibroblasts was significantly associated with clinical progression by promoting angiogenesis [28].
PDE6D encodes phosphodiesterase 6δ, a RAS chaperone protein, and was found to mediate the antegrade trafficking of prenylated KRAS to the cell membrane, where KRAS is activated [29, 30]. Studies suggested that targeting PDE6D-KRAS interaction is an effective approach to tackle both KRAS wild type and mutated cancer types [31–33]. Moreover, PDE6D has been found to be significantly expressed in cancer cells and tissues and was considered as potential novel biomarker for colorectal cancer [34]. However, there is no evidence yet to suggest an underlying role of the trafficking chaperone PDE6D in lung cancer.
Peroxisome proliferator-activated receptor delta (PPARD) is a ligand-dependent nuclear receptor that functions as a transcription factor has pleiotropic effects on cell homeostasis [35]. The expression of PPARD is upregulated in many cancers, such as breast [36], gastric[37], and colon [38]cancer and associated with significantly reduced metastasis-free survival. Zuo et al. [39] reported that PPARD expression in cancer cells drastically affected epithelial-mesenchymal transition, migration, and invasion, further underscoring its necessity for metastasis. These founds demonstrate that PPARD is an important molecular target in pan-cancer.
RAS protein activator like 2 (RASAL2) is a member of the family of RAS GTPase-activating proteins. The RASAL2 protein negatively regulates the RAS signaling pathway by catalyzing the hydrolysis of RAS-GTP to RAS-GDP in many cellular activities and acts as a vital regulator of the RAS signaling pathway. However, its tumor-suppressive or oncogenic roles in cancer development remain controversial. Studies indicate that the biological function of RASAL2 is influenced by cellular context to influence its pro or anti-oncogenic activity in human cancers and different signaling pathways of RAS signaling pathway, PI3K/AKT/mTOR signaling pathway, and NF-κB pathway may account for the different biological outcomes of RASAL2 activity [40–44].
The GSVA revealed that the high-risk group was mainly enriched in proliferation and survival pathways associated with cell cycle, DNA replication, and base repair. Patients in the low- and high- risk score groups showed significant differences in TME, TMB, and drug sensitivity. Univariate and multivariate Cox analyses confirmed that the novel glycolysis-related signature was an independent prognostic indicator for LUAD. ROC curves further showed the efficacy of the glycolysis-related risk score in predicting survival rate. Similar results were obtained from the independent validation cohort, demonstrating that the glycolysis-related signature may be a robust biomarker for evaluating the prognosis of LUAD. Finally, we established a nomogram for clinical use by combining the glycolysis-related signature with several clinicopathological features.
Despite recent advances in immunotherapy for LUAD, choosing the appropriate therapeutic regimen for patients remains a clinical challenge [45]. In addition, some patients do not obtain effective benefits from immunotherapy [46–48] and some patients experience severe side effects during therapy [49]. Therefore, it is critical to explore a novel method to guide the individualized and precise treatment of patients with LUAD. We speculated that patients stratified using the glycolysis-related signature would show distinct immunotherapeutic responses, which was investigated based on the associations among glycolysis-related score groups, TME factors, and the TIDE score.
The highly acidic microenvironment produced by tumor glycolysis may affect the infiltration of immune cells to varying degrees, eventually leading to tumor progression and immune escape [50]. In this study, we found that the infiltration of CD4+ T cells, CD8+ T cells, DCs, and neutrophils differed significantly between high- and low-risk groups, demonstrated that glycolysis affects the composition of immune cell populations in TME of LUAD. It was reported that TIDE could be an accurate biomarker to predict the immunotherapeutic effects in non-small cell lung cancer, which is negatively associated with the efficacy of ICIs [19]. Another recent study demonstrated the clinical application of TIDE in predicting and evaluating the immunotherapeutic response [51]. In our study, compared with patients in the high-risk group, those with lower risk scores had lower TIDE scores, suggesting that patients in the low-risk group may obtain more clinical benefits from immunotherapy, which was verified in the IPS analysis. Collectively, these findings highlight a crucial role of glycolysis in mediating the clinical response to ICIs therapy by affecting immune cell infiltration. Thus, the glycolysis-based signature is a potential biomarker for assessing immunotherapeutic response and tailoring individualized treatment for patients with LUAD.
This study also has some limitations that should be acknowledged. First, despite the large scale of sample size, the data included in this study were derived from public databases, resulting in selection bias, thus affecting the generalizability of the results. Second, the potential functional mechanisms of the glycolysis-based risk score have not been fully verified, which requires follow-up functional experiments at the molecular level both in vivo and in vitro. Finally, there are missing data for clinical variables such as targeted therapy and treatment after recurrence, which require improvement, and more clinical variables should be integrated to further validate the clinical value of the glycolysis-related prognostic signature.