TRP channels are cation channels on the cell membrane surface that allow cations such as Ca2+, Mg2+, Na+, and K + to pass through. In the tumor microenvironment, an imbalance in the expression level of TCRGs can change the adaptability of cells to the surrounding environment and regulate the occurrence and development of tumors. Research shows that blocking or interfering with TRP channels is expected to become a new target for tumor molecular therapy. A pan-cancer analysis found that higher WHO grade and stage were substantially correlated with unbalanced TCRG expression, and shorter survival, increased tumor mutational burden, and activation of tumor-related pathways in patients(19). Previous studies have found that TRPML1 blocks the autophagic flux of human glioblastoma cells to lysosomes by inducing autophagy inhibition, resulting in the accumulation of damaged mitochondria, which in turn damages DNA in cancer cells and inhibits tumor growth(20). Another study reported that elevated expression levels of TRPML2 were associated with resistance to temozolomide therapy in GBM patients and were associated with poorer OS. Interfering with TRPML2 expression was expected to be a new therapeutic target(21). However, there is no literature systematically evaluating the potential prognostic value and mechanism of TCRGs in glioma, so our study has certain significance.
In this study, 37 differentially expressed TCRGs in glioma tissues were first identified by differential analysis, and 30 genes were further screened by univariate Cox regression analysis to associate with patient survival and prognosis. Due to the complex molecular heterogeneity of glioma, the identification of different molecular subtypes can help develop better treatment options(22). To this end, based on 30 prognostic TCRGs, we used the consensus clustering algorithm of the "ConsensusClusterPlus" package, selected the optimal number of clusters (k = 3), and identified 3 subtypes, which were confirmed reliability by PCA, UMAP and tSNE. We found that Cluster B patients had the worst prognosis, and patients in Cluster C had the longest survival. Further biological and immune-related analyses found that Cluster B had a higher degree of immune infiltration and a higher level of immunosuppression. At the same time, multiple signaling pathways related to cancer progression were significantly enriched, which may be the reason for its poor prognosis. Our subtype identification method provides reference for the molecular typing of glioma.
Although the WHO classification method has been the gold standard for prognostic grading of glioma for many years, the identification of more tumor biomarkers based on bioinformatics methods and a large amount of gene sequencing data has become a new technological advancement and contributes to precise medical realization. The prognostic value of a single biomarker is very limited, and integrating multiple biomarkers into one model can improve the prediction efficiency and accuracy(23). For example, a study constructed a prognostic model for glioma patients based on three necroptosis-related genes, and high-risk patients had higher immune infiltration rates and immune checkpoint genes expression than low-risk patients, which were positively associated with poor prognosis(24). Another study constructed a prognostic model in patients with LGG based on cellular senescence-related genes and found that for patients, cellular senescence-related scores could be used as an independent predictor, and patients with high scores had a worse prognosis. It is also well validated in other cohorts(25). We constructed a 10-gene prognostic model, and patients were divided into two groups. The findings indicated that the overall survival of patients in the high-risk was significantly lower, and two external validation sets (CGGA_325 and GSE16011) corroborated this finding favorably. Then we performed an immune microenvironment analysis. The results showed that the infiltration of immune cells was higher in patients of the high-risk group. The coexistence of immune-suppressive and immune-activating cells suggested that in the high-risk group, there are complex immune microenvironment disturbances in patients, and effective immune intervention is expected to improve the survival of such patients.
Since traditional gene sequencing methods can only obtain the results of averaging the intracellular gene expression information of different types of tissue samples, the samples include tumor cells and various cellular components of the surrounding microenvironment. These analyses are general analyses of large tumor samples, which cannot effectively identify and describe the types and states of individual cells in the tumor microenvironment, which may obscure key information. scRNA-seq uses DNA next-generation sequencing technology to analyze the DNA, RNA or DNA methylation levels of a single cell, revealing its genomic, transcriptomic and epigenetic characteristics and understanding the function and state of a single cell. scRNA-seq can not only identify the heterogeneity of cells in solid tumors but also help to elucidate the molecular mechanisms of immune cells in the tumor microenvironment on tumor cell occurrence, development, metastasis, drug resistance, and immune escape. The clinical diagnosis, treatment and prognosis prediction of patients have become more accurate(26, 27). Therefore, on the basis of scRNA-seq, we localized the 10 genes of the model.
TRPV3 mainly exists in sensory nerve cells and skin keratinocytes in the human body and senses temperature stimuli by forming a complex with TRPV1(28). Studies have shown that in renal clear cell carcinoma and non-small cell lung cancer, the high expression of TRPV3 is significantly correlated with increased tumor grade and poor prognosis, and it affects the accumulation of T cells in various tumor immune microenvironments, which is related to tumor immune infiltration(29, 30). Our analysis of single-cell data found that in malignant cells, oligodendrocytes, and endothelial cells, it was expressed in various cells, such as monocytes and macrophages, and may play a complex regulatory role.
MAPK13 is a subtype of the p38 mitogen-activated protein kinase family, which is highly conserved and involved in the regulation of inflammatory responses, cell proliferation(31, 32). Studies have confirmed that MAPK13 promotes the over-proliferation of epidermal cells and tumorigenesis by inhibiting the expression of proinflammatory cytokines and chemokines in the development of squamous cell carcinoma(33). Analysis at the single-cell level found that it was significantly expressed in exhausted CD8 + T cells, suggesting that it may be related to the exhaustion of CD8 + T cells in the glioma microenvironment, thereby inhibiting the antitumor immune process and promoting glioma progression.
PRKCB is a member of the serine- and threonine-specific protein kinase C family and is involved in signal transduction responses to various hormones and growth factors(34). PRKCB functions in the B-cell receptor signaling pathway and is involved in B-cell development, and its over-expression distorts B-cell development in mice as a phenotypic feature of chronic lymphocytic leukemia(35). In hepatocellular carcinoma, PRKCB interacts with ribosomal RACK1 to increase translation of a potent oncogene in hepatoma cells, which is associated with tumor development and recurrence after chemotherapy(36). In the immune escape system of tumors, tumor cells reduce the abundance of PRKCB in myeloid cells by enhancing the STAT3 signaling pathway, affecting the differentiation of dendritic cells, thus causing the immune escape of tumor cells(37). This was consistent with our analysis at the single-cell level that PRKCB was mainly expressed in exhausted CD8 + T cells and may be involved in the immune escape process of glioma cells.
Our study firstly explored the prognostic value of TRP channel-related genes in glioma, which has certain innovation and research value. However, this is a bioinformatics study based on an open databases, so a larger multicenter studies are needed to confirm the validity of the constructed prognostic model, and sufficient validation and mechanistic exploration are needed, which will be included in the follow-up experimental design. We hope that through the existing research results, more researchers will be attracted to participate in research on the correlation between the TRP channel and the mechanism of the occurrence and development of glioma and provide a more theoretical basis for the development of therapeutic targets for this type of tumor.