Cuproptosis, as a novel type of metal ion-related death, regulates a variety of cellular metabolic processes in vivo independently of several other known modes of cell death and has been associated with a variety of diseases.Specifically, low concentrations of copper ions in cells can affect the activity of many important enzymes and related metabolic processes, affecting cell survival; conversely, if copper ions concentrations exceed a threshold, they can also cause toxic effects on cells and induce cell death[18]. Copper ionophores are small molecules bound to copper that transport copper into cells, making it a powerful tool for studying copper toxicity. Some copper ionophores have even been used to fight and kill cancer cells.However, studies of Cuproptosis in tumors have not yet yielded definitive results and are still in their infancy, especially in ccRCC.Here, we distinguished two independent subtypes with different clinical features, prognosis, PD-L1 expression, and TIME by consensus clustering of 14 Cuprotosis regulators.Among them, DLAT was identified as a potential regulator of immune infiltration-associated Cuprotosis.The Cuprotosis regulator DLAT showed a predictive value and warrants further investigation.Based on pan-cancer analysis, we obtained that DLAT was closely associated with PD-L1 expression and has a lower overall survival rate in multiple cancer types.
Kidney cancer is a common cancer. With the increase in awareness and research advances in renal clear cell carcinoma, some effective treatments have been achieved, but the clinical results in patients with ccRCC are still unsatisfactory, especially those diagnosed with advanced ccRCC.Due to heterogeneity and individualized differences in the cancer genome, some patients do not benefit from immunotherapy. It is crucial to study the mechanisms by which immune components are modulated to improve the effectiveness of ccRCC immunotherapy.For example, Bai et al. divided kidney cancer patients into two distinct subgroups based on their level of immune infiltration[19], the high TII score group and the low TII score group. Patients with high-risk immune subtypes responded more strongly to immune checkpoint blockade therapy, showing significant therapeutic advantages and clinical benefits.First, we divided the differences in the expression of Cuproptosis regulators in patients with renal clear cell carcinoma into two subtypes by consensus clustering analysis. We found that cluster 1 had lower tumor histological stages and grades, a better prognosis, and more expression of PD-L1.This suggests that even when distant metastases occur, patients can get better clinical efficacy from the application of PD-L1 inhibitors in cluster 1.Further analysis showed higher levels of infiltration of Monocytes, Macrophage M1 and Macrophage M2 in Cluster 1. However, T cell CD8+,T cell regulatory (Tregs), NK cell activated and T cell follicular helper had significantly higher levels of infiltration in cluster 2, showing a worse prognosis.This result has been widely confirmed[20].That is, with the progression of renal cancer, the levels of M0 macrophages, follicular helper T cells, CD8 + T cells, activated CD4 + memory T cells, plasma cells and regulatory T cells gradually increased.Unlike the vast majority of cancers, high CD8 + T cell infiltration levels are considered a poor prognostic factor for ccRCC[21, 22, 23], a view that has been shared by most people and confirmed in our results.
By differential gene expression, prognostic analysis, and correlation with PD-L1, we identified a key Cuproptosis regulator, DLAT.DLAT is a subunit of the pyruvate dehydrogenase complex.PDCs play a key role in cellular mitochondrial respiration[24, 25]. It is a key substance for aerobic glucose metabolism in cells, and the low expression of DLAT may be one of the mechanisms leading to excessive accumulation of glycogen and lactic acid in the cytoplasm of ccRCC, promoting tumor growth, proliferation and metastasis. The large accumulation of lactic acid may be one of the important factors causing tumor immune escape in ccRCC[36, 37].Based on the analysis, we can get that although there are a large number of CD8 + T cells and activated NK cells infiltrated in the low-expression DLAT group, it is frustrating to show a worse prognosis.This has a strong link to excessive accumulation of lactic acid, which has been confirmed in some studies[33, 34, 35].FDX1 is an upstream regulator of protein lipid acylation, and the four lipid acylation-modifying proteins are known in mammals, DBT (branched-chain α-ketoacid dehydrogenase complex component), GCSH (glycine lysis system protein H), DLST (α-ketoglutarate dehydrogenase complex component), and DLAT (pyruvate dehydrogenase complex component), are core components of an important metabolic enzyme complex in cells that regulate carbon entry into the tricarboxylic acid cycle[26].Therefore, we analyzed the expression of the upstream factor of DLAT lipid acylation in ccRCC, and the result showed that its expression was also reduced, which may be one of the reasons for the insensitivity of ccRCC patients to copper ion carriers.In GO and KEGG enrichment analyses, we noticed that the PPAR signaling pathway, carbon metabolism, purine ribonucleotide metabolism, and phosphoglyphate ribosome metabolism were downscaled.Peroxisome proliferators-activated receptor-α (PPARα) play an important role in inflammation regulation and tumorigenesis[27, 28], PPARα directly inhibits the gene transcription by binding the Glut1 gene promoter region, thereby reducing glucose uptake and finally inhibiting the mTOR signaling pathway and tumor growth[29].PPARγ agonists can significantly inhibit the proliferation of kidney cancer cells[30, 31, 32].In summary, we could find that the metabolic process of aerobic glucose was overly inhibited in ccRCC with low DLAT expression and unfavorable survival rates. Subsequently, we performed ICB analysis on ccRCC patients with high and low DLAT expression in different groups, and the results showed that patients with high expression of DLAT could obtain better clinical benefits from ICB more often.Finally, we performed a pan-cancer analysis of DLAT, which was strongly associated with the expression of immune checkpoint genes, particularly PD-L1, in most cancer types. Low DLAT expression showed poor OS in five cancer types. This implies that DLAT may be a target for immunotherapy in these cancers, allowing for better achieve precision treatment.
However, there are still shortcomings in this study, all the 14 Cuproptosis regulators included in this study are from literature searches and may have missing genes. And also the role of FDX1 in lipid acylation downstream of DLAT was not clearly stated.In terms of data, we also did not have enough specimens for validation and relied only on samples included in the TCGA database for analysis. In the future, a large number of tumor samples need to be collected in the clinic for verification. In addition, in vivo and in vitro experiments are needed to validate the reliability and safety of immune checkpoint blockade therapies.
In general, copper ions not only affect the growth, metastasis of tumors and the function of immune cells, but also have an impact on the tumor microenvironment. What role copper ions play in tumors and how they affect the outcome of tumors still requires a series of basic studies to demonstrate.