KIRC is a relatively common type of cancer in adults. Because KIRC is not easily detected in the early stages, most patients with KIRC are diagnosed in the middle to late stages and have progressed to metastasis [34]. Few biomarkers are available for early diagnosis or treatment of KIRC, resulting in a relatively poor prognosis [35]. Immunotherapy can be used to treat patients with kidney cancer. However, two-thirds of patients with advanced disease respond poorly to ICI therapy possibly because of factors in TME that help tumour cells evade immunotherapy [36]. To improve the diagnosis of patients with early-stage KIRC and reduce the likelihood of metastasis, we screened for prognosis-related biomarkers for KIRC using bioinformatic tools. These markers may help to develop more effective immunotherapeutic strategies.
PCD is an active cell death mode mediated by specific genes and proteins. It plays an essential role in maintaining the growth and development of the body and the normal physiological functions of tissues and organs [37]. The PCD mechanisms reported in KIRC are ferroptosis, autophagy and apoptosis. Researchers have attempted to induce PCD through some targets and subsequently kill cancer cells to achieve the goal of treating tumours. Targeted inhibition of ISCA2 reduces HIF-1/2α levels, increases lipid peroxidation, induces iron death and inhibits tumour growth in KIRC [38]. Silencing of the obesity-associated protein FTO enhances N6-methyladenosine (m6A)-mediated autophagic flux and inhibits tumour growth and metastasis in KIRC [39]. In addition, knockdown of KEAP1 inhibits the resistance of KIRC cells to axitinib and promotes apoptosis [40]. Wang et al. constructed a 6-cuprotosis-related-gene signature to predict the prognosis of KIRC accurately [41]. Recent studies have proposed a novel disulfide stress-mediated PCD mode called disulfidptosis [7].
Excessive accumulation of intracellular disulfide molecules causes disruption of the actin network because actin cytoskeletal proteins are especially vulnerable to disulfide stress. Studies have demonstrated a close relationship between actin and apoptosis at the cellular and tissue levels. Actin binds to the α-actin protein, predisposing osteoblasts at focal adhesion sites to apoptosis [42]. Apoptotic cells can be expelled by the assembly of F-actin and myosin [43]. The precise alignment of disulfide bonds is essential for maintaining the structural integrity of intracellular cysteine-rich cytokines [44]. Oxidised cysteine residues in actin in sickle cell anaemia can form disulfide bonds that reduce the dynamics of actin filaments and lead to disintegration of the erythrocyte cytoskeleton [45]. The thiol–disulfide oxidoreductase PDI1;1 reduces and degrades disulfide bonds in the high-molecular-weight structure of rice actin [46]. In addition, the surface virulence factor IcsA plays an important role in actin-based motility in Shigella through three cysteine residues [47].
In-depth studies have revealed that lncRNAs can either promote or suppress tumours by participating in gene signalling regulation and can serve as promising potential biomarkers [48–50]. In a study, eight ferroptosis-associated lncRNAs were used to construct a predictive model that accurately predicted the prognosis of KIRC and suggested treatment options [51]. However, the role of DRlncRNAs in KIRC remains elusive. In this study, we identified DRlncRNAs based on disulfidptosis-related genes and investigated how lncRNAs regulating disulfidptosis affect tumour progression and prognosis in KIRC.
Stepwise dimensionality reduction was performed sequentially through lasso and Cox regression analyses to reduce the number of feature parameters and construct a prognostic model. This method has been reported in several studies [52, 53]. Five DRlncRNAs significantly associated with the prognosis of KIRC, namely, SPINT1-AS1, AL161782.1, OVCH1-AS1, AC131009.3 and AC108673.3, were identified and used to construct a prognostic model. Subsequently, a nomogram was developed to improve the prediction of OS of patients with KIRC at 1, 3 and 5 years. Of the five DRlncRNAs, three lncRNAs, namely, OVCH1-AS1, AC131009.3 and AC108673.3 have not been investigated previously, whereas the other two lncRNAs have been closely associated with cancer. The lncRNA SPINT1-AS1 has been extensively investigated. It is inconsistently expressed in different cancers and is essential for inhibiting or promoting cancer progression. Initially, the expression of lncRNA SPINT1-AS1 was found to be elevated in colorectal cancer (CRC), negatively associated with the mRNA expression of SPINT1 and associated with the prognosis of CRC [54]. Subsequent studies have demonstrated that SPINT1-AS1 promotes CRC progression by suppressing miR-214 and increasing HDGF expression [55]. In addition, SPINT1-AS1 is an important breast cancer (BC) regulator that may interact with miRNA let-7 a/b/i-5p, and its knockdown inhibits the proliferative and migratory abilities of BC cells and promotes the resistance of BC cells to lapatinib [56, 57]. SPINT1-AS1 is upregulated in cervical cancer, inhibits miR-214 via DNM3OS, activates the Wnt/β-catenin signalling pathway and is associated with a poor prognosis [58]. In addition, SPINT1-AS1 expression is downregulated in oesophageal squamous cell carcinoma (ESCC), and patients with low expression of SPINT1-AS1 have shorter OS [59]. Furthermore, the expression of SPINT1-AS1 is significantly increased in growth hormone-secreting pituitary adenomas (GH-PAs) and is strongly associated with the aggressiveness of cancer [60]. In a study, 14 immune-related lncRNAs, including SPINT1-AS1, were used to construct a risk model for predicting the prognosis of melanoma [61]. The lncRNA AL161782.1 is considered an m6A- and cuproptosis-related lncRNA in KIRC [62, 63]. In this study, AL161782.1 was identified as a DRlncRNA. We speculate that it is involved in multiple PCD modes.
The biological functions and signalling pathways of the five DRlncRNAs were examined via enrichment analysis. The results of GO and KEGG analyses indicated that the DRlncRNAs were associated with several immune and metabolic pathways. Several proteins involved in complement and coagulation cascade reactions are upregulated in the serum of patients with thymoma [64]. The DRlncRNAs were found to be associated with complement and coagulation cascades in this study. GSEA revealed that the DRlncRNAs can influence immune- and apoptosis-related pathways in KIRC. However, further studies are warranted to verify these findings.
Changes in the TME of kidney cancer may lead to disease progression [65]. We examined the relationship between risk scores and changes in the TME of KIRC. Both immune and estimate scores were significantly higher in the high-risk group. In addition, patients in the high-risk group had higher immune cell infiltration and enhanced immune function, which explains, to some extent, differences in the OS of patients with KIRC between the two risk groups. The NF-KB signalling pathway is significantly activated in infiltrating CD8+ T cells, inducing pro-apoptosis and leading to a worse overall prognosis [66], which is consistent with the results of this study. Tregs have been strongly associated with a poor prognosis and poor immunotherapy outcomes in KIRC [67]. Th2 cells belong to a subpopulation of CD4+ T cells that secrete IL-4 and IL-10 to promote tumour growth by suppressing the host immune system [68]. This phenomenon was observed in the high-risk group in this study. We speculate that disulfidptosis mediates alterations in immune function and hence influences the progression of KIRC. However, relevant basic studies demonstrating the relationship between disulfidptosis and immunity in KIRC are lacking. In this study, the abundance of most immune cells and immune function scores were higher in the high-risk group, suggesting that immune activity was stronger in patients with high risk scores. Furthermore, the TIDE algorithm was used to estimate the relationship between risk scores and response to ICIs. The results revealed that the high-risk group had a poorer response to ICI treatment, suggesting that DRlncRNAs are promising biomarkers for predicting response to ICIs in KIRC.
Higher TMB is associated with poorer survival outcomes and may inhibit immune infiltration in KIRC [69]. In this study, the risk scores were found to be significantly positively correlated with TMB scores. The high-risk-score and high-TMB-score groups had the shortest survival and the worst prognosis, whereas the low-risk-score and low-TMB-score groups had the highest survival rate and the best prognosis. This finding demonstrates the accuracy of the risk score in predicting immunotherapy outcomes in patients with KIRC. Furthermore, we evaluated the sensitivity of patients with KIRC to anti-cancer drugs in the two risk groups. Axitinib, ibrutinib, osimertinib and ruxolitinib were more effective in patients in the low-risk group, whereas crizotinib, lapatinib, linsitinib and nilotinib were more effective in patients in the high-risk group. These findings may help guide the treatment of patients with KIRC in clinical settings.