Tumors represent a significant threat to human health. Despite extensive efforts to advance both the diagnosis and treatment of tumors, the 5 year overall survival rates for most cancers remain distressingly low [21]. The imperative for novel diagnostic and therapeutic approaches is clear. Utilizing the comprehensive multi-omics data from The Cancer Genome Atlas (TCGA), which encompasses analyses of 33 prevalent tumor types, presents a unique opportunity to discern gene functions across various cancerous contexts [22, 23]. Recent advances in bioinformatics algorithms and the expansion of databases have spurred a surge in studies aimed at identifying and elucidating the roles of molecular biomarkers in cancer. In this study, we leveraged an open-access database combined with in vitro experimental approaches to examine both the prognostic relevance and oncogenic mechanisms of NSUN5 in clear cell renal carcinoma.

In this investigation, we initially detected elevated expression levels of NSUN5 within the TCGA-KIRC (KIRC, kidney renal clear cell carcinoma) and SYSUCC cohorts, revealing its upregulation and suggesting its potential as a significant oncogenic factor. We further explored the correlation between NSUN5 expression and various clinical parameters, including TNM stage, pathological grade, WHO/ISUP grade, tumor size, and the presence of necrosis. Kaplan–Meier analysis indicated that high NSUN5 expression correlates with adverse prognostic outcomes. Utilizing data from both the TCGA-KIRC and SYSUCC cohorts, Cox regression analysis confirmed the independent prognostic significance of high NSUN5 expression, establishing it as an independent risk factor for poor outcomes in tumors. Additionally, the integration of NSUN5 with other clinical parameters to construct prognostic models revealed enhanced predictive power, surpassing the accuracy and prognostic value of both the conventional TNM staging system and isolated NSUN5 expression. By employing a nomogram-defined scoring system, we were able to categorize patients into distinct risk groups: low, intermediate, high, and very high. These stratifications have shown significant potential in predicting the risk associated with ccRCC. These findings underscore the utility of such models in optimizing therapeutic strategies and advancing population screening in future research endeavors.

Cellular senescence is a process triggered in damaged cells that prevents their proliferation. Although cellular damage alone does not directly manifest as overt signs of senescence, when such damage accumulates beyond a certain threshold, cells halt their proliferation, leading to observable tissue weakening and the development of physiological aging phenotypes [24]. Senescent cells enter a state of growth arrest and secrete a wide array of pro-inflammatory cytokines, chemokines, growth factors, and proteases through autocrine and paracrine mechanisms, impacting the microenvironment of adjacent cells and tissues. This activity promotes aging and related diseases [25]. The secretory behavior of these senescent cells is referred to as the senescence-associated secretory phenotype (SASP) [25]. The SASP exhibits a dual function: it can both sustain the anti-proliferative state of cells and facilitate the immune-mediated clearance of senescent cells. However, as senescent cells accumulate and the aging process accelerates, the SASP may paradoxically stimulate cellular proliferation and promote the transformation of preneoplastic cells, thus fostering tumorigenesis and tumor progression [26]. Noteworthy components of SASP, such as IL-6, IL-8, CXCL12, CXCR4, TGF-β1, and matrix metalloproteinases (MMPs), play crucial roles in regulating cell proliferation and differentiation, maintaining orderly tissue and cellular development, and are closely linked to tumorigenesis. IL-6, a principal element of the SASP, is upregulated in various cancer types, including skin, breast, lung, esophageal, liver cancers, and melanoma [27]. The elevated expression of IL-6 in tumor cells, driven by signaling pathways such as JAK/STAT3, RAS/MAPK, and PI3K/AKT, enhances tumor cell growth and proliferation [28]. IL-6 exacerbates tumor progression by upregulating MMP-2, MMP-9, and MMP-14, increasing telomerase activity, and intensifying the paracrine effects of the SASP through mechanisms like p53 inactivation, epithelial-mesenchymal transition (EMT) induction, and augmented tumor cell invasiveness [25]. These findings underscore the pivotal role of IL-6 in tumor progression within the senescent cell microenvironment. Similarly, the senescent cell milieu is characterized by a significant abundance of IL-8, which can downregulate p53 and activate the RAS pathway, imparting stem cell-like properties to breast cancer MCF-7 cells and enhancing their invasiveness [25, 29]. It is noteworthy that MMPs, as direct modulators of tumor development within the SASP, could serve as biomarkers for intuitively assessing tumor onset and progression. MMP-9 is particularly effective in promoting melanoma cell migration [30], while MMP-13 plays a critical role in facilitating liver metastasis of colorectal cancer [31]. In pancreatic cancer tissues, the expression levels of MMP-2 and MMP-9 correlate positively with microvessel density (MVD), with vascular distribution being essential for rapid tumor growth [32].

Over the last decade, the strategic inhibition or blockade of Senescence-Associated Secretory Phenotype (SASP)-related signaling pathways has emerged as a targeted therapeutic approach in oncology. For instance, the obstruction of the IL-6 receptor (IL-6R) has effectively mitigated resistance to anti-trastuzumab therapy in a murine model of breast cancer. Moreover, the synergistic application of an anti-IL-6R antibody with trastuzumab has significantly suppressed tumor metastasis, demonstrating enhanced therapeutic efficacy compared to trastuzumab monotherapy [33]. A clinical investigation revealed that among patients with metastatic renal cell carcinoma treated with sunitinib, elevated serum levels of IL-6 served as a predictive marker for reduced adverse events during the therapeutic regimen [34]. Targeting IL-8 receptor α and IL-8 receptor β with antibodies has been found to inhibit the IL-8 signaling cascade and downregulate Bcl-2 expression, thereby enhancing the susceptibility of breast cancer cells to cisplatin treatment [35]. Additionally, silencing of IL-8 expression has been identified as a means to overcome resistance to gefitinib in PC9 cells, underscoring the potential utility of targeting IL-8 as a therapeutic strategy for lung cancer [36]. Sunitinib, widely employed in treating kidney, liver, lung, and gastrointestinal stromal cancers, functions as a multi-target small-molecule tyrosine kinase inhibitor, targeting growth factors such as PDGFR and VEGFR [37]. Trastuzumab, employed in lung, gastric, breast, ovarian, and renal cancer treatments, effectively inhibits human epidermal growth factor receptor 2 (HER2) and activates the PI3K/AKT pathway to regulate tumor proliferation and metastasis [38]. Furthermore, everolimus and pazopanib, used in renal cancer therapy, act as VEGF inhibitors, impeding tumor progression by disrupting VEGF-related signaling pathways [39]. However, current drug therapies are prone to drug resistance or exhibit high toxicity levels. Further research into more efficient and less toxic combination therapies is essential to provide novel avenues for tumor treatment.

Based on above findings, the investigation into NSUN5's role in carcinogenesis and its risk implications involved comprehensive analyses using the 786-O and 769-P renal cancer cell lines. Silencing NSUN5 in these cell lines resulted in significant reductions in cell proliferation and migration, supporting the hypothesis that NSUN5 plays a crucial role in tumor progression. Additionally, senescence-associated β-galactosidase staining revealed an increase in senescent cells following NSUN5 knockdown, suggesting a shift toward a senescent phenotype. Moreover, key components of the senescence-associated secretory phenotype (SASP) such as tumor necrosis factor-alpha (TNF-α), interleukins (IL-1, IL-6, IL-8), MMP3, CXCL10, and TNFα, showed significant transcriptional downregulation upon NSUN5 silencing. This indicates that NSUN5 not only contributes to tumor cell proliferation and migration but also influences the inflammatory and tumor-promoting environment mediated by SASP factors. These findings provide strong evidence for the role of NSUN5 in renal cancer pathogenesis and suggest that therapeutic strategies targeting NSUN5, potentially in combination with drugs that inhibit SASP-related signaling pathways, such as tyrosine kinase inhibitors (TKIs) or VEGF inhibitors, could enhance treatment efficacy for patients with clear cell renal cell carcinoma. This approach could offer a more targeted and effective treatment regimen by not only inhibiting tumor growth directly but also modulating the tumor microenvironment to reduce the inflammatory and pro-tumorigenic effects of SASP. Further research and clinical trials are essential to validate these potential therapeutic strategies and determine their practical effectiveness and safety profiles.

In summary, our study has unveiled significant insights into the regulatory role of NSUN5 expression in the progression of clear cell renal cell carcinoma (ccRCC) and its involvement in the overactivation of cellular senescence signaling. Additionally, the integration of NSUN5 expression levels with other clinicopathological factors into a nomogram has demonstrated remarkable discriminative performance. This integrated approach significantly surpasses the predictive efficacy of TNM staging alone for assessing ccRCC prognosis. This suggests that NSUN5 could serve as a valuable prognostic marker for ccRCC patients, potentially aiding in personalized treatment strategies and improving patient outcomes.