BCa ranks among the most prevalent cancers globally and is the fourth most common malignancy in males(He et al. 2021). Over the past decade, it has been reported that more than 200,000 individuals succumb to BCa annually worldwide(Peng et al. 2024). This malignancy can be categorized into two types: non-muscle invasive and muscle-invasive BCa. The latter constitutes approximately 25% of all cases and is characterized by its aggressive nature, rapid progression, early metastasis, and elevated rates of recurrence and mortality(Huang et al. 2024). Consequently, there is a pressing need to identify novel biomarkers for the early diagnosis, treatment, and prognostic evaluation of BCa.
In recent years, lncRNAs have emerged as a significant area of research. Genome-wide association studies have identified lncRNAs in tumor samples that are associated with various cancers, indicating their potential as innovative biomarkers and potential therapeutic targets(Bhan, Soleimani, and Mandal 2017). For instance, lncRNA CCAT1 has been shown to enhance the proliferation, migration, and invasion of BCa cells(Zhang et al. 2019). Additionally, lncRNA RP11-89 has been implicated in promoting tumorigenesis and resistance to ferroptosis in BCa by facilitating PROM2-mediated iron output through the sponging of miR-129-5p(Luo et al. 2021). LncRNA RNF144A-AS1, also referred to as GRASLND, has been recognized for its significant role in the progression of several cancers. GRASLND has been shown to promote the advancement of skin cutaneous melanoma by targeting the miR-218-5p/STAM2 axis. Furthermore, elevated levels of GRASLND are associated with poor prognostic outcomes and diminished efficacy of immunotherapy(Ma et al. 2024). In gastric cancer, GRASLND is markedly upregulated and correlates with poor prognosis and advanced disease stages, facilitating metastasis and proliferation through the miR-30c-2-3p/LOX axis(Li et al. 2021). Research by Binghai Chen et al. has indicated a close relationship between GRASLND and the prognosis of papillary renal cell carcinoma. However, the specific role of GRASLND in BCa warrants further investigation, which is the objective of this study.
For our analysis, we utilized the TCGA-BLCA cohort from the public database. Analysis of transcriptome data from both unpaired and paired samples revealed that GRASLND is significantly overexpressed in BCa tissues compared to normal tissues. The ROC curve analysis further indicated that GRASLND serves as an effective biomarker for differentiating BCa from normal tissue. Additionally, we investigated the correlation between GRASLND expression and various clinicopathological features, finding significant associations with pathological stage, histological grade, and subtype. Subgroup analyses based on these clinicopathological characteristics suggest that high GRASLND expression may be linked to disease progression. Notably, GRASLND expression levels in non-papillary BCa were significantly higher than those in papillary BCa. Therefore, GRASLND may serve as a valuable biomarker for the diagnosis of BCa, with its expression levels potentially predictive of disease progression and tissue type.
Subsequent Kaplan-Meier curve analysis indicated that patients exhibiting elevated expression levels of GRASLND experienced reduced overall survival and a poorer prognosis compared to those with lower expression levels. This finding was statistically significant, suggesting that GRASLND may serve as a biomarker for overall survival in individuals diagnosed with BCa. However, no statistically significant differences were observed in the Kaplan-Meier curve results concerning disease-specific survival, implying that GRASLND may not be a reliable predictor of specific survival outcomes in this patient population. Then cox regression was used to analyze the influencing factors of overall survival. GRASLND expression, Age, Pathologic T stage, Pathologic N stage, Pathologic M stage, Pathologic stage and Subtype were significantly correlated with overall survival. Notably, the pathologic N stage is an independent risk factor. Consequently, the integration of GRASLND expression with these clinicopathological characteristics may enhance the prognostic prediction for patients with BCa.
In the end, the single-sample gene set enrichment analysis algorithm and Spearman correlation were used to analyze the relationship between GRASLND expression and immune infiltration within BCa tissue. The enrichment abundance of macrophages, Tgd and Tem exhibited a positive correlation with GRASLND expression, with these immune cells being significantly overrepresented in BCa relative to normal tissues. Macrophages constitute a primary component of leukocyte infiltration in the tumor microenvironment, with M1 and M2 macrophages being the two predominant subtypes(Ngambenjawong, Gustafson, and Pun 2017). Increasing evidence suggests that M2 macrophages facilitate tumor proliferation, invasion, and metastasis(Jiang et al. 2022). Tumor-associated macrophages have been implicated in the progression of BCa through mechanisms that enhance cell growth, migration, invasion, and cytokine production(Huang, Liu, and Shyr 2020). Additionally, macrophage presence has been associated with prognosis and response to systemic therapies in patients with muscle-invasive BCa(Koll et al. 2023). Elevated infiltration levels of Tgd have also been observed in the immune microenvironments of various cancers, including hepatocellular carcinoma(Xie et al. 2021), lung adenocarcinoma(Tong et al. 2023), oral squamous cell carcinoma(Sun et al. 2022), etc. Moreover, high levels of Tem infiltration correlate with improved prognoses in several malignancies, such as gastric cancer(Ning et al. 2020), colon cancer(Ding et al. 2023), melanoma(Jiang et al. 2024), and so on. The efficacy of Bacillus Calmette Guerin therapy against superficial BCa is also contingent upon the activity of immune cells, such as Tem(Reale et al. 2002). The aggregation and infiltration of immune cells represent critical mechanisms of anti-tumor activity within the human body. The overexpression of GRASLND appears to significantly enhance the invasion of macrophages, Tgd, Tem and other factors. Therefore, GRASLND may not only predict the prognosis of patients with BCa, but may even become a new therapeutic target.
This study does have certain limitations. Firstly, the sample size is relatively small, necessitating larger datasets for further validation. Secondly, the analysis was conducted using data sourced from public databases; thus, future research should involve the collection of tissue or cell specimens for verification purposes. Lastly, while this study establishes GRASLND as a potential biomarker for BCa and a prospective therapeutic target, additional cellular and animal studies are required to elucidate the biological processes associated with GRASLND and to develop innovative treatment strategies.