MTHFD1L in muscle invasive bladder cancer: a multi-cohort study on prognosis and therapeutic response

BACKGROUND: Bladder cancer is one of the most common malignancies of the urinary tract. Among its subtypes, muscle invasive bladder cancer (MIBC) is particularly aggressive and often associated with poor prognosis. The efficacy of platinum-based neoadjuvant chemotherapy and radical cystectomy remains unsatisfactory. In recent years, immune checkpoint inhibitors have shown promising therapeutic potential in MIBC. However, reliable biomarkers for predicting treatment response are still lacking. Moreover, traditional clinical parameters, such as TNM staging, often fail to accurately assess patient outcomes. Therefore, identifying novel biomarkers is crucial for improving prognosis and optimizing treatment strategies in MIBC. METHODS: We first analyzed the expression pattern and prognostic significance of methylenetetrahydrofolate dehydrogenase (NADP + dependent) 1-like (MTHFD1L) across multiple cancer types. Subsequently, MIBC patient samples from three independent cohorts (TCGA-BLCA, GSE169455, and GSE48075) were used to evaluate the prognostic value of MTHFD1L through univariate and multivariate Cox regression analyses combined with Kaplan-Meier survival analysis. Gene Set Enrichment Analysis and Gene Set Variation Analysis were performed to explore the biological functions of MTHFD1L. Mutation characteristics and immunotherapy response-related features were further analyzed based on MTHFD1L expression levels. Finally, the results were further verified by immunohistochemistry and cell function experiments. RESULTS: MTHFD1L was upregulated in multiple cancer types, and its elevated expression was significantly associated with unfavorable outcomes. In all independent MIBC cohorts, high MTHFD1L expression served as an independent risk factor for poor prognosis. Gene Set Enrichment Analysis indicated that MTHFD1L may promote tumor progression by activating immune-related and proliferative pathways while suppressing metabolic processes. Mutation analysis revealed a higher frequency of TP53 mutations in the MTHFD1L high-expression group. Moreover, immune response prediction suggested that patients with low MTHFD1L expression were more likely to benefit from immune checkpoint inhibitors therapy. Immunohistochemistry confirmed the overexpression of MTHFD1L in MIBC tissues, and cell function experiments demonstrated that MTHFD1L knockdown markedly inhibited bladder cancer cell proliferation, colony formation, and migration. CONCLUSIONS: MTHFD1L represents a promising and reliable biomarker for predicting prognosis and immunotherapy response in MIBC, providing a new foundation for the development of precision and personalized therapeutic strategies.