The SP4–NUPR1–SELM Axis Promotes Glycolytic Reprogramming and Stemness-Associated Phenotypes in Bladder Cancer

Background: Metabolic adaptation and stemness-associated programs contribute to bladder cancer growth. This study investigated the regulatory and functional relationships among specificity protein 4 (SP4), nuclear protein 1 (NUPR1), and selenoprotein M (SELM). Methods: TCGA-BLCA analyses were combined with silencing, overexpression, and rescue experiments in 5637 and T24 cells. Viability, migration, invasion, colony formation, glucose uptake, lactate production, extracellular acidification, oxygen consumption, and OCT4/SOX2 expression were assessed. Protein interactions and promoter-associated regulation were examined using co-immunoprecipitation, immunofluorescence, chromatin immunoprecipitation, and reporter assays. Xenograft experiments in female BALB/c nude mice evaluated NUPR1 depletion with or without SP4 overexpression. Results: Higher NUPR1 expression was associated with higher glycolysis- and stemness-associated transcriptional scores in TCGA-BLCA tumors. NUPR1 depletion reduced viability, glycolytic activity, glucose uptake, lactate production, and OCT4/SOX2 expression while increasing oxygen consumption. SP4 interacted with NUPR1 and showed enrichment at the NUPR1 promoter region. NUPR1 promoted SELM expression and reporter activity, with enrichment detected at the SELM promoter region. SP4 or SELM overexpression partially rescued the effects of NUPR1 depletion. SELM silencing attenuated NUPR1-associated increases in viability, migration, invasion, and colony formation. NUPR1 depletion suppressed xenograft growth, which was partially rescued by SP4 overexpression. Conclusions: These findings support functional relationships among SP4, NUPR1, and SELM that connect glycolytic activity with stemness-associated phenotypes in bladder cancer models. The results provide a basis for further investigation of this regulatory network in cancer metabolism.