Inflammatory cancer-associated fibroblasts (iCAFs) are closely related to progression, anticancer therapeutic resistance, and poor prognosis of bladder cancer (BCa). However, the functional role of iCAFs in BCa has been poorly studied. In our study, two BCa scRNA-seq datasets (GSE130001 and GSE146137) were obtained and integrated by the Seurat pipeline. Based on reported markers (COL1A1 and PDGFRA), iCAFs were identified and the related signature of 278 markers was developed. Following unsupervised consensus clustering, two molecular subtypes of TCGA-BLCA were identified and characterized by distinct dysregulated cancer hallmarks, immunological tumor microenvironments, prognoses, responses to chemotherapy/immunotherapy, and stemness. Subsequently, the robustness of the signature-based clustering, in terms of prognosis and therapeutic response prediction, was validated in a GEO-meta cohort with seven independent GEO datasets of 519 BCa patients, and three immune checkpoint inhibitor (ICI)-treated cohorts. Considering the heterogeneity, re-clustering of iCAFs was performed and a subpopulation, named “LOXL2+ iCAFs”, was identified. Co-culture CM derived from LOXL2 overexpression/silencing CAFs with T24 cells revealed that overexpression of LOXL2 in CAFs promoted while silencing LOXL2 inhibited the proliferation, migration, and invasion of T24 cells through IL32. Moreover, the positive correlation between LOXL2 and CD206, an M2 macrophage polarization marker, has been observed and validated. Collectively, integrated single-cell and bulk RNA sequencing analyses revealed an iCAF-related signature that can predict prognosis and response to immunotherapy for BCa. Additionally, the hub gene LOXL2 may serve as a promising target for BCa treatment.

Background: Bladder cancer (BCa) is a prevalent and aggressive malignancy characterized by high recurrence and metastasis rates. Despite advances in treatment, the prognosis for patients with advanced BCa remains poor. This study aimed to investigate the role of SAPCD2 in BCa progression and its potential as a therapeutic target. Methods: We performed a series of in vitro and in vivo experiments to assess the expression and function of SAPCD2 in BCa. The correlation between SAPCD2 expression and clinicopathological features was analyzed using tissue samples from BCa patients. Functional assays, including cell proliferation, migration, invasion, and metastasis tests, were conducted to evaluate the biological impact of SAPCD2. Mechanistic studies focused on the MAPK signaling pathway, TANK stabilization, and the interaction between SAPCD2 and the PLAGL2–CREB feedback loop. Results: Our results showed that SAPCD2 was significantly upregulated in BCa tissues and correlated with advanced clinicopathological features and poor prognosis. Overexpression of SAPCD2 promoted cell proliferation, migration, invasion, and metastasis, while its silencing led to the opposite effects. Mechanistically, SAPCD2 activated the MAPK signaling pathway by stabilizing TANK and preventing its degradation by SYVN1. Furthermore, we identified a positive feedback loop in which SAPCD2 enhanced PLAGL2 expression through CREB phosphorylation, further amplifying SAPCD2 expression and MAPK signaling. Conclusions: This study indicated that SAPCD2 could serve as a critical driver of BCa malignancy, emphasizing its role in sustaining oncogenic signaling through the SAPCD2–TANK–MAPK axis and the PLAGL2–SAPCD2–CREB feedback loop. Targeting this pathway may offer novel therapeutic strategies for treating aggressive BCa.