Abstract
BACKGROUND: Neoadjuvant immune checkpoint blockade (nICB) has revolutionized cancer treatment, yet the underlying mechanisms of resistance in bladder cancer remain to be explored. METHODS: We conducted single-cell RNA sequencing (scRNA-seq) on peripheral blood mononuclear cells, tumor tissues, adjacent normal tissues, and metastatic lymph nodes from 2 nICB-naïve and 10 nICB-treated patients with bladder cancer (5 responders and 5 non-responders). Spatial RNA sequencing was performed on tumor slides from two responders and four non-responders. Findings were validated by multiplex immunohistochemistry, mice orthotopic bladder cancer model, and flow cytometry assays. RESULTS: nICB remodeled the tumor microenvironment of bladder cancer from both single-cell and spatial perspectives. scRNA-seq analysis revealed a significant increase in MYBL2(hi) cancer stem cells (CSCs) among non-responders. Analysis of the myeloid population showed that SPP1+ macrophages associated with angiogenesis were linked to CD8+ T cell exclusion. Further investigation into cell-cell communication revealed a propensity for bidirectional crosstalk between MYBL2(hi) CSCs and SPP1+ macrophages in non-responders. MYBL2(hi) CSCs derived CCL15, which bound to CCR1 and induced SPP1 upregulation in macrophages which reciprocally enhanced bladder cancer stemness and resistance to nICB through the SPP1-ITGα9β1 axis. Additionally, we identified an aged CCL3+ neutrophil population that interacted with SPP1+ macrophages through a positive feedback loop, contributing to nICB resistance. Finally, in vivo studies demonstrated that combined MYBL2 knockdown and SPP1 targeting synergistically enhanced ICB efficacy in bladder cancer. CONCLUSIONS: Our research reveals transcriptomic characteristics associated with distinct therapeutic responses to nICB treatment, offering a foundation for optimizing personalized neoadjuvant strategies in bladder cancer.