TIMP1 Derived from Mesenchymal Stem Cells Promotes Bladder Cancer Progression by Regulating the Formation of VDIMs through the RAP1 Pathway.

The pro-tumor function of mesenchymal stem cells (MSCs) in bladder cancer (BC) is not fully elucidated. This study integrates clinical cohorts, organoid models, and patient-derived xenografts (PDX) to dissect MSCs-derived TIMP1 as a key driver of BC progression. Using multiplex fluorescent immunohistochemistry and enzyme-linked immunosorbent assays, we found that elevated infiltration level of MSCs in BC tissues and TIMP1 levels in tissues/urine correlated with advanced tumor-stage, lymphovascular invasion, and reduced recurrence-free survival time, with MSCs infiltration positively associated with TIMP1 expression. Single-cell data analysis and mass spectrometry revealed TIMP1 as the predominant cytokine secreted by MSCs. Mechanistically, MSC-derived TIMP1 binds to ADAM10 to inhibit its extracellular shedding, thereby stabilizing cMet phosphorylation and activating the RAP1 signaling axis. Functional studies revealed that TIMP1 enhances intracellular Ca2+ levels and VDAC1 expression through the RAP1 pathway, promoting the formation of vesicles derived from the inner mitochondrial membrane (VDIMs) to regulate mitochondrial quality control. Crucially, the TIMP1 inhibitor FXR agonist 3 suppressed MSCs-driven BC proliferation in vitro and attenuated tumor growth in PDX models by disrupting the cMet-RAP1 signaling pathway without systemic toxicity. Our findings propose targeting the MSCs-TIMP1-RAP1 axis as a novel therapeutic strategy for BC.