CX3CL1-CX3CR1 signaling orchestrates malignant progression of prostate cancer through luminal progenitor-macrophage crosstalk.

PURPOSE: Progression to castration-resistant prostate cancer (CRPC) is shaped by dynamic interactions within the tumor microenvironment (TME). However, the specific cellular crosstalk driving therapeutic resistance and metastasis remains incompletely defined. This study aims to identify key signaling axes between therapy-resistant luminal progenitor (luminal-2) cells and immune components in the TME, particularly tumor-associated macrophages (TAMs), and to determine how these interactions promote immunosuppression and cancer stem-like cell expansion during disease progression. METHODS: We employed an integrative phenomics approach combining single-cell transcriptomics with genetically engineered mouse models (GEMMs) and orthotopic allograft models of prostate cancer. Spatiotemporal changes in cell populations were profiled across disease stages. The functional contribution of the CX3CL1-CX3CR1 axis was evaluated through genetic ablation of Cx3cr1 in host mice, followed by assessment of TAM infiltration, luminal progenitor cell dynamics, tumor growth, and immunosuppression signature score. RESULTS: Single-cell profiling revealed a distinct luminal-2 progenitor population with high CX3CL1 expression that recruits CX3CR1(+) TAMs and supports a pro-tumoral program. These CX3CL1(hi) luminal-2 cells and CX3CR1(hi) TAMs expand in a stage-specific manner and co-evolve during CRPC progression, forming an immunosuppressive and pro-metastatic niche. Host Cx3cr1 deletion disrupted this signaling axis, leading to reduced TAM infiltration, suppression of luminal progenitor cells expansion, and significant inhibition of tumor growth and progression. CONCLUSION: The CX3CL1-CX3CR1 axis functions as a critical mediator of reciprocal signaling between luminal-2 progenitors and TAMs that promotes immune evasion, stemness maintenance, and therapeutic resistance in prostate cancer. Disrupting this pathway impairs the pro-tumoral niche and may represent a promising therapeutic approach for advanced prostate cancer.