From clinical evidence to biological mechanisms: GPRC5B as a key mediator of metabolic syndrome-associated prostate cancer.

Metabolic syndrome (MetS) is a recognized risk factor for prostate cancer (PCa), yet the precise biological mechanisms driving this association remain poorly understood. Unraveling these molecular pathways is essential for developing targeted interventions to improve patient outcomes. In this study, we analyzed NHANES (2005-2014) data to examine associations between MetS and PCa outcomes, finding that MetS was significantly associated with higher PCa risk (OR = 1.52), all-cause mortality (HR = 1.53), and cancer-specific mortality (HR = 2.17). Through integrated multi-omics, weighted gene co-expression network analysis, and machine learning, we identified the orphan receptor GPRC5B as a critical hub gene downregulated in both conditions. Single-cell transcriptomic analysis further confirmed that GPRC5B is predominantly expressed in endothelial cells. Mechanistically, GPRC5B loss was found to hyperactivate p38 MAPK signaling through a specific dual mechanism: increasing phosphorylation of upstream MKK3/6 kinases while concurrently suppressing the negative feedback phosphatase DUSP1. This synergistic dysregulation drove enhanced endothelial proliferation, migration, and tube formation in vitro. In vivo, endothelial GPRC5B deficiency significantly accelerated tumor growth and neovascularization, phenotypes that were effectively reversed by the p38 inhibitor SB202190. Clinical specimens corroborated reduced GPRC5B expression and increased microvessel density in MetS-associated PCa. Collectively, our findings establish endothelial GPRC5B downregulation as a key molecular driver promoting pathological angiogenesis via the MKK3/6-DUSP1-p38 axis, suggesting that targeting this signaling cascade offers a promising therapeutic strategy for managing MetS-associated PCa aggression.