A blood-urine regulatory axis: Tumor-derived factors reprogram urine-derived stem cells via CXCL2/CXCR2/ERK signaling to drive bladder cancer stemness.

The malignant progression of bladder cancer is closely linked to the tumor microenvironment, yet the role of urine-derived stem cells (USCs) remains poorly understood. USCs were isolated from healthy individuals and bladder cancer patients, followed by multi-omic and functional characterization. The bladder cancer cell line T24 was used for in vitro co-culture and in vivo co-injection assays. Sustained exposure to tumor-derived factors (TNF-α, IL-6, and TGF-β) reprogrammed normal USCs (N-USCs) into tumor-associated USCs (T-USCs). This transition was marked by E-cadherin downregulation, vimentin upregulation, cell cycle arrest, and reduced adhesion, facilitating detachment and shedding of USCs into urine. Consequently, urine from tumor-bearing conditions showed increased USC counts and elevated CXCL2 levels. USC-derived CXCL2 activated the CXCR2 receptor on bladder cancer cells, triggering the ERK/β-catenin axis. This significantly upregulated stemness markers (CD44, ALDH1A1), promoting malignant progression. In a co-injection model, T-USCs and bladder cancer cells formed an organized stromal sheath that facilitated tumor invasion. In vivo, USCs drove tumor growth and microenvironment remodeling, effects suppressed by targeting the CXCL2/CXCR2/ERK axis. We propose a model in which hematogenous tumor factors induce urinary USC reprogramming, potentially establishing a CXCL2-enriched niche that fuels malignancy. These findings suggest a biologically plausible "tumor associated USCs-CXCL2-bladder cancer" circuit, providing insights into a putative blood-urine interactive regulatory axis and revealing a potential therapeutic target.