Cell Line-Based Human Bladder Organoids with Bladder-like Self-Organization—A New Standardized Approach in Bladder Cancer Research

Three-dimensional tumor models have gained significant importance in bladder cancer (BCa) research. Organoids consisting of different cell types better mimic solid tumors in terms of 3D architecture, proliferation, cell–cell interaction and drug responses. We developed four organoids from human BCa cell lines with fibroblasts and smooth muscle cells of the bladder, aiming to find models for BCa research. The organoids were characterized in terms of cytokeratins, vimentin, α-actin and KI67 by immunoreactivity. Further, we studied ligand-dependent activation of the Wnt/β-catenin pathway and investigated the responses to anti-tumor therapies. The organoids mimicked the structure of an inverse bladder wall, with outside urothelial cells and a core of supportive cells. The cytokeratin staining patterns and proliferation rate were in conjunction with the origins of the BCa cells. RT-112 even showed stratification of the epithelium. Treatment with Wnt10B led to increased β-catenin (active) levels in high-grade organoids, but not in low-grade BCa cells. Doxorubicin treatment resulted in clearly reduced viability (10–30% vs. untreated). In contrast, the effectivity of radiotherapy depended on the proliferation status of BCa cells. In conclusion, cell-line-based organoids can form bladder-like structures and reproduce in vivo features such as urothelial differentiation and stratification. Thus, they can be useful tools for functional studies in BCa and anti-cancer drug development.