ARID1A and urinary bladder cancer: Finding truncations to be the most common mutation, we generated loss‐ and gain‐of‐function models to conduct RNA‐Seq, interactome analyses, Omni‐ATAC‐Seq, and functional studies to characterize ARID1A‐affected pathways potentially suitable for the treatment of ARID1A‐deficient bladder cancers.