Based on other cancer organoid cultures, the basal medium (BM) used to culture UTUC organoids contained the Wnt agonist R‐spondin1, the transforming growth factor beta (TGF‐β) inhibitor Noggin, the reactive oxygen species (ROS) scavenger N‐acetyl‐L‐cysteine, nicotinamide, the activin receptor‐like kinase (ALK) inhibitor A83‐01, the p38 mitogen‐activated protein (MAP) kinase inhibitor SB202190, B‐27 supplement, fibroblast growth factor (FGF) 10, epidermal growth factor (EGF), and the Rho‐associated, coiled‐coil‐containing protein factor (ROCK) inhibitor Y‐27632. The gene discussed is EGF; the disease is cancer.