ALDH1A1 and urothelial carcinoma: In this study, we successfully isolated urothelial carcinoma CSCs/CICs using the UC cell line UM-UC3 based on the ALDH1 activity assay and identified the glutamate receptor, ionotropic, kainate 2 (GRIK2) gene as a gene involved in the invasion ability of ALDH1 high activity cells.