For immunofluorescence, antigen retrieval was performed with citrate buffer (pH 6) before primary antibody incubation at 4 C overnight. Sections were stained with primary antibodies against Upk (Ab78196, 1:200; Abcam), Krt5 (Ab52635, 1:100; Abcam), and RFP (Ab62341, 1:50; Abcam), and secondary antibodies Alexa Fluore488 and Alexa Fluore594 (10 mg/mL; Thermo Fisher Scientific, Paisley, UK) for 1 hour at room temperature. Slides were mounted with Mowiol 488 (Sigma-Aldrich, Dorset, UK) containing DAPI (Vectashield Mounting Medium with DAPI, H-1200; Vector Laboratories, Burlingame, CA). Images were taken on a Leica confocal laser microscope (TCS SP8; Leica Microsystems, Wetzler, Germany).
Histopathologic evaluation of the bladder tissues was performed in a blind fashion by one pathologist at Kyoto Histopathology Study Group, Inc., and by two trained urologists (N.M. and T.K.), based on the 2004 World Health Organization Classification of Bladder Tumors.