The RT4/JAK-Stat Pathway Firefly luciferase Reporter stable cell line, a well-studied human bladder cancer cell line derived from a transitional cell papilloma, is widely employed to investigate bladder tumor biology, urothelial differentiation, and cancer progression. This cell line expresses markers of urothelial differentiation, such as CK20 and uroplakin, and retains wild-type p53. It is ideal for mechanistic studies of tumor suppression and exhibits low tumorigenicity in vivo, serving as a model for early-stage disease. It is frequently used as a control in contrast to high-grade invasive bladder cancer lines.