METTL3 is the major writer of N6-Methyladenosine (m⁶A) and has been associated with controversial roles in cancer. This is best illustrated in urothelial carcinoma of the bladder (UCB), where METTL3 was described to have both oncogenic and tumor-suppressive functions. Here, we reinvestigated the role of METTL3 in UCB. METTL3 knockout reduced the oncogenic phenotype and m⁶A levels of UCB cell lines. However, complete depletion of METTL3/m⁶A was not achieved due to selection of cells …