PTGS2 and cancer: In other MIBC xenograft and patient-derived xenograft models, our previous study and others reported chemotherapy induction of the COX-2/PGE2 axis in promoting chemoresistance, via inducing compensatory proliferation of residual cancer stem cells25, and enhancing stemness via promoter methylation of let-7 and upregulation of the self-renewal gene SOX252.