miR-21 targets many genes that can be involved in the formation and development of cancer, including TP53 [207], PTEN, TIMP3 (tissue inhibitor of metalloproteinase 3) (both inhibitors of the matrix metalloproteinases), BCL-2 (regulator of apoptosis) [208], and many others; its overexpression is linked to loss of function of TP53, which is most commonly observed in high-grade MIBC [209]. This evidence concerns the gene TP53 and cancer.