Analysis of the data obtained from TCGA and GTEx revealed that the expression level of RRM2 in the tumor tissues of ACC, BLCA, BRCA, CESC, CHOL, COAD, DLBC, ESCA, GBM, HNSC, KIRP, KIRC, LAML, LGG, LUAD, LIHC, LUSC, OV, PAAD, PRAD, READ, STAD, SKCM, THCA, TGCT, UCEC, THYM, UCS (P < 0.0001), SARC, and PCPG (P < 0.05) was higher than that of the control tissues (Figure 1B). This evidence concerns the gene RRM2 and bladder transitional cell carcinoma.