As illustrated in the heatmaps, pyrimidine metabolic rate–limiting enzymes CAD, CTPS, CTPS2, DHODH, DTYMK, NT5C3, RRM1, RRM2, TK2, TYMS, UCK2, and UCKL1 were upregulated in lung cancer tissues (Fig. 2). This evidence concerns the gene DHODH and lung carcinoma.