The upregulation of a number of rate-limiting enzymes in pyrimidine biosynthesis such as deoxythymidylate kinase (DTYMK), thymidylate synthase (TYMS), and thymidine kinase 1 (TK1) in HCC is associated with cancer stemness and poor prognosis [3, 4, 74]. Here, TK1 is linked to hepatocellular carcinoma.