As shown in our knockdown efficiencies of TK1, TYMS and DTYMK at protein level with shRNAs, we demonstrated that knockdown either one of the 3 RLEs in dTTP biosynthesis pathway decreased the protein expression and the cellular concentration of dTTP in poorly-differentiated HCC cells Sk-Hep1 and SNU449 (Figure 5D and 5E). Here, TK1 is linked to hepatocellular carcinoma.