DCK and leukemia: Since the conversion of 5hmdC to 5hmdU for genomic incorporation depends on the expression of Dck, Dctd, Cda, and Dnph1 (Fugger et al. 2021), we examined their expression in these cells, and the results suggested that the high expression of Dck and Dctd in AML1-ETO9a cells correlated well with the inhibitory effect of 5hmdC on the colony formation of these leukemia cells (Fig. 2E).