NUDT1 and cancer: A difference in the efficiency of plasmid maintenance was also observed when the coding sequence for the human cancer target Mth1 (Gad et al. 2014) was expressed from pET28a-Mth1 (Tn903.1) compared to pET15b-Mth1 (Tn3.1) for 20 h (Fig. 1E).