In addition, considering that overexpression of human MTH1 did not rescue cells from the cell death induced by small-molecule MTH1 inhibitors (Fig. 6a,b) and knockdown of MTH1 did not suppress cancer cell growth (Fig. 6c–f), the cytotoxic effects of MTH1 inhibitors are probably attributable to their effects on off-target molecules rather than MTH1 inhibition. This evidence concerns the gene NUDT1 and cancer.