ITPA and neoplasm: Our results extend this finding to 5-FU, 5-FC, 6-azauracil and 5-FOA (Fig. 1), and suggests that a wide range of noncanonical pyrimidine triphosphates may be targeted by Ham1p and its human homolog, ITPA. This raises the possibility that amplification and/or overexpression of ITPA may contribute to acquired resistance to 5-FU and other pyrimidine analogues in tumour cells.