PPAT and melanoma: In addition, it has been demonstrated that c-Myc plays a critical role in the maintenance of expression of PRPS2, PPAT, TrifGART, PAICS and IMPDH2 in melanoma cells (Mannava et al., 2008) and of PPAT, IMPDH1, IMPDH2 but not PAICS in a human lymphoma model cell line (Liu et al., 2008).