Moreover, the i.p. administrations of other potent inhibitors of PP1 and PP2A, such as microcystin-LR, and nodularin, into mice induced tumor promotion in rat liver initiated with diethylnitrosamine (DEN) (Nishiwaki-Matsushima et al. 1992; Ohta et al. 1994). Here, PTPA is linked to neoplasm.