PTPA and cancer: In our previous article in Adv Cancer Res (Fujiki and Suganuma 1993), we considered how the okadaic acid pathway is related to human cancer, and pointed out two key points: effects of the okadaic acid class of compounds can be mimicked by those of cytokines such as tumor necrosis factor-α (TNF-α) and interleukin-1 (IL-1) (Guy et al. 1992), and the inhibitory effect of small-t antigen on dephosphorylation by PP2A could explain its role in transformation (Scheidtmann et al. 1991).