PTPA and colorectal cancer: On the other hand, previous studies have shown or implicated COX-2 (Williams et al., 1997) and other cellular components as targets of Aspirin’s anti-tumor effects; and protein phosphatase 2A (PP2A) was suggested to mediate the effect of Aspirin on the Wnt/β-catenin pathway in colorectal cancer cells (Bos et al., 2006).