PP2A activity is further regulated by several endogenous inhibitors (e.g., KIAA1524/CIP2A, SET), the expression of which is often increased in cancer cells [22, 23], and by cellular activators (e.g., PTPA), the expression of which is often decreased in tumors [24, 25] (Additional file 1: Fig. S1B). This evidence concerns the gene PTPA and cancer.