PTPA and neoplasm: Because inhibition of PP2A activity or loss of PP2A expression results in E-cadherin endocytosis [37, 38], PP2A is considered to be involved in the establishment and maintenance of E-cadherin-mediated cell-cell adhesion as well as in a wide variety of biological processes such as tumor suppression [39–41], formation of tight junctions [42], and integrin-mediated cell-substratum adhesion [43–48].