PTPA and neoplasm: Currently, PP2A is defined as a putative tumor suppressor, mostly based on the loss-of-function analyses using inhibitors for the highly conserved A/C subunits, such as okadaic acid (C-subunit inhibitor), short interfering RNA (siRNA) against the A/C subunits, or viral oncoproteins displacing the B subunits (e.g., SV40 small-t)6,8,9.