The present invention provides a method of inhibiting protein phosphatase 2A (PP2A) in a human subject in need thereof comprising administering to the subject an amount of from 0.1 mg/m2 to 5 mg/m2 of a compound having the structureor a salt, zwitterion, or ester thereof, so as to thereby inhibit protein phosphatase 2A (PP2A) in the subject.
