Disclosed herein are acridine, anthracene, xanthene, dibenzosuberone compounds of formula I, wherein X is selected from CH2, O, CO and C=NORA Y is O, S, NORA or NRA, and U and V are each O=S=O and the other substituents are as defined within the specification, processes for their preparation, compositions comprising said compounds and uses thereof in preventing, treating or ameliorating cancer or tumor metastasis in a mammal.