XIAP and cancer: To verify the specific structural basis of XIAP for regulation of cancer cell migration, we transfected different HA-tagged XIAP cDNA constructs, including full-length (HA-XIAP), RING domain-deletion (HA-XIAPΔRING), total BIR deletion (HA-XIAPΔBIR), and a point mutation H467A, which results in loss of E3 ubiquitin ligase activity, into XIAP−/− cells respectively, and the stable transfectants were identified (Fig. 3B).