XIAP and cancer: In wound healing assay, we found that reconstitutive expression of full length HA-XIAP and HA-XIAP ΔBIR, both of which have RING domain, into XIAP−/− HCT116 cells restored cancer cell motility, whereas introduction of HA-XIAP ΔRING or H467A mutant, which abolished its E3 ligase function, did not show obvious restoration, demonstrating that E3 ligase activity of XIAP RING domain played a role in XIAP regulation of cancer cell motility.