XIAP and cancer: In our previous study, we reported that XIAP RING domain and its E3 ligase activity are required for XIAP's upregulation of cyclin d1 transcription and cancer cell growth [15], whereas XIAP RING domain and not its E3 ligase plays an important role in XIAP binding with RhoGDIα and inhibits RhoGDIα SUMOylation [16, 17].