XIAP associated factor-1, also known as XAF1, is a human gene. X-linked inhibitor of apoptosis (XIAP;MIM 300079) is a potent member of the IAP family. All members of this family possess baculoviral IAP (BIR) repeats, cysteine-rich domains of approximately 80aa that bind and inhibit caspases.1 XAF1 antagonizes the anticaspase activity of XIAP and may be important in mediating apoptosis resistance in cancer cells.2 And alteration in XAF1 and XIAP RNA expression levels may lead to increased apoptotic resistance and proliferation due to unregulated XIAP function in cancer cells.