X-linked inhibitor of apoptosis (XIAP)-associated factor 1 (XAF1) is a zinc finger protein that antagonizes the anti-apoptotic activity of XIAP. XAF1 is widely expressed in normal tissues, with highest levels in the heart and ovary, but is mostly reduced in cancer lines. Expression of XAF1 can be induced by interferons via Stat transcriptional activity. A number of studies have shown that XAF1 can function as a tumor suppressor protein and low levels of XAF1 transcript may enhance cancer cell-survival through the relative increase in XIAP anti-apoptotic function. Research studies suggest that expression of XAF1 may be a prognostic biomarker for some cancers.
