Apoptosis inhibitor 5 (API5) is an antiapoptotic factor which may have a role in protein assembly. API5 expression is often upregulated in tumor cells, particularly in metastatic cells. It is a critical determinant of E2F1-induced apoptosis, acting downstream of E2F to suppress E2F-dependent apoptosis without generally blocking E2F-dependent transcription. Alternate Names: AAC 11, AAC11, Antiapoptosis clone 11 protein, API 5, API5, API5 like 1, API5L1, Cell migration inducing gene 8 protein, Fibroblast growth factor 2 interacting factor 2, FIF, MIG 8, MIG8, Migration inducing protein MIG8, Protein XAGL.