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.