NAIP and melanoma: XIAP is a ubiquitously expressed protein and a member of the inhibitor of apoptosis (IAP) family, which also includes cellular IAP1 (cIAP1), cellular IAP2 (cIAP2), melanoma IAP (ML-IAP), neuronal apoptosis inhibitory protein (NAIP), survivin, Appolon and IAP-like protein 2 (ILP2) [4].