**4. Inhibitor of apoptosis protein (IAP) family as therapeutic target**

In the apoptotic pathway, the balance between pro and anti-apoptotic proteins is tightly regulated, so an imbalance directed to the anti-apoptotic regulation involves the apparition of survival advantages onto the initiating cancerous cells. In this way, the role of the IAPs family proteins is important. This family was first identified in baculovirus and the main characteristic is the presence of a baculovirus IAP repeat (BIR) domain, that mediates interactions with a number of proteins, including caspases and also other structural domains such as a RING or caspase activation recruitment domain (CARD) [122] (Figure 6).

In the IAP family we can find proteins involved in the inhibition of apoptosis through inhibition of caspases or modulation of the nuclear factor kB (NF-kB) signalling pathways. This family includes eight members in mammals (BIRC1– BIRC8), also known as neuronal apoptosis inhibitory protein (NAIP), cellular IAP1 (cIAP1) and IAP2 (cIAP2), Xchromosome linked IAP (XIAP), survivin, Apollon (BRUCE), livin (ML-IAP) and ILP2 [123] (Figure 6).
