SKP2 and neoplasm: Based on their biological functions, SCF E3 ligases have been further divided into three groups: oncogenic (SKP2), tumor suppressive (FBW7) and context-dependent (β-TRCP) E3-ubiquitin ligase, in which loss-of-function mutation/deletion of tumor suppressive F-box proteins, such as FBW7, have been shown to regulate tumorigenesis (Welcker and Clurman, 2008; Akhoondi et al., 2007).