As a member of the F-box protein family, S phase kinase-associated protein 2 (Skp2) and Skp1, Cull, and Rbxl constitute E3 ligase, which is involved in the process of catalyzing the transformation of cells from G1 to S phase.170 The overexpression of Skp2 is extremely common in human cancer cells, and Skp2 overexpression promotes cancer invasion and metastasis.171 The interaction between Skp2 and Skp1 is the precondition of the completeness of Skp2–SCF complex and the key to exerting its E3 ligase activity. Here, KITLG is linked to cancer.