Among the other six Cullins, only CUL4A was slightly overexpressed (~1.4–1.7-fold induction) in osteosarcoma cells, but not the other five Cullins, including CUL1, CUL2, CUL3, CUL5 and CUL7 (Fig. 1A). Here, CUL5 is linked to osteosarcoma.