Mice with conditional double deletions of Trp53 and Rb1 in early limb bud mesenchymal cells induced through Prx1‐Cre displayed osteosarcoma and hibernoma, as well as rhabdomyosarcoma, and deletion of Trp53 alone could also cause osteosarcoma.7, 9. This evidence concerns the gene RB1 and osteosarcoma.