Additionally, osteosarcoma has been also observed in osteoblast‐committed cells when Trp53 and Rb1 are deleted through the use of Col1a1‐Cre and OCN‐Cre transgenic lines,9 suggesting that mesenchymal cells and osteogenic lineage cells may be critical for osteosarcoma formation. This evidence concerns the gene COL1A1 and osteosarcoma.