TP53 and osteosarcoma: p53 loss is strongly associated with osteosarcomagenesis (Pourebrahim et al., 2017; Overholtzer et al., 2003; Chen et al., 2014), and these data indicate previously unreported Pdx1-CreTg activity in an osteosarcoma precursor cell, revealed due to the robust consequences of homozygous p53 loss.