TP53 and osteosarcoma: When compared to heterozygous (p53+/−) or null (p53−/−), mutant p53 (p53+/Mut) mice developed osteosarcomas and carcinomas that metastasized at a higher frequency, increased tumor proliferation, and presented a cooperative action with activated ras in cell transformation (Lang et al., 2004; Olive et al., 2004).