TP53 and sarcoma: It is important to note that the p53515A mice used in the current study constitutively expressed the arginine to histidine substitution at amino acid 172 of p53. As previously reported [27], mice harboring the homozygous constitutively expressed mutant p53515A/515A allele developed tumors with an incidence, latency and spectrum (e.g., lymphomas and sarcomas) similar to that of homozygous p53 knockout mice [32], [33].