TP53 and osteosarcoma: We had previously shown that the basic leucine zipper (bLZip) domain-containing transcription factor, Zhangfei/CREBZF/SMILE inhibits the growth and the unfolded protein response (UPR) in the D–17 canine osteosarcoma (OS) cell line [5] and that the effects of Zhangfei are mediated by stabilizing the tumour suppressor protein p53 [6].