PTPRZ1 and osteosarcoma: However, in a later study using Ptprz1−/− 129SV/Ev Trp53-heterozygous mice, it was found that Ptprz1 gene deletion enhanced osteosarcoma development, characterized by enhanced tyrosine phosphorylation and cell proliferation, suggesting that PTPRZ1 acts as a tumor-suppressor for osteosarcoma [103].