PTEN and osteosarcoma: However, RPTPζ deficiency promoted osteosarcoma development in Trp53-heterozygous mice.47 Loss of PTEN has also been implicated in bone malignancies, including osteosarcoma.259 PTEN not only inhibits the proliferation, migration, and invasion of osteosarcoma cells but also facilitates their apoptosis.259 Thus, PTEN is an important tumor suppressor in skeletal tissues.