In support of this, PTEN is commonly down regulated, mutated, or deleted in many canine and human osteosarcomas (Levine et al., 2002; MacEwen et al., 2004) and is associated with elevated AKT activation, suggesting that PI3K/AKT may play a causative role in osteosarcoma formation. The gene discussed is PTEN; the disease is osteosarcoma.