Osteosarcoma is the most common tumour of bone. Recent success in targeting immune checkpoint blockers such as Programmed death-1 (PD-1) in genomically complex tumours suggests that osteosarcomas may be amenable to such strategies. We will characterise the role of the PD-1 pathway in osteosarcoma development and growth. Using preclinical mouse models we will investigate the biology of the PD-1 pathway and study its potential as a therapeutic target in advanced and resectable osteosarcoma.