The first FDA approved PARP inhibitor olaparib was selected for the examination of its effects on osteosarcoma growth and lung metastasis in two most commonly used orthotopic OS mouse models: immunodeficient NOD/SCID mice challenged with a human OS cell line 143B, and immunocompetent BALB/c mice challenged with a mouse OS cell line K7M2 (Fig. 1A). The gene discussed is PARP1; the disease is osteosarcoma.