RB1 and osteosarcoma: A significantly greater sensitivity of RB1-depleted CAL72 was also observed using niraparib (Fig. 4e–g, Supplementary Table 2, and Supplementary Fig. 4b), although with a smaller differential in median IC50 between groups (6–7-fold), consistent with observations comparing naturally RB1-defective and RB1-normal osteosarcoma lines.