RB1 and osteosarcoma: Treatment using either PARP inhibitor olaparib (Fig. 9e–g) or talazoparib (Fig. 9h–j) revealed a significantly higher dose sensitivity of the RB1-defective PDX (PDX-OS19-C2) assessed using clonogenic survival compared to either of the RB1-normal lines (PDX-OS25-C1 and PDX-OS16-C2), with IC50 values in the submicromolar range for olaparib (Fig. 9g) and the low nanomolar range for talazoparib (Fig. 9j), in line with values obtained for the RB1-defective group of established osteosarcoma cell lines analysed earlier.