PGP and synovial sarcoma: Importantly, incubation of synovial sarcoma cells with DXR (0.1 μM, 72 h) provoked a significant upregulation of P-gp levels (55.2±21.0%), which is generally considered as the central molecular mechanism of MDR in response to DXR treatment and which was fully blocked by nilotinib (Fig. 8A).