Figure 5

Inhibition of PLK1 was the key factor of synergistic therapy-induced apoptosis and was achieved by the inhibition of protein synthesis.(A) Dasatinib inhibited PLK1 dose and time dependently. (B) The effects of combination treatment of dasatinib and SN38 on the protein expression of PLK1 and p-4EBP1 were analysed by western blotting. Both PLK1 and p-4EBP1 level were reduced. (C, D) Twenty-four hours after transfection with PLK1 expression plasmid or empty vector (PCMV6), HCC cells were treated with both 20 nM SN38 and 80 nM dasatinib for 48 h, and the inhibition of proliferation was observed by optical microscopy, while cleaved PARP and PLK1 were assessed by western blotting. Both cell death and c-PARP level were partially reversed. The reversed cell death was also confirmed by PI staining and flow cytometry. (E) HepG-2 cells were pretreated with CQ (10 μ M) or MG132 (2 μ M) for 2 h and then treated with both SN38 (20 nM) and dasatinib (80 nM) for 24 h, and the protein levels of PLK1 were measured by western blotting. (F) HepG2 cells were pretreated with both SN38 (20 nM) and dasatinib (80 nM) or not before exposing to CHX (10 μ M) for different times, and PLK1 protein levels were detected by western blotting.