Figure 4

PLK1 is an important factor restricting antitumour effect of SN38 on HepG-2 cell line.(A) SN38 could downregulate PLK1 in both dose- and time-dependent manner. The downregulation was not thorough. (B) Results of qRT-PCR showed that SN38 reduced PLK1 mRNA level in HepG-2 cells. (C) PLK1 knockdown was achieved by transfection with different PLK1 siRNAs, and western blotting with specific antibodies to PLK1 and cleaved PARP were used to confirm the effects of PLK1 knockdown. (D) Different concentrations of PLK1 siRNAs were used to downregulate PLK1, and the protein levels of PLK1 and cleaved PARP were detected by western blotting. (E) Twenty-four hours after silence of PLK1 by siRNA, HepG-2 cells were treated with 20 nM SN38 for 24 h. PLK1 siRNA was able to enhance the uprising of c-PARP level induced by SN38 treatment. (F) Twenty-four hours after transfection with PLK1 expression plasmid or empty vector (PCMV6), HepG-2 cells were treated with 80 nM SN38 for 24 h. Overexpression of PLK1 by plasmid was able to reverse the arisen c-PARP level induced by SN38 in vector (PCMV6) group.