Figure 4.

Inhibition of TOP2A synergizes with regorafenib to suppress cell viability, promote apoptosis, and strengthen sensitivity of sorafenib-resistant HCC cells to regorafenib in vitro. (A-D) HepG2-SR and Huh7-SR as well as corresponding parental cells were exposed to different concentrations of doxorubicin (Dox) or/and regorafenib (Reg) for 48 h (A, B); or incubated for different periods in the presence or absence of regorafenib (7.5 μM) and doxorubicin (160 nM) (C, D). Cell viability (%) was compared with control. (E) Huh7-SR and HepG2-SR cells were incubated with 7.5 μM regorafenib or/and 160 nM doxorubicin for 48 h. The protein expression profile of cyclin D1 and cleaved caspase-3 was detected by Western blot. Density of each band was normalized to that of β-actin. (F) Migration of sorafenib-resistant HCC cells was examined by Wound healing assay (100 ×). (G) Transwell assays to examine synergistic effects of doxorubicin with regorafenib on migration and invasion (100 ×). (H) Synergistic effects of doxorubicin and regorafenib on 3D invasion (40 ×). *P < 0.05; **P < 0.01; indicating a significant difference from untreated cells. #P < 0.05; ##P < 0.01 compared with regorafenib treatment. †P < 0.05; ††P < 0.01 compared with doxorubicin treated cells.