Fig. 3

MKP-4 inhibits cell proliferation and cancer stem cell (CSC) traits through ERK1/2 pathway. a MKP-4 reduced the colony formation of HepG2 or SK-Hep1 cells via the interaction with ERK1/2. For colony formation assay, MKP-4 knockdown, MKP-4 overexpression or pre-incubation with 10 μM PD98059 by 24 h cells were seeded into each well of six-well-plate colonies and stained with crystal violet after 2 weeks. b CCK-8 assay showed that overexpression of MKP-4 or pre-incubation with 10 μM PD98059 by 24 h inhibited cell proliferation in HepG2 and SK-Hep1 cells while MKP-4 depletion promoted cell proliferation. The data are mean ± SEM of three independent experiments. (*P < 0.05, compared with the control group). c MKP-4 inhibited DNA synthesis via the interaction with ERK1/2 by using the Click-iT Edu Alexa Fluor Imaging Kit in HepG2 and SK-Hep1 cells. The bar chart demonstrated the DNA synthesis of liver tumor cells. The data were mean ± SEM of three independent experiments (*P < 0.05, compared with the control group). d The interaction of MKP-4 and ERK1/2 plays an essential role in sphere formation. Downregulation of MKP-4 promoted sphere formation ability while overexpression of MKP-4 or pre-incubation with 10 μM PD98059 by 24 h inhibited the ability. The bar chart showed the number of sphere formation per 500 cells. The data were mean ± SEM of three independent experiments (*P < 0.05, compared with control group)