Juglone induces proliferation inhibition and apoptosis of cervical cancer cells via promoting c-Myc ubiquitination

Abstract

To observe the expression of c-Myc protein in cervical cancer HeLa cells and explore the effect of juglone on the proliferation and apoptosis of HeLa cells by affecting c-Myc ubiquitination. HeLa cells treated with different concentrations (0, 10, 20, or 50 μmol/L) of juglone or with 20 μmol/L juglone for different time lengths were examined for expression of c-Myc protein with Western blotting. The half-life of c-Myc protein was determined using cycloheximide (CHX) and c-Myc protein degradation was detected using coimmunoprecipitation. We also assessed the effects of 20 μmol/L juglone combined with 0, 1.0 or 2.0 μmol/L MG132 (a proteasome inhibitor) on c-Myc expression. The effects of 20 μmol/L juglone on the proliferation and apoptosis of HeLa cells with RNA interference-mediated knockdown of c-Myc were evaluated with MTT assay and flow cytometry. Treatment with juglone significantly lowered c-Myc protein expression in HeLa cells in a concentration-and time-dependent manner (P < 0.05). Juglone obviously shortened the half-life of c-Myc protein, and the addition of MG132 significantly up-regulated the expression level of c-Myc protein (P < 0.05). Juglone treatment also promoted ubiquitination of c-Myc protein in HeLa cells. Compared with the cells transfected with a negative control construct, the cells transfected with si-c-Myc showed significantly decreased proliferation inhibition and a lowered cell rate with early apoptosis after juglone treatment (P < 0.05). Juglone inhibits proliferation and promotes apoptosis of HeLa cells by affecting the ubiquitination of c-Myc protein.