Abstract: This study was undertaken to explore the anti-tumor activity of purple sweet potato juice and its apoptosis-inducing mechanism in HepG2 cells. The inhibitory effect of purple sweet potato juice at various concentrations on cell proliferation was examined by Alamar Blue assay. Cell apoptosis was determined by Hoechst 33258 fluorescence staining, scanning electron microscopy (SEM) and agarose gel electrophoresis. Reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blotting analysis were used to detect the expression of apoptosis-related factors in HepG2 cells treated with purple sweet potato juice at different concentrations for 24 h and 48 h, respectively. The results showed that the cell proliferation was inhibited by purple sweet potato juice in a dose-dependent manner. Cell shrinkage and apoptotic bodies after treatment for 48 h in HepG2 cells were observed. Typical DNA ladders in apoptotic cells were also observed. In addition, purple sweet potato juice up-regulated Fas, FADD, Caspase-3, -8 and p53 mRNA and protein expression levels. Moreover, active fragments of Caspase-3, -8 and -9 showed a significant increase, especially Caspase-3. Therefore, purple sweet potato juice can inhibit the proliferation of cancer cells and induce the apoptosis of HepG2 cells through extrinsic apoptotic pathway and p53 may also play an important role in this pathway.

Key words:  purple sweet potato, HepG2, anti-tumor activity, apoptosis