Ellagitannin-enriched fraction from Fragaria vesca leaves induces G2/M cell cycle arrest in the human hepatocellular carcinoma cell line HepG2
The hepatocellular carcinoma has a poor prognostic and a lower survivor rate. The inefficacy of the conventional therapies highlights the importance of discovering new compounds with anti-tumor effects. Previous studies performed in our laboratory demonstrated that a hydroalcoholic extract of Fragaria vesca L. leaves affects cellular proteolitic pathways through the reduction of proteasome activity and modulation of autophagic machinery, mechanisms that are therapeutic targets in cancer treatment. Thus, the aim of this study was to evaluate the anti-cancer properties of an ellagitannin-enriched fraction (EEF) from Fragaria vesca leaves (characterized by HPLC/PDA/ESI-MSn), in human hepatocellular carcinoma cells (HepG2). To evaluate half-maximal inhibitory concentration (IC-50) for cell viability, the cells were treated for 24h and then assayed by resazurin. IC-50 (113 µg/mL) and lower concentrations were used to evaluate the effect of the fraction on cell cycle. As evidenced by propidium iodide addition, after 24h of treatment, EEF induced cell cycle arrest at G2/M checkpoint, and this effect was not reverted after 48h. Cell cycle analysis also suggests that apoptotic cell death is not responsible for the cytotoxic effects. Moreover, by western blot we observed an increased in the ratio of expression of LC3II/LC3-I. LC3 is a marker of autophagossomes, and the conversion of LC3-I to LC3-II is an evidence of an accumulation of these structures, thus suggesting a strong modulation of the autophagic process, by increasing autophagy or through inhibition of the autophagic flux. In conclusion, EEF promotes cell cycle arrest at G2/M checkpoint and modulates autophagy, processes that are targets for therapeutic strategies in oncological diseases.
Acknowledgements: FCT and POFC/FEDER for financial support. Research supported by FCT PhD fellowship SFRH/BD/72918/2010, projects PTDC/SAU-FCF/105429/2008 and PEst-OE/SAU/UI0177/2011.