Targeting redox balance and autophagy by grape pomace extract: a critical point to decide cancer cell fate

In the last decades, polyphenols have received particular attention for their potential therapeutic benefits. This study explores the anticancer properties of a hydro alcoholic extract (HE) from Sicilian white grape pomace, which is rich in phenolic compounds (gallic acid, catechin, and epicatechin) as identified by the UPLC-MS characterization. HE effects were tested on two cancer models: colon (HCT116) and breast (MDA MB231) cancer cells. Cytotoxic tests showed that colon cancer cells were more sensitive to HE compared to breast tumor cells after 48 h. The triggering of cell death in HCT116 cells was demonstrated by the appearance of subG0-G1 peak in cell cycle analysis, and the activation of caspase3/PARP1 apoptotic pathway. MDA MB231 cells did not undergo apoptosis and only showed G0-G1 phase arrest and increase in p21 expression. Being these events possibly related to the induction of oxidative stress, the role of ROS and antioxidant systems was investigated. HE induced an early increase in HE induced an early increase in ROS levels, which diminished in HCT116 after 24 h, as a consequence of the upregulation of antioxidant proteins Nrf-2, SOD-2, and HO-1. Differently, in MDA MB231 cells, ROS levels were maintained high and antioxidant systems were less expressed. Western blot and fluorescence analyses showed the involvement of autophagy as evidenced by the increase in p62 and LC3II levels and the appearance of autophagic vacuoles in both cell lines. However, the autophagic flux seemed to be impaired in MDA MB231 cells. Antioxidant N-acetylcysteine pre-treatment decreased the expression of autophagic markers, thus indicating the relationship between ROS and autophagy. The autophagic response had a protective role, indeed the autophagy inhibitor bafilomycin A1 increased the effect of HE in breast cancer cells. In conclusion, HE is able to perturb the complex relationship between redox balance and autophagy in cancer cells, thus deciding cancer cell fate. expressed. Western blot and fluorescence analyses showed the involvement of autophagy as evidenced by the increase in p62 and LC3II levels and the appearance of autophagic vacuoles in both cell lines. However, the autophagic flux seemed to be impaired in MDA MB231 cells. Antioxidant N-acetylcysteine pre-treatment decreased the expression of autophagic markers, thus indicating the relationship between ROS and autophagy. The autophagic response had a protective role, indeed the autophagy inhibitor bafilomycin A1 increased the effect of HE in breast cancer cells. In conclusion, HE is able to perturb the complex relationship between redox balance and autophagy in cancer cells, thus deciding cancer cell fate.