Effect of quercetin and chrysin and its association on viability and cell cycle progression in MDA-MB-231 and MCF-7 human breast cancer cells.

Pharmacological properties of flavonoids have been reported, with an anticancer role amongst them, however, its mechanisms are not fully elucidated. In this study, the activity of quercetin and chrysin towards MCF-7 and MDA-MB-231 breast cancer cells was investigated. Cellular viability was determined after treatment with the compounds in different concentrations for 24 h. Secondly, cells were treated with fixed concentration of chrysin and different concentrations of quercetin with preincubation for 1 h. Both compounds inhibited cellular proliferation in dose-dependent manner. The association showed improvement in their cytotoxicity, more expressively with preincubation of quercetin. Quercetin and chrysin association induced cell cycle arrest in sub-G0/G1 phase in MDA-MB-231 cells, modified the expression of caspases-3 and -8,-8, inducing late apoptosis cell death. Taken together, our results demonstrate that both flavonoids inhibited cells growth in a dose-dependent manner and the association of quercetin improved chrysin's toxic effect over the cell lines.

Pro-Oxidant Effect of Resveratrol on Human Breast Cancer MCF-7 Cells is Associated with CK2 Inhibition.

Casein kinase 2 (CK2) plays a critical role in the proliferation and apoptosis of cancer cells. Resveratrol is a bioactive compound with anticancer and anti-inflammatory effects. This study investigated the pro-oxidant cytotoxic effects of resveratrol in association with the inhibition of CK2 activity on human breast carcinoma cells MCF-7. We showed that resveratrol and TBB, an inhibitor of CK2, decreased cell viability in a concentration dependent manner with an IC50 value of 238 µM and 106 µM after 24 h, of treatment, respectively. Resveratrol and TBB decreased CK2 activity by 1.6 and 1.4-fold, respectively, and both significantly decreased mitochondrial membrane potential. However, only resveratrol increased reactive oxygen species (ROS) levels by 1.7-fold as opposed to TBB, which did not affect ROS levels. Indeed, incubating MCF-7 cells with the antioxidant polyethylene glycol-catalase (PEG-CAT) preserved cell viability from the cytotoxic effects of resveratrol, but not from TBB toxicity. This effect seemed to be related to PEG-CAT ability to prevent CK2 inhibition induced by resveratrol incubation. In conclusion, this study demonstrated that the cytotoxic effect of resveratrol on MCF-7 cells might be associated with its pro-oxidant action, which inhibited CK2 activity, affecting cell viability and mitochondrial function.