Antioxidants May Protect Cancer Cells from Apoptosis Signals and Enhance Cell Viability

Quercetin is one of the most abundant dietary flavonoids widely present in many fruits and vegetables. Previousin vitro studies has shown that quercetin acts as an antioxidant and anti-inflammatory agent and it has potentanticarcinogenic properties as an apoptosis inducer. In this study we examined apoptotic effects of quercetin onthe K562 erythroleukemia cell line. K562 cells were induced to undergo apoptosis by hydrogen peroxide. Cellviability and apoptosis level were assessed by annexin V and PI staining methods using flow cytometry. Viabilityof K562 cells was increased by low dose of quercetin (5-100 μM) for 3 hours. High doses of quercetin provedtoxic (100-500 μM, 24 hours) and resulted in decrease of K562 cell viability as expected (p<0.01). As to results,100 μM quercetin was defined as a protective dose. Also, K562 cell apoptosis due to hydrogen peroxide wasdecreased in a dose dependent manner. As indicated in previous studies, reduction of superoxides by free radicalscavengers like quercetin could be beneficial for prevention of cancer but consumption of such flavonoids duringcancer treatment may weaken effects of chemotherapeutics and radiotherapy. Especially cancer patients shouldbe carefully considered for traditional phytotherapy during cancer treatment, which can lead to controversialresults.