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

Abstract

Quercetin is one of the most abundant dietary flavonoids widely present in many fruits and vegetables. Previous in vitro studies has shown that quercetin acts as an antioxidant and anti-inflammatory agent and it has potent anticarcinogenic properties as an apoptosis inducer. In this study we examined apoptotic effects of quercetin on the K562 erythroleukemia cell line. K562 cells were induced to undergo apoptosis by hydrogen peroxide. Cell viability and apoptosis level were assessed by annexin V and PI staining methods using flow cytometry. Viability of K562 cells was increased by low dose of quercetin (5-100 μM) for 3 hours. High doses of quercetin proved toxic (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 was decreased in a dose dependent manner. As indicated in previous studies, reduction of superoxides by free radical scavengers like quercetin could be beneficial for prevention of cancer but consumption of such flavonoids during cancer treatment may weaken effects of chemotherapeutics and radiotherapy. Especially cancer patients should be carefully considered for traditional phytotherapy during cancer treatment, which can lead to controversial results.

Photodynamic apoptosis and antioxidant activities of Brassica napus extracts in U937 and SK-HEP-1 cells

“…BNCE, which most effectively suppressed cell proliferation, had the weakest antioxidant effect. Our results correspond to several reports that antioxidants increased cancer cell proliferation due to eliminating radical and ROS induced by apoptosis [27,28]. In addition, these results were due to complex interactions among the various compounds contained in B. napus.…”

Influence of Trolox and Quercetin Combinations on Human Ovarian Cancer Cell Line A2780 and Human Breast Cancer Cell Line T47D-KBluc

“…It has also been found that its anticancer activity against leukaemia cells can be enhanced by certain water-soluble antioxidants (Chen et al, 2004). In erythroleukemia cells, concentrations above 100 µM are toxic, while those below this limit increase viability (Akan and Garip, 2013). A similar effect, but with a threshold level of 40 µM has been observed in ovarian cancer cells, if Quercetin was combined with anti-neoplastic agents such as Cisplatin, Taxol, Pirarubicin and 5-Fluorouracil (Maciejczyk and Surowiak, 2013;Li et al, 2014).…”

Luteolin-loaded Phytosomes Sensitize Human Breast Carcinoma MDA-MB 231 Cells to Doxorubicin by Suppressing Nrf2 Mediated Signalling

“…Therefore, identification of potent and unique Nrf2 inhibitor for sensitizes a broad spectrum of cancer cells urgently needed (Zhu et al, 2013) Flavonoids act as a free radical scavenger, immune system modulator, and antioxidant agent. These characteristics with low toxicity, making them good option for cancer chemoperventive agent (Lopez-Lazaro, 2009;Xu et al, 2009;Akan and Garip, 2013).…”