Quercetin attenuates the proliferation of arsenic-related lung cancer cells via a caspase-dependent DNA damage signaling

Exposure to arsenic (As) mainly through contaminated drinking water enhances the lung tumor progression, invasion, and metastasis. The carcinogenic effect of As is due to the generation of Reactive Oxygen Species (ROS) and DNA damage, and interference with DNA repair machinery. Herein, we investigated the potential therapeutic function of quercetin on As-treated lung Cancer cells. Quercetin is a natural product with antioxidative, anti-inflammatory, and antiproliferative properties. We showed that quercetin induced cell death in the As-exposed lung Cancer cells in a dose-dependent manner. Quercetin was able to significantly inhibit the proliferation of the As-treated cells over a period of 5 weeks. In addition, quercetin induced ROS-mediated DNA double-strand breaks in the As-treated lung Cancer cells. We also showed that ROS generation induced by quercetin activated Caspase-3 to a sufficient level to induce DNA damage but insufficient to induce death in As-treated lung Cancer cells. Moreover, transient activation of caspase-2 was detected in quercetin- and As-cotreated cells. The flow cytometry-based cell cycle analysis showed that the antiproliferative function of quercetin was mediated by S-phase cell cycle arrest, which was associated with upregulation of the Ataxia Telangiectasia-mutated (ATM), but not ATM and RAD3-related. In conclusion, quercetin synergized the As-driven ROS generation and DNA damage, and induced the S-phase arrest, thus inhibiting the proliferation of As-exposed lung Cancer cells. This data suggested that quercetin is an alternative reagent to chemo-drugs to prevent the growth of As-exposed lung Cancer cells.