Genistein Enhances TRAIL-Mediated Apoptosis Through the Inhibition of XIAP and DcR1 in Colon Carcinoma Cells Treated with 5-Fluorouracil

Objectives: Colorectal cancer is one of the most common cancers worldwide. However, surgical intervention and chemotherapy provide only limited benefits for the recovery and survival of patients. The anticarcinogenic effect of genistein has attracted attention because epidemiological studies have shown that soybean consumption is associated with a decrease in the incidence of cancer. There are limited studies on the effects of genistein in colorectal carcinoma cells. We aimed to investigate the cytotoxic, genotoxic, and apoptotic effects of genistein in SW480 and SW620 colon adenocarcinoma cells treated with 5-fluorouracil, the basis of chemotherapy, and the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) ligand, the mediator of apoptosis, both alone and in combination. Materials and Methods: Cytotoxicity and genotoxicity were determined by MTT and comet assays, respectively. The apoptotic effects were evaluated by reverse transcription-polymerase chain reaction assay, with the additional use of Annexin V FITC, mitochondrial membrane potential (MMP), caspase 3, 8, and 9 activity, and reactive oxygen species (ROS) assay kits. Results: According to our findings, genistein, 5-fluorouracil, and TRAIL had synergistic apoptotic effects because of DR5 upregulation, ROS production, and DNA damage, which were mediated by increased caspase-8, and -9 activity and decreased MMP. Conclusion: The applied combinations of these compounds may contribute to the resistance problem that may occur in treating colorectal cancer, with a decrease in DcR1 and XIAP genes.