Biochanin A enhances the radiotoxicity in colon tumor cells in vitro

Herbs and other plant-based compounds have increasingly been recognized as useful for the prevention and treatment of cancer. There exists enormous scope for screening and evaluation of herbal/plant products to develop an effective radiosensitizer and radioprotector that is relevant for cancer therapy. Anticancer agents that can effectively trigger the process of cell death in tumor cells need to be developed. This study describes the effect of the flavonoid biochanin A (BCA), administered alone or in combination with gamma radiation, on the growth of radioresistant human colon cancer HT29 cells in vitro. Proliferation studies were carried out using MTT assay with increasing concentration of BCA (1-100 µM) followed by gamma irradiation at a dose of 2 Gy. Induced reactive oxygen species, mitochondrial membrane potential, lipid peroxidation, and caspase-3 activation were measured by fluorescence assays and the magnitude of induced apoptosis in cells was evaluated by flow cytometry. Cellular DNA damage was determined by comet assay. Combined treatment caused a significant decrease in cell proliferation, a substantial increase in the generation of reactive oxygen species, enhanced lipid peroxidation, and increased mitochondrial membrane potential in treated HT29 cells compared with controls. Significantly enhanced apoptosis and DNA damage were found with a combination of drug and radiation treatments. Furthermore, it was found that combined treatment yielded an additive increase of caspase-3 in these cells. Our findings indicate that BCA acts as a remarkable pro-oxidant, significantly enhancing the radiotoxicity of colon cancer cells in vitro.