Guaraná a Caffeine-Rich Food Increases Oxaliplatin Sensitivity of Colorectal HT-29 Cells by Apoptosis Pathway Modulation

We investigated the in vitro effects of guarana and its main metabolites (caffeine, theobromine and catechin) on cytotoxicity and cell proliferation on colorectal cancer (CRC) line HT-29 cells and on oxaliplatin sensitivity. The cells were exposed to different concentrations of guarana extract with and without oxaliplatin. The concentrations of bioactive molecules were also estimated considering their potential proportion on guarana hydro-alcoholic extract. Apoptosis effect was analyzed by annexin V quantification using flow cytometry, while apoptosis pathway gene modulation (p53, Bax/Bcl-2 genes ratio, caspases 8 and 3) was determined by qRT-PCR analysis. Cells exposed to guarana at a concentration of 100 μg/mL presented a similar cytotoxic effect as HT-29 cells treated with oxaliplatin and did not affect the sensitivity of the drug. Guarana presented cell anti-proliferative effect and increased anti-proliferative oxaliplatin sensitivity at all concentrations tested here. Guarana was able to induce apoptosis and up-regulate the p53 and Bax/Bcl-2 genes.