Physiological concentrations of phytosterols enhance the apoptotic effects of 5-fluorouracil in colon cancer cells

Abstract Combining natural products as co-adjuvants in 5-fluorouracil (5-FU) chemotherapy might enhance the effectiveness of 5-FU by avoiding a high dosage and/or reducing treatment times. We explored the anticancer efficacy of the phytosterols (PS) at concentrations achievable in the human colon, as well as their potential as sensitizing agents of human colon cancer cells (Caco-2 and HT-29) to 5-FU treatment. Cells proliferation, combination index, cell cycle, apoptosis, caspases activation, ROS production, and ΔΨm were determined. Co-treatment (PS+5-FU) had an antiproliferative additive effect, and moreover, in general a significantly improved efficacy was observed on cell cycle arrest at S phase, apoptosis induction and increase in caspases activation compared to 5-FU alone, while no significant effects were observed on ROS levels and ΔΨm. Our results suggest, for the first time, the ability of PS to sensitize colon cancer cells to 5-FU chemotherapy and warrant further in vivo studies to confirm our preclinical findings.