Lung cancer continues to be the deadliest cancer worldwide. A new strategy of combining chemotherapeutics with naturally occurring anticancer compounds, such as lactoferrin, might improve the efficacy and toxicity of current chemotherapy. The aim of this study was to evaluate the effect of recombinant human lactoferrin (rhLf) in combination with etoposide on anticancer activity in human lung adenocarcinoma cells. In addition, we examined the impact of rhLf on etoposide-induced cytotoxicity of human endothelial cells. We found that treatment of A549 cells with a combination of etoposide and rhLf resulted in significantly greater inhibition of cancer cell growth as compared to etoposide alone. The combination repressed cancer cell growth by cell cycle arrest in the G2/M phase and induction of apoptosis. In contrast to cancer cells, rhLf did not affect endothelial cell viability. Importantly, rhLf significantly diminished the etoposide-induced cytotoxicity of endothelial cells. Analysis of the type of drug interaction based on combination index value showed that rhLf synergized with etoposide to induce anticancer activity. The calculated dose reduction index indicated that the combination treatment reduced a 10-fold of etoposide dose to achieve the same anticancer effect. Our data demonstrate that rhLf enhanced the anticancer activity of etoposide and diminished etoposide-induced cytotoxic effect in endothelial cells.
Keywords: combination strategy; etoposide; lung cancer; recombinant human lactoferrin; synergistic effect.