Transepithelial transport of lunasin and derived peptides: Inhibitory effects on the gastrointestinal cancer cells viability

Lunasin is a soybean peptide with demonstrated chemopreventive properties. Upon its oral intake, studies dealing with the effect of the digestive process on lunasin's properties are crucial. The present study describes, for the first time, the behavior of lunasin and fragments derived from its digestion in the Caco-2 cell monolayer. The sequences SKWQHQQDSC and KIQGRGDDDDDDDDD showed a notable resistance against the epithelial brush-border peptidases, although some fragments were generated as cellular hydrolysis products. Lunasin and RKQLQGVN were absorbed intact across the intestinal epithelium. The tight junction disruptor cytochalasin D increased their transport, suggesting that the paracellular passive diffusion was the main mechanism involved. The study on the cancer cells viability showed that lunasin and SKWQHQQDSC exerted the highest effects on colorectal cancer HT-29 cells. The stability assay suggested that the cell line type was determinant in the behavior of lunasin added to the culture medium, and therefore in the anti-proliferative activity of released fragments.