Screening for cytotoxic activity of ovotransferrin and its enzyme hydrolysates

The aim of this study was to investigate the cytotoxic activities of ovotransferrin (OTF) from egg white and its enzyme hydrolysates (OTH). The OTF was hydrolyzed at 45°C for 3 h using neutrase, alcalase, acid (0.03 N HCl, pH 2.5), protamex, protex 6L, flavorzyme, α-chymotrypsin, trypsin, and collupulin MG. The enzyme to substrate ratio was 1:25 (wt/wt) in all experiments. Using the 3-(4,5-dimethylthizol-2-yl)-2,5-diphenylatetetrazolium bromide (MTT) assay, the cytotoxicity of OTF and OTH was evaluated in human cancer cell lines of various tissue origins, including the lung (A549 and SK-MES-1), stomach (AGS), breast (MCF-7), larynx (Hep-2), cervix (HeLa), and liver (HepG2). The growth of all cancer cell lines was inhibited by both OTF and OTH in a dose-dependent manner. In particular, OTF displayed relatively high cytotoxicity (≤60% inhibition effects) at 40 mg/mL. At lower concentrations (≤5 mg/mL), however, OTF- and OTH-mediated cytotoxic effects were not significant in all cancer cell lines tested. The MCF-7 cells were the least sensitive to all treatments among all cancer cell lines tested. The OTH-trypsin and OTH-neutrase showed a potent cytotoxicity (over 90% cytotoxicity) to HeLa cells at the 10 mg/mL level. The OTH-trypsin, OTH-protamex, OTH-protex 6L, and OTH-collupulin MG caused 95, 96, 86, and 87% growth inhibition, respectively, in AGS cells. These results indicated there are possibilities that OTF and OTH can be used as natural growth inhibitors of human cancer cell lines.