Bovine lactoferrin and bovine lactoferricin are internalized by colon cancer cells and exhibit elevated apoptosis

Lactoferrin (Lf) is an iron‐binding glycoprotein and is present at high concentrations in milk from several species. Bovine lactoferricin (bLfcin) is a peptide fragment produced by acid‐pepsin hydrolysis of bovine lactoferrin (bLf). BLfcin consists of amino acid residues 17–42 proximal to the N‐terminal of bLf and a cysteine–cysteine disulfide bond between residues 19 and 36 creating a cyclic form. Both bLf and BLfcin have been shown to have anti‐tumor activities. Colorectal cancer is the 2nd most common cause of cancer deaths in developed countries. Therefore, we hypothesized that both bLf and bLfcin are internalized by colon cancer cells (HT‐29) and stimulate apoptosis of these cells. Confocal microscopy showed that bLfcin in linear and cyclic forms and bLf were internalized by HT‐29 cells. ApoTox‐Glo Triplex Assay (Promega) results show that bLfcin and bLf significantly stimulated apoptosis of colon cancer cells in a concentration‐dependent pattern and maximal effects were obtained at 12‐h of treatment. No significant differences were found between the two forms of bLfcin, but the effect on apoptosis triggered by bLfcin was stronger than that by bLf. In summary, both bLfcin and bLf are internalized by colon cancer cells and stimulate apoptosis of these cells, suggesting potential clinical applications for bLf and bLfcin in colon cancer.