EFFECTS OF LACTOFERRIN AND ITS PEPTIDES ON PROLIFERATION OF RAT INTESTINAL EPITHELIAL-CELL LINE, IEC-18, IN THE PRESENCE OF EPIDERMAL GROWTH-FACTOR

The cell growth-stimulating activity of lactoferrin (LF) in combination with epidermal growth factor (EGF),vas evaluated by using a rat intestinal epithelial cell line, IEC-18. LF was found to be more effective than EGF for inducing an increase in cell numbers when cultured for over 6 days using a medium containing 0.2% fetal calf serum (FCS), although the H-3-thymidine incorporation-stimulating activity of EGF was more potent than that of LF, A synergistic effect of LF and EGF was observed in both cell proliferation and DNA synthesis assays, The increase in cell numbers when stimulated with LF plus EGF corresponded to about 5 times that of the control, Tron was not required for manifestation of these effects of LF, On the other hand, iron-saturated transferrin (TF) had cell-growth-stimulating activity, but iron-free TF did not, either in the presence or absence of EGF, These results indicate that LF induces cell proliferation by a mechanism distinct from that of TF, A pepsin-generated hydrolysate of LF (LFH) had an activity similar to that of undigested LF, and a peptide with cell-growth-stimulating activity from bovine LFH was isolated by monitoring its effects in combination with EGF on DNA synthesis in IEC-18 cells, Sequence analysis indicated that the peptide has the structure Ala-Glu-Ile-Tyr-Gly-Thr-Lys-Glu-Ser-Pro-Gln-Thr-His-Tyr-Tyr, corresponding to residues 79-93 of bovine LF.