Apo‐lactoferrin regulates transcription of the TGFβ1 gene and may thus stimulate intestinal differentiation

Lactoferrin (Lf), an iron‐binding protein in breast milk, has been demonstrated to be partly resistant to proteolysis in the gastrointestinal tract during early infancy. Lf is capable of binding to DNA and three Lf specific DNA binding sites have been described. Bioinformatics analysis indicates that the TGFβ1 gene is a potential target gene for Lf. TGFβ1 has been shown to induce a range of differentiation responses in intestinal epithelial cells. Therefore, we hypothesized that Lf regulates transcription of the TGFβ1 gene and thus stimulates intestinal differentiation. Alkaline phophatase assays indicated that only apo‐Lf but not holo‐Lf significantly stimulated differentiation of intestinal epithelial cells (Caco‐2). The promoter from a ~3100 bp 5β‐flanking region of the human TGFβ1 gene was cloned into a promoter‐less luciferase reporter vector and transiently transfected into Caco‐2 cells. Transfection assays showed that the TGFβ1 promoter was functional and promoter activity significantly increased upon apo‐Lf treatments. In addition, deletion analysis revealed six Lf response elements in the TGFβ1 promoter. In agreement with effects on differentiation, only apo‐Lf stimulated transcription of the TGFβ1 gene according to real time PCR results. In summary, apo‐Lf regulates transcription of the TGFβ1 gene and may thus stimulate differentiation of intestinal epithelial cells.