Abstract
Bovine lactoferrin (bLF) is a glycosylated protein with purported beneficial properties. The aim of this work was to determine the role of bLF glycosylation in the adhesion, internalization, and growth inhibition of cancer cells. The viability of cervix (HeLa) and colon (Caco-2) cancer cells (MTT assay and epifluorescence microscopy) was inhibited by bLF, while deglycosylated bLF (bLFdeg) had no effect. Adhesion to cell surfaces was quantified by immunofluorescence assay and showed that bLF was able to bind more efficiently to both cell lines than bLFdeg. Microscopic observations indicated that bLF glycosylation favored bLF binding to epithelial cells and that it was endocytosed through caveolin-1-mediated internalization. In addition, the mechanism of action of bLF on cancer cell proliferation was investigated by determining the amount of phosphorylated intermediates of signaling pathways such as epidermal growth factor receptor (EGFR), extracellular signal-regulated kinase (ERK) and protein kinase B (known as Akt). Chemoluminescence immunoassay of phosphorylated intermediates showed that bLF inhibited Akt phosphorylation, consistent with its growth inhibiting activity. This assay also indicated that the bLF receptor/signaling pathways may be different in the two cell lines, Caco-2 and HeLa. This work confirmed the effect of glycosylated bLF in inhibiting cancer cell growth and that glycosylation is required for optimal surface adhesion, internalization, and inhibition of the ERK/Akt pathway of cell proliferation through glycosylated cell surface receptors.