ABSTRACT
BACKGROUND: The integrin-binding protein osteopontin is strongly associated with tumour development, yet is an abundant dietary component as a constituent of human and bovine milk. Therefore, we tested the effect of orally administered osteopontin (o-OPN) on the development of subcutaneous tumours in mice. METHODS: Bovine milk osteopontin was administered in drinking water to tumour-bearing immune-competent mice. Tumour growth, proliferation, necrosis, apoptosis and blood vessel size and number were measured. Expression of the α9 integrin was determined. RESULTS: o-OPN suppressed tumour growth, increased the extent of necrosis, and induced formation of abnormally large blood vessels. Anti-OPN reactivity detected in the plasma of OPN-null mice fed OPN suggested that tumour-blocking peptides were absorbed during digestion, but the o-OPN effect was likely distinct from that of an RGD peptide. Expression of the α9 integrin was detected on both tumour cells and blood vessels. Potential active peptides from the α9 binding site of OPN were identified by mass spectrometry following in vitro digestion, and injection of these peptides suppressed tumour growth. CONCLUSIONS: These results suggest that peptides derived from o-OPN are absorbed and interfere with tumour growth and normal vessel development. o-OPN-derived peptides that target the α9 integrin are likely involved.
Subject(s)
Blood Vessels/drug effects , Neoplasms, Experimental/blood supply , Neoplasms, Experimental/drug therapy , Osteopontin/administration & dosage , Administration, Oral , Animals , Binding Sites , Blood Vessels/metabolism , Cattle , Cell Growth Processes/drug effects , Female , Integrin alpha Chains/metabolism , Mice , Mice, Inbred C57BL , Neoplasms, Experimental/metabolism , Neovascularization, Pathologic/pathology , Oligopeptides/metabolism , Osteopontin/blood , Peptides/blood , Peptides/metabolism , Protein BindingABSTRACT
In this study we evaluated the effect of chitosan nanoparticles on the acid tolerance response (ATR) of adhered Streptococcus mutans. An ATR was induced by exposing S. mutans to pH 5.5 for 2 h and confirmed by exposing the acid-adapted cells to pH 3.5 for 30 min, with the majority of cells appearing viable according to the LIVE/DEAD® technique. However, when chitosan nanoparticles were present during the exposure to pH 5.5, no ATR occurred as most cells appeared dead after the pH 3.5 shock. We conclude that the chitosan nanoparticles tested had the ability to hinder ATR induction in adhered S. mutans.
