Oleuropein inhibits tumour growth and metastases dissemination in ovariectomised nude mice with MCF-7 human breast tumour xenografts

Abstract Oleuropein (OL), the precursor of olive oil secoiridoids, has been shown to possess a strong in vitro anti-cancer activity. The in vivo effect of OL on a BC animal model consisting of MCF-7 cells xenograft growth in ovariectomised nude mice was investigated. After subcutaneous implantation of 17-β E2 pellet, BC xenografts were established by injection of MCF-7 cells into the mouse mammary fat pads. Animals, divided into two groups, were fed a basal diet (BD) and an OL enriched diet (OLD, 125 mg OL/kg of diet). Animals in the BD group lost weight more consistent than those of the OLD group while the MCF-7 xenograft growth was faster in the BD group compared to the OLD group. Tumour volume reached about 1300 mm 3 28 and 35 days after MCF-7 cells injection in the BD and OLD groups, respectively. At these times the animals were sacrificed for the evaluation of pulmonary metastases. OL prevented both peripulmonary and parenchyma lung metastases in a highly significant manner. These data demonstrate for the first time a strong in vivo chemopreventive activity of OL on BC.