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

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 mm3 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