Challenging metastatic breast cancer with the natural defensin PvD₁

Metastatic breast cancer is a very serious life threatening condition that poses many challenges for the pharmaceutical development of effective chemotherapeutics. As the therapeutics targeted to the localized masses in breast improve, metastatic lesions in the brain slowly increase in their incidence compromising successful treatment outcomes overall. The blood-brain-barrier (BBB) is one important obstacle for the management of breast cancer brain metastases. New therapeutic approaches are in demand for overcoming the BBB's breaching by breast tumor cells. In this work we demonstrate the potential dual role of a natural antimicrobial plant defensin, PvD₁: it interferes with the formation of solid tumors in the breast and concomitantly controls adhesion of breast cancer cells to human brain endothelial cells. We have used a combination of techniques that probe PvD₁'s effect at the single cell level and reveal that this peptide can effectively damage breast tumor cells, leaving healthy breast and brain cells unaffected. Results suggest that PvD1 quickly internalizes in cancer cells but remains located in the membrane of normal cells with no significant damage to its structure and biomechanical properties. These interactions in turn modulate cell adhesiveness between tumor and BBB cells. PvD₁ is a potential template for the design of innovative pharmacological approaches for metastatic breast cancer treatment: the manipulation of the biomechanical properties of tumor cells that ultimately prevent their attachment to the BBB.