PGP and breast cancer: Specifically, we showed that MPs were spontaneously shed from P-gp and MRP-1 overexpressed MDR leukaemic/breast cancer cells and contain significant amounts of functional resistance proteins (P-gp and MRP1), together with numerous other proteins and nucleic acids that can establish a functional MDR phenotype, increased metastatic capacity and alter the biomechanical properties of recipient cells [47, 55, 56, 59, 60–63].