PGP and breast cancer: P-gp is a classical ABC transporter that is overexpressed in many human solid and hematologic cancers [9], and is a confirmed marker of chemo-resistance and decreased survival in leukemia [10], lymphoma [9, 11], osteosarcoma [12], small-cell lung cancer [13] and breast cancer [14], Therefore the development of P-gp inhibitors is very important for chemotherapy.