PGP and breast cancer: Of these, decreasing in the intracellular accumulation of hydrophobic chemotherapeutics due to members of the ABC transporter superfamily constitute a major mechanisms of drug resistance, and P-gp, that is one of the ABC transporter family, is an important molecule causing multidrug resistance in various cancer cells [13, 14] The silencing o RPN2 decreased the glycosylation and membrane localization of P-gp, and downregulation of RPN2 efficiently induced apoptosis in docetaxel-resistant human breast cancer cells in the presence of docetaxel [8].