title: Upregulation of drug transporter expression by osteopontin in prostate cancer cells.
abstract: Multidrug resistance is a major cause of chemotherapy failure. Recent studies indicate that drug resistance can be rapidly induced by some soluble factors, such as cytokines, chemokines, growth factors, and cell adhesion factors in the tumor microenvironment. Osteopontin (OPN), an extracellular matrix protein, has a functional arginine-glycine-aspartic acid (RGD) domain for binding to integrin. Here we found OPN expression to be upregulated by hypoxic condition in PC-3 prostate tumor cells. OPN increased the mRNA and protein expression of p-glycoprotein (P-gp), a subfamily of ATP-binding cassette transporter in a concentration- and time-dependent manner. The increase in P-gp transporter by OPN was mediated by binding to αvβ3 integrin. Daunomycin (DUN), a chemotherapeutic agent with autofluorescence, was used to evaluate the pump activity, and OPN increased the drug pumping-out activity. OPN inhibited DUN-induced cell death, which was antagonized by αvβ3 monoclonal antibody. Long-term treatment with DUN further enhanced the expression of OPN. Knockdown of endogenous OPN potentiated the DUN-induced apoptosis of PC-3 cells. Furthermore, knockdown of OPN enhanced cell death caused by other drugs, including paclitaxel, doxorubicin, actinomycin-D, and rapamycin, which are also P-gp substrates. The animal studies also showed that OPN knockdown enhanced the cytotoxic action of DUN. These results indicate that OPN is a potential therapeutic target for cancer therapy to reduce drug resistance in sensitive tumors.
authors: Department of Pharmacology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors: I-Shan
authors: IS
authors: Hsieh
authors: Wei-Hsun
authors: WH
authors: Huang
authors: Houng-Chi
authors: HC
authors: Liou
authors: Woei-Jer
authors: WJ
authors: Chuang
authors: Rong-Sen
authors: RS
authors: Yang
authors: Wen-Mei
authors: WM
authors: Fu
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D016923:Cell Death / Q000187:drug effects / Q000235:genetics; D015687:Cell Hypoxia / Q000502:physiology; D045744:Cell Line, Tumor; D003630:Daunorubicin / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D006801:Humans; D039302:Integrin alphaVbeta3 / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D053495:Osteopontin / Q000096:biosynthesis* / Q000235:genetics* / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism*; D015854:Up-Regulation; D023041:Xenograft Model Antitumor Assays
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D039302:Integrin alphaVbeta3; D053495:Osteopontin; D003630:Daunorubicin