title: Overexpression of multidrug resistance-associated protein (MRP) increases resistance to natural product drugs.
abstract: Amplification of the gene encoding multidrug resistance-associated protein (MRP) and overexpression of its cognate mRNA have been detected in multidrug-resistant cell lines derived from several different tumor types. To establish whether or not the increase in MRP is responsible for drug resistance in these cell lines, we have transfected HeLa cells with MRP expression vectors. The transfectants display an increase in resistance to doxorubicin that is proportional to the levels of a M(r) 190,000, integral membrane protein recognized by anti-MRP antibodies. The transfectants are also resistant to vincristine and VP-16 but not to cisplatin. The results demonstrate that MRP overexpression confers a multidrug resistance phenotype similar to that formerly associated exclusively with elevated levels of P-glycoprotein.
authors.affiliation: Cancer Research Laboratories, Queen's University, Kingston, Ontario, Canada.
authors.forename: C E
authors.initials: CE
authors.lastname: Grant
authors.forename: G
authors.initials: G
authors.lastname: Valdimarsson
authors.forename: D R
authors.initials: DR
authors.lastname: Hipfner
authors.forename: K C
authors.initials: KC
authors.lastname: Almquist
authors.forename: S P
authors.initials: SP
authors.lastname: Cole
authors.forename: R G
authors.initials: RG
authors.lastname: Deeley
mesh_terms: D018288:Carcinoma, Small Cell / Q000235:genetics / Q000378:metabolism; D004317:Doxorubicin / Q000494:pharmacology; D004351:Drug Resistance / Q000235:genetics / Q000502:physiology; D005784:Gene Amplification / Q000235:genetics*; D006367:HeLa Cells; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism; D009363:Neoplasm Proteins / Q000737:chemistry / Q000235:genetics*; D010641:Phenotype; D012333:RNA, Messenger / Q000032:analysis; D012334:RNA, Neoplasm / Q000032:analysis; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D009363:Neoplasm Proteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D004317:Doxorubicin