title: Overexpression of P-glycoprotein but not its mRNA in multidrug resistant cells selected with hydroxyrubicin.
abstract: Previous studies have revealed that cultured cells treated with lipophilic natural products containing aromatic rings and basic amino group usually yielded multidrug resistant (MDR) variants. These MDR cells overexpress P-glycoprotein (P-gp), most often due to gene amplification or transcriptional activation of mdr/P-gp genes. Doxorubicin (Dox) is an anthracycline that belongs to this group of compounds. To explore the possible resistance mechanism(s) to anthracyclines that do not involve P-gp, we use a Dox analog, hydroxyrubicin (HyR) or WP159, which contains a C3' hydroxy group in replacement of the amino group in the sugar moiety of Dox thereby reducing basicity and eliminating positive charge in the parental compound to establish HyR-resistant cell lines. These resistant cells displayed the MDR phenotype and overexpressed P-gp as analyzed by Western blot analyses and immunohistochemical staining using two different anti-P-gp antibodies. Strikingly, the levels of P-gp mRNA in the majority of these MDR cells remained comparable to those in the drug-sensitive counterparts by slot blot hybridization. These results implicate that the basic center of the selecting agent is a critical determinant for generating diverse MDR variants, and that HyR may have a posttranscriptional effect on P-gp biosynthesis. This is the first report suggesting that cultured cells exposed to a particular selecting agent may give rise to particular subtype of MDR variants.
authors.affiliation: Department of Molecular Pathology, University of Texas M.D. Anderson Cancer Center, Houston 77030.
authors.forename: J Y
authors.initials: JY
authors.lastname: Zhao
authors.forename: N
authors.initials: N
authors.lastname: Savaraj
authors.forename: R
authors.initials: R
authors.lastname: Song
authors.forename: W
authors.initials: W
authors.lastname: Priebe
authors.forename: M T
authors.initials: MT
authors.lastname: Kuo
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D016466:CHO Cells / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D002999:Clone Cells; D006224:Cricetinae; D018076:DNA, Complementary / Q000032:analysis / Q000235:genetics; D004317:Doxorubicin / Q000494:pharmacology; D018432:Drug Resistance, Multiple / Q000235:genetics; D015251:Epirubicin / Q000031:analogs & derivatives* / Q000494:pharmacology; D015870:Gene Expression; D006367:HeLa Cells; D006801:Humans; D007150:Immunohistochemistry; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D010641:Phenotype; D012313:RNA / Q000032:analysis / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018076:DNA, Complementary; D012333:RNA, Messenger; D015251:Epirubicin; D012313:RNA; C042907:3'-deamino-3'-hydroxydoxorubicin; D004317:Doxorubicin