title: UDP-glucuronosyltransferase 1A6 overexpression in breast cancer cells resistant to methotrexate.
abstract: Methotrexate is a chemotherapeutic agent used in breast cancer treatment, but the occurrence of resistance limits its therapeutic use. A microarrays analysis between sensitive and methotrexate resistant MCF7 and MDA-MB-468 breast cancer cells pointed out the UDP-glucuronosyltransferase 1A (UGT1A) family as a common deregulated node in both cell lines. This family of genes is involved in Phase II metabolism. UGT1A6 was the main isoform responsible for UGT1A family overexpression in these cells. Its overexpression was not due to gene amplification. Transfection of a vector encoding for UGT1A6 in sensitive cells counteracted the cytotoxicity caused by methotrexate. Methotrexate increased the transcriptional activity from a luciferase reporter driven by the UGT1A6 promoter and induced UGT1A6 mRNA and enzymatic activity. Promoter analysis suggested that UGT1A6 induction by methotrexate could be driven by the transcription factors ARNT (HIF-1) and AhR/ARNT. Cells incubated with anticancer drugs susceptible to glucuronidation, such as tamoxifen or irinotecan, together with methotrexate, showed a lesser degree of cytotoxicity, due to UGT1A6 induction. The pharmacological effect of this induction should be taken into account when combining methotrexate with other drugs that are glucuronidated.
authors.affiliation: Department of Biochemistry and Molecular Biology, School of Pharmacy, University of Barcelona, Av. Diagonal 643, E-08028 Barcelona, Spain. cdealmagro@ub.edu
authors.forename: M Cristina
authors.initials: MC
authors.lastname: de Almagro
authors.forename: Elisabet
authors.initials: E
authors.lastname: Selga
authors.forename: Rémi
authors.initials: R
authors.lastname: Thibaut
authors.forename: Cinta
authors.initials: C
authors.lastname: Porte
authors.forename: Véronique
authors.initials: V
authors.lastname: Noé
authors.forename: Carlos J
authors.initials: CJ
authors.lastname: Ciudad
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000188:drug therapy*; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D019008:Drug Resistance, Neoplasm; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D014453:Glucuronosyltransferase / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008727:Methotrexate / Q000008:administration & dosage / Q000494:pharmacology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013629:Tamoxifen / Q000008:administration & dosage / Q000494:pharmacology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D012333:RNA, Messenger; D014157:Transcription Factors; D013629:Tamoxifen; C110655:UDP-glucuronosyltransferase, UGT1A6; D014453:Glucuronosyltransferase; D008727:Methotrexate