title: Inhibition of MDR1 expression by retinol treatment increases sensitivity to etoposide (VP16) in human neoplasic cell line.
abstract: Multidrug resistance (MDR) is the major obstacle to cancer chemotherapy. MDR phenotype is mainly related to the over-expression of MDR1 gene, being responsible for tumor resistance to several chemotherapeutic drugs. It has been suggested that MDR1 expression is redox-regulated and we have recently described a pro-oxidative effect of retinol. Here we tested the therapeutic use of retinol as a modulator of MDR1 gene expression in tumor cell lines, and verified in situ the enhancement of anticancer drug efficacy. Two human colorectal adenocarcinoma cell lines (HT29, SW620) with different degrees of MDR1 expression were used. Cells were pre-treated with a sublethal dose of retinol and then challenged with the etoposide (VP16) drug. The drug GI50 was assessed by SRB method and levels of MDR1 expression were determined by semi-quantitative rtPCR. Retinol treatment caused a 40% decrease in MDR1 expression and increased VP16 toxicity. MDR1 expression and drug sensitivity were restored to control values when mannitol (a hydroxyl radical scavenger) was co-administrated. Our data point a role to the use of retinol as an adjuvant in the treatment of tumors with MDR phenotype.
authors.affiliation: Centro de Estudos em Estresse Oxidativo, Departamento de Bioquímica, ICBS/Universidade Federal do Rio Grande do Sul, Av. Ramiro Barcelos 2600 - anexo, Porto Alegre, RS 90035-003, Brazil. 00025267@ufrgs.br
authors.forename: Fábio
authors.initials: F
authors.lastname: Klamt
authors.forename: Daniel Thompsen
authors.initials: DT
authors.lastname: Passos
authors.forename: Mauro Antônio Alves
authors.initials: MA
authors.lastname: Castro
authors.forename: Daniel Pens
authors.initials: DP
authors.lastname: Gelain
authors.forename: Ivana
authors.initials: I
authors.lastname: Grivicich
authors.forename: José Cláudio Fonseca
authors.initials: JC
authors.lastname: Moreira
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000187:drug effects* / Q000378:metabolism; D000230:Adenocarcinoma / Q000188:drug therapy / Q000473:pathology; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000188:drug therapy / Q000473:pathology; D018432:Drug Resistance, Multiple / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D005047:Etoposide / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D019073:HT29 Cells; D006801:Humans; D016133:Polymerase Chain Reaction; D014801:Vitamin A / Q000494:pharmacology*
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000972:Antineoplastic Agents, Phytogenic; D014801:Vitamin A; D005047:Etoposide