title: Long-chain polyunsaturated fatty acids promote paclitaxel cytotoxicity via inhibition of the MDR1 gene in the human colon cancer Caco-2 cell line.
abstract: OBJECTIVE
  Accumulating evidence in both humans and animal models indicates that dietary intake of long-chain polyunsaturated fatty acids (PUFAs) can improve response to chemotherapy. The intent of this study was to determine the mechanisms by which PUFAs affect the response to anticancer chemotherapy.
  
  
  METHODS
  Human colorectal cancer cell line Caco-2 was used as a model system in this study. Caco-2 cells were treated with different concentrations of three PUFAs: eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and arachidonic acid (AA). Real-time polymerase chain reaction was used to determine mdr1 gene (codes for P-glycoprotein [P-gp]) expression. Western blotting and calcein-acetoxymethylester efflux assay were used for P-gp expression and functional evaluation, respectively. Furthermore, apoptosis assay was conducted by adding PUFAs with paclitaxel to confirm the synergetic effect. Finally, gene expression of nuclear receptors CAR and PXR were estimated to evaluate the possible mechanisms.
  
  
  RESULTS
  Both classes of PUFAs, omega-3 (ω-3) and omega-6 (ω-6), can cause a modest but very reproducible reduction of gene expression, protein production, and pump activity of MDR1. Incubation of cells with PUFAs greatly enhanced the cytotoxicity of the anticancer drug paclitaxel, manifested mainly through enhanced paclitaxel-induced apoptosis. Furthermore, PUFAs increased the messenger RNA (mRNA) levels of the nuclear receptors CAR and PXR, thus implicating these two transcription factors as cellular targets of PUFAs in cells but not directly affecting MDR1 regulation.
  
  
  CONCLUSIONS
  Our results suggest that inhibition of the multidrug resistance MDR1/P-gp is one mechanism through which dietary polyunsaturated fatty acids exert a synergetic effect on the response of tumor cells to anticancer drugs.
authors.affiliation: Department of Biosystems Engineering, Clemson University, South Carolian, USA.
authors.forename: Cheng-Yi
authors.initials: CY
authors.lastname: Kuan
authors.forename: Terry H
authors.initials: TH
authors.lastname: Walker
authors.forename: Pengju G
authors.initials: PG
authors.lastname: Luo
authors.forename: Chin-Fu
authors.initials: CF
authors.lastname: Chen
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism*; D000970:Antineoplastic Agents / Q000008:administration & dosage*; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D018938:Caco-2 Cells; D004281:Docosahexaenoic Acids; D018432:Drug Resistance, Multiple / Q000187:drug effects; D015118:Eicosapentaenoic Acid; D043371:Fatty Acids, Omega-6 / Q000008:administration & dosage; D005231:Fatty Acids, Unsaturated / Q000008:administration & dosage*; D005395:Fish Oils / Q000008:administration & dosage*; D005786:Gene Expression Regulation; D006801:Humans; D017239:Paclitaxel / Q000378:metabolism*; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D012333:RNA, Messenger; D060888:Real-Time Polymerase Chain Reaction
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000970:Antineoplastic Agents; D043371:Fatty Acids, Omega-6; D005231:Fatty Acids, Unsaturated; D005395:Fish Oils; D012333:RNA, Messenger; D004281:Docosahexaenoic Acids; D012313:RNA; D015118:Eicosapentaenoic Acid; D017239:Paclitaxel