title: Genetic determinants of methotrexate toxicity in rheumatoid arthritis patients: a study of polymorphisms affecting methotrexate transport and folate metabolism.
abstract: OBJECTIVE
  Methotrexate (MTX) is a disease-modifying antirheumatic drug used in the treatment of rheumatoid arthritis (RA). Genetic polymorphisms of reduced folate carrier (RFC1 A80G), P-glycoprotein (MDR1 G2677T>A/C and C3435T), 5,10-methylenetetrahydrofolate reductase (MTHFR C677T and A1298C), thymidylate synthase (TS 2R-->3R), methionine synthase (MS A2756G) and methionine synthase reductase (MTRR A66G) modify MTX transport and metabolic effects and may influence the treatment response.
  
  
  METHODS
  A genotyping approach was used to determine the studied polymorphisms in 213 RA patients.
  
  
  RESULTS
  We observed that 56 (26.3%) patients discontinued MTX treatment due to poor response and/or toxicity. RFC1 A80G and MDR1 C3435T polymorphisms increased the risk for overall MTX toxicity (P = 0.039, OR = 3.574, 95% CI = 1.065-11.993 and P = 0.032, OR = 7.801, 95% CI = 1.194-50.960 respectively), while MTHFR A1298C polymorphism had a protective effect on overall MTX toxicity (P = 0.027, OR = 0.170, 95% CI = 0.035-0.820).
  
  
  CONCLUSIONS
  Our results suggest that genetic polymorphisms in the folate metabolic pathway and MTX transporters modify the toxicity but not the efficacy of MTX treatment.
authors.affiliation: Institute of Biochemistry, Faculty of Medicine, University of Ljubljana, Vrazov trg 2, 1000 Ljubljana, Slovenia. petra.bohanec@mf.uni-lj.si
authors.forename: Petra
authors.initials: P
authors.lastname: Bohanec Grabar
authors.forename: Dusan
authors.initials: D
authors.lastname: Logar
authors.forename: Boris
authors.initials: B
authors.lastname: Lestan
authors.forename: Vita
authors.initials: V
authors.lastname: Dolzan
mesh_terms: D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase / Q000235:genetics; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000188:drug therapy*; D001692:Biological Transport; D005260:Female; D005287:Ferredoxin-NADP Reductase / Q000235:genetics; D005492:Folic Acid / Q000378:metabolism*; D006801:Humans; D008297:Male; D026901:Membrane Transport Proteins / Q000235:genetics; D008727:Methotrexate / Q000378:metabolism* / Q000633:toxicity*; D042965:Methylenetetrahydrofolate Reductase (NADPH2) / Q000235:genetics; D008875:Middle Aged; D011110:Polymorphism, Genetic; D013940:Thymidylate Synthase / Q000235:genetics
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D026901:Membrane Transport Proteins; C120043:SLC19A2 protein, human; D005492:Folic Acid; C111241:methionine synthase reductase; D005287:Ferredoxin-NADP Reductase; D042965:Methylenetetrahydrofolate Reductase (NADPH2); D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase; D013940:Thymidylate Synthase; D008727:Methotrexate