A mutation in the drug transporter gene ABCC2 associated with impaired methotrexate elimination

Abstract

Human multidrug resistance protein 2 (MRP2, encoded by ABCC2) is involved in active efflux of anionic drugs such as methotrexate. MRP2 is expressed on the luminal side of hepatocytes and renal proximal tubular cells, indicating an important role in drug elimination. We postulated that loss-of-function mutations in ABCC2, which are involved in the Dubin-Johnson syndrome, may be associated with impaired methotrexate elimination and an increased risk of toxicity. We studied the biological phenotype and ABCC2 coding sequence in a patient receiving a high-dose methotrexate infusion for large B-cell lymphoma and who had an unusual pharmacokinetic profile, mainly characterized by a three-fold reduction in the methotrexate elimination rate. This resulted in severe methotrexate over-dosing and reversible nephrotoxicity. An inversion of the urinary coproporphyrin isomer I/III ratio (a specific biological marker of the Dubin-Johnson syndrome) was observed in this patient. Genetic analysis of ABCC2 identified a heterozygous mutation replacing a highly conserved arginine by glycine in the cytoplasmic part of the second membrane-spanning domain (position 412 of MRP2), a region associated with substrate affinity. This genetic variant was not found in a control population. Functional analysis in transiently transfected Chinese hamster ovary cells revealed a loss of transport activity of the G412 MRP2 mutant protein. An ABCC2 mutation altering MRP2-mediated methotrexate transport and resulting in impaired drug elimination and subsequent renal toxicity was identified. Candidates for methotrexate therapy should be considered for MRP2 functional testing.

Functionally Overlapping Roles of Abcg2 (Bcrp1) and Abcc2 (Mrp2) in the Elimination of Methotrexate and Its Main Toxic Metabolite 7-Hydroxymethotrexate In vivo

“…When one is absent, the other can (at least partly) compensate for its loss. These findings provide direct explanations for previously found correlations between ABCC2 and ABCG2 polymorphisms/mutations and MTX pharmacokinetics or toxicity in patients (38,40,43,48), and show the potential value of Abcc2;Abcg2 -/-mice for studying the pharmacokinetics of endogenous and exogenous compounds in vivo.…”

“…Whether the effects of Abcc2 and/or Abcg2 found here are also valid for higher doses or longer infusion times remains to be elucidated. Interestingly, associations between ABCC2 and ABCG2 mutations/polymorphisms, and MTX pharmacokinetics or toxicities in patients were found previously after highdose (1-5 g/m 2 ) MTX infusions (40,43,45), suggesting that our results are also relevant for higher doses and longer infusions.…”

“…Interestingly, renal failure after high-dose MTX treatment in a patient with an ABCC2 mutation has been reported (43). In contrast, because Abcg2 seems to mediate -/-, and Abcc2;Abcg2 -/-mice.…”

Dose-Dependent Disposition of Methotrexate in Abcc2 and Abcc3 Gene Knockout Murine Models

“…Our observation of increased hepatic formation of 7OH-MTX and urinary excretion of MTX in Abcc2(Ϫ/Ϫ) mice suggests that patients with low ABCC2 activity may have increased risk of MTX-induced hepatic and renal toxicity. In fact, there are several clinical studies that have identified polymorphisms in ABCC2 in different patient populations that led to increased MTX toxicity, particularly hepatotoxicity and nephrotoxicity (Hulot et al, 2005;Ranganathan et al, 2008).…”

Pharmacogenomics Dictate Pharmacokinetics: Polymorphisms in Drug-Metabolizing Enzymes and Drug-Transporters

“…P-gp genes have a wide range of substrates including anti cancer agents, antiarrhythmics and immunosuppressive drugs (Drescher S, 2002;Hulot JS, 2005;Elens L, 2007;Thervet E, 2008). P-gp expression is widely distributed, liver, the intestines both small and large, and the blood brain barrier (BBB) endothelial cells.…”