Purpose: ABCC2 (MRP2) and ABCG2 (BCRP) transport various endogenous and exogenous compounds, including many anticancer drugs, into bile, feces, and urine. We investigated the possibly overlapping roles of Abcg2 and Abcc2 in the elimination of the anticancer drug methotrexate (MTX) and its toxic metabolite 7-hydroxymethotrexate (7OH-MTX). Experimental Design: We generated and characterized Abcc2;Abcg2 -/-mice, and used these to determine the overlapping roles of Abcc2 and Abcg2 in the elimination of MTX and 7OH-MTX after i.v. administration of 50 mg/kg MTX. Results: Compared with wild-type, the plasma areas under the curve (AUC) for MTX were 1.6-fold and 2.0-fold higher in Abcg2 -/-and Abcc2 -/-mice, respectively, and 3.3-fold increased in Abcc2;Abcg2 -/-mice. The biliary excretion of MTX was 23-fold reduced in Abcc2;Abcg2-/-mice, and the MTX levels in the small intestine were dramatically decreased. Plasma levels of 7OH-MTX were not significantly altered in Abcg2 -/-mice, but the areas under the curve were 6.2-fold and even 12.4-fold increased in Abcc2 -/-and Abcc2;Abcg2 -/-mice, respectively. This indicates that Abcc2 compensates forAbcg2 deficiency but that Abcg2 can only partly compensate for Abcc2 absence. Furthermore, 21-fold decreased biliary 7OH-MTX excretion in Abcc2;Abcg2 -/-mice and substantial 7OH-MTX accumulation in the liver and kidney were seen. We additionally found that in the absence of Abcc2, Abcg2 mediated substantial urinary excretion of MTX and 7OH-MTX. Conclusions: Abcc2 and Abcg2 together are major determinants of MTX and 7OH-MTX pharmacokinetics. Variations in ABCC2 and/or ABCG2 activity due to polymorphisms or coadministered inhibitors may therefore substantially affect the therapeutic efficacy and toxicity in patients treated with MTX.

Purpose: ATP-binding cassette sub-family C member 2 [ABCC2; multidrug resistanceâ ssociated protein 2 (MRP2)] and ABCC3 (MRP3) mediate the elimination of toxic compounds, such as drugs and carcinogens, and have a large overlap in substrate specificity.We investigated the roles of Abcc2 and Abcc3 in the elimination of the anticancer drug methotrexate (MTX) and its toxic metabolite 7-hydroxymethotrexate (7OH-MTX) in vivo. Experimental Design: Abcc2;Abcc3 -/-mice were generated, characterized, and used to investigate possibly overlapping or complementary roles of Abcc2 and Abcc3 in the elimination of MTX and 7OH-MTX after i.v. administration of 50 mg/kg MTX. Results: Abcc2;Abcc3 -/-mice were viable and fertile. In Abcc2 -/-mice, the plasma area under the curve (AUC i.v. ) for MTX was 2.0-fold increased compared with wild type, leading to 1.6-fold increased urinary excretion, which was not seen in Abcc2;Abcc3 -/-mice. Biliary excretion of MTX was 3.7-fold reduced in Abcc2 -/-but unchanged in Abcc2;Abcc3 -/-mice. The plasma AUC i.v. s of 7OH-MTX were 6.0-fold and 4.3-fold increased in Abcc2 -/-and Abcc2;Abcc3 -/-mice, respectively, leading to increased urinary excretion. The biliary excretion of 7OH-MTX was 5.8-fold reduced in Abcc2 -/-but unchanged in Abcc2;Abcc3 -/-mice. 7OH-MTX accumulated substantially in the liver of Abcc2 -/-and especiallyAbcc2;Abcc3 -/-mice. Conclusions: Abcc2 is important for (biliary) excretion of MTX and its toxic metabolite 7OH-MTX.When Abcc2 is absent, Abcc3 transports MTX and 7OH-MTX back from the liver into the circulation, leading to increased plasma levels and urinary excretion. Variation in ABCC2 and/or ABCC3 activity may therefore have profound effects on the elimination and severity of toxicity of MTX and 7OH-MTX after MTX treatment of patients.The multidrug resistance proteins (MRP) ATP-binding cassette sub-family C member 2 (ABCC2; MRP2) and ABCC3 (MRP3) are members of the ATP-binding cassette (ABC) transporter super-family. ABCC2 is present in the apical membranes of hepatocytes and the epithelial cells of the small intestine and kidney, and is involved in the elimination of both endogenous and exogenous compounds from the body (1). ABCC3 is also found in the liver, kidney, and small intestine as well as in the adrenal glands and pancreas. In contrast to ABCC2, ABCC3 localizes to the basolateral membrane of polarized cells (2). Both transporters are expressed in various tumors and can transport a range of (anticancer) drugs (1, 2). There is a large overlap in the substrate specificity of ABCC2 and ABCC3. They can, for example, both transport bilirubin glucuronides (3 -5) and, in patients with the Dubin-Johnson syndrome, who have functionally deficient ABCC2 (6, 7), both plasma bilirubin glucuronide levels and ABCC3 protein levels are increased. It has been speculated that these two findings are related: ABCC3 up-regulation in the absence of ABCC2 would allow increased basolateral efflux of bilirubin glucuronides from the liver (7). Because Abcc2 and Abcc3 are both invol...

The multidrug transporters ABCC2, ABCC3, and ABCG2 can eliminate potentially toxic compounds from the body and have overlapping substrate specificities. To investigate the overlapping functions of Abcc2, Abcc3, and Abcg2 in vivo, we generated and characterized Abcc3;Abcg2 −/− and Abcc2;Abcc3;Abcg2 −/− mice. We subsequently analyzed the relative impact of these transport proteins on the pharmacokinetics of the anticancer drug methotrexate (MTX) and its main, toxic, metabolite 7-hydroxymethotrexate (7OH-MTX) after i.v. administration of MTX (50 mg/kg). Whereas in single and double knockout mice, the plasma and liver concentrations of MTX and 7OH-MTX decreased rapidly after MTX administration, in the Abcc2;Abcc3;Abcg2 −/− mice, they remained very high. One hour after administration, 67% of the MTX dose was still present in livers of Abcc2;Abcc3;Abcg2 −/− mice as MTX or 7OH-MTX versus 7% in wild-type, showing dramatic liver accumulation of these toxic compounds when Abcc2, Abcc3, and Abcg2 were all absent. Furthermore, the urinary and fecal excretion of the nephrotoxic metabolite 7OH-MTX were increased 27-and 7-fold, respectively, in Abcc2;Abcc3;Abcg2 −/− mice. Thus, Abcc2, Abcc3,

ABSTRACT:The ATP-binding cassette (ABC) transporters ABCC2 [multidrug resistance-associated protein (MRP) 2], ABCC3 (MRP3), and ABCG2 (breast cancer resistance protein) are involved in the efflux of potentially toxic compounds from the body. We have shown before that ABCC2, ABCC3, and ABCG2 together influence the pharmacokinetics of the anticancer and antirheumatic drug methotrexate (MTX) and its toxic metabolite 7-hydroxymethotrexate (7OH-MTX) after intravenous MTX administration. We now have used Abcc2;Abcc3;Abcg2(؊/؊) and corresponding single and double knockout mice to investigate the relative impact of these transporters on MTX and 7OH-MTX pharmacokinetics after oral MTX administration (50 mg/kg). The plasma areas under the curve (AUC plasma ) in Abcg2(؊/؊) and Abcc2;Abcg2(؊/؊) mice were 1.7-and 3.0-fold higher than those in wild-type mice, respectively, suggesting additive effects of Abcc2 and Abcg2 on oral MTX pharmacokinetics. However, the AUC plasma in Abcc2;Abcc3; Abcg2(؊/؊) mice was not different from that in wild-type mice, indicating that Abcc3 protein is necessary for increased MTX plasma concentrations in the absence of Abcc2 and/or Abcg2. Furthermore, 2 h after administration, MTX liver levels were increased in Abcg2-deficient strains and MTX kidney levels were 2.2-fold increased in Abcc2;Abcg2(؊/؊) mice compared with those in wild-type mice. The absence of Abcc2 and/or Abcg2 also led to significantly increased liver and kidney levels of 7OH-MTX. Our results suggest that inhibition of ABCG2 and/or ABCC2, genetic polymorphisms or mutations reducing expression or activity of these proteins may increase the oral availability of MTX. Such conditions may also present risk factors for increased MTX-related toxicity in patients treated with oral MTX.

P-glycoprotein ( P-gp ) largely influences the pharmacokinetics (PK) and toxicities of xenobiotics in a patient-specific manner so that personalized drug scheduling may lead to significant patient’s benefit. This systems pharmacology study investigated P-gp activity in mice according to organ, sex, feeding status, and circadian time. Sex-specific circadian changes were found in P-gp ileum mRNA and protein levels, circadian amplitudes being larger in females as compared to males. Plasma, ileum and liver concentrations of talinolol, a pure P-gp substrate, significantly differed according to sex, feeding and circadian timing. A physiologically-based PK model was designed to recapitulate these datasets. Estimated mesors (rhythm-adjusted mean) of ileum and hepatic P-gp activity were higher in males as compared to females. Circadian amplitudes were consistently higher in females and circadian maxima varied by up to 10 h with respect to sex. Fasting increased P-gp activity mesor and dampened its rhythm. Ex-vivo bioluminescence recordings of ileum mucosae from transgenic mice revealed endogenous circadian rhythms of P-gp protein expression with a shorter period, larger amplitude, and phase delay in females as compared to males. Importantly, this study provided model structure and parameter estimates to refine PK models of any P-gp substrate to account for sex, feeding and circadian rhythms.