ABC-transporter gene-polymorphisms are potential pharmacogenetic markers for mitoxantrone response in multiple sclerosis.
Escalation therapy with mitoxantrone (MX) in highly active multiple sclerosis is limited by partially dose-dependent side-effects. Predictors of therapeutic response may result in individualized risk stratification and MX dosing. ATP-binding cassette-transporters ABCB1 and ABCG2 represent multi-drug resistance mechanisms involved in active cellular MX efflux. Here, we investigated the role of ABC-gene single nucleotide polymorphisms (SNPs) for clinical MX response, corroborated by experimental in vitro and in vivo data. Frequencies of ABCB1 2677G>T, 3435C>T and five ABCG2-SNPs were analysed in 832 multiple sclerosis patients (Germany, Spain) and 264 healthy donors. Using a flow-cytometry-based in vitro assay, MX efflux in leukocytes from individuals with variant alleles in both ABC-genes (designated genotype ABCB1/ABCG2-L(ow), 22.2% of patients) was 37.7% lower than from individuals homozygous for common alleles (ABCB1/ABCG2-H(igh), P < 0.05, 14.8% of patients), resulting in genotype-dependent MX accumulation and cell death. Addition of glucocorticosteroids (GCs) inhibited MX efflux in vitro. ABC-transporters were highly expressed in leukocyte subsets, glial and neuronal cells as well as myocardium, i.e. cells/tissues potentially affected by MX therapy. In vivo significance was further corroborated in experimental autoimmune encephalomyelitis in Abcg2(-/-) animals. Using a MX dose titrated to be ineffective in wild-type animals, disease course and histopathology in Abcg2(-/-) mice were strongly ameliorated. Retrospective clinical analysis in MX monotherapy patients (n = 155) used expanded disability status scale, relapse rate and multiple sclerosis functional composite as major outcome parameters. The clinical response rate [overall 121 of 155 patients (78.1%)] increased significantly with genotypes associated with decreasing ABCB1/ABCG2-function [ABCB1/ABCG2-H 15/24 (62.5%) responders, ABCB1/ABCG2-I(ntermediate) 78/98 (79.6%), ABCB1/ABCG2-L 28/33 (84.8%), exact Cochran-Armitage test P = 0.039]. The odds ratio for response was 1.9 (95% CI 1.0-3.5) with each increase in ABCB1/ABCG2 score (from ABCB1/ABCG2-H to -I-, and -I to -L). In 36 patients with severe cardiac or haematological side effects no statistically relevant difference in genotype frequency was observed. However, one patient with biopsy proven cardiomyopathy only after 24 mg/m2 MX exhibited a rare genotype with variant, partly homozygous alleles in 3 ABC-transporter genes. In conclusion, SNPs in ABC-transporter genes may serve as pharmacogenetic markers associated with clinical response to MX therapy in multiple sclerosis. Combined MX/GC-treatment warrants further investigation.
Cotte
S
S
Institute for MS-Research, Medical Faculty, University of Göttingen and Gemeinnützige Hertie-Stiftung, Göttingen, Germany.
von Ahsen
N
N
Kruse
N
N
Huber
B
B
Winkelmann
A
A
Zettl
U K
UK
Starck
M
M
König
N
N
Tellez
N
N
Dörr
J
J
Paul
F
F
Zipp
F
F
Lühder
F
F
Koepsell
H
H
Pannek
H
H
Montalban
X
X
Gold
R
R
Chan
A
A
D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis / Q000235:genetics*; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000096:biosynthesis / Q000235:genetics*; D000328:Adult; D000818:Animals; D018432:Drug Resistance, Multiple / Q000235:genetics; D004359:Drug Therapy, Combination; D004681:Encephalomyelitis, Autoimmune, Experimental / Q000188:drug therapy / Q000235:genetics; D005260:Female; D005786:Gene Expression Regulation; D005787:Gene Frequency; D005819:Genetic Markers; D005838:Genotype; D005938:Glucocorticoids / Q000627:therapeutic use; D006801:Humans; D008297:Male; D051379:Mice; D008875:Middle Aged; D008942:Mitoxantrone / Q000009:adverse effects / Q000493:pharmacokinetics / Q000627:therapeutic use*; D009103:Multiple Sclerosis / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide; D012333:RNA, Messenger / Q000235:genetics; D012189:Retrospective Studies; D016896:Treatment Outcome
C513055:ABCB1 protein, human; C116614:ABCG2 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; C501412:Abcg2 protein, mouse; D005819:Genetic Markers; D005938:Glucocorticoids; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D008942:Mitoxantrone; C507084:Abcb1b protein, mouse