van der Straaten R J H M, Wessels Judith A M, de Vries-Bouwstra Jeska K, Goekoop-Ruiterman Yvonne P M, Allaart Cornelia F, Bogaartz Judith, Tiller Marco, Huizinga Tom W J, Guchelaar Henk-Jan
Leiden University Medical Center, Department of Clinical Pharmacy and Toxicology, P.O. Box 9600, 2300 RA Leiden, The Netherlands.
Pharmacogenomics. 2007 Feb;8(2):141-50. doi: 10.2217/14622416.8.2.141.
The enzyme folylpoly-gamma-glutamase synthethase (FPGS) plays an important role in the intracellular polyglutamation of the disease-modifying antirheumatic drug methotrexate (MTX) and the length of the polyglutamated MTX product correlates with the time that MTX resides in the cell. The glutamates are released from MTX by activity of the enzyme gamma-glutamyl-hydrolase (GGH), thereby allowing the efflux of MTX. GGH 452C>T has been associated with decreased catalytic activity and higher accumulation of long-chain MTX-polyglutamate. However, single nucleotide polymorphisms (SNPs) in FPGS and GGH genes have not yet been explored for association with MTX efficacy or toxicity. We selected for SNPs with frequencies higher than 10% or, in case of FPGS 114G>A, causing an amino acid change with no known frequencies. In this study, frequencies of two SNPs in FPGS (1994A>G and 114G>A, rs10106 and rs10760502, respectively) and GGH genes (452C>T and 16T>C, rs11545078 and rs1800909, respectively), were determined using a newly developed method in rheumatoid arthritis patients (n = 352) and in a group of healthy controls (n = 360). Next, the SNPs were associated with response to MTX in rheumatoid arthritis patients treated with MTX monotherapy. In rheumatoid arthritis patients, allele frequencies of FPGS 1994A>G were 0.534 (A) and 0.466 (G), and for FPGS 114G>A 0.714 (G) and 0.286 (A). Allele frequencies of GGH 16T>C were 0.737 (T) and 0.263 (C) and for GGH 452C>T 0.912 (C) and 0.088 (T). No significant differences in allele frequencies between rheumatoid arthritis patients and healthy controls were found. In addition, the SNPs were not associated with good clinical response to MTX. Only patients with the GGH 16C-allele and one or no copies of the GGH 452C-16T haplotype were associated with good clinical improvement at 3 months upon treatment with MTX. No associations with efficacy at 6 months and MTX-induced toxicity were found. Therefore we conclude that despite the positive association of the GGH 16C-allele and one or no copies of the GGH 452C-16T haplotype with good clinical improvement at 3 months upon treatment with MTX, the tested SNPs in GGH and FPGS genes are suggested not to be clinically important for MTX treatment outcome.
叶酸多聚-γ-谷氨酰胺合成酶（FPGS）在改善病情抗风湿药甲氨蝶呤（MTX）的细胞内多聚谷氨酸化过程中起重要作用，且多聚谷氨酸化MTX产物的长度与MTX在细胞内停留的时间相关。谷氨酸通过γ-谷氨酰水解酶（GGH）的活性从MTX中释放出来，从而使MTX流出。GGH 452C>T与催化活性降低及长链MTX-多聚谷氨酸的更高积累有关。然而，尚未探究FPGS和GGH基因中的单核苷酸多态性（SNP）与MTX疗效或毒性的关联。我们选择了频率高于10%的SNP，或者对于FPGS 114G>A这种导致氨基酸改变且频率未知的情况。在本研究中，使用一种新开发的方法在类风湿关节炎患者（n = 352）和一组健康对照者（n = 360）中测定了FPGS基因（分别为1994A>G和114G>A，rs10106和rs10760502）及GGH基因（分别为452C>T和16T>C，rs11545078和rs1800909）中两个SNP的频率。接下来，在接受MTX单药治疗的类风湿关节炎患者中，将这些SNP与对MTX的反应相关联。在类风湿关节炎患者中，FPGS 1994A>G的等位基因频率分别为0.534（A）和0.466（G），FPGS 114G>A的等位基因频率分别为0.714（G）和0.286（A）。GGH 16T>C的等位基因频率分别为0.737（T）和0.263（C），GGH 452C>T的等位基因频率分别为0.912（C）和（0.088）（T）。未发现类风湿关节炎患者与健康对照者之间等位基因频率有显著差异。此外，这些SNP与对MTX的良好临床反应无关。仅携带GGH 16C等位基因且GGH 452C - 16T单倍型为一个拷贝或无拷贝的患者在接受MTX治疗3个月时与良好的临床改善相关。未发现与6个月时的疗效及MTX诱导的毒性有关联。因此我们得出结论，尽管GGH 16C等位基因且GGH 452C - 16T单倍型为一个拷贝或无拷贝与接受MTX治疗3个月时的良好临床改善呈正相关，但GGH和FPGS基因中所检测的SNP对MTX治疗结果在临床上似乎并不重要。
