Genetic polymorphisms of enzyme proteins and transporters related to methotrexate response and pharmacokinetics in a Japanese population

Background

Methotrexate (MTX) is currently the anchor drug widely used worldwide in the treatment of rheumatoid arthritis (RA). However, the therapeutic response to MTX has been shown to vary widely among individuals, genders and ethnic groups. The reason for this has been not clarified but it is considered to be partially due to several mechanisms in the cellular pathway of MTX including single-nucleotide polymorphisms (SNPs). The purpose of this study was to investigate the allelic frequencies in different ethnic and/or population groups in the 10 polymorphisms of enzyme proteins and transporters related to the MTX response and pharmacokinetics including MTHFR, TYMS, RFC1, FPGS, GGH, ABCB1, ABCC2 and ABCG2 in unrelated healthy Japanese adults and patients with RA.

Methods

Ten polymorphisms, methylenetetrahydrofolate reductase (MTHFR) 1298, thymidylate synthase (TYMS) 3'-UTR, reduced folate carrier 1 (RFC1) 80 and−43, folypolyglutamyl synthase (FPGS) 1994, γ-glutamyl hydrolase (GGH) 452 and−401, the ABC transporters (ABCB1 3435, ABCC2 IVS23 + 56, ABCG2 914) of enzyme proteins and transporters related to MTX response and pharmacokinetics in 299 unrelated healthy Japanese adults and 159 Japanese patients with RA were investigated to clarify their contributions to individual variations in response and safety to MTX and establish personalized MTX therapy. SNPs were evaluated using real-time polymerase chain reaction (PCR).

Results

Comparison of allelic frequencies in our study with other ethnic/population groups of healthy adults and RA patients showed significant differences in 10 polymorphisms among healthy adults and 7 among RA patients. Allelic frequencies of MTHFR 1298 C, FPGS 1994A and ABCB1 3435 T were lower in Japanese than in Caucasian populations and those of ABCC2 IVS23 + 56 C and ABCG2 914A were higher in Japanese than in Caucasian/European populations in both healthy adults and RA patients. Allelic frequencies of MTHFR 1298 C, GGH−401 T, ABCB1 3435 T, and ABCG2 914A were higher in healthy Japanese adults than in an African population, and those of RFC1 80A, RFC1−43C and ABCC2 IVS23 + 56 C in healthy Japanese adults were lower than in Africans. However, no significant differences were seen in the distribution of allelic frequencies between healthy Japanese adults and RA patients.

Conclusion

The variations in allelic frequencies in different ethnic and/or population groups in healthy adults and RA patients may contribute to individual variations in MTX response and toxicity.

Preliminary study for predicting better methotrexate efficacy in Japanese patients with rheumatoid arthritis

BACKGROUND

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by systemic inflammatory status, joint destruction, disability, and pain. Methotrexate (MTX) has been confirmed to reduce disease activity and delay or stabilize the development of bone erosions. However, major drawbacks are that patients show great interindividual variability in response to MTX and the unpredictable occurrence of side effects. A strategy for personalized MTX treatment to predict its efficacy and toxicity has not yet been determined. To establish personalized MTX therapy in Japanese patients with rheumatoid arthritis, we performed a preliminary study for predicting better methotrexate efficacy including single-nucleotide polymorphisms (SNPs) for MTX-related transporters/enzymes.

METHODS

Disease control status (good or poor) was judged by the number of Disease Activity Scores (DAS28) of <2 for 6-12 months. The response index R was calculated by the improved area under the curve (AUC) of the DAS28 score for 0-3 or 0-6 months by dividing the cumulative dose of MTX during 0-3 or 0-6 months, respectively. Genotyping of alleles of RFC1 80G > A, RFC1 -43 T > C, FPGS 1994G > A, GGH 401C > T, MTHFR 1298A > C, and TYMS 3'-UTR (-6/+6) was performed using the real-time PCR system.

RESULTS

Seven of 21 patients were judged as good responders in terms of disease control, and the remainder as poor responders. For 0-3 months after starting MTX administration, the median cumulative dose and improved DAS28 AUC in the good and poor response groups were 96.0 mg and 25.4 and 118.0 mg and 23.4, respectively. For 0-6 months, the median cumulative dose and improved DAS28 AUC in the good and poor response groups were 192.0 mg and 51.0 and 214.0 mg and 47.6, respectively. Statistically significant differences between the 2 groups in the 0-6-month period were observed in DAS28 AUC improvement and index R. A slight tendency for a correlation between G/G genotypes and A allele genotypes in RFC1 80 genotypes was observed, although it did not reach statistical significance.

CONCLUSION

This study suggested that aggressive RA treatment with MTX from the early period of administration is necessary to obtain a good response after 6 months, although no SNPs predicting a better treatment response to MTX were identified.

Mechanism-based approach using a biomarker response to evaluate tocilizumab subcutaneous injection in patients with rheumatoid arthritis with an inadequate response to synthetic DMARDs (MATSURI study)

A multicenter, open-label, dose-escalation phase 1/2 study was undertaken to evaluate the optimal subcutaneous tocilizumab dose that would result in exposure comparable to the intravenous tocilizumab 8-mg/kg approved dose in patients with rheumatoid arthritis. A pharmacokinetic and biomarker approach was used to estimate the clinical optimal dose regimen of subcutaneous tocilizumab. Safety and efficacy of subcutaneous tocilizumab were assessed as secondary end points. Patients received subcutaneous tocilizumab at 81 mg every 2 weeks (q2w) (n = 8), 162 mg q2w (n = 12), or 162 mg weekly (qw) (n = 12) for 24 weeks. 88% of 162-mg q2w patients and 100% of 162-mg qw patients maintained mean serum trough tocilizumab concentrations of ≥1 µg/mL, and had exposure comparable with the approved intravenous tocilizumab dose of 8 mg/kg; this resulted in normalized C-reactive protein levels and improvement in ACR20/50/70 responses. The most common adverse events were abnormal laboratory results, which were mild in severity. Anti-tocilizumab antibodies were detected in a few patients in the 81-mg q2w and 162-mg qw groups. In conclusion, coupled with efficacy and tolerability results, the appropriate dose of subcutaneous tocilizumab was determined to be 162 mg q2w for Japanese patients.

Changes in concentrations of type IV collagen and tissue inhibitor of metalloproteinase-1 in patients with paraquat poisoning

Respiratory failure is one of the major causes of death in patients with paraquat poisoning. In paraquat-poisoned lungs, abnormal extracellular matrix regulation occurs. The aim of the present study is to determine whether serum concentrations of type IV collagen and tissue inhibitor of metalloproteinase-1 (TIMP-1) are altered during the course of paraquat poisoning and whether haemoperfusion therapy affects these concentrations. Twenty-one patients were admitted within 3 h after ingestion of paraquat and all patients received direct haemoperfusion therapy. Five out of 21 patients survived and 16 patients died within 28 days. Plasma paraquat concentrations in non-survivors (5740 +/- 380 microg l(-1)) were not significantly different from those in survivors ( 5920 +/- 280 microg l(-1)) before treatment. Haemoperfusion reduced these concentrations in both non-survivors (120 +/- 7 microg l(-1)) as well as survivors (136 +/- 9 microg l(-1)) on day 5. Serum concentrations of type IV collagen and TIMP-1 in survivors showed little change between day 1 (type IV collagen, 90.4 +/- 3.6 ng ml(-1); TIMP-1, 172.2 +/- 7.0 ng ml(-1)) and day 5 (type IV collagen, 92.6 +/- 4.2 ng ml(-1); TIMP-1, 174.2 +/- 7.2 ng ml(-1)). In contrast, these concentrations in non-survivors on day 5 (type IV collagen, 143.6 +/- 7.8 mg ml(-1); TIMP-1, 246.8 +/- 13.6 ng ml(-1)) were significantly higher than those on day 1 (type IV collagen, 88.4 +/- 4.2 ng ml(-1), P < 0.01; TIMP-1, 170.6 +/- 9.2 ng ml(-1), P < 0.05). These data suggest that serum concentrations of type IV collagen and TIMP-1 may be useful indicators for the development of respiratory failure in patients with paraquat poisoning.

Effect of plasma exchange on serum tissue inhibitor of metalloproteinase 1 and cytokine concentrations in patients with fulminant hepatitis

AIMS

The present study assessed whether the serum concentrations of tissue inhibitor of metalloproteinase 1 (TIMP-1) and cytokines are altered in patients with fulminant hepatitis and whether plasma exchange affects these concentrations.

METHODS

Fifteen patients with fulminant hepatitis, 14 patients with severe acute hepatitis, and 20 healthy controls were included in this study. The serum levels of tumor necrosis factor alpha (TNF-alpha), interleukin 1beta (IL-1beta), interleukin 6 (IL-6), transforming growth factor beta (TGF-beta), and TIMP-1 were determined in all patients upon hospital admission and before and after a single course of plasma exchange in the patients with fulminant hepatitis.

RESULTS

Ten out of the 15 patients with fulminant hepatitis and all patients with severe acute hepatitis survived. Serum TNF-alpha, IL-6, TGF-beta, and TIMP-1 levels in patients with fulminant hepatitis were significantly higher than the levels in patients with severe acute hepatitis (p < 0.01). IL-1beta was not detectable in either group. Plasma exchange reduced the increased serum concentrations of TNF-alpha, IL-6, TGF-beta, and TIMP-1 in patients with fulminant hepatitis (p < 0.01).

CONCLUSIONS

These data suggest that increased serum levels of TIMP-1 and cytokines may reflect severe hepatic inflammation and that plasma exchange is an effective therapy to reduce these levels.

Normal developing rat brain expresses a platelet-derived growth factor B chain (c-sis) mRNA truncated at the 5' end

The 5' untranslated sequence (5' UTS) of platelet-derived growth factor B (PDGF-B/c-sis) mRNA is highly preserved through evolution, and inhibits translation of downstream coding sequences. In this study, using Northern analysis we identified two PDGF-B/c-sis mRNAs (3.5 kb and 2.6 kb) expressed in normal developing rat brain. In contrast to the constitutive expression of 3.5 kb mRNA, the expression of 2.6 kb mRNA increased markedly in accordance with those stages of brain development at which we had previously demonstrated an increased immunoreactivity for PDGF-B/c-SIS in neurons (Sasahara et al., 1992). By PCR cloning and the RNase protection assay, we determined the complete sequence of rat PDGF-B/c-sis, and found that the 2.6 kb transcript was a form of the 3.5 kb message truncated at the 5' end, and that the predominant 2.6 kb mRNA commenced 15 nt upstream of the signal peptide. Accordingly, it is suggested that the truncation of 5' UTS contributes to the expression of PDGF-B/c-SIS protein in the CNS. Lack of translational inhibitory 5' UTS of PDGF-B/c-sis transcript and resultant efficient protein translation have been reported in only a few transformed cells and cultured umbilical vein endothelial cells. We have extended this knowledge to the developing rat brain, and suggest that a similar mechanism could operate widely in non-transformed tissue in vivo.

Kidney transplantation and liaison psychiatry, part II: A case of dissociative identity disorder

The authors examined the case of an adolescent patient with dissociative identity disorder secondary to psychological shock of a transplant rejection response. Psychiatric symptoms consisted of three components: visual hallucinations and delusions as a psychological defense against the anxiety of a transplant rejection; appearance of three personalities including proper self, the dead child (donor), and a prophet with strong predicting power; and a twilight state. These psychiatric symptoms may have been related to two psychological factors: immature personality characteristics formed during hemodialysis, and post-traumatic stress caused by a chronic rejection reaction from the patient's first transplant.

HLA-DR2 antigen linkage in patients with apical hypertrophic cardiomyopathy in Japan

Apical hypertrophic cardiomyopathy, a very common disorder in Japan, is characterized by giant negative T waves on the electrocardiogram and abnormal apical hypertrophy on the ventriculogram. This histocompatibility complexes (HLA-A, -B, -C, -DR) of 20 unrelated patients with apical hypertrophic cardiomyopathy (18 male, 2 female) were examined. There was no significant difference in the frequency of HLA-A, -B, -C antigens between patients and controls (n = 100). However, HLA-DR 2 was more frequent in patients with apical hypertrophic cardiomyopathy (65.0%) than controls (33.0%) (p < 0.01). We conclude that apical hypertrophic cardiomyopathy might be associated with genes in the HLA-DR region and that genetic factors linked to HLA play a role in the pathogenesis of this disease.

A case of transverse colon cancer secondarily involving the liver, duodenum, and pancreas

A 68-year-old woman presented with transverse colon cancer invading the liver, duodenum, and pancreas. The patient underwent a curative resection including a right hemicolectomy, partial hepatectomy, and pancreaticoduodenectomy (PD). The pathological examination showed adenocarcinoma of the colon with a direct extension into the duodenum, liver, and pancreas. Several lymph nodes were also involved. The patient is still alive and disease-free 2 years and 6 months after the operation. This case illustrates that even in patients with locally advanced colon cancer, a favorable prognosis can be obtained by aggressive surgery incorporating the resection of the adjacent involved organs.

Increase in cardiac muscle fructose content in streptozotocin-induced diabetic rats

To evaluate the activation of the sorbitol pathway in cardiac muscle in diabetic rats, we measured sorbitol, fructose, and myo-inositol content in cardiac tissue obtained from control and streptozotocin-diabetic rats, with or without an 8-week insulin treatment, using gas chromatography-mass spectrometry (GC-MS). Cardiac fructose and sorbitol content in 10-week diabetic rats increased by 60-fold and 3.9-fold of those of control rats, respectively (P less than .001). In contrast, cardiac myo-inositol content in 10-week diabetic rats decreased to 56% (P less than .025) of the control value. The abnormalities in cardiac fructose, sorbitol, and myo-inositol content were completely normalized by the 8-week insulin treatment, which was initiated 2 weeks after the induction of diabetes. There was no difference in cardiac aldose reductase activity between control and diabetic rats. However, cardiac sorbitol dehydrogenase activity in diabetic rats was 151% (P less than .005) higher than that of control rats, although hepatic sorbitol dehydrogenase activity was not different between the two groups. These results indicate that the sorbitol pathway is significantly activated in cardiac tissue obtained from streptozotocin-induced diabetic rats, which results in the marked cardiac accumulation of fructose.

Simultaneous extensive resection of the liver and the pancreas in dogs

Mortality, morbidity, liver function and regeneration were evaluated in dogs that had undergone simultaneous major resection of the liver and the pancreas. The 10-week survival rate was only 25% in the dogs that underwent 70% hepatectomy with more than 92% pancreatectomy, and many of them died of liver failure. Long-term survival was observed in more than 60% of the dogs after 70% hepatectomy with less than 92% pancreatectomy or after 40% hepatectomy with more than 92% pancreatectomy. The liver regeneration rate was reduced with the extent of the pancreatectomy, and the reduction was remarkable especially when more than 92% of the pancreas was resected. The frequency of diabetes was reduced when the pancreatectomy was combined with hepatectomy. Hyperlipemia and fatty liver were noted in all the dogs of the group that underwent more than 92% pancreatectomy alone. They were observed also in the postoperative diabetic groups but not in non-diabetic groups. The postoperative recovery of hepatic function and liver regeneration were delayed after simultaneous hepatectomy-pancreatectomy. Also, postoperative carbohydrate and lipid metabolism was better maintained in the hepatectomy-pancreatectomy groups than in the pancreatectomy-alone groups.

Stimulation and inhibition of interferon-beta production of human diploid fibroblasts by foodstuffs

We screened for foodstuffs affecting interferon-beta (IFN-beta) production of human foreskin diploid fibroblasts, in the presence of poly I.poly C, cycloheximide, and actinomycin D. alpha- and beta-caseins stimulated IFN-beta production dose-dependently, but kappa-casein inhibited it. Of the two chymosin fragments of kappa-casein, glycomacropeptide was an inhibitor but p-kappa-casein was not. beta-lactoglobulin stimulated IFN-beta production weakly, but lactoferrin inhibited it strongly. It was also shown that serum contained some factors inhibiting IFN-beta induction and stimulating its production.

Arrhythmogenic plasma levels of epinephrine during halothane, enflurane, and pentobarbital anesthesia in the dog

Plasma levels of epinephrine which correspond to the arrhythmogenic doses were determined during halothane, enflurane, and pentobarbital anesthesia in the dog. The arrhythmogenic dose was established by a series of 3-min infusion of epinephrine at 10-min intervals. The mean values of the arrhythmogenic doses and the corresponding plasma levels of epinephrine were: 2.18 micrograms X kg-1 X min-1 and 38.7 ng/ml during halothane; 11.43 micrograms X kg-1 X min-1 and 206.3 ng/ml during enflurane; and 15.27 micrograms X kg-1 X min-1 and 296.5 ng/ml during pentobarbital anesthesia. The arrhythmogenic plasma levels of norepinephrine during halothane anesthesia was nearly the same as that of epinephrine.