3435CC Genotype Research Articles

Genetic Polymorphisms in Metabolic and Cellular Transport Pathway of Methotrexate Impact Clinical Outcome of Methotrexate Monotherapy in Japanese Patients with Rheumatoid Arthritis

The aim of this study was to investigate the impact of genetic polymorphisms in the metabolic and cellular transport pathway of methotrexate (MTX) on the clinical outcome of MTX monotherapy in Japanese rheumatoid arthritis (RA) patients. Fifty-five patients were treated with MTX monotherapy at a dose of 4-10 mg/week. The total concentration of MTX-polyglutamates (MTX-PGs) was measured at steady-state in red blood cells (RBCs) by high performance liquid chromatography. The genotype at 16 polymorphic sites in 11 genes (ABCB1, ABCG2, ABCC2, RFC1, PCFT, SLCO1B1, MTHFR, GGH, ATIC, MTR, and MTRR) was analyzed. No significant association between the total concentration of MTX-PGs in RBCs and clinical outcome was found. However, patients with the ABCB1 3435TT genotype had a significantly lower mean disease activity score (DAS) 28 than did patients with the ABCB1 3435CC genotype (p = 0.02). Similarly, patients with the ABCB1 2677AA/AT/TT genotypes had a significantly lower mean DAS28 than did patients with the ABCB1 2677GG/GA/GT genotypes (p = 0.04). The patients with the MTHFR 1298AA genotype had a significantly lower mean DAS28 than those with the MTHFR 1298AC/CC genotypes (p = 0.04). In conclusion, the ABCB1 3435C>T, ABCB1 2677G>A/T, and MTHFR 1298A>C polymorphisms influenced the efficacy of MTX monotherapy.

Associations of ABCB1 3435C>T and IL-10-1082G>A Polymorphisms With Long-Term Sirolimus Dose Requirements in Renal Transplant Patients

Sirolimus (SRL) absorption and metabolism are affected by p-glycoprotein-mediated transport and CYP3A enzyme activity, which are further under the influences of cytokine concentrations. This retrospective study determined the associations of adenosine triphosphate-binding cassette, subfamily B, member 1 (ABCB1) 1236C>T, 2677 G>T/A, and 3435C>T, cytochrome P450, family 3, subfamily A, polypeptide 4 (CYP3A4) -392A>G, cytochrome P450, family 3, subfamily A, polypeptide 5 (CYP3A5) 6986A>G and 14690G>A, interleukin (IL)-10 -1082G>A, and tumor necrosis factor (TNF) -308G>A polymorphisms with SRL dose-adjusted, weight-normalized trough concentrations (C/D) at 7 days, and at 1, 3, 6, and 12 months after initiation of SRL. Genotypes for 86 renal transplant patients who received SRL-based maintenance immunosuppressive therapy were determined using polymerase chain reaction followed by chip-based mass spectrometry. The changes of log-transformed C/D over the days posttransplantation were analyzed using a linear mixed-effects model, with adjustments for body mass index and weight-normalized doses of tacrolimus, prednisone, clotrimazole, and statins. ABCB1 3435C>T and IL-10 -1082G>A were significantly associated with log C/D (P=0.0016 and 0.0394, respectively). Mean SRL C/D was 48% higher in patients with ABCB1 3435CT/TT genotype than those with 3435CC genotype, and was 24% higher in IL-10 -1082GG compared with -1082AG/AA. ABCB1 3435C>T and IL-10 -1082G>A were significantly associated with long-term SRL dose requirements. Genetics can play a significant role in SRL dosing and may be useful in therapeutic monitoring of SRL in renal transplantation. Future replication studies are needed to confirm these associations.

Association of the MDR1 3435 polymorphism in patients with refractory rheumatoid arthritis in a Chinese population

To evaluate whether the multidrug resistance gene 1 (MDR1) exon 26 polymorphisms are associated with the refractory rheumatoid arthritis (RRA). The study was carried out on two hundred and twenty-three patients with RA treated and one hundred and three normal controls. The RA treated were divided into two groups according the response to disease-modifying antirheumatic drugs (DMARDs). There were 108 patients in the effective group and 115 patients in the ineffective group. Genotypes of the C3435T polymorphism were determined by polymerase chain reaction followed by restriction digestion (PCR-RFLP). There were significant differences in the genotype frequency and allele frequency among three groups. Compared to responders and controls, the nonresponders carried more CC genotype (χ(2) = 5.306, P = 0.021; χ(2) = 7.810, P = 0.005) and more C allele (χ(2) = 6.601, P = 0.010; χ(2) = 12.172, P = 0.000). But, there were no statistically significant differences in genotype nor allele frequency between RA and healthy controls. The results from our study suggest that the C3435T MDR1 gene polymorphism may not be related with the RA susceptibility, but may influence the efficacy of RA therapy with DMARDs, and the 3435CC genotype may be related with RRA.

IMPROVEMENT IN MULTIFOCAL ELECTRORETINOGRAPHY AFTER HALF-DOSE VERTEPORFIN PHOTODYNAMIC THERAPY FOR CENTRAL SEROUS CHORIORETINOPATHY

This study explored the association of 14 single nucleotide polymorphisms in three genes coding for influx transporters (SLC22A1, SLCO1B1, and SLCO1B3), two genes coding for efflux transporters (ABCB1 and ABCG2), and four genes coding for enzymes (CYP2C9, CYP2C19, CYP2D6, and CYP3A5) with the pharmacokinetics of imatinib in Japanese patients with chronic myeloid leukemia. Pharmacokinetic parameters were estimated by a population pharmacokinetic analysis based on 622 plasma samples from 34 patients at steady state. Approximately 4.6-fold variability in individual clearance was observed (range, 3.4-15.5 L/hr). The individual estimated clearance was significantly increased in patients with the SLCO1B3 334GG genotype (median value ± standard deviation, 9.5 ± 3.1 L/hr; n = 19) compared with SLCO1B3 334TT and TG genotypes (7.0 ± 3.1 L/hr; n = 15) (P = 0.019). Patients with the ABCB1 3435CC genotype had significantly higher imatinib clearance (12.7 ± 3.0 L/hr; n = 7) compared with patients with ABCB1 3435CT and TT genotypes (7.9 ± 2.7 L/hr; n = 27) (P = 0.035). In conclusion, the present study suggests that single nucleotide polymorphisms of the influx transporter SLCO1B3 and the efflux transporter ABCB1 were functionally associated with individual variability of imatinib pharmacokinetics in Japanese patients with chronic myeloid leukemia.

General maternal medication use, folic acid, the MDR1 C3435T polymorphism, and the risk of a child with a congenital heart defect

We sought to investigate maternal and child functional MDR1 C3435T polymorphism, periconception medication, folic acid use, and the risk of a congenital heart defect (CHD) in the offspring. MDR1 3435C>T genotyping was performed in 283 case triads (mother, father, child) and 308 control triads. Information on periconception medication and folic acid use was obtained through questionnaires. Mothers with MDR1 3435CT/TT genotype and using medication showed a significant association with the risk of a child with CHD (odds ratio [OR], 2.4; 95% confidence interval [CI], 1.3-4.3) compared to mothers with MDR1 3435CC genotype not using medication. This risk increased without folic acid use (OR, 2.8; 95% CI, 1.2-6.4), and decreased in folic acid users (OR, 1.7; 95% CI, 0.8-3.7). Children carrying the MDR1 3435CT/TT genotype and periconceptionally exposed to medication without folic acid did not show significant risks. Mothers carrying the MDR1 3435T allele, using medication without folic acid, are at nearly 3-fold increased risk for CHD in the offspring.

Abstract P2-09-36: Role of ABCB1 Polymorphisms as Predictive Markers in Patients with HER-2 FISH Positive Metastatic Breast Cancer Who Were Treated with Taxane Plus Trastuzumab First Line Chemotherapy

Abstract Background: ABCB1 polymorphisms could predict treatment results of taxane therapy in several malignancies. FCGR2A and FCGR3A polymorphisms were associated with clinical outcomes in several diseases after treatment with monoclonal antibody drugs which had antibody-dependent cell-mediated cytotoxicity activity. These polymorphisms could be possible predictive markers after taxane plus trastuzumab (TH) chemotherapy in patients with HER-2-positive metastatic breast cancer (MBC). Methods: Fifty-seven patients with HER-2 FISH positive MBC who received TH chemotherapy as the 1st-line treatment were enrolled. We analyzed 5 polymorphisms using DNA from peripheral blood mononuclear cells: ABCB1 1236C>T (rs1128503), ABCB1 2677G>T/A (rs2032582), ABCB1 3435C>T (rs1045642), FCGR2A 131H/R (rs1801274), and FCGR3A 158V/F (rs396991), then correlated them to treatment results of patients. Results: Among 57 patients, 22 patients (38.6%) received weekly paclitaxel plus trastuzumab, 26 patients (45.6%) tri-weekly paclitaxel plus trastuzumab, and 9 patients (15.8%) tri-weekly docetaxel plus trastuzumab. After a median follow-up of 30.6 (range, 0.6-75.9) months, median progression-free survival (PFS) was 15.1 (95% confidence interval (CI), 10.3-19.8) months. ABCB1 2677T allele carriers had longer PFS than the others (42.1 (95% CI, 12.7-71.4) months vs. 13.0 (95% CI, 10.6-15.4) months; p=0.037) along with a tendency toward higher response rate (RR) (86.4% vs. 76.0%; p=0.470) and longer overall survival (OS) (54.7 (95% CI, 43.0-66.4) months vs. 38.9 (95% CI, 18.1-59.7) months; p=0.057). In addition, ABCB1 3435CC genotype carriers had shorter PFS than the others (13.0 (95% CI, 10.8-15.2) months vs. 19.1 (95% CI, 0.0-38.5) months; p=0.039) along with a tendency toward lower RR (78.6% vs. 100%; p=0.567) and shorter OS (38.9 (95% CI, 19.7-58.1) months vs. 54.7 (95% CI, 43.0-66.4) months; p=0.093). ABCB1 1236C>T, FCGR2A 131H/R, and FCGR3A 158V/F were not significantly associated with RR, PFS, and OS. None of these polymorphisms were associated with any grades of hematologic or cardiac toxicities. Conclusions: Our results support that ABCB1 2677G>T/A and 3435C>T may have predictive roles after the 1st-line TH chemotherapy in patients with HER-2-positive MBC. In contrast, ABCB1 1236C>T, FCGR2A 131H/R, and FCGR3A 158V/F could not predict response after TH treatment. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P2-09-36.

Antidepressants and ABCB1 Gene C3435T Functional Polymorphism: A Naturalistic Study

Introduction: Pharmacogenetic factors may explain some of the interindividual variability of response to antidepressants in depressed patients. We focused on P-glycoprotein (P-GP), whose expression depends on a functional polymorphism of the ABCB1 gene (C3435T variants: dbSNP: rs1045642), the 3435CC genotype being linked to a high level of P-GP expression. Acting as an efflux pump at the blood-brain barrier, P-GP reduces the intracellular penetration of many drugs. Little is known about the interaction between P-GP and response to antidepressants. The objective of this study is to assess whether the response to antidepressants in depression differs in patients with the 3435CC genotype as compared to patients with the 3435CT and 3435TT genotypes. Methods: 117 in-patients with a major depressive episode requiring a new antidepressant treatment were enrolled in this prospective naturalistic 4-week study. Response to antidepressants was assessed using the Hamilton Depression Rating Scale, the Beck Depression Inventory, the Clinician Global Impression Improvement and Therapeutic Index, and weight change. ABCB1 genotyping was performed using the Taqman method. Clinical assessment was performed blind from genotypes. Results: We failed to show any significant effect of the ABCB1 polymorphism in position 3435 on antidepressant efficacy or tolerance. Discussion: While some in vitro studies showed an influence of P-GP on cerebral concentrations of antidepressants, our results do not support the hypothesis that the C3435T polymorphism is involved in therapeutic response and safety of antidepressants in naturalistic clinical conditions, confirming results of previous studies on efficacy. Nonetheless, some methodological limitations may explain our negative results.

260 Tumour vascular occlusion by vascular targeted photodynamic therapy

The aim of this study was to investigate the impact of genetic polymorphisms in the metabolic and cellular transport pathway of methotrexate (MTX) on the clinical outcome of MTX monotherapy in Japanese rheumatoid arthritis (RA) patients. Fifty-five patients were treated with MTX monotherapy at a dose of 4–10mg/week. The total concentration of MTX-polyglutamates (MTX-PGs) was measured at steady-state in red blood cells (RBCs) by high performance liquid chromatography. The genotype at 16 polymorphic sites in 11 genes (ABCB1, ABCG2, ABCC2, RFC1, PCFT, SLCO1B1, MTHFR, GGH, ATIC, MTR, and MTRR) was analyzed. No significant association between the total concentration of MTX-PGs in RBCs and clinical outcome was found. However, patients with the ABCB1 3435TT genotype had a significantly lower mean disease activity score (DAS) 28 than did patients with the ABCB1 3435CC genotype (p = 0.02). Similarly, patients with the ABCB1 2677AA/AT/TT genotypes had a significantly lower mean DAS28 than did patients with the ABCB1 2677GG/GA/GT genotypes (p = 0.04). The patients with the MTHFR 1298AA genotype had a significantly lower mean DAS28 than those with the MTHFR 1298AC/CC genotypes (p = 0.04). In conclusion, the ABCB1 3435C>T, ABCB1 2677G>A/T, and MTHFR 1298A>C polymorphisms influenced the efficacy of MTX monotherapy.

Maternal medication use, carriership of the ABCB1 3435C > T polymorphism and the risk of a child with cleft lip with or without cleft palate

Gene-environment interactions in the periconceptional period play an increasing role in the pathogenesis of birth defects, including cleft lip and/or cleft palate (CL/P). The P-glycoprotein, encoded by the ABCB1 gene, is suggested to protect the developing embryo from medication and other xenobiotic exposures. Furthermore, maternal medication use during early pregnancy is a significant risk factor for CL/P offspring. Therefore, the aim of this study is to investigate the association between the maternal and child's functional ABCB1 3435C > T polymorphism, periconceptional medication exposure, and the risk of a child with CL/P. A case-control study was performed among 175 mothers and 98 of their children with CL/P and 83 control mothers and their 65 children. Information on medication and folic acid use was collected. Mothers carrying the 3435TT genotype and using medication showed a 6.2-fold (95% CI = 1.6-24.2) increased risk of having a child with CL/P compared to mothers carrying the 3435CC genotype and not using medication. Periconceptional folic acid use reduced this risk by approximately 30% (OR = 3.9, 95% CI = 0.9-18.0). Mothers carrying the 3435TT genotype, using medication and not taking folic acid showed the highest risk estimate (OR = 19.2, 95% CI = 1.0-369.2). These data suggest that mothers who carry the ABCB1 3435C > T polymorphism are at significantly increased risk for having offspring with CL/P, especially mothers using medication in the periconceptional period.

Pharmacogenomic variations in treatment protocols for childhood acute lymphoblastic leukemia

This retrospective study evaluates the role of pharmacogenomic determinants in the treatment of childhood acute lymphoblastic leukemia (ALL) in the Taiwanese population. A total of 105 childhood ALL patients received combined chemotherapy of different intensities based on risk-directed Taiwan Pediatric Oncology Group (TPOG)-ALL-93 protocols. Seventeen genetic polymorphisms in 13 pharmacogenomic targets were analyzed by PCR-based restriction fragment length polymorphism (RFLP) and sequence-specific oligonucleotide (SSO) probe hybridization. Pharmacogenomic polymorphisms were correlated with event-free survival (EFS) of patients, with confounding effects adjusted by multivariate regression. Three polymorphic alleles in the multi-drug resistance 1 (MDR1) ABCB1 gene, and homozygotic MDR1 2677GG, 3435CC, and 2677G-3435C genotypes were highly associated with a significant reduction in EFS in those patients treated by the standard risk (SR) protocol (TPOG-ALL-93-SR). The hazard ratios were 6.8 (p = 0.01), 21.7 (p = 0.009), and 6.8 (p = 0.01), respectively. Independent pharmacogenomic determinants associated with treatment outcome were identified in subsets of Taiwanese ALL patients.

Polymorphism of the MDR1/ABCB1 C3435T drug‐transporter and resistance to anticonvulsant drugs: A meta‐analysis

Approximately one-third of patients with epilepsy patients have recurrent seizures despite therapy. It has been suggested that therapeutic failure is associated with high expression of the multidrug efflux ABCB1 (MDR1) drug-transporter; specifically, that patients with the 3435CC genotype have higher efflux of anticonvulsants out of brain tissue, with correspondingly lower concentrations in the central nervous system. We conducted a meta-analysis to examine the association between MDR1 polymorphisms and the response to anticonvulsants. We included all published studies until September 2007, in which patients with responsive and unresponsive seizure disorders underwent genotyping for ABCB1 C3435T. Individual and summary odds ratios were calculated using a random effects model. A secondary analysis was also performed, stratifying the studies by their ethnic distribution to account for genetic heterogeneity. We also performed a cumulative analysis by date of publication for the included studies using a random effects model. We identified 11 case-control studies involving 3,371 patients (1,646 patients with drug-resistant epilepsy and 1,725 controls). We identified no significant association between anticonvulsant drug resistance and MDR1 polymorphism [odds ratio 1.15; 95% confidence interval (CI) 0.78-1.70; p = 0.48). Subanalysis of studies according to ethnicity yielded similar findings [European cohort: OR = 1.31; 95% CI 0.89-1.94, p = 0.18; Asian cohort: OR = 0.99; 95% CI 0.51-1.89, p = 0.96). We found no association between ABCB1 genotype and response to anticonvulsant drugs. At the present time, genetic typing for MDR1 polymorphism is not warranted for patients with drug-resistant epilepsy.

Effects of ABCB1 3435C>T genotype on serum levels of cortisol and aldosterone in women with normal menstrual cycles

ABCB1, also known as MDR1/P-glycoprotein, can transport cortisol and aldosterone. We examined the effects of ABCB1 polymorphisms on serum levels of cortisol and aldosterone among different phases of the normal menstrual cycle in 51 non-pregnant healthy Japanese female volunteers (22 +/- 1 years old). The menstrual cycle was divided into three phases: premenstrual phase (14 days preceding the onset of menstruation, N = 22; menstrual phase, N = 11, and postmenstrual phase, N = 18). ABCB1 -129T>C, 1236C>T, 2677G>A/T, and 3435C>T genotypes were determined. Serum levels of cortisol, aldosterone, estradiol, progesterone, and testosterone were measured. The serum levels of estradiol in the pre- and post-menstrual phases and of progesterone in the premenstrual phase were significantly increased when compared to their serum levels in the menstrual phase (P < 0.005). In the postmenstrual phase, the mean serum cortisol level in subjects with the 3435CT and 3435TT genotype was 7.6 +/- 3.4 microg/dL (mean +/- SD, N = 7), which was significantly lower than in women with the 3435CC genotype (9.9 +/- 1.8 microg/dL, N = 11) (P = 0.037). The opposite effect was observed in the serum aldosterone level during the postmenstrual phase (97.2 +/- 23.4 and 141.2 +/- 48.5 pg/mL for 3435CC and 3435CT + 3435TT, respectively; P = 0.041). These findings suggest that ABCB1 3435C>T genotype can influence serum levels of cortisol and aldosterone during the postmenstrual phase of the normal menstrual cycle.

Influence of CYP3A5, ABCB1 and NR1I2 polymorphisms on prednisolone pharmacokinetics in renal transplant recipients

The objective of this study was to evaluate whether genetic polymorphisms of CYP3A5 (A6986G, CYP3A5*3), ABCB1 (C1236T, G2677T/A, C3435T) and NR1I2 (A7635G) significantly impact the pharmacokinetics of prednisolone in renal transplant recipients. Ninety-five recipients were given repeated doses of triple therapy immunosuppression consisting of prednisolone, tacrolimus and mycophenolate mofetil. Twenty-eight days after renal transplantation, plasma prednisolone concentrations were measured by high-performance liquid chromatography. Comparisons of the CYP3A5 and ABCB1 genotypes revealed no significant differences in the prednisolone pharmacokinetics. The mean prednisolone C max for recipients ( n = 14) having both the ABCB1 3435CC genotype and the CYP3A5*3/*3 genotype was significantly higher than those ( n = 11) having both ABCB1 3435TT and CYP3A5*3/*3 genotypes (180 ng/mL versus 129 ng/mL, P = 0.0392). The plasma concentrations of prednisolone in recipients having both ABCB1 3435CC and CYP3A5*3/*3 genotypes tended to be higher than those having both ABCB1 3435TT and CYP3A5*3/*3 genotypes. The mean AUC 0–24 and C max values for prednisolone in recipients having the NR1I2 7635G allele (AG: n = 45, GG: n = 32) were significantly lower than in patients having the 7635AA allele ( n = 18) (7635GG versus 7635AA, P = 0.0308 for AUC 0–24, P = 0.0382 for C max of prednisolone). In conclusion, NR1I2 (A7635G) rather than CYP3A5 or ABCB1 allelic variants affected patient variability of plasma prednisolone concentration. Recipients carrying the NR1I2 7635G allele seemed to possess higher metabolic activity for prednisolone in the intestine, greatly reducing its maximal plasma concentration.

Tacrolimus dose requirement in relation to donor and recipientABCB1 andCYP3A5 gene polymorphisms in Chinese liver transplant patients

The aim of this study was to investigate whether the heterogeneity in tacrolimus dose requirement is associated with ABCB1 and CYP3A5 gene polymorphisms in Chinese liver transplant patients during the first month after transplantation. ABCB1 and CYP3A5 genotyping was performed using the polymerase chain reaction restriction sites polymorphism-based procedure in Chinese liver transplant recipients (n = 50) and their corresponding donors (n = 50). Tacrolimus whole-blood trough concentrations were measured by immunoassays on the IMx analyzers (Abbott Diagnostics Laboratories, Abbott-Park, IL). Doses required to achieve target blood concentrations and dose-adjusted trough concentrations (concentration/dose [C/D] ratios) were compared among patients according to allelic status of ABCB1 and CYP3A5. The ABCB1 3435CC was observed in 23 subjects (23%), whereas 64 (64%) carried 3435CT and 13 (13%) carried 3435TT. The CYP3A5*1/*1 was observed in 13 subjects (13%), 50 (50%) carried *1/*3, and 37 (37%) carried*3/*3. The tacrolimus C/D ratios were obviously lower in recipients carrying ABCB1 3435CC genotype. For CYP3A5, recipients who received organs from CYP3A5*3/*3 donors had higher C/D ratios. But the donors' ABCB1 and recipients' CYP3A5 genotype did not affect the recipients' pharmacokinetics. Analysis of the combination of recipients' ABCB1 and donors' CYP3A5 genotypes revealed that the tacrolimus C/D ratios were significantly lower in the ABCB1 3435CC-carrying recipients, regardless of donors' CYP3A5 genotype. In conclusion, our finding suggests that the recipients' ABCB1 and donors' CYP3A5 genotype affect the tacrolimus dose requirements. ABCB1 C3435T polymorphism is a major determinant of tacrolimus trough concentration in Chinese liver transplant recipients, and recipients with 3435CC genotype will require higher dose of tacrolimus.

Analysis of Common Single Nucleotide Polymorphisms in MDR1 Gene in Patients with Multiple Myeloma.

P-glycoprotein (P-gp) encoded by MDR1 gene is a xenobiotic transporter involved in protection of normal tissues against environmental toxicants and multi-drug resistance of cancer cells. Recently, a number of authors, including our group, have indicated that phenomenon of single nucleotide polymorphism (SNP) in MDR1 may influence susceptibility or prognosis in various diseases as well as pharmacokinetics of P-gp substrates. Although environmental chemicals are suspected carcinogens in multiple myeloma (MM) and P-gp transported drugs are used in the treatment of this malignancy, little data is known on the significance of MDR1 SNPs in MM. In this study, three common MDR1 SNPs: C1236T, G2677T/A and C3435T were assessed in 89 MM patients using automated sequencing and RFLP method. Moreover, in the control group of 215 healthy individuals MDR1 C3435T SNP was genotyped in all subjects and P-gp expression and activity were examined in a proportion of subjects. The haplotypes were inferred using Partition-Ligation algorithm showing highest frequency of the haplotype with wild-type alleles at all sites studied (1236C-2677G-3435C, 30%), followed by haplotype with all mutant alleles (1236T-2677T-3435T; 27%) and 1236C-2677G-3435T haplotype (12%). Carriers of a mutant allele at MDR1 1236 site showed a trend to longer overall survival as compared to wild-type homozygotes MDR1 1236CC (p=0.08), while no correlations with survival were observed regarding other polymorphisms. As compared to the control group, the MDR1 C3435T SNP allele frequency did not differ in MM patients, however the carriers of at least one T-allele (CT and TT genotypes) were significantly more frequent in the MM cohort (79% vs. 65%, p=0.02). The flow cytometry results of anti-P-gp MRK16 antibody staining and functional rhodamin123/PSC833 assay performed on peripheral blood mononuclear cells, CD19+ B-lymphocytes and CD3+ T-lymphocytes were similar among healthy individuals having MDR1 3435CC, CT and TT genotypes. In conclusion, we observed that MDR1 gene SNPs may exert some effect in genetic predisposition and prognosis in MM, which should be further examined in larger cohorts of uniformly treated patients.

The MDR1 3435 polymorphism in patients with rheumatoid arthritis.

Rheumatoid arthritis (RA) is a multifactorial disease, the pathogenesis of which involves immunological, genetic and environmental factors. P-glycoprotein (P-gp) encoded by the MDR1 gene, is an important transporter for many drugs, xenobiotics and cytokines and may be associated with many immunological processes and apoptosis. The activity of P-gp is genetically determined. Naturally occurring MDR1 polymorphisms have been described and correlated with potential clinical effects. Several mutations in the MDR1 gene have been recognized, but only some of them are associated with P-gp expression. The C3435T polymorphism was found to correlate with the activity of P-glycoprotein. The aim of the study was to evaluate the C3435T MDR1 polymorphism in patients with rheumatoid arthritis and to investigate a possible correlation with disease susceptibility, activity and severity. The study was carried out in 92 patients with rheumatoid arthritis and 97 healthy subjects as a control group. The C3435T polymorphism was determined using the PCR-RFLP method. The distribution of C3435TT MDR1 genotypes in RA patients did not differ significantly from that in a control group and was as follows: 3435CC in 25 (26.9%) subjects, 3435CT in 50 (53.8%) and 3435TT in 17 (18.3%). The probability of remission of RA symptoms after therapy with methotrexate and glucocorticosteroids however, was 2.89-fold greater in patients with the 3435TT genotype compared to patients with the genotypes 3435CC and 3435CT. The risk of having an active form of rheumatoid arthritis resistant to therapy with disease-modifying antirheumatic drugs in patients with 3435CC and 3435CT genotypes was 2.89 times greater than in homozygous 3435TT subjects. We suggest that the C3435T MDR1 polymorphism is not an important genetic risk factor for RA susceptibility, but that this polymorphism may have an influence on the activity of the disease and its response to therapy with disease-modifying antirheumatic drugs.