Is C3435T polymorphism of MDR1 related to inflammatory bowel disease or colorectal cancer in Korean?]

BACKGROUND/AIMS: Multidrug resistance 1 (MDR1) gene encodes P-glycoprotein in intestinal epithelium, which serves as a transmembrane efflux pump of various toxins. mdr1 knockout mice develop spontaneous colitis under specific pathogen free conditions. However, it is unclear that C3435T polymorphism of MDR1 is related to ulcerative colitis. Other studies suggest MDR1 may have an important role in colorectal carcinogenesis. Thus, we evaluated whether MDR1 C3435T polymorphism is present in Korean and it is associated with inflammatory bowel disease or colorectal cancer. METHODS: The genotype distributions of the C3435T polymorphism were investigated by PCR-RFLP method in 94 patients with ulcerative colitis, 24 patients with Crohn's disease, 64 patients with colorectal cancer and each of gender-matched controls with equal numbers. RESULTS: There was no significant difference in frequencies of 3435T allele and 3435TT genotype between patients with ulcerative colitis and controls (p=0.443, p=0.194). No significant difference was present in frequencies of 3435T allele and 3435TT genotype between patients with Crohn's disease and controls (p=0.378, p=1.000). There was neither significant difference in frequencies nor 3435T allele or 3435TT genotype between patients with colorectal cancer and controls (p=0.250, p=0.211). C3435T genotype was not associated with the age of onset or other clinical characteristics in patients with ulcerative colitis, Crohn's disease or colorectal cancer. CONCLUSIONS: MDR1 C3435T polymorphism is also present in Korean and the dominant allele is C. However, there is no evidence that C3435T polymorphism of MDRI is associated to inflammatory bowel disease or colorectal cancer in Korean.     

Association between the C3435T MDR1 gene polymorphism and susceptibility for ulcerative colitis

BACKGROUND & AIMS: The human multidrug resistance 1 (MDR1) gene product P-glycoprotein is highly expressed in intestinal epithelial cells, where it constitutes a barrier against xenobiotics. The finding that mdr1a knockout mice develop a form of colitis that is similar to ulcerative colitis, which can be prevented by antibiotics, indicates a barrier function for P-glycoprotein against the invasion of bacteria or toxins. Because the MDR1 single nucleotide polymorphism C3435T is associated with lower intestinal P-glycoprotein expression, we tested whether this polymorphism predisposes to development of ulcerative colitis. METHODS: Allele frequencies and genotype distributions of the C3435T single nucleotide polymorphism were investigated in 149 patients with ulcerative colitis, 126 patients with Crohn's disease, and sex-matched healthy controls. RESULTS: Significantly increased frequencies of the 3435T allele and the 3435TT genotype were observed in patients with ulcerative colitis compared with controls (3435T: P = 0.049; odds ratio, 1.4; 95% confidence interval, 1.02-1.94; 3435TT: P = 0.045; odds ratio, 2.03; 95% confidence interval, 1.04-3.95). In contrast, frequencies of the T allele and the TT genotype were the same in patients with Crohn's disease as in controls (P = 0.66 and P = 0.59, respectively). In comparison to 998 non-sex-matched controls, the effect for the TT genotype in ulcerative colitis patients was more pronounced (P = 0.0055; odds ratio, 2.1). CONCLUSIONS: The higher frequency of the 3435TT genotype in patients with ulcerative colitis corroborates the findings from the mdr1a knockout mice. The results support the notion that P-glycoprotein plays a major role in the defense against intestinal bacteria or toxins. Impairment of barrier function in 3435TT subjects could render this genotype more susceptible to the development of ulcerative colitis.     

Multidrug resistance gene (MDR1) polymorphisms are associated with major molecular responses to standard-dose imatinib in chronic myeloid leukemia

Despite the excellent efficacy of imatinib in chronic myeloid leukemia (CML), the response in patients is heterogeneous, which may in part be caused by pharmacogenetic variability. Imatinib has been reported to be a substrate of the P-glycoprotein pump. In the current study, we focused on the ABCB1 (MDR1) genotype. We analyzed the 3 most relevant single nucleotide polymorphisms of MDR1 in 90 CML patients treated with imatinib. Among the patients homozygous for allele 1236T, 85% achieved a major molecular response versus 47.7% for the other genotypes (P = .003). For the 2677G>T/A polymorphism, the presence of G allele was associated with worse response (77.8%, TT/TA; vs 47.1%, GG/GA/GT; P = .018). Patients with 1236TT genotype had higher imatinib concentrations. One of the haplotypes (1236C-2677G-3435C) was statistically linked to less frequent major molecular response (70% vs 44.6%; P = .021). Hence, we demonstrated the usefulness of these single nucleotide polymorphisms in the identification of CML who may or may not respond optimally to imatinib.     

Effect of ABCB1 3435C>T transporter gene polymorphism on plasma efavirenz concentration in HIV-1 infected Thai adults

Objective:To investigate the influence of ABCB1 polymorphisms on the plasma level of efavirenz in Thai adult cases infected with HIV-1.Methods:A single nucleotide polymorphism of ABCB1 3435 CT(rs1045642) in the gene encoding ABCB1 was genotyped using real-time PCR-based alleles in 149 HIV-infected Thai adults receiving efavirenz treatment.Plasma concentrations of efavirenz were measured by high-performance liquid chromatography 12 hr after administration.The relationship between plasma efavirenz concentrations and ABCB1 3435 CT polymorphisms was analyzed.Results:Logistic regression analysis showed no significant predictors of high plasma efavirenz concentration in relation to age,gender,body weight,CD4 count and plasma HIV-1 RNA,blood biochemical parameters,antiretroviral duration or ABCB1 3435 CT polymorphisms,except for height(OR=0.902,95% CI:0.835-0.973)(P0.05).The minor allele frequency of ABCB1 3435 CT was0.446.The frequency of the heterozygous mutant ABCB1 3435 C/T was 53.02%(n=79),ABCB1 3435 T/T homozygous mutant was 18.12%(n=21) and the wild type ABCB1 3435 C/C genotype was 28.86%(n=43).The overall median plasma concentration of efavirenz in 149 HIV-infected Thai cases was 2.41 mg/L [IQR:(1.46-4.12) mg/L].The plasma concentration of efavirenz was higher in cases with ABCB1 3435 T/T homozygous mutant [2.73 mg/L,IQR:(2.02-4.19) mg/L] and ABCB1 3435 C/T heterozygous mutant [2.29 mg/L,IQR:(1.41-4.28) mg/L] genotypes compared to the wild type ABCB1 3435 C/C homozygous [2.1 mg/L,IQR:(1.37-3.53) mg/L].However,there was no statistically significant difference in the efavirenz concentration between the different genotypes(P0.05).Objective: To investigate the influence of ABCB1 polymorphisms on the plasma level of efavirenz in Thai adult cases infected with HIV-1.Methods: A single nucleotide polymorphism of ABCB1 3435 CT(rs1045642) in the gene encoding ABCB1 was genotyped using real-time PCR-based alleles in 149 HIV-infected Thai adults receiving efavirenz treatment. Plasma concentrations of efavirenz were measured by high-performance liquid chromatography 12 hr after administration. The relationship between plasma efavirenz concentrations and ABCB1 3435 CT polymorphisms was analyzed. Results: Logistic regression analysis showed no significant predictors of high plasma efavirenz concentration in relation to age, gender, body weight, CD4 count and plasma HIV-1 RNA, blood biochemical parameters, antiretroviral duration or ABCB1 3435 CT polymorphisms, except for height(OR=0.902, 95% CI: 0.835-0.973)(P0.05). The minor allele frequency of ABCB1 3435 CT was 0.446. The frequency of the heterozygous mutant ABCB1 3435 C/T was 53.02%(n=79), ABCB1 3435 T/T homozygous mutant was 18.12%(n=27) and the wild type ABCB1 3435 C/C genotype was 28.86%(n=43). The overall median plasma concentration of efavirenz in 149 HIV-infected Thai cases was 2.41 mg/L [IQR:(1.46-4.12) mg/L]. The plasma concentration of efavirenz was higher in cases with ABCB1 3435 T/T homozygous mutant [2.73 mg/L, IQR:(2.02-4.19) mg/L] and ABCB1 3435 C/T heterozygous mutant [2.29 mg/L, IQR:(1.41-4.28) mg/L] genotypes compared to the wild type ABCB1 3435 C/C homozygous [2.1 mg/L, IQR:(1.37-3.53) mg/L]. However, there was no statistically significant difference in the efavirenz concentration between the different genotypes(P0.05).Conclusions: There is no statistical significance for a tendency toward higher plasma efavirenz concentration in the ABCB1 3435 T/T and ABCB1 3435 C/T genotypes. No parameters of physiological characteristics in this study except for height were found to be predictors of high plasma efavirenz concentration in Thai HIV-1 infected cases.     

Multi-drug resistance 1 polymorphism is associated with reduced risk of gastric cancer in the Japanese population

BACKGROUND AND AIMS: Host genetic factors play a key role in gastric carcinogenesis, but the mechanism has not been clarified. The multi-drug resistance 1 (MDR1) gene mediates the expression of P-glycoprotein, which has a role in active transport of various substrates, including xenobiotics, and thus has a protective function in various tissues and organs like gastrointestinal epithelial cells. C3435T polymorphism in exon 26 of the MDR1 gene influences P-glycoprotein expression and activity in the gastrointestinal tract. We investigated the influences of MDR1 gene polymorphism on the risk of gastric cancer. METHOD: The study was performed on 157 patients with gastric cancer (GC) and 104 patients without GC as the control group. C3435T polymorphism of MDR1 was investigated by PCR-RFLP in all of the patients. RESULTS: The MDR1 3435 TT genotype showed a significantly higher frequency in controls than in GC patients (OR = 0.43; 95% CI = 0.23-0.79). There were no significant differences of the CT and CC genotype frequencies between GC patients and controls. We also found that the 3435TT genotype of MDR1 was associated with a lower risk of non-cardiac cancer (OR = 0.42; 95% CI = 0.23-0.79), middle-third cancer (OR = 0.36; 95% CI = 0.17-0.77), advanced cancer (OR = 0.31; 95% CI = 0.13-0.73), venous invasion (OR = 0.30; 95% CI = 0.10-0.91), and lymph node metastasis (OR = 0.28; 95% CI = 0.13-0.65). CONCLUSION: Our data suggest that 3435T/T polymorphism of MDR1 is associated with a reduced risk of gastric cancer in the Japanese population.     

MDR1 polymorphisms and response to azathioprine therapy in patients with Crohn's disease

BACKGROUND: To investigate the contribution of multidrug resistance 1 (MDR1) gene pharmacogenetics (G2677T/A and C3435T) to the efficacy of azathioprine in inducing remission in patients with Crohn's disease (CD). METHODS: A cohort of 327 unrelated Spanish patients with CD recruited from a single center was studied. All patients were rigorously followed up for at least 2 years (mean time, 11.5 years). A case-control analysis of MDR1 G2677T/A and C3435T SNPs and 2 loci haplotypes in 112 steroid-dependent CD patients treated with azathioprine was performed. Patients were classified on the basis of response to azathioprine. RESULTS: A total 76 patients treated with azathioprine for longer than 3 months were included. Remission was achieved in 42 CD patients (55.3%). A higher frequency of the 2677TT genotype was found in nonresponders than in responders (17.65% versus 7.14%; OR = 2.8; 95% CI; 0.6-12.1; P = 0.11). Nonresponders to azathioprine were found to have a higher frequency of the 3435TT genotype than did CD patients who had achieved clinical remission (17.64% versus 4.76%; OR = 4.3; 95% CI, 0.8-22.8; P = 0.06). The 2677T/3435T haplotype was also more abundant in nonresponders (29.4% versus 20.2%), whereas the 2677G/3435C haplotype was more frequent in responders (58.3% versus 47.1%). Lack of response to azathioprine therapy in CD patients was 1.8-fold greater in carriers of the 2677T/3435T haplotype than in carriers of the 2677G/3435C haplotype (OR = 1.8; 95% CI, 0.82-3.9; P = 0.14). CONCLUSIONS: The results of our study indicate higher frequencies of the 2677TT and 3435TT genotypes and the 2677T/3435T haplotype in CD patients who did not respond to azathioprine. Additional replications in independent populations would confirm the real impact of these polymorphisms in response to azathioprine therapy.     

Associations of allelic variants of the multidrug resistance gene (ABCB1 or MDR1) and inflammatory bowel disease and their effects on disease behavior: a case-control and meta-analysis study

BACKGROUND: Allelic variants of the ATP-binding cassette, subfamily B member 1 (ABCB1), also known as the multidrug resistance gene (MDR1) that encodes the membrane-bound efflux transporter P-glycoprotein 170 (PGP-170), have been associated with inflammatory bowel disease but with conflicting results. METHODS: The present study examined the association of ABCB1 C3435T and G2677T/A in a large British case-control cohort of 828 Crohn's disease, 580 ulcerative colitis (UC) cases, and 285 healthy controls. The effect of these variants was further examined with respect to phenotypic and epidemiological characteristics. A meta-analysis was carried out of our results and those from 8 previously published association studies of the C3435T variant in inflammatory bowel disease. RESULTS: The 2677T allele was significantly increased in British UC cases compared with controls (45.2% vs. 39.6%; P = 0.034). In particular, the TT genotype was significantly associated with severe UC (odds ratio [OR] 1.90; 95% CI 1.01-3.55) and the use of steroids in UC (OR 1.77; 95% CI 1.08-2.88). No significant association was seen with C3435T and UC, Crohn's disease, or any clinical subgroup. A meta-analysis of 9 association studies of C3435T showed a significant association of the 3435T allele with UC (OR 1.12; 95% CI 1.02-1.23; P = 0.013) but not with CD. CONCLUSIONS: These results indicate that ABCB1 sequence variants are associated with a small increase in the risk of developing UC and may influence disease behavior.     

Multidrug resistance gene-1 polymorphisms and resistance to cyclosporine A in patients with steroid resistant ulcerative colitis

BACKGROUND: Cyclosporine A (CsA) is inconstantly effective in inducing remission in acute attacks of ulcerative colitis (UC) not responding to steroids. This study aimed to establish whether multidrug resistance gene (MDR)1 polymorphisms would be associated with CsA failure. PATIENTS AND METHODS: The distribution of the different genotypes of single nucleotide polymorphisms (SNP) G2677T/A and C3435T of MDR1 exons 21 and 26, respectively, was studied in 154 patients (mean age, 44 yr) who had received CsA to treat severe attacks of steroid resistant UC in 11 centers in France and Belgium. Patients were classified as CsA failure (n = 50) when they needed colectomy within 30 days after CsA initiation. The SNPs were detected by use of a 5' nuclease allelic discrimination assay. RESULTS: There was a significant association between the G2677T/A polymorphism distribution (exon 21) and the risk for CsA failure (P = 0.0001). The TT genotype of exon 21 was significantly associated with the risk compared with the two other genotypes (odds ratio, 3.77; 95% confidence interval, 1.42-9.97, P = 0.007). There was no significant association between the genotype C3435T distribution (exon 26) and the risk of CsA failure (P = 0.23). CONCLUSION: The TT genotype of exon 21 MDR1 polymorphisms is associated with a higher risk of CsA failure in patients with steroid resistant UC. Further studies should be performed to establish whether other treatments could be more efficient to avoid surgery in this subset of patients.     

MDR1 gene: susceptibility in Spanish Crohn's disease and ulcerative colitis patients

BACKGROUND: The multidrug resistance MDR1 gene codes for a membrane transporter associated with inflammatory bowel disease. The polymorphism Ala893Ser/Thr (G2677T/A) previously showed significant association with Crohn's disease (CD) and the Ile1145Ile (C3435T) with ulcerative colitis (UC). We studied the association of both polymorphisms in an independent population to reveal the impact of the MDR1 gene on predisposition to inflammatory bowel disease. METHODS: Case-control study with 321 CD and 330 UC white Spanish patients recruited from the same center, and 352 healthy ethnically matched controls. RESULTS: A significant association of MDR1 C3435T with CD was observed (CC vs (CT + TT): P = 0.007; OR [95% CI] = 1.58 [1.12-2.23]). A CD susceptibility haplotype 2677T/C3435 was identified. No difference between UC patients as a whole and controls could be detected. CONCLUSIONS: New evidence supports the role of the MDR1 gene on CD susceptibility. Therefore, considering our results and those from others, the MDR1 gene behaves as a common risk factor for both CD and UC. We discovered that the C3435 allele conferring susceptibility to CD is different from the described 3435T UC risk allele.     

Impact of ABCB1 Gene (C3435T/A2677G) Polymorphic Sequence Variations on the Outcome of Patients with Chronic Myeloid Leukemia and Acute Lymphoblastic Leukemia in Kashmiri Population: A Case–Control Study

Inherited polymorphic sequence variations in drug transport genes like ABCB1 impact a portion of patients with hematologic malignancies that show intrinsic or acquire resistance to treatment. Keeping in view inter-individual sensitivities for such drugs, we through this case–control study tested whether ABCB1 C3435T and G2677T polymorphisms have any influence on the risk and treatment response in patients with chronic myeloid leukemia (CML) and B-acute lymphoblastic leukemia (B-ALL). Genotyping for ABCB1 polymorphisms was performed by polymerase chain reaction-restriction fragment length polymorphism in 100 CML and 80 B-ALL patients along with 100 age and gender matched healthy controls. ABCB1 C3435T and G2677T polymorphism showed no association with CML. Genotype distribution revealed significant higher frequency of TT genotype for both SNPs in B-ALL cases and associated with increased B-ALL risk (OR 2.5, p = 0.04 for 3435TT; OR 2.4, p = 0.04 for 2677TT). There was no significant difference in genotype frequency of 3435C > T and 2677G > T among resistant and responsive groups for the two leukemia types. Kaplan–Meier survival plots revealed significantly lower event free survival in CML and B-ALL patients that were carriers of 3435TT genotype (p < 0.05). Multivariate analysis considered 3435TT genotype as independent risk factor for imatinib resistance in CML cases (HR 6.24, p = 0.002) and increased relapse risk in B-ALL patients (HR 4.51, p = 0.03). The current study provides preliminary evidence of a significant association between variant TT genotype and increased B-ALL risk. Also, results suggest that ABCB1 3435TT genotype increases imatinib resistance in CML and influence therapeutic outcome in B-ALL.     

ABCB1 C3435T polymorphism influences methotrexate sensitivity in rheumatoid arthritis patients

OBJECTIVE: Methotrexate (MTX) is most widely used for the treatment of rheumatoid arthritis (RA). However, it has certain drawbacks with regard to individual differences in its therapeutic effects as well as the differences in the patients' response to MTX therapy. We investigated whether multi-drug resistance-1 (ABCB1) C3435T, reduced folate carrier-1 (RFC1) G80A, 5-aminoimidazole-4-carboxamide ribonucleotide transformylase (ATIC) C347G and a 6bp-deletion polymorphism in the 3'-untranslated region of the thymidylase synthase (TYMS) gene are predictive of MTX sensitivity and its adverse effects. METHODS: Patients whose last maintenance dosage of MTX was 6 mg/week or those in whom MTX therapy was changed due to poor response to MTX were regarded as non-responders. The data of 124 RA patients who had received MTX treatment were retrospectively analyzed for polymorphisms in the ABCB1, RFC1, ATIC and TYMS genes, MTX sensitivity and MTX toxicity. RESULTS: There were no significant differences in MTX sensitivity among the genotypes of RFC1, ATIC and TYMS genes. ABCB1 3435TT cases included statistically significantly more non-responders than 3435CC cases according to univariate analysis (crude odds ratio (OR) = 8.91, p = 0.001) and multivariate analysis (adjusted OR = 8.78, p = 0.038). There were no significant differences in MTX toxicity among the genotypes of all the genes. CONCLUSION: These results suggested that the genetic diagnosis of ABCB1 C3435T can be applied to determine MTX sensitivity for the treatment of RA patients. However, further pharmacokinetics studies are required in this regard.     

心房颤动患者ABCB1基因多态性与达比加群酯临床疗效的关系

目的 探索维吾尔族(维族)心房颤动患者ABCA1基因C3435T位点多态性与达比加群酯治疗效果的关系.方法 选取2015年1月至2016年12月在新疆医科大学第五附属医院住院或门诊就诊的维族、汉族心房颤动患者166例作为研究对象.检测入选患者的ABCA1基因C3435T位点多态性,再分别检测并比较不同基因型患者达比加群...     

MDR1基因G2677T/C3435T多态性对鼻咽癌放疗疗效的影响

目的探讨多药耐药基因（MDR1）21外显子G2677T和26外显子C3435T多态性对鼻咽癌根治性放疗疗效的影响。方法采用PCR和限制性片断长度多态性（RFLP）对59例鼻咽癌患者行MDR1基因分型,并用测序法验证。结果G2677T GG基因型携带者行根治性放疗的效果优于GT和TT基因型,但差异无显著性;C3435T CC基因型携带者放射敏感性显著强于CT和TT基因型携带者（P=0．026）。结论MDR1基因多态性可作为鼻咽癌患者放射敏感度的遗传学标志。     

P-glycoprotein expression in Helicobacter pylori-positive patients: the influence of MDR1 C3435T polymorphism

OBJECTIVE: The aim of this study was to determine whether the presence of Helicobacter pylori (H. pylori) infection and multidrug resistance protein 1 (MDR1) C3435T polymorphism had an influence on P‐glycoprotein (P‐gp) expression in the upper gastrointestinal tract. METHODS: A total of 76 patients who underwent upper gastroendoscopy at Sir Charles Gairdner Hospital in Western Australia from October 2010 to July 2011 were enrolled in the study. Antral and duodenal biopsies were collected for P‐gp examination. Blood samples were taken and analyzed for MDR1 C3435T polymorphism. H. pylori infection status was confirmed by culture and polymerase chain reaction. RESULTS: A significant difference was found in P‐gp expression between H. pylori‐positive and H. pylori‐negative patients (P = 0.028). For the MDR1 C3435T polymorphism, the TT genotype had a significantly lower P‐gp expression compared with the CC genotype in antral specimens (P = 0.041). The homozygous TT genotype with H. pylori infection was also significantly different in P‐gp expression compared with H. pylori‐negative patients (P = 0.029). CONCLUSIONS: P‐gp expression in the upper gastrointestinal tract is associated with H. pylori infection, and the TT genotype appeared to be associated with lower P‐gp expression than the CC genotype in the stomach.     

Genetic factors influencing atazanavir plasma concentrations and the risk of severe hyperbilirubinemia

BACKGROUND: Hyperbilirubinemia is frequently seen in patients treated with atazanavir (ATV). Polymorphisms at the uridin-glucoronosyl-transferase 1A1 (UGT1A1) and multidrug resistance 1 (MDR1) genes may influence, respectively, bilirubin and ATV plasma concentrations. PATIENTS AND METHODS: HIV-infected individuals receiving ATV 300 mg daily plus ritonavir 100 mg daily at one clinic were examined. ATV plasma concentrations were measured at steady state. MDR1-3435C>T and UGT1A1 polymorphisms were examined in DNA extracted from blood mononuclear cells. RESULTS: A total of 118 patients (all Caucasian) were analysed. The median ATV plasma concentration was 465 ng/ml [interquartile range (IQR), 233-958]. MDR1-3435 genotypes were as follows: CC (32%), CT (47%) and TT (21%). CC patients showed higher ATV minimum concentration than those with CT/TT genotypes: 939 ng/ml (IQR, 492-1266) versus 376 ng/ml (IQR, 221-722) (P = 0.001). In multivariate analyses, having at least one T allele at MDR1-3435 was independently associated with lower ATV plasma concentrations (beta: -427 [95% confidence interval (CI), -633 to -223]; P < 0.001). The proportion of patients with grade 3-4 hyperbilirubinemia varied with distinct UGT1A1 genotypes: 80% for 7/7, 29% for 6/7 and 18% for 6/6 (P = 0.012). In the multivariate analysis, having at least one 7 allele at UGT1A1 was independently associated with severe hyperbilirubinemia (odds ratio, 2.96; 95% CI, 1.29-6.78; P = 0.01). CONCLUSIONS: Polymorphisms at MDR1-3435 significantly influence ATV plasma concentrations, as does being Caucasian patients with CT/TT genotypes, having lower ATV levels, even using ritonavir boosting. On the other hand, although ATV plasma concentrations directly correlate with bilirubin levels, the risk of severe hyperbilirubinemia is further increased in the presence of the UGT1A1-TA7 allele.     

鼻咽癌放射敏感性与MDR1基因多态性的相关性

目的探讨鼻咽癌放射敏感性差异与多药耐药基因（MDRI）多态性的相关性。方法选择48例行根治性放疗的鼻咽癌患者,根据放疗疗效分为抵抗组和敏感组,针对MDR1基因多态性（21外显子G2677T和26外显子C3435T）行PCR扩增、基因测序分型及构建G2677T—C3435T单体型。结果G2677T TT基因型放射敏感性显著低于GG和GT基因型（P=0．017）,C3435T TT基因型放射敏感性显著低于CC和CT基因型（P=0．022）,携带2677T-3435T单体型的患者放射敏感性显著低于其他单体型携带者（P=0．013）。结论MDR1 G2677T和C3435T多态性可能提示鼻咽癌根治性放疗的疗效。     

MDR1 polymorphism influences the outcome of multiple myeloma patients

The multidrug resistance gene (MDR1) has been reported to be an additional prognostic factor in acute myeloid leukaemia patients. This study evaluated the prognostic role of MDR1 in the outcome of 115 multiple myeloma patients treated with DAV (dexamethasone, doxorubicin [adryamicin] and vincristine) regimen followed by autologous transplantation. In particular, when investigating the C3435T polymorphism, a prognostic value of MDR1 genotypes for overall survival (OS) was observed. Our data suggested a longer OS for patients with C/T and T/T genotypes (log-rank test, P = 0.02) compared with patients with C/C genotype.     

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.