Do polymorphisms in MDR1 and CYP3A5 genes influence the risk of cytogenetic relapse in patients with chronic myeloid leukemia on imatinib therapy?

Influence of polymorphisms in the genes coding for imatinib transporters and metabolizing enzymes on cytogenetic relapse in patients with chronic myeloid leukemia (CML) is not known. One hundred and four patients (52 cases with cytogenetic relapse and 52 controls without relapse) with chronic-phase CML on imatinib therapy and have completed 5 years of follow-up were enrolled. The following single nucleotide polymorphisms (SNPs) were genotyped; C1236T, C3435T, G2677T/A in MDR1 gene and A6986G in CYP3A5 gene, using PCR-RFLP method and validated by direct gene sequencing. Imatinib trough levels were measured using LC-MS/MS. Patients with CC genotype for MDR1-C1236T polymorphism were at significantly higher risk for cytogenetic relapse [OR =4.382, 95% CI (1.145, 16.774), p = .022], while those with TT genotype for MDR1-C3435T polymorphism had significantly lower risk of relapse [OR =0.309, 95% CI (0.134, 0.708), p = .005]. Imatinib trough levels were lower in patients with relapse compared to those without relapse (1551.4 ± 1324.1 vs. 2154.2 ± 1358.3 ng/mL; p = .041). MDR1-C3435T genotype [adjusted-OR: 0.266; 95% CI (0.111, 0.636); p = .003] and trough levels (p = .014) were independent predictors of relapse in multivariate analysis. To conclude, C1236T and C3435T polymorphisms in MDR1 gene and trough levels significantly influence the risk of cytogenetic relapse. MDR1-C3435T genotype might emerge as a potential biomarker to predict the risk of cytogenetic relapse in patients with CML.

Influence of MDR1 and CYP3A5 genetic polymorphisms on trough levels and therapeutic response of imatinib in newly diagnosed patients with chronic myeloid leukemia.

Polymorphisms in genes coding for imatinib transporters and metabolizing enzymes may affect imatinib pharmacokinetics and clinical response. Aim of this study was to assess the influence of polymorphisms in MDR1 and CYP3A5 genes on imatinib trough levels, cytogenetic and molecular response in patients with CML. Newly diagnosed patients with chronic-phase CML started on imatinib therapy were enrolled and followed up prospectively for 24 months. The following single nucleotide polymorphisms were genotyped; C1236T, C3435T, G2677T/A in MDR1 gene and A6986G in CYP3A5 gene. Genotyping was done using PCR-RFLP method and validated by direct gene sequencing. Trough levels of imatinib were measured using LC-MS/MS. Cytogenetic response was assessed by conventional bone-marrow cytogenetics. Molecular response was assessed by qRTPCR using international scale. A total of 173 patients were included, out of which 71 patients were imatinib responders, while 102 were non-responders. Marked inter-individual variability in trough levels of imatinib was seen. Patients with GG genotype for CYP3A5-A6986G (P=0.016) and TT genotype for MDR1-C3435T (P=0.013) polymorphisms had significantly higher trough levels of imatinib. Patients with AA genotype for CYP3A5-A6986G [RR=1.448, 95% CI (1.126, 1.860), P=0.029] and CC genotype for MDR1-C1236T [RR=1.397, 95% CI (1.066, 1.831), P=0.06] &MDR1-C3435T [RR=1.508, 95% CI (1.186, 1.917), P=0.018] polymorphisms were at high risk for failure of imatinib therapy. Patients with CGC haplotype for MDR1 polymorphisms had significantly lower imatinib trough levels and were at a higher risk of imatinib failure [RR=1.547, 95% CI (1.324, 1.808), P<0.001]. GG vs. non-GG genotype for CYP3A5-A6986G [adjusted OR: 0.246; 95% CI (0.116, 0.519); P<0.001] and TT vs. non-TT genotype for MDR1-C1236T [adjusted OR: 0.270; 95% CI (0.110, 0.659); P=0.004] &MDR1-C3435T [adjusted OR: 0.289; 95% CI (0.135, 0.615); P=0.001] polymorphisms were independent factors predicting imatinib response in multivariate analysis. To conclude, MDR1 and CYP3A5 genetic polymorphisms significantly influence plasma trough levels and therapeutic response of imatinib in patients with CML. Genotyping of these polymorphisms could be of value to individualize the therapy and optimize the clinical outcomes.

Association of Angiotensin-converting enzyme insertion(I)/deletion (D) genotype in Alzheimer's disease patients of north Indian population.

Several lines of evidence support for the role of angiotensin-converting enzyme (ACE) in Alzheimer's disease (AD) patients. Most human genetic studies have focussed on ACE insertion (I)/deletion (D) polymorphism and have yielded conflicting results. We have evaluated the association of ACE polymorphism with serum ACE activity in 95 AD patients and 110 healthy controls from north Indian population. In Alzheimer's patients a higher frequency of D allele was detected (I/D ratio 0.53:0.47) compared with the control group (I/D ratio 0.54:0.45), the difference being not statistically significant (p > .05). AD patients were found to be more homozygous for the D allele (26.3%) compared with controls (20.8%). The observed genotype distribution was in agreement with Hardy-Weinberg equilibrium. We observed that the D/D genotype is more in patients with a higher serum ACE activity. The D allele and the D/D genotype in AD patients may influence increased risk of cognitive impairment.

Association of SPINK1 gene mutation and CFTR gene polymorphisms in patients with pancreas divisum presenting with idiopathic pancreatitis.

BACKGROUND: Pancreas divisum has been associated with idiopathic pancreatitis. However, the causal association remains controversial. OBJECTIVE: To study the gene mutations in patients with pancreas divisum presenting with idiopathic pancreatitis. METHODS: All consecutive patients with pancreas divisum presenting with recurrent pancreatitis were included in the study. Fifty healthy volunteers, 30 patients with chronic pancreatitis, and 14 patients with idiopathic recurrent acute pancreatitis without pancreas divisum served as controls. Patients and controls were tested for cationic trypsiongen gene, CFTR gene and SPINK1 gene mutations. RESULTS: Of the 12 patients with pancreas divisum and idiopathic pancreatitis, 4 had SPINK1 N34S gene mutation-3 were heterozygous and 1 was homozygous, and 1 had P55S mutation compared with 1 of 50 healthy controls with N34S mutation (P=0.001). The frequency of SPINK1 mutation was similar among patients with pancreas divisum and pancreatitis (41.6%), chronic pancreatitis (43.3%), and recurrent acute pancreatitis without pancreas divisum (35.7%). Five patients with pancreas divisum had polymorphisms in the CFTR gene. CONCLUSION: Patients with pancreas divisum presenting with idiopathic pancreatitis had a higher frequency of SPINK1 gene mutation compared with healthy controls, which might be responsible as the sole-factor or a co-factor in causing pancreatitis in them.

Characterisation of mutations and genotype-phenotype correlation in cystic fibrosis: experience from India.

BACKGROUND: Very little is known about the genetics of cystic fibrosis (CF) from the Indian subcontinent. The aims of the study were to identify the mutations and study the relation of genotype with phenotype in Indian children with CF. METHODS: A total of 100 patients with CF were screened for mutations in the CFTR gene. These included c.1521_1523delCTT (p.F508del) and c.3849+10 kb C>T mutations followed by single strand conformation polymorphism/heteroduplex analysis for mutations in 19 out of 27 exons of the CFTR gene. RESULTS: At least one mutation was identified in 40 patients. The most common mutation identified was p.F508del; 20 patients were homozygous and 13 heterozygous. In addition, c.3849+10 kb C>T, c.1161delC, and p.S549N were identified in two patients each and p.R352Q, p.R1158X and p.R75Q were identified in one patient each. Three novel mutations, viz. c.1002-7_1002-5delTTT, p.G149X and p.L183I were also identified. Majority of patients who were p.F508del positive originated from Pakistan and north-western states of India. The phenotypes of all patients were classical. Genotype-phenotype correlation revealed that p.F508del positive patients had a more severe disease, manifesting at an earlier age. CONCLUSIONS: A strategy for mutation screening for CF in India must involve testing for p.F508del followed by c.1161delC, c.3849+10 kb C>T and p.S549N. There is a need for large multicentric studies using more sensitive techniques for the identification of mutations in Indian CF patients.

Carrier frequency of F508del mutation of cystic fibrosis in Indian population.

BACKGROUND: Cystic fibrosis (CF) is considered to be very rare in Indian subcontinent. Based on reports of CF in migrants from Indian subcontinent to United Kingdom and United States of America, the prevalence of CF is estimated to be between 1/10,000 and 1/40,000 in this ethnic group. The present study was done to estimate the carrier frequency of F508del mutation among neonates using cord blood samples to reflect the prevalence of CF in the study population. METHODS: 955 mothers delivering at our hospital between December 1999 and November 2000 were enrolled. Cord blood samples were analyzed for F508del mutation using polymerase chain reaction and gel electrophoresis. The frequency of patients homozygous for F508del mutation in the population was estimated using Hardy-Weinberg principle. The prevalence of CF was estimated by using the proportion of F508del homozygous cases out of all CF patients, as reported in various studies (19-44%) from Indian subcontinent. RESULTS: Out of 955 cord blood samples, 4 were positive for F508del mutation. The carrier frequency and gene frequency of F508del mutation in the Indian population was calculated to be 1/238 (0.42%) and 1/477 (0.21%), respectively. Frequency of CF patients homozygous for F508del mutation is 1/228,006. The estimated prevalence of CF is 1/43,321 to 1/100,323 in Indian population. CONCLUSION: CF does occur in Indian subcontinent though the prevalence is lesser than the Caucasian population.