Influence of ABCB1 C3435T and C1236T gene polymorphisms on tumour response to docetaxel-based neo-adjuvant chemotherapy in locally advanced breast cancer patients of South India.

WHAT IS KNOWN AND OBJECTIVE: Variable response to docetaxel-based neo-adjuvant chemotherapy (NACT) in breast cancer patients had been reported. Genetic polymorphisms in the ABCB1 gene coding for the efflux transporter MDR1 (P-glycoprotein, P-gp) could result in altered tumour response. Hence, this study was proposed to assess the effect of single nucleotide polymorphisms (SNPs) of ABCB1 gene on tumour response in locally advanced breast cancer patients (LABC) of South India who have a distinct genetic makeup. METHODS: Out of 162 LABC patients recruited, 129 patients were included for the final analysis. DNA was extracted by "phenol-chloroform extraction method" from the WBCs, and genotyping for SNPs rs1045642 (C3435T) and rs1128503 (C1236T) in ABCB1 gene was performed with real-time PCR system using validated TaqMan® SNP genotyping assay method. Tumour response was assessed by RECIST criteria based on the MRIs taken before and after completion of four cycles of docetaxel therapy. RESULTS AND DISCUSSION: A total of 102 (79.1%) patients were found to be responders and 27 (20.9%) patients were found to be non-responders to docetaxel therapy. Patients with "CT/TT" genotypes (response rate: 83.3%) of ABCB1 (C1236T) gene showed better tumour response than those with "CC" genotype (response rate: 16.6%) [OR = 2.94 (CI: 1.15-7.52); P = 0.03]. However, on performing binary logistic regression, neither the studied SNPs nor the non-genetic factors like age, BMI, postmenopausal status, laterality of the tumour, ER status, PR status and Her-2/neu status were found to be associated with tumour response to docetaxel (P > 0.05). WHAT IS NEW AND CONCLUSION: The tumour response to docetaxel was significantly influenced by the SNP C1236T of ABCB1 gene coding for the P-gp. However, when adjusted for other non-genetic factors, neither of the ABCB1 variants were found to be associated with tumour response to docetaxel-based NACT in LABC patients of South India.

Serotonin transporter gene (SLC6A4) polymorphisms are associated with response to fluoxetine in south Indian major depressive disorder patients.

PURPOSE: Up to 30-40 % of the major depressive disorder patients do not respond sufficiently to antidepressant treatment. Genetic variations in the serotonin transporter gene have been implicated in modulating treatment response to selective serotonin reuptake inhibitors, and this association is influenced by ethnicity. We investigated the influence of serotonin transporter gene variants 5-HTTLPR and rs25531 in Indian population on fluoxetine response. METHODS: One hundred and two major depressive disorder patients were started on fluoxetine treatment and after 6 weeks, classified as responders (n = 56) and non-responders (n = 46) using Hamilton depression rating scale and genotyped. Fisher's exact test was used to compare genotype frequencies between responders and non-responders. One-way analysis of variance and student t test were used to compare the percentage reduction (week 0-6) in Hamilton depression rating scores between genotype and haplotype groups. RESULTS: We observed a significant association between LL genotype of 5-HTTLPR and fluoxetine treatment response (p = 0.0066, OR (95 %) = 4.0 (1.45-11.03)) but not with the functional groups of 5-HTTLPR -rs25531. However, there was a significant difference in percentage reduction in HAM-D scores (week 0-6) between 5-HTTLPR genotypes (LL vs. LS + SS, p = 0.0036; LL vs. LS, p = 0.0109) as well as the functionally grouped haplotypes of 5-HTTLPR -rs25531 (LALA carriers vs. non-carriers of LALA, p = 0.0118; LALA vs. LAS+ LALG, p = 0.0419). CONCLUSION: The LL genotype and LALA haplotype of SLC6A4 are associated with favorable treatment response to fluoxetine in south Indian major depression patients.

Evaluation of interleukin-6 and serotonin as biomarkers to predict response to fluoxetine.

OBJECTIVE: Only 30% of major depressive disorder (MDD) patients achieve complete remission with a serotonergic antidepressant (selective serotonin reuptake inhibitor). We investigated the potential of serotonin (5-HT) and interleukin-6 (IL-6) to serve as functional biomarkers of fluoxetine response. METHODS: Serum IL-6 and 5-HT were measured in 73 MDD patients (39 responders and 34 non-responders) pre- and 6 weeks post-treatment and in 44 normal controls with ELISA. Fluoxetine and norfluoxetine were measured using LC MS/MS. RESULTS: IL-6 levels were significantly higher in MDD patients when compared with controls (p < 0.01), and 5-HT levels were significantly lower in non-responders compared with controls (p = 0.0131). Pre- and post-treatment levels of both biomarkers individually and in combination did not significantly differ between responders and non-responders. Area under the receiver operating characteristics curve for the biomarkers was 0.5. Significant correlation was seen between the percentage change in IL-6 and percentage change in Hamilton Rating Scale for Depression score in responders. Fluoxetine and norfluoxetine concentrations were not significantly different in responders and non-responders, and there was no correlation between fluoxetine concentrations and percentage reduction in 5-HT from week 0 to 6. CONCLUSION: 5-HT and IL-6 may not serve as useful markers of response to fluoxetine because of inconsistent results across different studies. Copyright © 2016 John Wiley & Sons, Ltd.

An acenocoumarol dosing algorithm exploiting clinical and genetic factors in South Indian (Dravidian) population.

OBJECTIVE: The objective of this study was to determine the influence of CYP2C9, VKORC1, CYP4F2, and GGCX genetic polymorphisms on mean daily dose of acenocoumarol in South Indian patients and to develop a new pharmacogenetic algorithm based on clinical and genetic factors. METHODS: Patients receiving acenocoumarol maintenance therapy (n = 230) were included in the study. Single nucleotide polymorphisms (SNP) of CYP2C9, VKORC1, CYP4F2, and GGCX were genotyped by real-time polymerase chain reaction (RT-PCR) method. RESULTS: The mean daily acenocoumarol maintenance dose was found to be 3.7 ± 2.3 (SD) mg/day. The CYP2C9 *1*2, CYP2C9 *1*3, and CYP2C9 *2*3 variant genotypes significantly reduced the dose by 56.7 % (2.0 mg), 67.6 % (1.6 mg), and 70.3 % (1.5 mg) than wild-type carriers 4.1 mg, p < 0.0001. The genetic variants of CYP2C9 and GGCX (rs11676382) were found to be associated with lower acenocoumarol dose, whereas CYP4F2 (rs2108622) was associated with higher doses. Age, body mass index (BMI), variation of CYP2C9, VKORC1, CYP4F2, and GGCX were the major determinants of acenocoumarol maintenance dose, accounting for 61.8 % of its variability (adjusted r (2) = 0.615, p < 0.0001). Among the VKORC1 variants, rs9923231 alone contributed up to 28.6 % of the acenocoumarol dose variation. CONCLUSION: VKORC1 rs9923231 polymorphism had the highest impact on acenocoumarol daily dose. A new pharmacogenetic algorithm was established to determine the acenocoumarol dose in South Indian population.

Effect of ADRB2 (adrenergic receptor ß2) gene polymorphisms on the occurrence of asthma and on the response to nebulized salbutamol in South Indian patients with bronchial asthma.

INTRODUCTION: Genetic mutations in the ß2 receptor could alter its functioning and the response to ß2 agonists. The study was done to find out the effect of two commonly occurring polymorphisms-Arg16Gly and Gln27Glu, on cause of asthma and on response to nebulized salbutamol in South Indian subjects of asthma. METHODS: After baseline measurements of Forced Expiratory Volume in 1st second (FEV1), Forced Vital Capacity (FVC) and Peak Expiratory Flow Rate (PEFR), five mg of nebulized salbutamol was administered and spirometry was repeated. The increase in these parameters was calculated and patients were included for genotyping if the percentage increase in FEV1 was ≥12%. The frequencies of these polymorphisms in patients were compared with those of healthy volunteers. RESULTS: 112 patients and 127 healthy volunteers were genotyped. The frequencies of the polymorphisms were found to be similar to previously published Dravidian population frequencies. The frequencies of genotypes in asthmatics were similar to healthy volunteers. The increase in FEV1, FVC and PEFR was similar across various genotypes and haplotypes in both the polymorphisms. The GG-CG haplotype was associated with 3.1 times increased occurrence of asthma (p value = 0.02). The G allele of the Arg16Gly polymorphism was associated with lower baseline FEV1, FVC and PEFR values, but these were not statistically significant. CONCLUSION: The Arg16Gly and Gln27Glu polymorphisms do not determine the occurrence of asthma individually, but the GG-CG haplotype is associated with an increased risk of asthma. There is no effect of the genotypes on the response to nebulized salbutamol.

Metabolomics: A Tool Ahead for Understanding Molecular Mechanisms of Drugs and Diseases.

To refer to metabolomics as a new field is injustice to ancient doctors who used ants to diagnose the patients of diabetes having glycosuria. Measuring the levels of molecules in biological fluids believing them to be the representatives of biochemical pathways of carbohydrates, fats, proteins, nucleic acids or xenobiotic metabolism and deciphering meaningful data from it is what can be called as metabolomics, just as high glucose in urine suggests diabetes mellitus. Genomics, epigenetics, proteomics, transcriptomics finally converge to metabolomics, which are the signatures of mechanisms of bodily processes which is why understanding this science can have many applications. Just as a heap of stones does not make a house, having data of metabolite levels does not make it a science. Analyzing this data would help us in constructing biochemical pathways and their interactions. Analyzing the changes caused by a drug in the metabolite levels would help us in deriving the mechanisms by which the drug acts. Comparing metabolite levels in diseased with non-diseased, good-responders with poor-responders to a particular drug can help in identifying new markers of a disease or response to a drug respectively. Also, metabolite levels of an endogenous substrate can tell us the status of a person's metabolizing enzymes and help in drug dose titration. Generating hypothesis by identifying the new molecular markers and testing their utility in clinics seems to be the most promising approach in future. This review narrates the modes of quantifying and identifying metabolome, its proposed applications in diagnosis, monitoring and understanding the diseases and drug responses. We also intend to identify hindrances in using metabolomics in clinical studies or experiments.

Single nucleotide polymorphism of CYP3A5*3 contributes to clopidogrel resistance in coronary artery disease patients among Tamilian population.

Clopidogrel is an antiplatelet drug. It is used for the treatment as well as for the prophylaxis of coronary artery disease. Clopidogrel resistance is an emerging problem in clinical settings. The aim of the present study was to evaluate the effect of CYP3A5*3 genetic polymorphism on clopidogrel resistance. One hundred and forty-seven patients from outpatient Department of Cardiology on 75 mg/day of clopidogrel as maintenance dose were recruited from April 2010 to July 2011. All subjects gave written informed consent to participate in the study. DNA extraction was performed using phenol chloroform extraction procedure and genotyping by standard Taqman based RT-PCR method. Platelet aggregation was done at the end of 7th and 14th day by using chronolog lumi Aggregometer which is expressed as impedance in ohms. Impedance values of >5 ohms at the end of 6 min were considered as clopidogrel resistance. Subjects (N = 147) were analysed for CYP3A5*3 polymorphism, of which 49 (33%) were found to be clopidogrel resistant. Homomutants of CYP3A5*3 gene had 2.78 (0.97-7.98; p < 0.05) fold risk and heteromutants had 2.4 (0.93-6.46; p < 0.05) fold risk of developing clopidogrel resistance. Carriers of defective allele G of CYP3A5*3 had higher propensity to cause clopidogrel resistance with an odds ratio of 1.63. Variant alleles and genotypes of CYP3A5*3 polymorphism contributed significantly to clopidogrel resistance with a higher odds ratio. Thus, pharmacogenomics paves way for the emergence of stratified medicine in clopidogrel therapy and personalised pharmacotherapy in ischaemic heart disease.

Effect of CYP2C9, VKORC1, CYP4F2 and GGCX genetic variants on warfarin maintenance dose and explicating a new pharmacogenetic algorithm in South Indian population.

OBJECTIVE: To determine the influence of genetic polymorphisms on warfarin maintenance dose and to explicate an algorithm using the pharmacogenetic and clinical factors to determine the maintenance and/or starting dose of warfarin in South Indian patients receiving warfarin therapy. METHODS: Patients receiving stabilized warfarin therapy (n=257) were included in the study. Single nucleotide polymorphisms (SNPs) of CYP2C9 (rs1799853 and rs1057910), VKORC1 (rs9923231, rs7196161, rs2884737, rs9934438, rs8050894, rs2359612 and rs7294), CYP4F2 (rs2108622) and GGCX (rs11676382) were genotyped by the quantitative real time-PCR method. RESULTS: The mean daily maintenance dose of warfarin was found to be 4.7 ± 2.1 mg/day. Patients with the CYP2C9*1/*2, *1/*3 and *2/*3 variant genotypes required a 51.0 (2.8 mg), 60.9 (2.3 mg) and 62.2 % (2.2 mg) lower daily maintenance dose of warfarin, respectively, than those patients with the CYP2C9*1/*1 wild-type genotype (5.2 mg) (p<0.0001). The genetic variants of CYP2C9, VKORC1 and GGCX were associated with decreased warfarin dose, except for rs7196161, rs7294 and rs2108622 which were associated with an increased warfarin dose. Genetic variations of CYP2C9 (*2 and *3), VKORC1 (rs9923231, rs7294, rs9934438 and rs2359612), CYP4F2, GGCX and non-genetic factors such as age, body weight, clinical status (post mechanical valve replacement) could explain up to 62.1 % of the overall variation (adjusted r (2) 60.2 %, p<0.0001) in warfarin maintenance dose. CONCLUSION: Genetic polymorphisms of CYP2C9, VKORC1, CYP4F2 and GGCX are important predictive factors of warfarin maintenance dose, and the developed algorithm will be useful to predict the required maintenance and/or starting warfarin dose in South Indian populations.

Ethnic Differences, Lung Cancer Risk, and Association of NRF2 Gene Polymorphism with Gemcitabine-Based Chemotherapy.

INTRODUCTION: The cancer burden is rising every year. Lung cancer is one of the most common cancers and non-small cell lung cancer is the most common type. Chemotherapy based on platinum drugs and third-generation nucleoside anti-metabolites such as gemcitabine are used widely. Gemcitabine has a complex metabolic pathway, with many mechanisms contributing to its cytotoxicity. Derangements in the metabolic pathway genes contribute to drug resistance and toxicity with this drug. Association studies including these genetic polymorphisms in the metabolic pathway, clinical outcomes, and cancer risk reported inter-individual differences. Thus, the aim of this study was to ascertain the role of these genetic variants in South Indian cancer patients treated with gemcitabine-based therapy. METHODS: The study was done with 184 healthy volunteers for frequency establishment and 123 cancer patients were treated with gemcitabine-based chemotherapy for response and toxicity assessment. The participants were aged 18-65 years and resided in the southern states of India. DNA extraction was done from the leukocyte fraction of the blood by phenol-chloroform extraction procedures and genotyping was done by reverse transcription-polymerase chain reaction (RT-PCR) techniques to identify DNA repair gene polymorphisms. Tumor response was determined using Response evaluation criteria in solid tumors (RECIST) guidelines and toxicity using Common Terminology Criteria for Adverse Events (CTCAE), version 4.03. The patients were followed up for survival analysis. RESULTS: The minor allele frequency of the single nucleotide polymorphism (SNP) NRF2-617 C>A (rs6721961) in the healthy population was 12.8%. SNPs were in Hardy-Weinberg equilibrium (p>0.05). Gender-based differences were not observed with the studied SNP in the healthy population and the lung cancer patients. These frequencies of NRF2 were found to be similar when compared to EUR (European) and all the South Asian subpopulations. They are significantly divergent compared to AFR (African), AMR (American), and EAS (East Asian) populations. The minor allele frequency in cancer patients was found to be 14.2% and the lung cancer risk with the SNP studied could not be detected. There was no association found with the response, toxicity, and survival among lung cancer patients. CONCLUSION: NRF2, being a multifaced molecule, did not show a significant association with lung cancer risk, response, and toxicity in patients with gemcitabine-based chemotherapy.

Inter and intra ethnic variation of vitamin K epoxide reductase complex and cytochrome P450 4F2 genetic polymorphisms and their prevalence in South Indian population.

BACKGROUND: Genetic variation in the vitamin K epoxide reductase complex (VKORC1) and cytochrome P450 4F2 (CYP4F2) genes were found to be strongly associated with the oral anticoagulant (OA) dose requirement. The distribution of genetic variation in these two genes was found to show large inter- and intra-ethnic difference. MATERIALS AND METHODS: A total of 470 unrelated, healthy volunteers of South Indians of either sex (age: 18-60 years) were enrolled for the study. A 5 ml of venous blood was collected and the genomic deoxyribonucleic acid (DNA) was extracted by using phenol-chloroform extraction method. Real-time quantitative polymerase chain reaction (RT-PCR) method was used for genotyping. RESULTS: The variant allele frequencies of VKORC1 rs2359612 (T), rs8050894 (C), rs9934438 (T) and rs9923231 (A) were found to be 11.0%, 11.8%, 11.7% and 12.0%, respectively. The variant allele VKORC1 rs7294 was (80.1%) more frequent and the variant allele CYP4F2 * 3 was found to be 41.8% in South Indians. The allele, genotype and haplotype frequencies of VKORC1 and CYP4F2 gene were distinct from other compared HapMap populations (P < 0.0001). CONCLUSION: The findings of our study provide the basic genetic information for further pharmacogenetic based investigation of OA therapy in the population.

Risperidone response in patients with schizophrenia drives DNA methylation changes in immune and neuronal systems.

Background: The choice of efficient antipsychotic therapy for schizophrenia relies on a time-consuming trial-and-error approach, whereas the social and economic burdens of the disease call for faster alternatives. Material & methods: In a search for predictive biomarkers of antipsychotic response, blood methylomes of 28 patients were analyzed before and 4 weeks into risperidone therapy. Results: Several CpGs exhibiting response-specific temporal dynamics were identified in otherwise temporally stable methylomes and noticeable global response-related differences were observed between good and bad responders. These were associated with genes involved in immunity, neurotransmission and neuronal development. Polymorphisms in many of these genes were previously linked with schizophrenia etiology and antipsychotic response. Conclusion: Antipsychotic response seems to be shaped by both stable and medication-induced methylation differences.

The most common way to treat schizophrenia is antipsychotic medication. However, not all antipsychotics work for all patients. The only way to find a suitable antipsychotic is to prescribe one and wait, sometimes for months, to see if it works. Finding an alternative to this trial-and-error method would help reduce patient suffering and costs for healthcare systems. The idea is to look in the DNA of our blood cells for specific marks that can change in response to our lifestyle or health condition. These marks could help us predict how patients will react to the drug. In other words, they can serve as biomarkers of antipsychotic response. The current work examined the blood of schizophrenia patients before and 4 weeks after starting medication. The patients who did not respond well to the drug had different marks on the genes involved in immune defense and nervous system functioning. Some of these genes also play roles in the development of schizophrenia, whereas others can directly affect what happens to the drug in the patient's body. Although marks that predict how patients will react were not identified with certainty, valuable targets for future research were identified.

Inter and intra-ethnic differences in the distribution of the molecular variants of TPMT, UGT1A1 and MDR1 genes in the South Indian population.

Molecular variants of polymorphic drug metabolizing enzymes and drug transporters are attributed to differences in individual's therapeutic response and drug toxicity in different populations. We sought to determine the genotype and allele frequencies of polymorphisms for major phase II drug-metabolizing enzymes (TPMT, UGT1A1) and drug transporter (MDR1) in South Indians. Allelic variants of TPMT (*2,*3A,*3B,*3C & *8), UGT1A1 (TA)6>7 and MDR1 (2677G>T/A & 3435C>T) were evaluated in 450-608 healthy South Indian subjects. Genomic DNA was extracted by phenol-chloroform method and genotype was determined by PCR-RFLP, qRT-PCR, allele specific PCR, direct sequencing and SNaPshot techniques. The frequency distributions of TPMT, UGT1A1 and MDR1 gene polymorphisms were compared between the individual 4 South Indian populations viz., Tamilian, Kannadiga, Andhrite and Keralite. The combined frequency distribution of the South Indian populations together, was also compared with that of other major populations. The allele frequencies of TPMT*3C, UGT1A1 (TA)7, MDR1 2677T, 2677A and 3435T were 1.2, 39.8, 60.3, 3.7, and 61.6% respectively. The other variant alleles such as TPMT*2, *3A, *3B and *8 were not identified in the South Indian population. Sub-population analysis showed that the distribution of UGT1A1 (TA)6>7 and MDR1 allelic variants differed between the four ethnic groups. However, the frequencies of TPMT*3C allele were similar in the four South Indian populations. The distribution of TPMT, UGT1A1 and MDR1 gene polymorphisms of the South Indian population was significantly different from other populations.

Functional characterization of promoter region polymorphisms of human CYP2C19 gene.

CYP2C19 is an enzyme involved in the metabolism of several clinically important drugs. The variations in the CYP2C19 promoter region may alter the transcription of the gene by altering the interaction between the trans and cis-acting elements. In the present study, CYP2C19 promoter region with different variant alleles were cloned into a pGL-3 basic luciferase reporter vector and transfected into HepG2 cell lines. Subsequently, dual luciferase activity was measured to evaluate the activity of the promoter region. Gel shift assays with predicted binding sites for CCAAT displacement protein, activating transcription factor-2 and glucocorticoid receptor were performed. Results from this study indicate that few variations present in the putative cis-acting elements of the CYP2C19 promoter region such as -1442T>C, -779A>C and -98T>C -1498T>G and -828del>T alter the transcription of the gene. Specific binding with nuclear proteins was also observed in gel shift assays. This may account for the interindividual variations in gene expression and genotype dependant differences in gene transcription. The results also suggest the role of activating transcription factor-2 and CCAAT displacement repressor protein on CYP2C19 gene transcription.

Association of plasma docetaxel levels with ABCB1 gene polymorphisms and tumour response in locally advanced breast cancer patients of South India on neo-adjuvant chemotherapy.

BACKGROUND: Genetic factors could be attributed to the variability in docetaxel plasma levels and its subsequent therapeutic response. The objectives of this study were to assess the effect of ABCB1 gene polymorphisms [SNPs rs1045642 (C3435T) and rs1128503 (C1236T)] on docetaxel plasma levels and also to analyze the influence of docetaxel plasma levels on tumour response in the ethnically distinct South Indian population. METHODS: 104 locally advanced breast cancer (LABC) patients on docetaxel-based neo-adjuvant chemotherapy (NACT) were included. The plasma docetaxel levels were estimated using the validated reverse phase liquid chromatography with mass spectrometry (LC-MS/MS). DNA was extracted (phenol-chloroform extraction method) and the real-time PCR system using validated TaqMan® SNP genotyping assay method was used for genotyping. Tumour response was assessed by RECIST criteria based on the MRI images. RESULTS: Patients with "CT/TT" genotype of the SNP C1236T had a C0/Ct ratio of 1.6 times higher than those with "CC" genotype (13.5 ± 6.5 vs 8.3 ± 3.1, p = 0.002). Though not significant, patients with "CT/TT" genotype had greater initial plasma concentration (C0) and area under the plasma concentration-time curve (AUC0-t). Conversely, the SNP C3435T was not associated with the plasma docetaxel levels. Furthermore, the C0 and normalized C0 were found to be higher in tumour responders compared to non-responders (p < 0.05). CONCLUSIONS: The plasma levels of docetaxel were significantly influenced by the SNP C1236T of ABCB1 gene coding for the MDR1 transporter (P-glycoprotein). The plasma levels of docetaxel were also found to influence its therapeutic effect.

Influence of CYP2C9 Polymorphisms on Plasma Concentration of Warfarin and 7-Hydroxy Warfarin in South Indian Patients.

BACKGROUND: Warfarin is primarily metabolized by cytochrome P450 2C9 (CYP2C9) enzyme, which is encoded by the CYP2C9 gene. CYP2C9*2 and CYP2C9*3 variants significantly influence warfarin metabolism and subsequently the required dose of warfarin. OBJECTIVES: The current retrospective study was aimed to determine the influence of CYP2C9 variants on warfarin metabolic ratio (MR, warfarin/7-hydroxy warfarin) and warfarin maintenance therapy in 210 patients (mean age 44.6±11.6 (SD) years; male to female ratio 81:129). METHODS: High-performance liquid chromatography (HPLC) with UV detector was used to measure plasma concentrations of warfarin and 7-hydroxy warfarin. Plasma samples were collected 12 h after the previous dose of warfarin was administered. CYP2C9 variants (rs1799853 and rs1057910) were identified using real-time polymerase chain reaction allele-discrimination method. RESULTS: The mean daily maintenance dose of warfarin was 4.6±1.8 (SD) mg. The mean plasma warfarin and 7-hydroxy warfarin concentrations were 3.7±1.6 (SD) µg/mL and 1.1±0.54 (SD) µg/mL, respectively. Patients carrying other CYP2C9 variants required 39% lower warfarin maintenance dose 3.3±1.2(SD)mg than CYP2C9*1*1 carrier 4.9±1.8(SD)mg, (p<0.0001). MRs differed significantly between CYP2C9 variant carriers (8.1±5.1) and normal genotype carriers (4.8±3.9) (p<0.0001). Probit analysis identified an MR value of 7.6 as the anti-mode (sensitivity of 84% and specificity of 55%) to differentiate poor and intermediate metabolizers (carriers of any CYP2C9*2 or CYP2C9*3 variants) from normal metabolizers (CYP2C9*1*1 genotype). CONCLUSION: The present study results provide, insights on the effect of CYP2C9 genetic polymorphisms on inter-individual variability in warfarin metabolism and emphasizes utility of phenotyping in a setting of genotype-guided dosing of warfarin in South Indian population.

Influence of CYP2C9 genetic polymorphism and undernourishment on plasma-free phenytoin concentrations in epileptic patients.

The objective of this study was to study the effect of CYP2C9 genetic polymorphism and undernourishment on free phenytoin concentrations in epileptic patients. The study was done in 70 patients who were taking phenytoin therapy for the treatment of epileptic seizures. Genotyping of CYP2C9 (*2 and *3) was determined by the polymerase chain reaction-restriction fragment length polymorphism method. Bound and free plasma phenytoin was separated using equilibrium dialysis technique. Total and free phenytoin concentrations were measured by the reverse-phase high-performance liquid chromatography method. Patients were broadly classified into well-nourished and undernourished and further subclassified by CYP2C9 genotypes. In well-nourished groups (G1 to G3 group), free phenytoin concentrations were significantly higher in the heterozygous poor metabolizer of CYP2C9 genotype (G2) group (3.1 ± 0.62 µg/mL) and homozygous poor metabolizer of CYP2C9 genotype (G3) group (4.3 ± 1.76 µg/mL) when compared with patients with the wild-type CYP2C9 (G1) group (1.1 ± 0.72 µg/mL). Similarly, in undernourished patient groups (G4-G6 group), free phenytoin concentrations were significantly higher in the wild-type CYP2C9 (G4) group (2.5 ± 0.52 µg/mL), heterozygous poor metabolizer of CYP2C9 genotype (G5) group (4.3 ± 1.76 µg/mL), and homozygous poor metabolizer of CYP2C9 genotype (G6) group (8.2 ± 1.08 µg/mL) when compared with well-nourished patients with the wild-type CYP2C9 (G1) group (1.1 ± 0.72 µg/mL). The percentage increase in free phenytoin concentration by undernourishment, CYP2C9 allelic variants, and undernourishment cum CYP2C9 allelic variants were 127%, 290%, and 472%, respectively, compared with well-nourished patients with the wild-type CYP2C9 genotype (G1) group. The contribution of undernourishment and genetic factors (CYP2C9 allelic variant) for developing phenytoin toxicity was calculated to have an odds ratio of 37.3 (P < 0.0001). Undernourishment and variant CYP2C9 alleles elevate free phenytoin concentrations individually and in combination show additive effects.

Genetic influence of DPYD*9A polymorphism on plasma levels of 5-fluorouracil and subsequent toxicity after oral administration of capecitabine in colorectal cancer patients of South Indian origin.

OBJECTIVES: High interindividual variability was reported with capecitabine toxicities among colorectal cancer (CRC) patients. DPYD*9A polymorphism was reported responsible for grade 3 or 4 toxicities. Finding the phenotypic association between DPYD*9A polymorphism and 5-fluorouracil (5-FU) plasma levels will give a better prediction for toxicity susceptibility. METHODS: A total of 145 CRC patients were included in the final analysis. Each patient received capecitabine of 1,000 mg/m2 twice daily for the first 14 days of a 21 day cycle. 5-FU levels were measured at two-time points 2 and 3 h post capecitabine administration across the 1st and 4th cycles of chemotherapy. 5-FU levels were measured using liquid chromatography and tandem mass spectrometry (LC-MS/MS). Genotyping analysis was done by real-time PCR (RT-PCR). RESULTS: The mean 5-FU drug levels measured during the 1st cycle at time points 2 and 3 h were found to be 267 ng/mL ± (29) and 124 ng/mL ± (22) respectively. Whereas, the observed 5-FU levels in the 4th cycle were 275 ng/mL ± (28) and 130 ng/mL ± (26) respectively. Patients with 5-FU levels in the range of 281-320 and 141-160 ng/mL at 2 and 3 h respectively showed a higher risk for the hand-foot syndrome (HFS) and thrombocytopenia. No association was found between DPYD*9A polymorphism and 5-FU drug levels measured at time point 2 h across both the cycles. However, the drug levels measured at 3 h were found to be significantly different across the DPYD*9A genotypes. Individuals with GG genotype showed significantly higher 5-FU levels when compared to AA genotype. CONCLUSIONS: DPYD*9A polymorphism had a significant influence on the plasma levels of 5-FU after capecitabine administration. The 5-FU levels measured at 3 h corresponding to elimination t1/2 was significantly higher in patients with GG genotype compared AA genotype.

Resequencing CYP2D6 gene in Indian population: CYP2D6*41 identified as the major reduced function allele.

Aim: The CYP2D6 gene is highly polymorphic and harbors population specific alleles that define its predominant metabolizer phenotype. This study aimed to identify polymorphisms in Indian population owing to scarcity of CYP2D6 data in this population. Materials & methods: The CYP2D6 gene was resequenced in 105 south Indians using next generation sequencing technology and haplotypes were reconstructed. Results & conclusion: Four novel missense variants have been designated as CYP2D6*110, *111, *112 and *113. The most common alleles were CYP2D6*1 (42%), *2 (32%), and *41 (12.3%) and diplotypes were CYP2D6*1/*2 (26%), *1/*1 (11%), *2/*41 (10%) and *1/*41 (7%) accounting for high incidence of extensive metabolizers in Indians.

Dopamine (DRD2) and Serotonin (HTR2A, 2C) Receptor Gene Polymorphisms do not influence early response to Risperidone in South Indian Patients with Schizophrenia.

Treatment response to antipsychotic drugs is variable and conflicting results have been obtained while studying the influence of DRD2 and HTR2 genetic variants on antipsychotic drug efficacy. To explore further, the present study aimed to assess the influence of DRD2 -141 C Ins/Del, Taq1A and HTR2A -1438 G/A, 102T/C and HTR2C -759 C/T genetic polymorphisms in response to risperidone in patients with schizophrenia. The study was conducted among the n = 320 South Indian patients with schizophrenia who received risperidone treatment (4-8 mg per day) for a minimum of four weeks. Genotyping was done by real-time PCR. Antipsychotic response was assessed using CGI-I score in cross-sectional group, PANSS score in prospective group at baseline and after receiving the risperidone therapy. DRD2 -141 C Ins/Del (n = 310, Ins/Ins = 177, Ins/Del+ Del/Del = 133, OR 0.70, 95% CI 0.4-1.2 p 0.2), Taq1A (n = 320, AA = 35, AG = 132, GG = 153, p 0.2), HTR2A -1438 G/A (n = 320, AA = 39, AG = 164, GG = 117, p 0.2), HTR2A 102T/C (n = 320, CC = 115, CT = 165, TT = 40, p 0.1) HTR2C -759 C/T (females n = 132, CC = 65, CT+TT = 67, OR 1.3, 95% CI 0.6-2.8, p 0.5; males n = 186, C = 120, T = 66, OR 1.2, 95% CI 0.6-2.4, p 0.4) genetic polymorphisms did not show any association with antipsychotic response to risperidone. DRD2 -141 C Ins/Del, Taq1A, HTR2A -1438 G/A, 102T/C and HTR2C -759 C/T genetic variants are not associated with antipsychotic response to risperidone.

Gender specific association of endothelial nitric oxide synthase gene (Glu298Asp) polymorphism with essential hypertension in a south Indian population.

BACKGROUND: Endothelial derived nitric oxide (NO) plays a major role in blood pressure regulation. The role of missense variant eNOS-Glu298Asp has been demonstrated by many studies with conflicting results. Our objective was to investigate the association of eNOS gene polymorphism with essential hypertension in a south Indian population. METHODS: We carried out a case control study in 438 hypertensive patients and 444 healthy control subjects in a homogenous population. Genotyping was done by PCR-RFLP method. Multiple logistic regression analysis was used to detect the association between genotype and hypertension. RESULTS: The homozygous variant genotype Asp298Asp was significantly associated with hypertension (odds ratio 2.4; 95% CI, 1.23-5.0, p<0.01). Gender specific analysis showed both the heterozygous (odds ratio, 2.0; 95% CI, 1.3-2.9, p<0.01) and homozygous variants (odds ratio, 7.9; 95% CI, 2.0-4.1, p<0.001) were positively associated with hypertension in females. The variant allele Asp was higher in female hypertensives when compared to male hypertensive cases (22% vs. 16%). CONCLUSION: The eNOS gene polymorphism is a candidate gene for hypertension and the association to be gender specific with respect to females in a south Indian Tamilian population.