Construction of a prognostic model with CAFs for predicting the prognosis and immunotherapeutic response of lung squamous cell carcinoma

Lung squamous cell carcinoma (LUSC) is one of the subtypes of lung cancer (LC) that contributes to approximately 25%-30% of its prevalence. Cancer-associated fibroblasts (CAFs) are key cellular components of the TME, and the large number of CAFs in tumour tissues creates a favourable environment for tumour development. However, the function of CAFs in the LUSC is complex and uncertain. First, we processed the scRNA-seq data and classified distinct types of CAFs. We also identified prognostic CAFRGs using univariate Cox analysis and conducted survival analysis. Additionally, we assessed immune cell infiltration in CAF clusters using ssGSEA. We developed a model with a significant prognostic correlation and verified the prognostic model. Furthermore, we explored the immune landscape of LUSC and further investigated the correlation between malignant features and LUSC. We identified CAFs and classified them into three categories: iCAFs, mCAFs and apCAFs. The survival analysis showed a significant correlation between apCAFs and iCAFs and LUSC patient prognosis. Kaplan-Meier analysis showed that patients in CAF cluster C showed a better survival probability compared to clusters A and B. In addition, we identified nine significant prognostic CAFRGs (CLDN1, TMX4, ALPL, PTX3, BHLHE40, TNFRSF12A, VKORC1, CST3 and ADD3) and subsequently employed multivariate Cox analysis to develop a signature and validate the model. Lastly, the correlation between CAFRG and malignant features indicates the potential role of CAFRG in promoting tumour angiogenesis, EMT and cell cycle alterations. We constructed a CAF prognostic signature for identifying potential prognostic CAFRGs and predicting the prognosis and immunotherapeutic response for LUSC. Our study may provide a more accurate prognostic assessment and immunotherapy targeting strategies for LUSC.

Being precise with anticoagulation to reduce adverse drug reactions: are we there yet?

Anticoagulants are potent therapeutics widely used in medical and surgical settings, and the amount spent on anticoagulation is rising. Although warfarin remains a widely prescribed oral anticoagulant, prescriptions of direct oral anticoagulants (DOACs) have increased rapidly. Heparin-based parenteral anticoagulants include both unfractionated and low molecular weight heparins (LMWHs). In clinical practice, anticoagulants are generally well tolerated, although interindividual variability in response is apparent. This variability in anticoagulant response can lead to serious incident thrombosis, haemorrhage and off-target adverse reactions such as heparin-induced thrombocytopaenia (HIT). This review seeks to highlight the genetic, environmental and clinical factors associated with variability in anticoagulant response, and review the current evidence base for tailoring the drug, dose, and/or monitoring decisions to identified patient subgroups to improve anticoagulant safety. Areas that would benefit from further research are also identified. Validated variants in VKORC1, CYP2C9 and CYP4F2 constitute biomarkers for differential warfarin response and genotype-informed warfarin dosing has been shown to reduce adverse clinical events. Polymorphisms in CES1 appear relevant to dabigatran exposure but the genetic studies focusing on clinical outcomes such as bleeding are sparse. The influence of body weight on LMWH response merits further attention, as does the relationship between anti-Xa levels and clinical outcomes. Ultimately, safe and effective anticoagulation requires both a deeper parsing of factors contributing to variable response, and further prospective studies to determine optimal therapeutic strategies in identified higher risk subgroups.

Association evaluations of oral anticoagulants with dementia risk based on genomic and real-world data

BACKGROUND

Several observational studies have suggested that oral anticoagulants (OACs) might reduce the risk of dementia in the elderly, but the evidence is inconclusive. And the consistency of this relationship across different OAC classes and dementia subtypes is still uncertain.

METHODS

To comprehensively evaluate this association, we applied Mendelian randomization (MR) combined with pharmacovigilance analysis. MR was used to assess the associations between genetic proxies for three target genes of OACs (VKORC1, F2, and F10) and dementia, including Alzheimer's disease (AD) and vascular dementia (VaD). This genetic analysis was supplemented with real-world pharmacovigilance data, employing disproportionality analysis for more reliable causal inference.

RESULTS

Increased expression of the VKORC1 gene was strongly associated with increased risk of dementia, especially for AD (OR = 1.28, 95% CI = 1.14-1.43; p value < 0.001). Based on pharmacovigilance data, vitamin K antagonists (VKAs, inhibitors targeting VKORC1) exhibited a protective effect against dementia risk (ROR = 0.43, 95% CI = 0.28-0.67). Additional sensitivity analyses, including different MR models and cohorts, supported these results. Conversely, no strong causal associations of genetically proxied F2 and F10 target genes with dementia and its subtypes were found.

CONCLUSIONS

This study reveals that the inhibition of genetically proxied VKORC1 expression or VKAs exposure is associated with a reduced risk of Alzheimer's dementia. However, there is little evidence to support similar associations with direct oral anticoagulants (F2 inhibitors and F10 inhibitors). Further research is warranted to clinically validate our findings.

Multi-omics characteristics of tumor-associated macrophages in the tumor microenvironment of gastric cancer and their exploration of immunotherapy potential

The incidence and mortality rate of gastric cancer (GC) have remained high worldwide. Although some progress has been made in immunotargeted therapy, the treatment effect remains limited. With more attention has been paid to the immune potential of tumor-associated macrophages (TAMs), but the specific mechanisms of tumor immunity are still unclear. Thus, we screened marker genes in TAMs differentiation (MDMs) through single-cell RNA sequencing, and combined with GC transcriptome data from TCGA and GEO databases, the clinical and TME characteristics, prognostic differences, immune infiltration, and drug sensitivity among different subtypes of patients with GC in different data sets were analyzed. A prognostic model of GC was constructed to evaluate the prognosis and immunotherapy response of patients with GC. In this study, we extensively studied the mutations in MDMs such as CGN, S100A6, and C1QA, and found differences in the infiltration of immune cells and immune checkpoints including M2 TAMs, T cells, CD274, and CTLA4 in different GC subtypes. In the model, we constructed a predictive scoring system with high accuracy and screened out key MDMs-related genes associated with prognosis and M2 TAMs, among which VKORC1 may be involved in GC progression and iron death in tumor cells. Therefore, this study explores the therapeutic strategy of TAMs reprogramming in-depth, providing new ideas for the clinical diagnosis, treatment, and prognosis assessment of GC.

Effect of asciminib and vitamin K2 on Abelson tyrosine-kinase-inhibitor-resistant chronic myelogenous leukemia cells

BACKGROUND

Abelson (ABL) tyrosine kinase inhibitors (TKIs) are effective against chronic myeloid leukemia (CML); however, many patients develop resistance during ABL TKI therapy. Vitamin K2 (VK2) is a crucial fat-soluble vitamin used to activate hepatic coagulation factors and treat osteoporosis. Although VK2 has demonstrated impressive anticancer activity in various cancer cell lines, it is not known whether VK2 enhances the effects of asciminib, which specifically targets the ABL myristoyl pocket (STAMP) inhibitor.

METHOD

In this work, we investigated whether VK2 contributed to the development of CML cell lines. We also investigated the efficacy of asciminib and VK2 by using K562, ponatinib-resistant K562 (K562 PR), Ba/F3 BCR-ABL, and T315I point mutant Ba/F3 (Ba/F3 T315I) cells.

RESULTS

Based on data from the Gene Expression Omnibus (GEO) database, gamma-glutamyl carboxylase (GGCX) and vitamin K epoxide reductase complex subunit 1 (VKORC1) were elevated in imatinib-resistant patients (GSE130404). UBIA Prenyltransferase Domain Containing 1 (UBIAD1) was decreased, and K562 PR cells were resistant to ponatinib. In contrast, asciminib inhibited CML cells and ponatinib resistance in a dose-dependent manner. CML cells were suppressed by VK2. Caspase 3/7 activity was also elevated, as was cellular cytotoxicity. Asciminib plus VK2 therapy induced a significantly higher level of cytotoxicity than use of each drug alone. Asciminib and VK2 therapy altered the mitochondrial membrane potential.

CONCLUSIONS

Asciminib and VK2 are suggested as a novel treatment for ABL-TKI-resistant cells since they increase treatment efficacy. Additionally, this treatment option has intriguing clinical relevance for patients who are resistant to ABL TKIs.

Lack of exposure to pharmacogenomics education among the health care providing students in the West Bank of Palestine

OBJECTIVES

Evaluating the knowledge in pharmacogenomics (PGx) is the first step toward the implementation of PGx testing in clinical practice. This survey aimed to evaluate the knowledge of PGx testing among healthcare providing students at the top-ranked university in the West Bank of Palestine.

METHODS

First an online questionnaire consisting of 30 questions regarding the demographic, knowledge, and attitude toward pharmacogenomics testing was structured and validated. Then the questionnaire was distributed to 1,000 current students from different fields.

RESULTS

696 responses was received. The results showed that almost half of the participants (n=355, 51.1%) have never took any courses about PGx during their university training. Only 81 (11.7%) of the students who took the PGx course stated that it helped them understanding how genetic variations affect drug response. The majority of the students were uncertain (n=352, 50.6%) or disagreed (n=143, 20.6%) that the lectures during university education described the effects of genetic variants on drug response. Although most of the students (70-80%) answered that genetic variants can indeed affect the drug's response, only 162 students (23.3%) responded that VKORC1 and CYP2C9 genotypes influence the response to warfarin. In addition, only 94 (13.5%) students were aware that many medicine labels include clinical information about PGx testing provided by the FDA.

CONCLUSIONS

It is concluded from the results of this survey that there is a lack of exposure to PGx education associated with poor knowledge of PGx testing among the healthcare providing students in the West Bank of Palestine. It is recommended to include and improve the lectures and courses regarding PGx as this will have a major impact on precision medicine.

The Association Between Bone Remodeling Markers, genes polymorphisms with Incidence of Osteopenia Among Young Saudi Female

Osteopenia and osteoporosis, are prevalent skeletal systemic conditions, cause weaker bones and an increased risk of fragility fractures. This work is aimed to evaluate the relation between bone-remolding markers and genotypes of four single nucleotide polymorphisms in young Saudi females (rs2297480 of farnesyl diphosphate synthase (FDPS), rs3736228 of Low-density lipoprotein receptor-related protein 5 (LRP5), rs1234612 of sclerostin (SOST), and rs9934438 of Vitamin K epoxide reductase complex subunit 1  (VKORC1) ). For this purpose, 750 premenopausal females aged 18 to 40 years old, either university students, postgraduates, or university employees were recruited and divided into three groups according to bone mineral density BMD (g/cm2) divided by T score into osteoporosis (n = 12), osteopenia (n = 147), and normal (n = 591). Serum SOST, BALP, calcium, phosphate, ALP, albumin, beta-CTXs and human VDR levels were determined. TaqMan SNP Genotyping assays were used to genotype four polymorphisms using real-time PCR (applied biosystem). Results showed that BALP, CTX-1 and SOST were significantly higher in the osteoporosis and osteopenia groups than in the normal group. Bone mineral density readings were considerably lower in females with the GG genotype in FDPS rs2297480 and TT genotype in LRP5 rs3736228, which increase the risk for osteopenia by 3. 6-fold and 3. 06-fold than control respectively. Also, females with the TT genotype in LRP5 rs3736228 have decreased average values for Bone Mineral Density. In conclusion, the GG genotype of FDPS rs2297480 and the TT genotype of LRP5 rs3736228 was shown to be strongly associated with osteopenia in young Saudi females with low bone mineral density and SOST levels.

Design and in silico study of the novel coumarin derivatives against SARS-CoV-2 main enzymes

The novel coronavirus (SARS-CoV-2) causes severe acute respiratory syndrome and can be fatal. In particular, antiviral drugs that are currently available to treat infection in the respiratory tract have been experienced, but there is a need for new antiviral drugs that are targeted and inhibit coronavirus. The antiviral properties of organic compounds found in nature, especially coumarins, are known and widely studied. Coumarins, which are also metabolites in many medicinal drugs, should be investigated as inhibitors against coronavirus due to their pharmacophore properties (low toxicity and high pharmacokinetic properties). The easy addition of substituents to the chemical structures of coumarins makes these structures unique for the drug design. This study focuses on factors that increase the molecular binding and antiviral properties of coumarins. Molecular docking studies have been carried out to five different proteins (Spike S1-subunit, NSP5, NSP12, NSP15, and NSP16) of the SARS-CoV-2 and two proteins (ACE2 and VKORC1) of human. The best binding scores for 17 coumarins were determined for NSP12 (NonStructural Protein-12). The highest score (-10.01 kcal/mol) in the coumarin group is 2-morpholinoethan-1-amine substituted coumarin. Molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) analyses of selected ligand-protein complexes were performed. The binding energies in each 5 ns were calculated and it was found that the interaction between ligand and target protein were stable.Communicated by Ramaswamy H. Sarma.

Combined genetic profiles of components and regulators of the vitamin K-dependent γ-carboxylation system affect individual sensitivity to warfarin

We examined the influence of combined genotypes on interindividual variability in warfarin dose-response. In 100 anticoagulated patients we quantified the effects of polymorphisms in: CYP2C9, VKORC1, calumenin (CALU), γ-glutamyl carboxylase (GGCX) and microsomal epoxide hydrolase (EPHX1) on warfarin dose requirements. The G1542C VKORC1 polymorphism was associated with decreased warfarin doses in the heteroand homozygous mutant patients (21% and 50% lower, respectively; p<0.0001). Warfarin daily dose was predominantly determined by VKORC1 and CYP2C9 genotypes (partial r2= 0.21; 0.20, respectively). Together with age and body weight, these two genotypes explained 63% of the dose variance. A single patient, homozygous for G11A CALU mutant allele, required an excep tionally high warfarin dose (20mg/day) and the prevalence of heterozygous 11A allele carriers in the upper 10th dose percentile was significantly higher (0.27 vs. 0.18, p<0.02). Combined genotype analysis revealed that CYP2C9 andVKORC1 wild type and CALU mutant patients required the highest warfarin doses (7. 8±1. 5mg/day; n=9) as compared to the CYP2C9 and VKORC1 mutant and CALU wild type genotypes (2. 8±0. 3mg/day; n=18; p<0.01). The odds ratio for doses <3mg/day was 5. 9 (1.9–18. 4) for this genotype. Compound genetic profiles comprising VKORC1, CALU and CYP2C9 improve categorization of individual warfarin dose requirements in more than 25% of patients at steady-state anticoagulation.

Genetic variants associated with warfarin dose in African-American individuals: a genome-wide association study

BACKGROUND

VKORC1 and CYP2C9 are important contributors to warfarin dose variability, but explain less variability for individuals of African descent than for those of European or Asian descent. We aimed to identify additional variants contributing to warfarin dose requirements in African Americans.

METHODS

We did a genome-wide association study of discovery and replication cohorts. Samples from African-American adults (aged ≥18 years) who were taking a stable maintenance dose of warfarin were obtained at International Warfarin Pharmacogenetics Consortium (IWPC) sites and the University of Alabama at Birmingham (Birmingham, AL, USA). Patients enrolled at IWPC sites but who were not used for discovery made up the independent replication cohort. All participants were genotyped. We did a stepwise conditional analysis, conditioning first for VKORC1 -1639G→A, followed by the composite genotype of CYP2C9*2 and CYP2C9*3. We prespecified a genome-wide significance threshold of p<5×10(-8) in the discovery cohort and p<0·0038 in the replication cohort.

FINDINGS

The discovery cohort contained 533 participants and the replication cohort 432 participants. After the prespecified conditioning in the discovery cohort, we identified an association between a novel single nucleotide polymorphism in the CYP2C cluster on chromosome 10 (rs12777823) and warfarin dose requirement that reached genome-wide significance (p=1·51×10(-8)). This association was confirmed in the replication cohort (p=5·04×10(-5)); analysis of the two cohorts together produced a p value of 4·5×10(-12). Individuals heterozygous for the rs12777823 A allele need a dose reduction of 6·92 mg/week and those homozygous 9·34 mg/week. Regression analysis showed that the inclusion of rs12777823 significantly improves warfarin dose variability explained by the IWPC dosing algorithm (21% relative improvement).

INTERPRETATION

A novel CYP2C single nucleotide polymorphism exerts a clinically relevant effect on warfarin dose in African Americans, independent of CYP2C9*2 and CYP2C9*3. Incorporation of this variant into pharmacogenetic dosing algorithms could improve warfarin dose prediction in this population.

FUNDING

National Institutes of Health, American Heart Association, Howard Hughes Medical Institute, Wisconsin Network for Health Research, and the Wellcome Trust.

Vkorc1 variation in house mice during warfarin and difenacoum field trials

BACKGROUND

Field studies guided by genetic monitoring of Vkorc1 need to be done to implicate mutations conclusively with rodent control problems due to the presence of animals resistant to anticoagulant rodenticides. Rodent control success in relation to Vkorc1 genotypes in house mice (Mus musculus domesticus) was studied on two farms (I and II) in Germany. Tests were carried out to determine whether certain resistance profiles and Vkorc1 genotypes displayed dynamics over the course of sequential treatments with warfarin and difenacoum that were consistent with single nucleotide polymorphisms (SNPs) in Vkorc1 as indicators of resistance.

RESULTS

On farms I and II, respectively, three (A to C) and two (A and B) types of control problem with anticoagulants (i.e. proxies for resistance) were encountered in spatially segregated subunits: A = none; B = control problems with warfarin but not with difenacoum; C = control problems with both anticoagulants. Unexpectedly, resistance was encountered in a population where only Vkorc1 wild-type mice were detected. In addition, the Arg58Gly Vkorc1 variant was found not to correlate with observed control failures.

CONCLUSION

Control problems were encountered that cannot be explained by Vkorc1 coding or intronic SNPs, and therefore are likely due to non-coding Vkorc1 SNPs or due to other genetic or non-genetic factors.

Coumatetralyl resistance of Rattus tanezumi infesting oil palm plantations in Indonesia

Rodent control is an important issue in human health and agriculture. Oil palm plantations are rapidly expanding in Indonesia and this is having a major economic and ecological impact. Rodent control in oil palm plantations is based principally on the use of anti-vitamin K (AVK), the main anticoagulant used being coumatetralyl, a first-generation AVK. We conducted a comparative study in two well established oil palm plantations in Indonesia: (1) one without chemical control in Riau and (2) another with intensive coumatetralyl use on Bangka Island. Rat species were identified by the molecular barcoding method. Susceptibility to coumatetralyl was then assessed within the two populations and we screened for mutations in vkorc1, which encodes the molecular target of AVK. Different species were found in the two areas: Rattus tiomanicus in Riau, and a mix of R. tanezumi and a close relative one in Bangka. The rats in Riau were much more susceptible to coumatetralyl than those in Bangka. This study is the first to demonstrate physiological tolerance to AVK in these species. vkorc1 displayed low levels of polymorphism, and no SNP was associated with the high-tolerance phenotypes of R. tanezumi clade, even those exposed to very high concentrations (32 × the effective dose of 0.36 mg kg(-1)). The biochemical basis of this tolerance remains unknown, but may involve the vkorc1 promoter and/or cytochrome P450 metabolism. We discuss our results and the selective role of anticoagulant use in the occurrence of phenotypic tolerance.

Distribution of rodenticide resistance and zoonotic pathogens in Norway rats in Lower Saxony and Hamburg, Germany

BACKGROUND

Genetically based resistance to anticoagulants has led to increasing difficulties in the control of rodents over recent decades. The possible impact of rodenticide-resistant rats on the infection risk of humans and livestock by zoonotic pathogens is generally unknown. Hence, in a monitoring programme in the German federal states of Lower Saxony and Hamburg, more than 500 Norway rats were analysed for both Tyr139Cys polymorphisms within the VKORC1 gene and zoonotic agents.

RESULTS

Evidence of resistance was almost completely restricted to the known resistance area in southern Lower Saxony. Homozygous mutations were only found in urban areas sampled owing to the occurrence of rat control problems and were missing in bycatches of rats by muskrat trappers in rural areas. In more than 25% of the rats, zoonotic bacteria (Leptospira, Salmonella, Yersinia and Coxiella) were detected. There was no obvious correlation between the occurrence of rats carrying zoonotic pathogens and anticoagulant resistance.

CONCLUSION

Zoonotic agents and genetically based resistance conferred by the Tyr139Cys polymorphism are both unevenly distributed in Lower Saxony. The study provides the basis for further studies focusing on districts with high levels of pathogens and resistance to assess the potential health risk of their combined occurrence.

Positive selection in the chromosome 16 VKORC1 genomic region has contributed to the variability of anticoagulant response in humans

VKORC1 (vitamin K epoxide reductase complex subunit 1, 16p11.2) is the main genetic determinant of human response to oral anticoagulants of antivitamin K type (AVK). This gene was recently suggested to be a putative target of positive selection in East Asian populations. In this study, we genotyped the HGDP-CEPH Panel for six VKORC1 SNPs and downloaded chromosome 16 genotypes from the HGDP-CEPH database in order to characterize the geographic distribution of footprints of positive selection within and around this locus. A unique VKORC1 haplotype carrying the promoter mutation associated with AVK sensitivity showed especially high frequencies in all the 17 HGDP-CEPH East Asian population samples. VKORC1 and 24 neighboring genes were found to lie in a 505 kb region of strong linkage disequilibrium in these populations. Patterns of allele frequency differentiation and haplotype structure suggest that this genomic region has been submitted to a near complete selective sweep in all East Asian populations and only in this geographic area. The most extreme scores of the different selection tests are found within a smaller 45 kb region that contains VKORC1 and three other genes (BCKDK, MYST1 (KAT8), and PRSS8) with different functions. Because of the strong linkage disequilibrium, it is not possible to determine if VKORC1 or one of the three other genes is the target of this strong positive selection that could explain present-day differences among human populations in AVK dose requirement. Our results show that the extended region surrounding a presumable single target of positive selection should be analyzed for genetic variation in a wide range of genetically diverse populations in order to account for other neighboring and confounding selective events and the hitchhiking effect.

Brodifacoum is effective against Norway rats (Rattus norvegicus) in a tyrosine139cysteine focus of anticoagulant resistance in Westphalia, Germany

BACKGROUND

The tyrosine to cysteine amino acid substitution at location 139 of the vkorc1 protein (i.e. tyrosine139cysteine or Y139C) is the most widespread anticoagulant resistance mutation in Norway rats (Rattus norvegicus Berk.) in Europe. Field trials were conducted to determine the incidence of the Y139C mutation at two rat-infested farms in Westphalia, Germany, and to estimate the practical efficacy against them of applications, using a pulsed baiting treatment regime, of a proprietary bait (Klerat™) containing 0.005% brodifacoum.

RESULTS

DNA analysis for the Y139C mutation showed that resistant rats were prevalent at the two farms, with an incidence of 80.0 and 78.6% respectively. Applications of brodifacoum bait achieved results of 99.2 and 100.0% control at the two farms, when measured by census baiting, although the treatment was somewhat prolonged at one site, possibly owing to the abundance of attractive alternative food.

CONCLUSION

The study showed that 0.005% brodifacoum bait is fully effective against Norway rats possessing the Y139C mutation at the Münsterland focus and is likely to be so elsewhere in Europe where this mutation is found. The pulsed baiting regime reduced to relatively low levels the quantity of bait required to control these two substantial resistant Norway rat infestations. Previous studies had shown much larger quantities of bromadiolone and difenacoum baits used in largely ineffective treatments against Y139C resistant rats in the Münsterland. These results should be considered when making decisions about the use of anticoagulants against resistant Norway rats and their potential environmental impacts.

Prevalence of VKORC1 and CYP2C9 gene polymorphisms in Indian population and its effect on warfarin response

OBJECTIVES

The clinical effectiveness of Warfarin is established. Patients require different warfarin dosages to achieve the target therapeutic anticoagulation. The variability of Warfarin dosage is largely genetically determined, and it can be partly explained by the C1173T and G-1639A polymorphisms of vitamin K epoxide reductase complex subunit 1 (VKORC1) which is its target and *2 and *3 allele of Cytochrome P-450 (CYP) 2C9 [CYP2C9] enzyme which metabolizes to its inactive form. Aim of the present study was to determine the prevalence of these variant alleles known to influence the warfarin dose and correlate genotypes with the average INR as well as mean dose of Warfarin required to maintain INR, in the Indian population.

METHODS

Study population included 100 healthy individuals and 83 patients operated for Aortic or Mitral Valve replacement and prescribed warfarin thereafter. Of these 83 patients records of INR for the period of six months and mean maintenance dose (stable therapeutic dose) of warfarin required to maintain INR were available for 26 patients. For the remaining patients, apart from their demographic data only maintenance dose was available. Genotyping of above mentioned polymorphisms was carried out by using PCR-based restriction digestion method.

RESULTS

Although less as compared to wild type alleles, the variant alleles of CYP2C9*2 and *3 as well as of VKORC1 polymorphisms (C1173T and G-1639A) were observed in our study population. Mean maintenance dose (mg/day) of Warfarin was in the decreasing order of patients as compared to the wild type genotypes for all above mentioned polymorphisms. The decrease in the dose was in the order of heterozygotes for CYP2C9*2 to CYP2C9*3 to C1173T and G-1639A of VKORC1 (P<0.001). There was significant correlation (r=0.51, P<0.001) observed between the dose estimated by pharmacogenetic algorithm of Sconce et al (2005) and actual stable therapeutic dose. INR was high for mutant variants (3.8 to 4) after first dose suggesting that they require decreased mean daily dose of Warfarin.

CONCLUSION

In the present study the effect of CYP2C9*2, *3, and VKORC1 (C1173T and G-1639A) genotypes on warfarin dose was observed. However, the genotyping has not been incorporated into daily practice. Perhaps more practical approach would be for clinicians to take genotype information into consideration along with other factors when dosing warfarin.

VKORC1 mutations detected in patients resistant to vitamin K antagonists are not all associated with a resistant VKOR activity

BACKGROUND

The VKORC1 gene codes for the VKORC1 enzyme, which is responsible for the reduction of vitamin K epoxide into vitamin K. VKORC1 enzyme is the target of vitamin K antagonists (VKA). Twenty-eight rare single mutations in the VKORC1 coding sequence have been reported from resistant patients receiving unusually high doses of VKA to achieve therapeutic anticoagulation.

OBJECTIVES

It has been suggested that these mutations are responsible for the resistant phenotype, while biochemical consequences of these mutations on the VKORC1 enzyme have not yet been evaluated. Therefore, the aim of this study was to investigate the causality of the VKORC1 mutations in the resistance phenotype.

METHODS

Wild-type VKORC1 and its spontaneous mutants were expressed in Pichia pastoris and susceptibility to VKA was assessed by the in vitro determination of kinetic and inhibition constants.

RESULTS AND CONCLUSIONS

The in vitro analysis revealed that six mutations only (A26P, A41S, V54L, H68Y, I123N and Y139H) were associated with increase in K(i) , suggesting their involvement in the resistance phenotype observed in patients. A41S and H68Y led to selective resistance, respectively, to indane-1,3-dione and 4-hydroxycoumarine derivatives. The other mutations did not increase the K(i). Furthermore, 10 mutations (S52L, S52W, W59L, W59R, V66M, V66G, G71A, N77S, N77T and L128R) led to an almost complete loss of activity. These results suggest the existence of other resistance mechanisms.

CYP2C9 and VKORC1 polymorphisms influence warfarin dose variability in patients on long-term anticoagulation

OBJECTIVES

The main aim of this study was to determine whether CYP2C9 and VKORC1 polymorphisms influence warfarin dose variability during initial dose-finding phase and during maintenance treatment after 360 days.

METHODS

Two hundred and six consecutive patients who were beginning warfarin therapy were selected. They were assessed for general and clinical characteristics; prescribed warfarin dose; response to therapy on days 7-10, 30, 60, 180, and 360; adverse events; and CYP2C9 2, 3, 5, 6, 8, 11, and VKORC1 1639G >A assays.

RESULTS

During the first 30 days of anticoagulation, the relative variability of warfarin dose was significantly associated with CYP2C9*2 and CYP2C9*3 polymorphisms (p = 0.02) and with VKORC1 1639G >A genotypes (p = 0.04). Warfarin variability was also statistically different according to predicted metabolic phenotype and to VKORC1 genotypes after 360 days of treatment, and in the phase between 180 and 360 days (long-term dose variability). Both CYP2C9 and VKORC1 polymorphisms were associated with the international normalized ratio (INR) made between 7 and 10 days/initial dose ratio, adjusted for covariates (p < 0.01 and p = 0.02, respectively). Patients carrying VKORC1 and CYP2C9 variants presented lower required dose (at the end of follow-up of 360 days) compared to patients carrying wild-type genotypes (p = 0.04 and p = 0.03, respectively).

CONCLUSIONS

Genetic information on CYP2C9 and VKORC1 is important both for the initial dose-finding phase and during maintenance treatment with warfarin.

The combined effects of clinical factors and CYP2C9 and VKORC1 gene polymorphisms on initiating warfarin treatment in patients after cardiac valve surgery

BACKGROUND AND AIM OF THE STUDY

Recent studies have shown that, after heart valve surgery, patients may require a more precise warfarin dosage than their non-surgical counterparts. The study aim was to analyze the influence of certain clinical factors and CYP2C9 and VKORC1 gene polymorphisms on the efficacy of initiation of warfarin treatment in patients after cardiac valve surgery.

METHODS

Following heart valve surgery, a total of 185 patients was genotyped for the CYP2C9*1, *2, *3 alleles and for VKORC1 (G-1639A) gene promoter polymorphism.

RESULTS

A hierarchical stepwise multivariate linear regression model was used to evaluate factors affecting the optimal warfarin dosage. Patient age and body weight, together with hepatic malfunction in the cohort population, accounted for 12% of the variation in warfarin dosage (R2 = 0.119). The introduction of concomitant medications, more than doubled (R2 = 0.316) the accuracy of the dosage algorithm. Medications such as cephalosporin, amiodarone, loop diuretics, ibuprofen or diclofenac, omeprazole and beta-blockers had significant effects on the warfarin daily dosage in this model. However, the greatest accuracy was obtained when the patient's CYP2C9 and VKORC1 genotype was introduced into the formula as the critical factor (R2 = 0.429).

CONCLUSION

The study results suggested that, after cardiac valve surgery, by combining the clinical, genetic and anthropometric data of a patient, the warfarin dose may be estimated to 43% accuracy at the initiation of anticoagulant therapy.

Influence of CYP2C9 and VKORC1 on patient response to warfarin: a systematic review and meta-analysis

Background

Warfarin is a highly effective anticoagulant however its effectiveness relies on maintaining INR in therapeutic range. Finding the correct dose is difficult due to large inter-individual variability. Two genes, CYP2C9 and VKORC1, have been associated with this variability, leading to genotype-guided dosing tables in warfarin labeling. Nonetheless, it remains unclear how genotypic information should be used in practice. Navigating the literature to determine how genotype will influence warfarin response in a particular patient is difficult, due to significant variation in patient ethnicity, outcomes investigated, study design, and methodological rigor. Our systematic review was conducted to enable fair and accurate interpretation of which variants affect which outcomes, in which patients, and to what extent.

Methodology/Principal Findings

A comprehensive search strategy was applied and 117 studies included. Primary outcomes were stable dose, time to stable dose and bleeding events. Methodological quality was assessed using criteria of Jorgensen and Williamson and data synthesized in meta-analyses using advanced methods. Pooled effect estimates were significant in most ethnic groups for CYP2C9*3 and stable dose (mutant types requiring between 1.1(0.7–1.5) and 2.3 (1.6–3.0)mg/day). Effect estimates were also significant for VKORC1 and stable dose for most ethnicities, although direction differed between asians and non-asians (mutant types requiring between 0.8(0.4–1.3) and 1.5(1.1–1.8)mg/day more in asians and between 1.5(0.7–2.2) and 3.1(2.7–3.6)mg/day less in non-asians). Several studies were excluded due to inadequate data reporting. Assessing study quality highlighted significant variability in methodological rigor. Notably, there was significant evidence of selective reporting, of outcomes and analysis approaches.

Conclusions/Significance

Genetic associations with warfarin response vary between ethnicities. In order to achieve unbiased estimates in different populations, a high level of methodological rigor must be maintained and studies should report sufficient data to enable inclusion in meta-analyses. We propose minimum reporting requirements, suggest methodological guidelines and provide recommendations for reducing the risk of selective reporting.

VKORC1 rs2359612C allele is associated with increased risk of coronary artery disease in the presence of coronary calcification

VKORC1 genetic polymorphisms affect warfarin dose response, aortic calcification, and the susceptibility of coronary artery disease as shown in our previous study. Little is known regarding the association of VKORC1 polymorphisms with coronary artery calcification (CAC) and the role of CAC in the association with coronary artery disease (CAD). Due to a natural haplotype block in the VKORC1 gene in Chinese, polymorphism rs2359612 was analyzed in a case-control study and a prospective study. The case-control study included 464 CAD patients with non-calcified plaque (NCP), 562 CAD patients with mixed calcified plaque (MCP), 492 subjects with calcified plaque (CP), and 521 controls. The rs2359612C was only associated with increased risk of MCP, the CAD in the presence of CAC; the odds ratio was 1.397 (95 % CI 1.008-1.937, P < 0.05), which was replicated in the second independent population. On the contrary, a negative correlation was observed between rs2359612 and log-transformed Agatston score, and rs2359612 was negatively associated with the number of calcified vessels. Moreover, in a prospective study including 849 CAD patients undergoing revascularization, rs2359612C predicted a higher incidence of cardiovascular events in MCP subgroup; the relative risk was 1.435 (95 % CI 1.008-2.041, P = 0.045), which was not observed in the NCP subgroup. We conclude that the rs2359612C was associated with a higher risk of CAD in the presence of CAC and a higher incidence of cardiovascular events in CAD patients with CAC, but a lower coronary calcification. VKORC1 polymorphisms may be associated with the endophenotype of CAD, calcification-related atherosclerosis.

Validation of pharmacogenetic algorithms and warfarin dosing table in Egyptian patients

BACKGROUND

Warfarin remains a difficult drug to use due to the large variability in dose response. Clear understanding of the accuracy of warfarin pharmacogenetic dosing methods might lead to appropriate control of anticoagulation.

OBJECTIVE

This study aims to evaluate the accuracy of warfarin dosing table and two pharmacogenetic algorithms, namely the algorithms of Gage et al. (Clin Pharmacol Ther 84:326-331, 2008), and the International Warfarin Pharmacogenetics Consortium algorithm (IWPC) in a real Egyptian clinical setting. Additionally, three non-pharmacogenetic dosing methods (the Gage, IWPC clinical algorithms and the empiric 5 mg/day dosing) were evaluated.

SETTING

Sixty-three Egyptian patients on a stable therapeutic warfarin dose were included. Patients were recruited from the outpatient clinic of the critical care medicine department.

METHODS

CYP2C9 and VKORC1 polymorphisms were genotyped by real time PCR system. Predicted doses by all dosing methods were calculated and compared with the actual therapeutic warfarin doses.

RESULTS

The Gage algorithm (adjusted R(2) = 0.421, and mean absolute error (MAE) = 3.3), and IWPC algorithm (adjusted R(2) = 0.419, MAE = 3.2) produced better accuracy than did the warfarin dosing table (adjusted R(2) = 0.246, MAE = 3.5), the two clinical algorithms (R(2) = 0.24, MAE = 3.7) and the fixed dose approach (MAE = 3.9). However, all dosing models produced comparable clinical accuracy with respect to proportion of patients within 1 mg/day of actual dose (ideal dose). Non-pharmacogenetic methods severely over-predicted dose (defined as ≥2 mg/day more than actual dose) compared to the three pharmacogenetic models. In comparison to non-pharmacogenetic methods, the three pharmacogenetic models performed better regarding the low dose group in terms of percentage of patients within ideal dose. In the high dose group, none of the dosing models predicted warfarin doses within ideal dose.

CONCLUSION

Our study showed that genotype-based dosing improved prediction of warfarin therapeutic dose beyond that available with the fixed-dose approach or the clinical algorithms, especially in the low-dose group. However, the two pharmacogenetic algorithms were the most accurate.

[Development of the high resolution melting method for genotyping CYP2C9*3 (1075A/C, rs1057910) and VKORC1 (-1639A/G, rs9923231)]

OBJECTIVE

To establish the high-resolution melting curve (HRM) approach for genotyping CYP2C9*3 (1075A/C, rs1057910) and VKORC1 (-1639A/G, rs9923231) and explore its value on estimation of the Warfarin initial dose in comparison with various traditional genotyping methods.

METHODS

CYP2C9*3 (1075A/C, rs1057910) and VKORC1 (-1639A/G, rs9923231) genotyping was detected in 100 patients receiving Warfarin therapy by the newly developed HRM method and traditional genotyping methods including PCR-restriction fragment length polymorphism (PCR-RFLP), TaqMan probe and DNA sequencing.

RESULTS

The results of the genotypes obtained from above mentioned methods to detect CYP2C9*3 (1075A/C, rs1057910) and VKORC1 (-1639A/G, rs9923231) were similar and consistent. The HRM method is simpler, more economical, and faster compared to the traditional methods. The frequencies of the VKORC1-1639 AA, AG, GG genotypes from these 100 clinical samples were 73 (73%), 23 (23%), 4 (4%), respectively; Frequencies of the CYP2C9 1075 AA, AC, CC genotypes were 94(94%), 6 cases (6%), 0, respectively.

CONCLUSIONS

HRM approach can effectively detect CYP2C9*3 (1075A/C, rs1057910) and VKORC1 (-1639A/G, rs9923231) polymorphisms and this method is simpler, more economical, and faster compared to the traditional methods for detecting CYP2C9*3 (1075A/C, rs1057910) and VKORC1 (-1639A/G, rs9923231) polymorphisms.

Biochemical and pharmacological evaluation of 4-hydroxychromen-2-ones bearing polar C-3 substituents as anticoagulants

The objective of this study was to investigate in vitro and in vivo anticoagulant activity of sixteen 4-hydroxycoumarin derivatives bearing polar C-3 scaffolds. The activity was evaluated by measuring prothrombin time. Enhanced anticoagulant activity in vitro was observed for all tested compounds. Upon successive administration of 0.5 mg/kg of body weight to adult Wistar rats, over a period of five days, four derivatives (2b, 4c, 5c and 9c) presented anticoagulant activity in vivo. The most active compound was 2b, with PT = 30.0 s. Low or non-toxic effects in vivo were determined based on the catalytic activity of liver enzymes and the concentration of bilirubin, iron and proteins. Metabolic pathways of the most active compounds in vivo were determined after GC/MS analysis of collected rat urine samples. The excretion occurs by glucuronidation of 7-hydroxy forms of tested derivatives. In vivo results were described using PLS-based CoMFA and CoMSIA 3D-QSAR studies, which showed CoMFA-SE (q(2) = 0.738) and CoMSIA-SEA (q(2) = 0.763) to be the statistically most relevant models. Furthermore, molecular docking and DFT mechanistic studies performed on the rat VKORC1 homology model revealed interactions between the 4-OH coumarin group in the form of phenolic anion and the Cys135 catalytic site in the transition state.

Accuracy assessment of pharmacogenetic algorithms for warfarin dose prediction in Chinese patients

A few warfarin pharmacogenetic dosing algorithms have been proposed,based on multiethnic or homogeneous populations, to estimate warfarin therapeutic doses. However, it remains to be proven that which algorithm is accurate in predicting warfarin dose in Chinese people. We selected eight warfarin dose predictive pharmacogenetic algorithms and retrospectively assessed the predictive accuracy of each algorithm in a total of 368 eligible outpatients by comparing the actual stable therapeutic dose to the dose predicted by the algorithm. Our results showed that a high level of performance was demonstrated by three algorithms,Gage et al., Anderson et al., and Wu et al., having a similar performance in coefficient of determination (R2) and percentage of patients predicted dose within 20% of actual dose. The Gage et al. algorithm had the lowest mean absolute error (MAE). These results indicated that the algorithm by Gage et al. provided a more accurate prediction than did the others,which suggests that this pharmacogenetic algorithm might be used in clinical practice to guide rational administration of warfarin.

An evaluation of gene-gene interaction between the CYP2C9 and VKORC1 genotypes affecting the anticoagulant effect of phenprocoumon and acenocoumarol

BACKGROUND

Previous studies have provided contradictory results regarding the interaction between the CYP2C9 and VKORC1 genotypes affecting various outcome measures.

OBJECTIVES

We aimed to provide a definite answer regarding the question whether there exists a gene-gene interaction between the CYP2C9 and VKORC1 genotypes affecting the anticoagulant effect of phenprocoumon and acenocoumarol.

PATIENTS/METHODS

The EU-PACT cohort dataset, which contains data on 624 phenprocoumon and 471 acenocoumarol patients, was used. Patient characteristics, pharmacogenetic data, International Normalized Ratios (INRs) and dosages were available. We investigated whether there was an interaction between the CYP2C9 and VKORC1 genotypes affecting the maintenance dose, time to severe over-anticoagulation and time to achieve stability during the first 180 days of phenprocoumon and acenocoumarol therapy, in addition to the effect of the separate genotypes. The interaction effect was investigated by adding the product term of the CYP2C9 and VKORC1 genotype classes for four different commonly used CYP2C9 classifications to the linear regression model - for the outcome measure maintenance dose - or to the Cox regression models - for the outcome measures time to severe over-anticoagulation and time to achieve stability.

RESULTS

No significant interactions - all P-values above 0.23 for phenprocoumon and 0.30 for acenocoumarol - were observed for all outcome measures.

CONCLUSIONS

There are no interactions between the CYP2C9 and VKORC1 genotypes affecting the maintenance dose, time to severe over-anticoagulation and time to achieve stability for phenprocoumon and acenocoumarol.

Long-term anticoagulant effects of the CYP2C9 and VKORC1 genotypes in acenocoumarol users

BACKGROUND

The required acenocoumarol dose and the risk of underanticoagulation and overanticoagulation are associated with the CYP2C9 and VKORC1 genotypes. However, the duration of the effects of these genes on anticoagulation is not yet known.

OBJECTIVES

In the present study, the effects of these polymorphisms on the risk of underanticoagulation and overanticoagulation over time after the start of acenocoumarol were investigated.

PATIENTS/METHODS

In three cohorts, we analyzed the relationship between the CYP2C9 and VKORC1 genotypes and the incidence of subtherapeutic or supratherapeutic International Normalized Ratio (INR) values (< 2 and > 3.5) or severe overanticoagulation (INR > 6) for different time periods after treatment initiation.

RESULTS

Patients with polymorphisms in CYP2C9 and VKORC1 had a higher risk of overanticoagulation (up to 74%) and a lower risk of underanticoagulation (down to 45%) in the first month of treatment with acenocoumarol, but this effect diminished after 1-6 months.

CONCLUSIONS

Knowledge of the patient's genotype therefore might assist physicians to adjust doses in the first month(s) of therapy.

Vitamin K requirement and reproduction in bromadiolone-resistant Norway rats

BACKGROUND

Nucleotide polymorphisms in the VKORC1 gene can be linked to anticoagulant rodenticide resistance in Norway rats (Rattus norvegicus Berkenhout). This provides a fitness advantage to rats exposed to anticoagulant actives, but may also cause fitness costs. The vitamin K requirement and reproductive parameters of bromadiolone-resistant rats (Westphalian resistant strain; VKOR variant Tyr139Cys) and bromadiolone-susceptible Norway rats were compared.

RESULTS

At vitamin K deficiency, blood clotting times increased in all homozygous resistant males within 8 days and in 80% of homozygous resistant females within 15 days. There was little effect on blood clotting in heterozygous males and no effect in heterozygous females and VKOR wild-type individuals. Litter size was about 20% higher in sensitive pairs compared with resistant pairs. Testes growth, male gonad weight, sperm motility and testis cell concentration were unaffected by the mutation.

CONCLUSIONS

The VKOR variant Tyr139Cys causes considerable physiological cost in Norway rats in terms of vitamin K requirement and reproduction. This may affect the distribution and spread of resistant individuals in the wild. Decreased litter size of resistant parents seems to be due to lowered female reproductive performance, as there was no significant effect of the mutation on any aspects of male reproduction considered, but this requires further study.

Distribution and frequency of VKORC1 sequence variants conferring resistance to anticoagulants in Mus musculus

BACKGROUND

Emerging resistance to anticoagulant rodenticides may significantly impair house mouse (Mus musculus L.) control. As in humans and rats, sequence variants in the gene vitamin K epoxide reductase complex subunit 1 (VKORC1) of house mice are strongly implicated in the responses of mice to anticoagulants. This study gives a first overview of the distribution and frequency of such potentially resistance-conferring sequence variants in house mice, based on tissue samples from 30 populations in Germany, Switzerland and the Azores.

RESULTS

Except for one population from south Germany, sequence variants were found in individuals from all locations sampled (29 out of 30 sites surveyed), with less than 10% of the individuals matching the wild-type genotype. The most frequent and widespread amino acid substitutions were Leu128Ser, Tyr139Cys and a group of linked sequence changes (Arg12Trp/Ala26Ser/Ala48Thr/Arg61Leu). Where these substitutions occurred as the sole variant, the proportion of homozygous individuals was 72-83%.

CONCLUSIONS

An evaluation of published data revealed that the three most frequently found sequence variants are associated with a substantial loss of rodenticide efficacy of first-generation anticoagulants (e.g. warfarin, coumatetralyl), as well as the second-generation compound bromadiolone and most probably also difenacoum. Knowledge of the distribution and frequency of resistance-conferring sequence variants will stimulate their further functional characterisation and facilitate the choice of effective active substances for house mouse control.

Pharmacogenetic warfarin dose refinements remain significantly influenced by genetic factors after one week of therapy

By guiding initial warfarin dose, pharmacogenetic (PGx) algorithms may improve the safety of warfarin initiation. However, once international normalised ratio (INR) response is known, the contribution of PGx to dose refinements is uncertain. This study sought to develop and validate clinical and PGx dosing algorithms for warfarin dose refinement on days 6-11 after therapy initiation. An international sample of 2,022 patients at 13 medical centres on three continents provided clinical, INR, and genetic data at treatment days 6-11 to predict therapeutic warfarin dose. Independent derivation and retrospective validation samples were composed by randomly dividing the population (80%/20%). Prior warfarin doses were weighted by their expected effect on S-warfarin concentrations using an exponential-decay pharmacokinetic model. The INR divided by that "effective" dose constituted a treatment response index . Treatment response index, age, amiodarone, body surface area, warfarin indication, and target INR were associated with dose in the derivation sample. A clinical algorithm based on these factors was remarkably accurate: in the retrospective validation cohort its R(2) was 61.2% and median absolute error (MAE) was 5.0 mg/week. Accuracy and safety was confirmed in a prospective cohort (N=43). CYP2C9 variants and VKORC1-1639 G→A were significant dose predictors in both the derivation and validation samples. In the retrospective validation cohort, the PGx algorithm had: R(2)= 69.1% (p<0.05 vs. clinical algorithm), MAE= 4.7 mg/week. In conclusion, a pharmacogenetic warfarin dose-refinement algorithm based on clinical, INR, and genetic factors can explain at least 69.1% of therapeutic warfarin dose variability after about one week of therapy.

Genetic polymorphisms of VKORC1, CYP2C9, CYP4F2 in Bai, Tibetan Chinese

BACKGROUND

VKORC1, CYP2C9 and CYP4F2 are three critical genes associated with inter-individual variation of warfarin dose. Many dosing algorithms containing these gene polymorphisms and demographic characteristics have been set up for better use of warfarin. However, with distinct gene mutation frequencies among different ethnics, dosing algorithms differ greatly. For Chinese, related research just concentrate on Han Chinese, ignoring other Chinese ethnicities. This study aims to detect the popular polymorphisms in these three critical genes in Bai, Tibetan Chinese, to start the exploration of better use of warfarin in Chinese minorities.

METHODS

PCR-based methods were used to analyze VKORC1 3673G > A, CYP2C9*3, CYP4F2 rs2108622 C > T in Han, Bai and Tibetan Chinese.

RESULTS

The differences among the mutation frequencies of the studied genes in three ethnicities were not statistically significant. The frequency of A-allele of VKORC1 3673G > A was 92.8%, 90.2%, 90.8% in Bai, Tibetan, Han Chinese, respectively. The frequency of *3-allele in CYP2C9*3 was low in Bai (4.5%), Tibetan (2.8%) and Han Chinese (4.6%). Approximately one fourth of each ethnic had the mutant T-allele of CYP4F2 rs108622. However, Bai Chinese got statistically higher A-allele frequency of VKORC1 3673G > A than previously studied Han Chinese did.

CONCLUSIONS

Bai Chinese got significant higher A-allele frequency of VKORC1 3673G > A.

[Factors influencing the variable response to treatment with oral anticoagulants]

During therapy with oral anticoagulants, which are the main drugs used for treatment and prevention of thromboembolic diseases, there is significant variability in individual doses required to achieve the therapeutic effect. Oral anticoagulant therapy requires regular monitoring of INR, which should be within the range of 2-3. Currently there is no reliable test predicting which patient will require an extremely high or low dose of these drugs. The variability of responses to oral anticoagulants is regulated by demographic factors such as age, sex, body mass; environmental factors and genetic factors. The personal factors include medication, diet, coexisting systemic diseases. Among genetic factors the most important are polymorphisms of two genes which take part in metabolism of vitamin K and oral anticoagulants. These are: a gene encoding CYP2C9, an enzyme which is involved in hepatic metabolism ofcoumarin derivatives and vitamin K epoxide reductase complex subunit 1 (VOKRC1), the target enzyme of action of oral anticoagulants. Less important are mutations in genes encoding other subunits of cytochrome P450, vitamin K dependent clotting factors, calumenin, gamma-glutamyl carboxylase, apolipoprotein E and microsomal epoxide hydrolase. All these factors can affect both the pharmacokinetics and pharmacodynamics of coumarin derivatives. Considering the main genetic and environmental factors we can predict the dose of oral anticoagulants required in about two-thirds of cases.

[Distribution of variant alleles association with warfarin pharmacokinetics and pharmacodynamics in the Han population in China]

OBJECTIVE

To investigate distribution of CYP2C9, CYP3A4, VKORC1 and GGCX gene polymorphisms in the Han population of Guangdong.

METHODS

The subjects included were 970 Chinese Han patients who received long-term warfarin anticoagulant therapy orally after valve replacement in Guangdong General Hospital between 2000 and 2008. By selecting and analyzing the 12 single nucleotide polymorphisms (SNPs) loci, rs12572351 G>A, rs9332146 G>A, rs4917639 G>T, rs1057910 A>C (CYP2C9*3), rs1934967 G>T, rs1934968 G>A, rs2242480 T>C, rs2246709 G>A, rs9923231 C>T (VKORC1-1639 G>A), rs2359612 G>A (VKORC1*2), rs10871454 C>T, and rs699664 T>C, in 4 genes including CYP2C9, CYP3A4, VKORC1 and GGCX that were possibly correlated with warfarin pharmacodynamics and pharmacokinetics through literature retrieval, the distribution of mutation frequencies of the 12 SNPs loci in Chinese Han population were obtained systematically. SNaPshot technique was used to detect gene SNPs, Hardy-Weinberg genetic equilibrium test was used to test population representativeness.

RESULTS

The allelic mutation frequency at CYP2C9 gene rs12572351 G>A, rs9332146 G>A, rs4917639 C>A, rs1057910 A>C (*3), rs1934967 G>T and rs1934968 G>A loci was 32.53%, 2.16%, 8.25%, 3.61%, 19.18% and 37.37%, respectively; the allelic mutation frequency at CYP3A4 gene rs2242480 T>C and rs2246709 G>A loci was 29.07% and 40.41%, respectively; the allelic mutation frequency at VKORC1 gene rs9923231 C>T, rs2359612 G>A and rs10871454 C>T SNPs loci was 87.99%, 87.94% and 91.34%, respectively; the allelic mutation frequency at GGCX gene rs699664 T>C locus was 31.86%.

CONCLUSION

It is of important clinical significance in individualized warfarin therapy to systematically study distribution of mutation frequencies at 12 polymorphisms loci in 4 genes including CYP2C9, CYP3A4 , VKORC1 and GGCX related to warfarin pharmacodynamics and pharmacokinetics in the Chinese Han population receiving valve replacement.

An instructive case suggesting warfarin resistance which is independent on the regulation of the CYP2C9 and VKORC1 genotype

To improve the safety and effectiveness of warfarin (WF) therapy, the initial dose trends to be practically decided based on single nucleotide polymorphism (SNP) genotyping of two genes, cytochrome P450 (CYP) 2C9 and vitamin K epoxide reductase complex1 (VKORC1). We encountered a 43-year-old female who was hospitalized for investigation and treatment because of intermittent convulsive seizures. Right brain cortical vein thrombi were confirmed by magnetic resonance imaging (MRI) scan; therefore, a 3 mg dose of WF was empirically initiated. The prothrombin time (PT), expressed as the international normalized ratio (INR), did not change at all, even when WF was increased to a dose of 11 mg/day. Direct sequence analysis revealed *3 in CYP2C9 and 3673 GA, 6484 CT, 6853 GC and 9041 GA in VKORC1, indicating that the genotypic pattern of the two genes is the responsible SNP for the moderate phenotype on WF sensitivity. Conclusively, our case may present an unknown mechanism other than the concern mentioned above.

Association of VKORC1 -1639 G>A polymorphism with carotid intima-media thickness in type 2 diabetes mellitus

AIMS

Media calcification is a predictor of cardiovascular mortality in type 2 diabetes mellitus (T2DM). Undercarboxylation of some vitamin K-dependent proteins, due to genetic polymorphisms of VKORC1, can lead to calcification. We examined a potential association between VKORC1 -1639 G>A polymorphism and T2DM and, also, the association of this polymorphism with carotid intima-media thickness (cIMT).

METHODS

VKORC1 -1639 G>A polymorphism was determined in 299 T2DM patients and 328 controls of Caucasian origin using PCR-RFLP. cIMT was measured in a subgroup of 118 T2DM patients.

RESULTS

The frequency of VKORC1 genotypes between diabetic and nondiabetic subjects differed significantly (p=0.01). VKORC1 genotype was associated with T2DM in an adjusted model (OR 1.36, p=0.009). A statistically significant difference was observed in the maximum value of cIMT among different genotypes. VKORC1 -1639 G>A polymorphism was an independent predictor of cIMT (p=0.029) after adjusting for established risk factors.

CONCLUSIONS

The association between VKORC1 -1639 G>A polymorphism and risk of T2DM could be due to the higher prevalence of calcification in T2DM patients. This is supported by the independent association between VKORC1 -1639 G>A polymorphism and maximum cIMT in T2DM patients which is likely due to atherosclerosis characterized by increased calcification.

Absence of novel CYP4F2 and VKORC1 coding region DNA variants in patients requiring high warfarin doses

OBJECTIVE

Warfarin is an FDA-approved oral anticoagulant for long-term prevention of thromboembolism. Substantial inter-individual variation in dosing requirements and the narrow therapeutic index of this widely-prescribed drug make safe initiation and dose stabilization challenging. Single nucleotide polymorphisms (SNPs) occurring in CYP2C9, VKORC1, and CYP4F2 genes are known to impact dose, and VKORC1 and CYP4F2 polymorphisms are associated with higher therapeutic dose requirements in our cohort. However, the most advanced regression models using personal, clinical, and genetic factors to predict individual stable dose account for only 50% to 60% of the observed variability in stable therapeutic dose in Caucasians.

DESIGN AND METHODS

In this study, we used DNA sequence analysis to determine whether additional variants in CYP4F2 and VKORC1 gene coding regions contribute to variable dosing requirements among individuals for whom the actual dose was the highest relative to regression model- predicted dose.

RESULTS AND CONCLUSIONS

No novel DNA variants in the coding regions of these genes were identified among subjects requiring high warfarin doses, suggesting that other factors yet to be defined contribute to variability in warfarin dose requirements in this subset of our cohort.

Extremely low warfarin dose in patients with genotypes of CYP2C9*3/*3 and VKORC1-1639A/A

BACKGROUND

Patients with the genotypes of both CYP2C9*3/*3 and VKORC1-1639 A/A are expected to require the lowest dose of warfarin, and to have a greatly increased risk of bleeding. The experience for the dosing of warfarin in such extremely rare cases has been seldom reported.

METHODS

Demographic and clinical data from two cases with stable low dose of warfarin in China were studied by resequencing the corresponding gene segments in their whole blood DNA. The potential clinical value of the pharmacogenetic algorithm for them was evaluated by calculating the stable dose of warfarin in pharmacogenetic algorithm developed by International Warfarin Pharmacogenetics Consortium.

RESULTS

Both cases (68-year-old female and 50-year-old male) were diagnosed as chronic nonvalvular atrial fibrillation needing warfarin treatment, with target international normalized ratio (INR) 2 to 3. Case 1 had stable warfarin dose of 0.625 mg/d and case 2 1.25 mg/d. They needed more than 1 month to stabilize their anticoagulation. Exceeding INR values were recorded for them when the dose of warfarin was no more than 2 mg/d. Hemorrhagic complication appeared in case 1 when the dose was titrated from 2.5 to 1.25 mg/d. No concomitant medicine to increase or decrease the INR value was recorded for them. Genotyping CYP2C9 and VKORC1 showed both patients were the carriers of the homozygous alleles -CYP2C9*3/*3 and VKORC1-1639 A/A. Their stable doses of warfarin calculated by the pharmacogenetic dose algorithm (0.672 mg/d for case 1 and 1.16 mg/d for case 2) were comparable with their actual stable therapeutic doses.

CONCLUSIONS

Two Chinese with the rare genotypes of both CYP2C9*3/*3 and VKORC1-1639 A/A were found to require the extremely low dose of warfarin. The pharmacogenetic algorithm incorporating the variances of VKORC1 and CYP2C9 genotypes, as well as the non-genetic factors could predict their stable dose of warfarin with high accuracy.

Influence of genetic, biological and pharmacological factors on warfarin dose in a Southern Brazilian population of European ancestry

AIMS

To investigate the influence of polymorphisms in CYP2C9, VKORC1, CYP4F2 and F2 genes on warfarin dose-response and develop a model including genetic and non-genetic factors for warfarin dose prediction needed for each patient.

METHODS

A total of 279 patients of European ancestry on warfarin medication were investigated. Genotypes for -1639G>A, 1173C>T, and 3730G>A SNPs in the VKORC1 gene, CYP2C9*2 and CYP2C9*3, 1347C>T in the CYP4F2 gene and 494C>T in the F2 gene were determined by allelic discrimination with Taqman 5'-nuclease assays.

RESULTS

The CYP2C9*2 and CYP2C9*3 polymorphisms in the CYP2C9 gene, -1639G>A and 1173C>T in the VKORC1 gene and 494C>T in the F2 gene are responsible for lower anticoagulant doses. In contrast, 1347C>T in the CYP4F2 gene and 3730G>A in the VKORC1 gene are responsible for higher doses of warfarin. An algorithm including genetic, biological and pharmacological factors that explains 63.3% of warfarin dose variation was developed.

CONCLUSION

The model suggested has one of the highest coefficients of determination among those described in the literature.

Are water vole resistant to anticoagulant rodenticides following field treatments?

The anti-vitamin Ks (AVKs) are widely used to control rodent populations. They inhibit Vitamin K regeneration by the Vitamin K Epoxide Reductase (VKOR) and cause a fatal hemorrhagic syndrome. Because of repeated use, some populations of commensal rodents have expressed resistance to these compounds. In Franche-Comté (France), the water vole exhibits cyclic population outbreaks. A second generation AVK, bromadiolone, has been used for the last 20 years to control vole populations. The aim of this study is to determine whether these repeated treatments could have led to the development of resistance to AVKs in water vole populations. We conducted enzymatic and genetic studies on water voles trapped in treated and non treated plot. The results indicate that voles from the most heavily treated area exhibit enzymatic changes in VKOR activity hence arguing for resistance to AVKs and that an intronic haplotype on the vkorc1 gene seems to be associated with these enzymatic changes.

[Possible application of pharmacogenomics to warfarin therapy]

Vitamin K-dependent gamma-carboxylation system is crucial to generate active coagulation factors. It consists of gamma-Glutamylcarboxylase (GGCX) and vitamin K-epoxide reductase (VKOR). Warfarin is an anticoagulant that blocks VKOR. Recent studies have shown that genetic variations in a subunit of VKOR complex, VKORC1, and in cytochrome P 450 (CYP) 2C9 genes are strong determinants of individuals' warfarin sensitivity. Algorithms have been proposed to predict warfarin doses, and about 55% of the variance in warfarin dose could be attributed to variations in the VKORC1 and CYP2C9 genes together with age, sex, body-surface area, and presence or absence of heart valve replacement. Contributions of polymorphisms in VKORC1 and CYP2C9 to inter-individual differences of warfarin dose, however, are different among races. Studies have shown that potential clinical and economic benefits of CYP2C9/VKORC1 genotype-guided dosing are only marginal. Thus, evidence is still limited and application of warfarin pharmacogenomics to clinical practice at present needs careful consideration.