Real-time PCR analysis of the N-acetyltransferase NAT1 allele *3, *4, *10, *11, *14 and *17 polymorphism in squamous cell cancer of head and neck

Association of N-acetyltransferases 1 and 2 Polymorphisms with Susceptibility to Head and Neck Cancers-A Meta-Analysis, Meta-Regression, and Trial Sequential Analysis

Background and objective:N-acetyltransferases 1 and 2 (NAT1 and NAT2) genes have polymorphisms in accordance with slow and rapid acetylator phenotypes with a role in the development of head and neck cancers (HNCs). Herein, we aimed to evaluate the association of NAT1 and NAT2 polymorphisms with susceptibility to HNCs in an updated meta-analysis. Materials and methods: A search was comprehensively performed in four databases (Web of Science, Scopus, PubMed/Medline, and Cochrane Library until 8 July 2021). The effect sizes, odds ratio (OR) along with 95% confidence interval (CI) were computed. Trial sequential analysis (TSA), publication bias and sensitivity analysis were conducted. Results: Twenty-eight articles including eight studies reporting NAT1 polymorphism and twenty-five studies reporting NAT2 polymorphism were involved in the meta-analysis. The results showed that individuals with slow acetylators of NAT2 polymorphism are at higher risk for HNC OR: 1.22 (95% CI: 1.02, 1.46; p = 0.03). On subgroup analysis, ethnicity, control source, and genotyping methods were found to be significant factors in the association of NAT2 polymorphism with the HNC risk. TSA identified that the amount of information was not large enough and that more studies are needed to establish associations. Conclusions: Slow acetylators in NAT2 polymorphism were related to a high risk of HNC. However, there was no relationship between NAT1 polymorphism and the risk of HNC.

Single-dose tolerability, pharmacokinetics, and pharmacodynamics of etamicastat (BIA 5-453), a new dopamine β-hydroxylase inhibitor, in healthy subjects

The safety, tolerability, pharmacokinetics, and pharmacodynamics of etamicastat (BIA 5-453), a novel dopamine β-hydroxylase (DβH) inhibitor, were investigated in 10 sequential groups of 8 healthy male subjects under a double-blind, randomized, placebo-controlled design. In each group, 6 subjects received a single dose of etamicastat (2, 10, 20, 50, 100, 200, 400, 600, 900, or 1200 mg) and 2 subjects received placebo. Etamicastat was well tolerated at all dose levels tested. Maximum plasma etamicastat concentrations occurred at 1 to 3 hours postdose. Elimination was biphasic, characterized by a first short early elimination half-life followed by a longer elimination phase of 16 to 20 hours for etamicastat doses of 100 mg and above. A high interindividual variability of pharmacokinetic parameters of etamicastat and its acetylated metabolite was observed. Pharmacogenomic data showed that N-acetyltransferase type 2 (NAT2) phenotype (rapid or slow N-acetylating ability) was a major source of variability. In NAT2 poor acetylators, the area under the plasma concentration-time curve from time zero to the last sampling time at which concentrations were at or above the limit of quantification (AUC0-t ) of etamicastat was twice that observed in rapid acetylators. Consistent with that finding, AUC0-t of the acetylated metabolite was markedly higher in NAT2 rapid acetylators compared with poor acetylators. Inhibition of DβH activity was observed, reaching statistical significance for etamicastat doses of 100 mg and above.

Association of CYP1A1 and CYP2D6 gene polymorphisms with head and neck cancer in Tunisian patients

The purpose of this study was to investigate the relationship between head and neck cancer (HNC) and environmental agents and polymorphisms in CYP1A1, CYP2D6, NAT1 and NAT2 metabolic enzymes genes. To the best of our knowledge, this is the first report on polymorphisms in CYP1A1 6310C>T, CYP2D6 Arg365His, NAT1 52936A>T and NAT2 Arg268Lys (NAT2*12A) genes and susceptibility to HNC in Tunisian population. We study the prevalence of these polymorphisms in 169 patients with HNC and 261 control subjects using polymerase chain reaction based methods in a Tunisian population. We detected an association between HNC and CYP1A1 6310C>T (TT) and CYP2D6 Arg365His (His/His) variant carriers (OR 1.75, P = 0.008 and OR 1.66, P = 0.016, respectively). No association was found between the polymorphisms genotypes of NAT1 52936T>A and NAT2 Arg268Lys and risk of HNC. An association between HNC and CYP1A1 (TT) genotype was found among patients with smoking (P = 0.011) and drinking habit (P = 0.009). The combinations of NAT1 (AT or AA) and NAT2 (AA) at-risk genotypes increased HNC risk (OR 4.23, P = 0.005 and OR 3.60, P = 0.048, respectively). However, the combinations of CYP1A1 (AA) and CYP2D6 (CC) genotypes decreased risk of HNC (OR 0.20; P = 0.006). Genetic polymorphisms in CYP1A1 and CYP2D6 may significantly associate with HNC in the Tunisian population. The results of this study suggest a possible gene-environment interaction for certain carcinogen metabolizing enzymes, but larger studies that fully evaluate the interaction are needed.

Polymorphisms in the human cytochrome P450 and arylamine N-acetyltransferase: susceptibility to head and neck cancers

The occurrence of head and neck cancer (HNC) is associated with smoking and alcohol drinking. Tobacco smoking exposes smokers to a series of carcinogenic chemicals. Cytochrome P450 enzymes (CYP450s), such as CYP1A1, CYP1B1, and CYP2D6, usually metabolize carcinogens to their inactive derivatives, but they occasionally convert the chemicals to more potent carcinogens. In addition, via CYP450 (CYP2E1) oxidase, alcohol is metabolized to acetaldehyde, a highly toxic compound, which plays an important role in carcinogenesis. Furthermore, two N-acetyltransferase isozymes (NATs), NAT1 and NAT2, are polymorphic and catalyze both N-acetylation and O-acetylation of aromatic and heterocyclic amine carcinogens. Genetic polymorphisms are associated with a number of enzymes involved in the metabolism of carcinogens important in the induction of HNC. It has been suggested that such polymorphisms may be linked to cancer susceptibility. In this paper, we select four cytochrome P450 enzymes (CYP1A1, CYP1BA1, CYP2D6, and CYP2E1), and two N-acetyltransferase isozymes (NAT1 and NAT2) in order to summarize and analyze findings from the literature related to HNC risk by focusing on (i) the interaction between these genes and the environment, (ii) the impact of genetic defect on protein activity and/or expression, and (iii) the eventual involvement of race in such associations.

Safety, tolerability, and pharmacokinetics of etamicastat, a novel dopamine-β-hydroxylase inhibitor, in a rising multiple-dose study in young healthy subjects

BACKGROUND

Activation of the sympathetic nervous system is an important feature in hypertension and congestive heart failure. A strategy for directly modulating sympathetic nerve function is to reduce the biosynthesis of norepinephrine (noradrenaline) via inhibition of dopamine-β-hydroxylase (DβH).

OBJECTIVE

To assess the safety, tolerability, and pharmacokinetics of etamicastat (BIA 5-453), a new DβH inhibitor, following repeated dosing.

METHODS

A double-blind, randomized, placebo-controlled study was conducted in healthy young male volunteers. Participants received once-daily doses of placebo or etamicastat 25, 50, 100, 200, 400, or 600 mg, for 10 days.

RESULTS

Etamicastat underwent N-acetylation to its metabolite BIA 5-961. Etamicastat and BIA 5-961 maximum concentrations were achieved at 1-3 and 2-4 hours, respectively, after dosing. Elimination half-lives ranged from 18.1 to 25.7 hours for etamicastat and 6.7 to 22.5 hours for BIA 5-961. Both etamicastat and BIA 5-961 followed linear pharmacokinetics. The extent of systemic exposure to etamicastat and BIA 5-961 increased in an approximately dose-proportional manner, and steady-state plasma concentrations were attained up to 9 days of dosing. Etamicastat accumulated in plasma following repeated administration. The mean observed accumulation ratio was 1.3-1.9 for etamicastat and 1.3-1.6 for BIA 5-961. Approximately 40% of the etamicastat dose was recovered in urine in the form of parent compound and BIA 5-961. There was a high variability in pharmacokinetic parameters, attributable to different N-acetyltransferase-2 (NAT2) phenotype. Urinary excretion of norepinephrine decreased following repeated administration of etamicastat. Etamicastat was generally well tolerated. There was no serious adverse event or clinically significant abnormality in clinical laboratory tests, vital signs, or ECG parameters.

CONCLUSION

Etamicastat was well tolerated. Etamicastat undergoes N-acetylation, which is markedly influenced by NAT2 phenotype. NAT2 genotyping could be a step toward personalized medicine for etamicastat.

TRIAL REGISTRATION

EudraCT No. 2007-004142-33.

Pharmacokinetics and tolerability of etamicastat following single and repeated administration in elderly versus young healthy male subjects: an open-label, single-center, parallel-group study

BACKGROUND

Etamicastat is a new dopamine-β-hydroxylase (DβH) inhibitor currently in clinical development for the treatment of hypertension and heart failure.

OBJECTIVES

To evaluate the pharmacokinetics and tolerability of etamicastat after single and repeated administration in elderly subjects (aged ≥65 years) relative to young adult healthy controls (aged 18-45 years).

METHODS

This was a single-center, open-label, parallel-group study in young male adults (n = 13; mean [SD] age 32.6 [16.4] years; range, 18-44 years; weight 79.0 [16.4] kg; systolic blood pressure 117 [12] mm Hg and diastolic blood pressure 61 [7] mm Hg) and 12 elderly male volunteers (n = 12; age 69.3 [3.3] years; weight 69.2 [9.5] kg; systolic blood pressure 115 [13] mm Hg and diastolic blood pressure 64 [4] mm Hg), conducted in 2 consecutive periods. All subjects were white, except for 1 black elderly subject. In Phase A, subjects received a single dose of 100 mg etamicastat. In Phase B, subjects received 100 mg/d etamicastat for 7 days. The pharmacokinetic parameters of etamicastat and its acetylated metabolite BIA 5-961 were calculated after the single dose of Phase A and the last dose of Phase B. Subjects' N-acetyltransferase type 1 (NAT1) and type 2 (NAT2) genotyping was performed and acetylator status inferred.

RESULTS

After a single dose of etamicastat 100 mg, mean (SD) plasma C(max) and plasma AUC(0-∞) were, respectively, 1.3 (0.5) ng/mL/kg and 12.4 (7.8) ng × h/mL/kg in elderly subjects, and 1.3 (0.4) ng/mL/kg and 10.0 (6.6) ng × h/mL/kg in young subjects. At steady-state, C(max) and AUC(0-24) were 1.8 (0.5) ng/mL/kg and 15.0 (6.4) ng × h/mL/kg in elderly subjects, and 1.5 (0.7) ng/mL/kg and 12.5 (6.5) ng × h/mL/kg in young subjects. Elderly/young geometric mean ratios and 90% CIs were, respectively, 0.944 (0.788-1.131) and 1.164 (0.730-1.855) for etamicastat C(max) and AUC(0-∞) after a single dose, and 1.225 (0.960-1.563) and 1.171 (0.850-1.612) for etamicastat C(max) and AUC(0-24) at steady state. Etamicastat steady-state plasma concentrations were reached after 3 to 4 days of dosing. The mean etamicastat accumulation ratio was 1.7 in both age groups. Following etamicastat single dose, mean (SD) BIA 5-961 C(max) and AUC(0-∞) were, respectively, 3.5 (2.1) ng/mL/kg and 28.4 (14.7) ng × h/mL/kg in elderly subjects, and 2.5 (1.5) ng/mL/kg and 16.5 (9.7) in young subjects. At steady state, BIA 5-961, C(max), and AUC(0-24) were 4.3 (2.6) ng/mL/kg and 34.6 (17.6) ng × h/mL/kg in elderly subjects, and 3.1 (2.0) ng/mL/kg and 22.2 (11.8) ng × h/mL/kg in young subjects. Large interindividual variability dependent on the NAT2 acetylator status was found in the pharmacokinetic parameters of etamicastat and BIA 5-961. Systemic exposure to etamicastat was higher and systemic exposure to BIA 5-961 was lower in NAT2 poor metabolizers compared with rapid metabolizers. No effect on heart rate and blood pressure was found in the young group. In the elderly, a decrease of supine blood pressure was observed. Postural changes in blood pressure were unaffected. Four adverse events (AEs) were reported by each group: nasopharyngeal pain, sciatica, asthenia, and back pain the elderly group, and headache (2 cases), insomnia, and myopericarditis by the young group. Myopericarditis led to study discontinuation for this subject and was considered to be of probable viral etiology. All other AEs were mild to moderate in intensity.

CONCLUSION

The pharmacokinetic profile of etamicastat was not significantly different in these small groups of healthy young versus elderly adult male volunteers.

Effect of food on the pharmacokinetic profile of etamicastat (BIA 5-453)

BACKGROUND

Etamicastat is a novel, potent, and reversible peripheral dopamine-β-hydroxylase inhibitor that has been administered orally at doses up to 600 mg once daily for 10 days to male healthy volunteers and appears to be well tolerated.

OBJECTIVE

The aim of this study was to investigate the effect of food on the pharmacokinetics of etamicastat.

MATERIAL AND METHODS

A single-center, open-label, randomized, two-way crossover study in 12 healthy male subjects was performed. Subjects were administered a single dose of etamicastat 200 mg following either a standard high-fat and high-calorie content meal (test) or 10 hours of fasting (reference). The statistical method for testing the effect of food on the pharmacokinetic parameters of interest was based upon the 90% confidence interval (CI) for the test/reference geometric mean ratio (GMR). The parameters of interest were maximum plasma concentration (C(max)), area under the plasma concentration-time curve (AUC) from time zero to the last measurable concentration (AUC(last)), and AUC from time zero to infinity (AUC(∞)). Bioequivalence was assumed when the 90% CI fell within the recommended acceptance interval (80, 125).

RESULTS

Etamicastat C(max), AUC(last), and AUC(∞) were 229 ng/mL, 1856 ng · h/mL, and 2238 ng · h/mL, respectively, following etamicastat in the fasting, and 166 ng/mL, 1737 ng · h/mL, and 2119 ng · h/mL, respectively, following etamicastat in the fed condition. Etamicastat test/reference GMR was 72.27% (90% CI 64.98, 80.38) for C(max), 93.59% (90% CI 89.28, 98.11) for AUC(last), and 96.47% (90% CI 91.67, 101.53) for AUC(∞). Time to C(max) was prolonged by the presence of food (p < 0.001). The C(max), AUC(last), and AUC(∞) values of the inactive metabolite BIA 5-961 were 275 ng/mL, 1827 ng · h/mL, and 2009 ng · h/mL, respectively, in the fasting, and 172 ng/mL, 1450 ng · h/mL, and 1677 ng · h/mL, respectively, in the fed condition. BIA 5-961 test/reference GMR was 62.42% (90% CI 56.77, 68.63) for C(max), 79.41% (90% CI 56.77, 68.63) for AUC(last), and 83.47% (90% CI 76.62, 90.93) for AUC(∞). A total of six mild to moderate unspecific adverse events were reported by four subjects. There was no clinically significant abnormality in laboratory assessments.

CONCLUSION

Etamicastat was well tolerated. The C(max) of etamicastat decreased 28% following oral administration of etamicastat in the presence of food, while AUC remained within the pre-defined acceptance interval. The delay in absorption and decrease in peak exposure of etamicastat is not clinically significant, and therefore etamicastat could be administered without regard to meals.

TRIAL REGISTRATION

EudraCT No. 2007-006530-33.

N-acetyltransferase 1 and 2 gene sequence variants and risk of head and neck cancer

Polymorphisms that alter the function of genes involved in the activation or detoxification of carcinogenic compounds can influence an individuals risk of developing cancer. Polymorphic changes modulating the acetylation capacity of the N-acetyltransferase (NAT) genes have been implicated in the risk of developing cancer. In this study the role of genetically determined individual NAT1 and NAT2 genotypes, haplotypes and haplotype combinations in the predisposition to head and neck cancer was investigated. Polymorphic regions of the NAT1 and NAT2 genes were analyzed in patients with head and neck cancer and healthy individuals by polymerase chain reaction-restriction fragment length polymorphism. Distribution of the genotypes, allele frequencies, diplotypes and haplotypes and correlation with clinical characteristics were evaluated. No association was observed between the NAT1*3, NAT1*10, NAT1*11, NAT2*5 and NAT2*6 genotypes and risk of head and neck cancer. The NAT2*7 slow genotype was associated with reduced risk of disease. A significant association was observed between the fast acetylator NAT2*4/NAT1*10 diplotype and risk of head and neck cancer. Combined haplotypes harboring the T1088A and C1095A variants characterizing the NAT1*10 allele were associated with increased risk. Our results suggest that NAT1 and NAT2 gene combinations may influence the risk of developing head and neck cancer.

Epidemiology of carcinogen metabolism genes and risk of squamous cell carcinoma of the head and neck

The risk association between tobacco and alcohol use with squamous cell carcinoma of the head and neck (SCCHN) is well recognized. However, clearly not all individuals who smoke or drink develop SCCHN. Individual genetic susceptibility differences in carcinogen-metabolizing enzyme function, mutagen sensitivity, apoptosis, and chromosomal aberrations either alone or in combination have been theorized to modify the risk of SCCHN. Nearly all carcinogens and procarcinogens require activation by metabolizing enzymes. Similarly, detoxifying enzymes exist and deactivate carcinogens as well as their intermediate by-products. Together these enzymes are termed xenobiotic-metabolizing enzymes; genetic polymorphisms of these enzymes can modify an individual's response to carcinogens and hence the carcinogenic potential of such exposures. In this review, we explore the available evidence in recent literature regarding the risk association between SCCHN and various xenobiotic-metabolizing enzymes, including cytochrome P450s, glutathione S-transferases, N-acetyltransferases, NAD(P)H:quinone oxidoreductase 1, alcohol dehydrogenase, and aldehyde dehydrogenase.

Genetic polymorphism of N-acetyltransferase 2 in the susceptibility to laryngeal squamous cell carcinoma

BACKGROUND

The purpose of this study was to investigate whether polymorphism of N-acetyltransferase 2 (NAT2) genotypes are associated with the risk of laryngeal squamous cell carcinoma (SCC).

METHODS

The study group consisted of 45 white patients with laryngeal SCC (42 men, with a mean age of 54 years [range, 37-70 years] and three women, with a mean age of 47 years [range, 32-55 years]) and 104 control subjects (68 men and 36 women; mean age, 50 years; range, 28-73 years). All of the patients were primarily treated with surgical intervention. Blood samples (5 mL) were obtained before surgery or from the patients under follow-up to 5 years after surgery (mean follow-up, 27 months; range, 6-48 months). DNA was extracted from the lymphocytes by high pure template preparation kit. NAT2*5A, NAT2*6A, NAT2*7A/B, and NAT2*14A were detected by use of LightCycler-NAT2 mutation detection kit by real-time polymerase chain reaction with Light Cycler instruments. The association between NAT2 polymorphisms and laryngeal SCC was prospectively modeled through multivariate logistic regression analysis.

RESULTS

We found that the risk of laryngeal SCC was 7.3-fold higher in individuals with NAT2*5 mutant allele, 3.8-fold higher in subjects with NAT2*6 heterozygote allele, and 38.3-fold higher in NAT2*6 mutant allele. We also found that individuals with NAT2*7 heterozygote allele had a 0.2-fold less risk for the development of laryngeal SCC (p = .018).

CONCLUSION

In this population, patients with NAT2*5 mutant and *6 heterozygous and mutant genotypes had a significantly higher risk for development of laryngeal SCC.

Nucleotide sequence-based multitarget identification

MULTIGEN technology (T. Vinayagamoorthy, U.S. patent 6,197,510, March 2001) is a modification of conventional sequencing technology that generates a single electropherogram consisting of short nucleotide sequences from a mixture of known DNA targets. The target sequences may be present on the same or different nucleic acid molecules. For example, when two DNA targets are sequenced, the first and second sequencing primers are annealed to their respective target sequences, and then a polymerase causes chain extension by the addition of new deoxyribose nucleotides. Since the electrophoretic separation depends on the relative molecular weights of the truncated molecules, the molecular weight of the second sequencing primer was specifically designed to be higher than the combined molecular weight of the first sequencing primer plus the molecular weight of the largest truncated molecule generated from the first target sequence. Thus, the series of truncated molecules produced by the second sequencing primer will have higher molecular weights than those produced by the first sequencing primer. Hence, the truncated molecules produced by these two sequencing primers can be effectively separated in a single lane by standard gel electrophoresis in a single electropherogram without any overlapping of the nucleotide sequences. By using sequencing primers with progressively higher molecular weights, multiple short DNA sequences from a variety of targets can be determined simultaneously. We describe here the basic concept of MULTIGEN technology and three applications: detection of sexually transmitted pathogens (Neisseria gonorrhoeae, Chlamydia trachomatis, and Ureaplasma urealyticum), detection of contaminants in meat samples (coliforms, fecal coliforms, and Escherichia coli O157:H7), and detection of single-nucleotide polymorphisms in the human N-acetyltransferase (NAT1) gene (S. Fronhoffs et al., Carcinogenesis 22:1405-1412, 2001).

Genetic susceptibility--molecular epidemiology of head and neck cancer

In parts of the developing world (South Central Asia in particular), squamous cell carcinoma of the head and neck (SCCHN) is one of the most common malignancies encountered. Although tobacco and alcohol are clearly defined as etiologic factors in these malignancies, clinical observations have suggested that inherited genetic factors put some individuals at increased risk for SCCHN. Emerging data (both phenotypic and genotypic) support this concept of genetic susceptibility to SCCHN and point to differences in DNA repair ability, carcinogen metabolism, and cell cycle control as the systems important to the risk of tobacco-induced malignancies. The ability to identify such high-risk individuals will have major influences on the practice of cancer prevention in the future.

Association of prostate cancer with rapid N-acetyltransferase 1 (NAT1*10) in combination with slow N-acetyltransferase 2 acetylator genotypes in a pilot case-control study

N-acetyltransferase-1 (NAT1) and N-acetyltransferase-2 (NAT2) are important in the metabolism of aromatic and heterocyclic amine carcinogens that induce prostate tumors in the rat. We investigated the association of genetic polymorphisms in NAT1 and NAT2, alone and in combination, with human prostate cancer. Incident prostate cancer cases and controls in a hospital-based case-control study were frequency-matched for age, race, and referral pattern. The frequency of slow acetylator NAT1 genotypes (NAT1*14, *15, *17) was 5.8% in controls but absent in cases. In contrast, in comparison with all other NAT1 genotypes the putative rapid acetylator NAT1 genotype (NAT1*10) was significantly higher in prostate cancer cases than controls (OR, 2.17; 95% CI, 1.08-4.33; P = 0.03). Combinations of NAT1*10 with NAT2 slow acetylator genotypes (OR, 5.08; 95% CI, 1.56-16.5; P = 0.008) or with NAT2 very slow (homozygous NAT2*5) acetylator genotypes (OR, 7.50; 95% CI, 1.55-15.4; P = 0.016) further increased prostate cancer risk. The results of this small pilot study suggest increased susceptibility to prostate cancer for subjects with combinations of NAT1*10 and slow (particularly very slow) NAT2 acetylator genotypes. This finding should be investigated further in larger cohorts and in other ethnic populations.