Functionally active duplications of the CYP2D6 gene are more prevalent among larynx and lung cancer patients.

The cytochrome P450 CYP2D6 is a polymorphic drug-metabolizing enzyme that is involved in the metabolism of several drugs and xenobiotics. Several independent studies indicate that the CYP2D6 metabolic status is a secondary factor in the risk of developing lung cancer, with individuals with high activity being at increased risk. The occurrence of functionally active duplications of the CYP2D6 gene is a phenomenon that affects 3-8% of Caucasians and up to 30% in some ethnic groups. These duplications cause ultrarapid metabolism of CYP2D6 substrates. In order to establish whether the highest CYP2D6 enzyme activity is associated with an increased risk of cancer, we analyzed the frequency of CYP2D6 gene duplications and enzyme-inactivating mutations in 199 Caucasian patients with lung or larynx cancer and in 335 healthy controls. A significantly increased frequency of carriers of the CYP2D6 gene duplication were found among lung and larynx cancer patients (13%), as compared with healthy controls (6.9%; p < 0.02). The frequency of the mutated active CYP2D6*9 allele was increased in lung cancer patients (p < 0.01) but not in larynx cancer patients. Global findings indicate that over 20% patients with lung or larynx cancer show CYP2D6 genotypes leading to ultrarapid metabolism or to the expression of an enzyme with altered kinetics (p < 0.01 vs. healthy controls). This may influence the metabolism of CYP2D6 substrates, including antineoplastic drugs and opioid derivatives used for pain relief in cancer patients. These patients would require higher doses than those considered as standard. We conclude that dosages for CYP2D6 substrates should be adapted to lung and larynx cancer patients.

CYP2D6 polymorphism is not associated with essential tremor.

Recent reports have shown an association between cytochrome P450IID6 (CYP2D6) polymorphism and Parkinson's disease. We investigated the association between this polymorphism and the risk for developing essential tremor (ET). Leukocytic DNA from 91 unrelated ET patients and a control group of 258 unrelated healthy individuals was studied for the occurrence of eight different CYP2D6 allelic variants by using allele-specific PCR amplification Xbal and EcoRI-RFLP's analyses. The prevalence for these allelic variants in the ET and control groups were, respectively: CYP2D6*1 76.9 and 78.7%, CYP2D6*2 0.5 and 0.2%, CYP2D6*3 0 and 1%, CYP2D6*4 12.1 and 12.2%, CYP2D6*5 1.6 and 1.7%, CYP2D6*9 4.4 and 2.9%, CYP2D6*2x2 4.4 and 3.2%. The prevalence of subjects with absent CYP2D6 activity (those carrying two defect genes) was 1.1 and 3.1% in ET and control groups, respectively. Both groups studied were in Hardy-Weinberg equilibrium. These results indicate that mutations at the CYP2D6 gene do not seem to be a major factor in determining susceptibility to ET, and reinforces the view that ET and parkinsonism are distinct conditions.

Increased risk for hepatocellular carcinoma in NAT2-slow acetylators and CYP2D6-rapid metabolizers.

The arylamine N-acetyltransferase (NAT2) is a polymorphic enzyme which is expressed in the liver in a genotype-determined manner. NAT2 is involved in activation and inactivation of carcinogens through N-acetylation. We studied the role of this polymorphism in the development of hepatocellular carcinoma (HCC). One hundred consecutive patients diagnosed for HCC and 258 healthy volunteers were studied for NAT2 genotype. The occurrence of seven enzyme-inactivating and silent point mutations in the coding region of the NAT2 gene was studied by mutation-specific PCR amplification. An excess of subjects homozygous for NAT2 loss of function alleles was observed among patients with HCC (68% vs 53.9% controls). The relationship between the slow acetylator NAT2 genotype and HCC risk is more pronounced in patients lacking serum HBV and HCV markers. The additional determination of alleles of the cytochrome P450 2D6 (CYP2D6) gene in the same subjects confirmed our previous findings that subjects with two active CYP2D6 genes are at increased risk of developing HCC. The genetic polymorphism of NAT2 is a relevant factor in the risk for developing HCC (inverse odds ratio slow vs rapid = 1.8; 95% CI 1.1-3.0). The inverse odds ratio for subjects with two risk genotypes (two defect NAT2 genes and two or more active CYP2D6 genes) is 2.6 (95% CI 1.6-4.4) for all patients with HCC, and 5.6 (95% CI 1.4-33.3) for patients without serum viral markers.

Frequency of CYP2D6 allelic variants in multiple sclerosis.

Recent reports have shown association between CYP2D6 polymorphism and neuronal degenerative diseases such as Parkinson's disease. We investigated the association between this polymorphism and the risk for developing multiple sclerosis (MS). Leucocyte DNA from 118 MS patients and a control group of 200 unrelated healthy individuals was studied for the occurrence of 8 different CYP2D6 allelic variants by using allele-specific PCR amplification, XbaI and EcoRI RFLP analyses. The frequencies for these allelic variants in the MS and control groups were, respectively: CYP2D6wt 75.0% and 79.3%, CYP2D6A 0.4% and 1.3%, CYP2D6B 11.4% and 12.0%, CYP2D6C 4.2% and 2.0%, CYP2D6D 3.0% and 2.3%, CYP2D6L 0.8% and 0.3%, CYP2D6L2 5.1% and 3.0%. The frequencies of subjects with high CYP2D6 activity (those carrying two or more functional genes) were 77.1% and 73.5% in MS and control groups. The frequencies of subjects with absent CYP2D6 activity (those lacking functional genes) were 3.4% and 4.5% in MS and control groups, respectively. These results indicate that mutations at the CYP2D6 gene do not seem to be a factor in determining susceptibility to MS.

CYP2D6 genes and risk of liver cancer.

We have studied by use of PCR and XbaI and EcoRI restriction-fragment-length polymorphism whether mutations at the polymorphic CYP2D6 (debrisoquine hydroxylase) gene locus are associated with liver cancer. The frequency of CYP2D6 genes containing inactivating mutations was lower among 75 liver cancer patients than 200 healthy controls, and 40 cirrhotic subjects that did not develop liver cancer (frequency for carriers of two or more functional genes was 95% vs 74% vs 78%, respectively). Subjects who were homozygous for functional CYP2D6 genes appear to be at higher risk of developing primary liver cancer (odds ratio 6.40 [95% Cl] 2.4-17.5).

Prevalence of CYP2D6 gene duplication and its repercussion on the oxidative phenotype in a white population.

The occurrence of multiple copies of the CYP2D6 gene was investigated 217 white healthy Spaniards by the combined use of Xba I and Eco RI restriction fragment length polymorphism (RFLP) analyses. About 3.5% of the alleles yielded an 12.1 kb Eco RI-RFLP product in combination with the 42 kb Xba I-RFLP product, which is indicative of multiple CYP2D6. The prevalence of subjects carrying multiple CYP2D6 was 7%. The 12.1 kb Eco RI-RFLP product was highly associated (60%) with the presence of the genotype 29wt/42wt, as characterized by mutation-specific polymerase chain reaction and Xba I-RFLP analyses. Six subjects who had multiple CYP2D6 had other genotypes, namely, 44wt/42wt (four subjects), 29C/42wt (one subject), and one subject had a 12.1 kb product plus the CYP2D6C mutation associated with the 44 kb/42 kb genotype. All subjects identified as carrying multiple CYP2D6 had only two CYP2D6 copies in the same chromosome and were classified as carriers of the (CYP2D6L)2 allelic variant. Phenotyping with debrisoquin indicated an increase in the oxidative capacity as a function of the number of functional CYP2D6 genes. The metabolic ratio and the 95% confidence limits were as follows: subjects lacking functional genes, 48.8 (95% confidence limits, 14.4 to 79.3); subjects with one functional gene, 2.14 (95% confidence limits, 0.61 to 3.67); subjects with two functional genes, 1.5 (95% confidence limits, 0.88 to 2.14); and subjects with three functional genes, 0.33 (95% confidence limits, 0.22 to 0.45).(ABSTRACT TRUNCATED AT 250 WORDS)

Molecular analysis of the arylamine N-acetyltransferase polymorphism in a Spanish population.

The arylamine N-acetyltransferase (NAT-2) polymorphism causes impaired drug metabolism in about half of the white population. By the combined use of polymerase chain reaction (PCR) and restriction mapping with the endonucleases Fok I and Dde I, we have studied the genetic basis underlying NAT-2 polymorphism in genomic deoxyribonucleic acid from 245 healthy Spaniards. The study of three mutations at the NAT-2 gene locus by PCR analysis (namely, 481T, 590A, and 857A) revealed that all these mutations were present in Spaniards at similar frequencies as described in other white populations, strongly contrasting with genetic differences in the CYP2D6 polymorphism between Spaniards and other white subjects. The frequencies for NAT-2 mutations were different in Spaniards compared with Hispanics. About 12% of the subjects studied were incorrectly genotyped by the PCR test. Further studies involving restriction mapping of PCR products revealed the occurrence of at least five NAT-2 mutations that, alone or combined, were present in eight allelic variants of the NAT-2 gene. The allele frequencies were as follows: wild type, 25.3%; 341C + 481T + 803G, 32.9%; 341C + 481T, 6.3%; 282T + 590A, 24.9%; 282T, 3.5%; 590A, 1.6%; 803G, 4.1%; and 857A, 1.4%. The prevalence of the poor acetylator genotype among Spaniards is 53%.

Genetic basis for differences in debrisoquin polymorphism between a Spanish and other white populations.

The debrisoquin hydroxylation polymorphism is an autosomic recessive trait of the cytochrome P450IID6, an enzyme involved in drug metabolism, that affects 5% to 10% of white subjects. The genetic basis of this polymorphism was studied in 258 unrelated Spanish white subjects. The results revealed that about 5% of the subjects were homozygous for mutant alleles and that about 1% of the subjects carried alleles that suggested CYP2D6 gene duplication. The extensive metabolizers who were homozygous for the wild-type allele had higher metabolic ratio than the heterozygous extensive metabolizers, indicating a gene-dose effect for the wild type allele. The CYP2D6 allele frequencies indicate a reduced frequency for the CYP2D6(B) allele and a higher frequency for the wild-type allele compared with other white populations. This is also reflected in an increased frequency of the subjects who were homozygous for the wild-type allele among extensive metabolizers. We conclude that the same CYP2D6 mutations are present in Spaniards and other white subjects. Nevertheless, the frequencies of such mutations are different in our population. This implies that a high number of Spanish subjects may behave differently than other white subjects in the effect of drugs metabolized by the CYP2D6 enzyme.

Debrisoquin oxidation genotype and susceptibility to lung cancer.

The association between the polymorphism of the cytochrome P450 debrisoquin hydroxylase (CYP2D6) and lung cancer is controversial. Previous reports suggested a link between CYP2D6 phenotype and lung cancer, with poor metabolizers having reduced susceptibility. Nevertheless, negative findings have also been published. By using allele-specific amplification, we have studied the frequency of four CYP2D6 (wild type and mutant) alleles in 89 patients with histologically proved bronchogenic carcinoma and in 98 healthy volunteers. Our findings confirm that poor metabolizers are underpresented among patients with lung cancer because of a different genetic background. Our findings also reveal that the rare CYP2D6(C) mutant allele is sixfold more frequent among patients with lung cancer (p < 0.0005). This suggests that the CYP2D6(C) allele could be considered as an additional risk factor because carriers could have higher susceptibility to the development of lung cancer.

[Pulp tissue response to a glass and silver filings ionomer used as a permanent capping material]. / Respuesta del tejido pulpar ante un cemento a base de ionómero de vidrio y limadura de plata usado como obturación permanente.

A study was undertaken to ascertain the effect of [glass-and-silver fillings ionomer] on the pulp tissue at different times (15, 30 and 60 days). For that purpose, 34 premolars were evaluated, on which a basic coating of calcium hydroxide was applied previous to their obturation with an ionomer cement (Ketac Silver). Dental organs were divided in four groups, namely: untreated control, and three groups of 10 premolars which were extracted after 15, 30 and 60 days. Results yielded by this research suggest that applying a calcium hydroxide coating is not enough to prevent the toxic effect of the glass ionomer on the pulp.

Respuesta del tejido pulpar ante un cemento a base de ionómero de vidrio y limadura de plata usado como obturación permanente / Pulp tissue response to a glass and silver filling ionomer used as a permanent capping material

Se llevó a cabo un estudio con el propósito de conocer el efecto que causa el ionómero de vidrio con limadura de plata sobre el tejido pulpar a diferentes tiempos (15, 30 y 60 días); para esto se valoraron 34 premolares a los que se les realizaron cavidades de V clase y se les aplicó una base de hidróxido de calcio para después obturarlos con un cemento a base de ionómero (Ketac Silver). Los órganos dentarios se dividieron en cuatro grupos: control sin tratamiento, y tres grupos de 10 premolares que se extrajeron a los 15, 30 y 60 días. Los resultados que arrojó esta investigación sugieren que colocar una capa de hidróxido de calcio no es suficiente para impedir el efecto tóxico del ionómero de vidrio sobre la pulpa