细胞色素P450介导的昆虫抗药性研究进展

昆虫细胞色素P450在昆虫抗药性、解毒代谢等方面具有重大研究价值。本文概述了昆虫细胞色素P450在昆虫抗药性中所起的作用及其目前的一些研究进展,从分子学角度分析了昆虫细胞色素P450介导昆虫抗药性的分子机制。     

The Anopheles gambiae detoxification chip: a highly specific microarray to study metabolic-based insecticide resistance in malaria vectors

Metabolic pathways play an important role in insecticide resistance, but the full spectra of the genes involved in resistance has not been established. We constructed a microarray containing unique fragments from 230 Anopheles gambiae genes putatively involved in insecticide metabolism [cytochrome P450s (P450s), GSTs, and carboxylesterases and redox genes, partners of the P450 oxidative metabolic complex, and various controls]. We used this detox chip to monitor the expression of the detoxifying genes in insecticide resistant and susceptible An. gambiae laboratory strains. Five genes were strongly up-regulated in the dichlorodiphenyltrichloroethane-resistant strain ZAN/U. These genes included the GST GSTE2, which has previously been implicated in dichlorodiphenyltrichloroethane resistance, two P450s, and two peroxidase genes. GSTE2 was also elevated in the pyrethroid-resistant RSP strain. In addition, the P450 CYP325A3, belonging to a class not previously associated with insecticide resistance, was expressed at statistically higher levels in this strain. The applications of this detox chip and its potential contribution to malaria vector insecticide resistance management programs are discussed.     

Pyrethroid activity-based probes for profiling cytochrome P450 activities associated with insecticide interactions

Pyrethroid insecticides are used to control diseases spread by arthropods. We have developed a suite of pyrethroid mimetic activity-based probes (PyABPs) to selectively label and identify P450s associated with pyrethroid metabolism. The probes were screened against pyrethroid-metabolizing and nonmetabolizing mosquito P450s, as well as rodent microsomes, to measure labeling specificity, plus cytochrome P450 oxidoreductase and b₅ knockout mouse livers to validate P450 activation and establish the role for b₅ in probe activation. Using PyABPs, we were able to profile active enzymes in rat liver microsomes and identify pyrethroid-metabolizing enzymes in the target tissue. These included P450s as well as related detoxification enzymes, notably UDP-glucuronosyltransferases, suggesting a network of associated pyrethroid-metabolizing enzymes, or “pyrethrome.” Considering the central role P450s play in metabolizing insecticides, we anticipate that PyABPs will aid in the identification and profiling of P450s associated with insecticide pharmacology in a wide range of species, improving understanding of P450–insecticide interactions and aiding the development of unique tools for disease control.Pyrethroids are synthetic analogs of pyrethrins, botanical chemicals derived from chrysanthemum flowers (1). They are highly potent insecticides with low mammalian toxicity that are used worldwide in ∼3,500 registered products in agricultural, medicinal, veterinary, and public health sectors. Importantly, they are the only class of insecticide recommended for insecticide-treated nets for malaria control. More than 254 million insecticide-treated nets were distributed across Africa between 2008–2010 (2). Similar to antibiotics, pyrethroids are critical for controlling a diverse spectrum of diseases. Unfortunately, similar to antibiotics, such intense exposure affects health and drives the rapid evolution of insecticide resistance (3).Pyrethroids are structurally highly diverse (4) but share a common architecture comprising a cyclopropane acid group coupled to an alcohol moiety, as exemplified by deltamethrin (Fig. 1A). Traditionally, they are divided into two classes (type 1 and type 2), depending on the absence (type 1) or presence (type 2) of an α-cyano group (Fig. 1B). Pyrethroids work by blocking the voltage-gated sodium channels, causing paralysis in arthropods, and resulting in death (3). Resistance is commonly associated with target site modification or metabolic resistance, in which increased rates of biotransformation, generally by P450s, esterases, and GSTs, reduce toxic potency (3).Open in a separate windowFig. 1.Conversion of deltamethrin into PyABPs. (A) Structure of deltamethrin with constituent acid and alcohol moieties. Primary sites of P450 hydroxylation are indicated by bold arrows at the 2′ and 4′ positions, and minor routes of hydroxylation are indicated with open arrows (1). (B) Conversion of deltamethrin to a PyABPP involves the addition of an alkyne warhead and a clickable handle. The structures of the general probe and the PyABPs synthesized are illustrated. Alkyne warhead groups were located in the 2′ or 4′ positions, whereas alkyne click handles replaced the cyano group (type 1) or terminal bromides (type 2). The general P450 probe 2-EN is boxed parallel to its type 1 pyrethroid analog, P2.Although the toxicity and metabolism of pyrethroids in mammals and insects have been extensively characterized (1), the role of specific enzymes and pathways involved in pyrethroid clearance is unclear. In insects, P450s are key enzymes involved with metabolic degradation, with constitutive overexpression of specific P450s leading to pyrethroid resistance (5, 6). Similarly, in mammals, the toxic potency of pyrethroids is inversely related to their rates of metabolic elimination (7), with both P450 oxidation and carboxyl esterase-mediated hydrolysis playing major roles. Humans have 57 P450 genes, rodents ∼80 P450 genes, and insects up to ∼200 P450 genes (8). Where genome information exists, genetic and microarray-based studies of pyrethroid-resistant versus susceptible populations have been used to identify P450s potentially capable of pyrethroid metabolism (3, 5). However, relatively few P450s have been functionally validated through recombinant P450 expression. Thus, probes able to identify pyrethroid-metabolizing enzymes directly would aid our understanding of the fundamental processes of insecticide–organism interactions, expanding our understanding of the risks of pyrethroid exposure to mammals and the enzymatic mechanisms of metabolism and resistance used by insects.Activity-based protein profiling (ABPP) has been described for the functional profiling of P450s (9, 10). The activity-based probes (ABPs) work in a mechanism-dependent manner to covalently label P450s, whereby the labeling events are detectable by adding a fluorescent reporter group via copper-catalyzed azide-alkyne cycloaddition (“click chemistry”) onto the probe−P450 adducts (9, 10). Furthermore, affinity tags can also be incorporated to pull down and identify probe–P450 adducts. The major advantage of ABPPs is their ability to directly assess enzyme activity. In this article, we have designed and synthesized a group of seven pyrethroid mimetic ABPs (PyABPs) on the basis of the deltamethrin scaffold (Fig. 1B) for the targeted identification of pyrethroid-metabolizing P450s in highly divergent organisms. We have investigated their reactivity profiles against pyrethroid metabolizing and nonmetabolizing recombinant mosquito P450s and mouse and rat liver microsomes. We show that PyABPs can be used to reveal pyrethroid structure–activity relationships, and they also have been used to identify pyrethroid-reactive P450s and related detoxification enzymes in rat liver microsomes, demonstrating their potential for directly assessing pyrethroid-metabolizing enzyme activity.     

Comparative molecular modeling of Anopheles gambiae CYP6Z1, a mosquito P450 capable of metabolizing DDT

One of the challenges faced in malarial control is the acquisition of insecticide resistance that has developed in mosquitoes that are vectors for this disease. Anopheles gambiae, which has been the major mosquito vector of the malaria parasite Plasmodium falciparum in Africa, has over the years developed resistance to insecticides including dieldrin, 1,1-bis(p-chlorophenyl)-2,2,2-trichloroethane (DDT), and pyrethroids. Previous microarray studies using fragments of 230 An. gambiae genes identified five P450 loci, including CYP4C27, CYP4H15, CYP6Z1, CYP6Z2, and CYP12F1, that showed significantly higher expression in the DDT-resistant ZAN/U strain compared with the DDT-susceptible Kisumu strain. To predict whether either of the CYP6Z1 and CYP6Z2 proteins might potentially metabolize DDT, we generated and compared molecular models of these two proteins with and without DDT docked in their catalytic sites. This comparison indicated that, although these two CYP6Z proteins share high sequence identity, their metabolic profiles were likely to differ dramatically from the larger catalytic site of CYP6Z1, potentially involved in DDT metabolism, and the more constrained catalytic site of CYP6Z2, not likely to metabolize DDT. Heterologous expressions of these proteins have corroborated these predictions: only CYP6Z1 is capable of metabolizing DDT. Overlays of these models indicate that slight differences in the backbone of SRS1 and variations of side chains in SRS2 and SRS4 account for the significant differences in their catalytic site volumes and DDT-metabolic capacities. These data identify CYP6Z1 as one important target for inhibitor design aimed at inactivating insecticide-metabolizing P450s in natural populations of this malarial mosquito.     

Dynamics of insecticide resistance in the malaria vector Anopheles gambiae s.l. from an area of extensive cotton cultivation in Northern Cameroon

Objective To explore temporal variation in insecticide susceptibility of Anopheles gambiae s.l. populations to the four chemical groups of insecticides used in public health and agriculture, in close match with the large‐scale cotton spraying programme implemented in the cotton‐growing area of North Cameroon. Methods Mosquito larvae were collected in 2005 before (mid June), during (mid August) and at the end (early October) of the cotton spraying programme. Larvae were sampled in breeding sites located within the cotton fields in Gaschiga and Pitoa, and in Garoua, an urban cotton‐free area that served as a control. Insecticide susceptibility tests were carried out with 4% DDT (organochlorine), 0.4% chlorpyrifos methyl (organophosphate), 0.1% propoxur (carbamate), 0.05% deltamethrin and 0.75% permethrin (pyrethroids). Results Throughout the survey, An. gambiae s.l. populations were completely susceptible to carbamate and organophosphate, whereas a significant decrease of susceptibility to organochlorine and pyrethroids was observed during spraying in cotton‐growing areas. Tolerance to these insecticides was associated with a slight increase of knockdown times compared to the reference strain. Among survivor mosquitoes, the East and West African Kdr mutations were detected only in two specimens of An. gambiae s.s. (n = 45) and not in Anopheles arabiensis (n = 150), suggesting metabolic‐based resistance mechanisms. Conclusions Environmental disturbance due to the use of insecticides in agriculture may provide local mosquito populations with the enzymatic arsenal selecting tolerance to insecticides.     

Extreme warfarin sensitivity in siblings associated with multiple cytochrome P450 polymorphisms

Warfarin use is complicated by an erratic dose response. Warfarin is metabolized by two distinct subfamilies of the cytochrome P450 (CYP) complex. We describe two siblings with extreme sensitivity to warfarin who share an unusual CYP genotype. These individuals illustrate both the importance of genetics in influencing the metabolism of warfarin as well as the potential utility of genetic testing as a guide to prescribing this medication.     

Cytochrome P450 2C19与氯吡格雷抵抗的研究

氯吡格雷是一种新型噻吩吡啶类衍生物,可选择性不可逆地抑制二磷酸腺苷诱导的血小板聚集。Cytochrome P4502C19具有遗传多态性,Cytochrome P450 2C19＊2等位基因变异所编码的功能缺陷性药物代谢酶与氯吡格雷抗血小板聚集的效果减弱有关。     

细胞色素P450 2C19多态性与对氯吡格雷的反应性研究进展

氯吡格雷是一种无活性的前体药物,进入体内后需要通过细胞色素P450（主要是细胞色素P450 2C19即CYP2C19）氧化为活性代谢物而发挥其抗血小板作用。越来越多的研究发现CYP2C19某些基因多态性（主要是细胞色素P450＊2）与氯吡格雷的活性代谢产物减少,血小板抑制程度减轻,及主要不良心血管事件及支架内血栓增加有关。现就细胞色素P450多态性对氯吡格雷的药代动力学、药效动力学与临床终点事件的影响,及对细胞色素P450等位基因携带者的处理最新研究进展进行综述。     

From the Cover: Honey constituents up-regulate detoxification and immunity genes in the western honey bee Apis mellifera

As a managed pollinator, the honey bee Apis mellifera is critical to the American agricultural enterprise. Recent colony losses have thus raised concerns; possible explanations for bee decline include nutritional deficiencies and exposures to pesticides and pathogens. We determined that constituents found in honey, including p-coumaric acid, pinocembrin, and pinobanksin 5-methyl ether, specifically induce detoxification genes. These inducers are primarily found not in nectar but in pollen in the case of p-coumaric acid (a monomer of sporopollenin, the principal constituent of pollen cell walls) and propolis, a resinous material gathered and processed by bees to line wax cells. RNA-seq analysis (massively parallel RNA sequencing) revealed that p-coumaric acid specifically up-regulates all classes of detoxification genes as well as select antimicrobial peptide genes. This up-regulation has functional significance in that that adding p-coumaric acid to a diet of sucrose increases midgut metabolism of coumaphos, a widely used in-hive acaricide, by ∼60%. As a major component of pollen grains, p-coumaric acid is ubiquitous in the natural diet of honey bees and may function as a nutraceutical regulating immune and detoxification processes. The widespread apicultural use of honey substitutes, including high-fructose corn syrup, may thus compromise the ability of honey bees to cope with pesticides and pathogens and contribute to colony losses.     

淡色库蚊细胞色素P450抗性相关基因克隆与初步鉴定

[目的 ]探讨淡色库蚊细胞色素P45 0与溴氰菊酯抗药性的关系。 [方法 ]采用一对昆虫细胞色素P45 0简并引物 ,以反转录 聚合酶链反应从淡色库蚊扩增特异片段 ,T/A直接克隆法筛选阳性克隆 ,对新序列进行cDNA芯片和逆Northern分析。 [结果 ]从淡色库蚊对溴氰菊酯敏感品系和抗性品系获得 112个阳性克隆 ,其中 2 4个阳性克隆测序后显示为细胞色素P45 0新序列 ,由GenBank登录上网 ;经国际细胞色素P45 0命名委员会鉴定分别属CYP4家族CYP4C、CYP4D、CYP4H和CYP4J等 4个亚家族 ;2 4个CYP4cDNA片段中 ,来自敏感品系的 2个片段(NYDS3和NYDS5 )和来自抗性品系的 4个片段 (NYDR6、NYDR9、NYDR15和NYDR17)在两品系间存在差别 ,cDNA芯片信号亮度值均是抗性品系大于敏感品系 ,倍数在 3 .1～ 9.7范围内 ;NYDR17仅与抗性探针杂交 ;逆Northern再鉴定 ,获得了与cDNA芯片一致的结果。 [结论 ]淡色库蚊CYP4与溴氰菊酯抗性相关 ;在淡色库蚊溴氰菊酯抗性机理中 ,可能存在P45 0基因点突变而导致的特异表达。     

花生四烯酸细胞色素P450代谢途径在高血压中作用的研究进展

花生四烯酸是人体必须脂肪酸之一，其代谢产物具有较强生物学活性并在众多生理病理过程中发挥着重要调节作用。其在人体内主要通过环氧化酶、脂氧化酶、细胞色素P450（CYP）三大途径进行代谢。其中，越来越多的研究表明，CYP代谢途径中其关键基因CYP通过调控经ω-羟化酶、表氧化酶作用的下游产物20羟-二十烷四烯酸及表氧一二十碳三烯酸的质／量，从而影响高血压的发生发展，并且对其分子生物学机制及遗传学的研究亦成为当前的研究焦点。本文主要对CYP途径在高血压中的作用简要做一综述。     

细胞色素氧化酶CYP2C9基因多态性及其与心血管药物代谢及疾病关系研究进展

细胞色素氧化酶P4502C9是人类肝脏中一种重要药物代谢酶,代谢约10%临床上常用药物,包括一些心血管系统疾病的用药。细胞色素氧化酶P4502C9基因具有高度多态性,在基因编码区和非编码区存在许多单碱基突变,这种基因多态性对心血管系统疾病的一些重要用药的代谢差异产生重要的影响,并可能和某些疾病的发生相关。     

Cytochrome P450 levels are altered in patients with esophageal squamous-cell carcinoma

AIM: To investigate the role of cytochrome P450 (CYP) in the carcinogenesis of squamous-cell carcinoma (SCC) in human esophagus by determining expression patterns and protein levels of representative CYPs in esophageal tissue of patients with SCC and controls. METHODS: mRNA expression of CYP2E1, CYP2C, CYP3A4, and CYP3A5 was determined using RT-PCR in both normal and malignant esophageal tissues of patients with untreated esophageal SCC (n = 21) and in controls (n = 10). Protein levels of CYP2E1, CYP2C8, CYP3A4, and CYP3A5 were measured by Western blot. RESULTS: Within the group of SCC patients, mRNA expression of CYP 3A4 and CYP2C was significantly lower in malignant tissue (-39% and -74%, respectively, P < 0.05) than in normal tissue. Similar results were found in CYP3A4 protein levels. Between groups, CYP3A4, CYP3A5, and CYP2C8 protein concentration was significantly higher in non-malignant tissue of SCC patients (4.8-, 2.9-, and 1.9-fold elevation, P < 0.05) than in controls. In contrast, CYP2E1 protein levels were significantly higher in controls than in SCC patients (+46%, P < 0.05). CONCLUSION: Significant differences exist in protein levels of certain CYPs in non-malignant esophageal tissue (e.g. CYP2C8, CYP3A4, CYP3A5, and CYP2E1) between SCC patients and healthy subjects and may contribute to the development of SCC in the esophagus.     

安徽淮南中华按蚊溴氰菊酯抗药性和P450单加氧酶活性随蚊龄变化的研究

目的 目的 研究蚊龄对安徽淮南中华按蚊溴氰菊酯抗性和P450单加氧酶活性的影响以及其抗性产生的分子机制。方法 方法 在安徽省淮南市现场采集中华按蚊幼虫, 饲养羽化, 分别在雌蚊羽化后1、 3、 6、 9、 12、 15 d和20 d时, 测定其抗药性和P450单加氧酶活性, 并以实验室敏感蚊作为对照组, 比较二者抗药性和P450单加氧酶活性。结果 结果 随蚊龄增长, 安徽中华按蚊溴氰菊酯抗性和P450单加氧酶活性曲线均呈不对称倒U形变化。1 d龄时, 抗性和P450单加氧酶活性较低; 其后迅速增加, 至3～9 d时达到顶峰, 进入平台期; 随后, 抗性和P450单加氧酶活性均逐渐降低。3～12 d龄蚊虫P450单加氧酶活性高于敏感蚊, 15 d与20 d龄蚊虫与敏感蚊类似, 1 d龄蚊虫则低于敏感蚊。 结论 结论 蚊龄是蚊虫抗性和酶活性检测的混杂因素。P450单加氧酶活性增强可能是当地中华按蚊溴氰菊酯抗性产生的原因之一。采用蚊龄不一致的现场蚊作为测试对象可能会低估其抗性水平, 误导杀虫剂的使用。     

From the Cover: Contribution of cyanobacterial alkane production to the ocean hydrocarbon cycle

Hydrocarbons are ubiquitous in the ocean, where alkanes such as pentadecane and heptadecane can be found even in waters minimally polluted with crude oil. Populations of hydrocarbon-degrading bacteria, which are responsible for the turnover of these compounds, are also found throughout marine systems, including in unpolluted waters. These observations suggest the existence of an unknown and widespread source of hydrocarbons in the oceans. Here, we report that strains of the two most abundant marine cyanobacteria, Prochlorococcus and Synechococcus, produce and accumulate hydrocarbons, predominantly C15 and C17 alkanes, between 0.022 and 0.368% of dry cell weight. Based on global population sizes and turnover rates, we estimate that these species have the capacity to produce 2–540 pg alkanes per mL per day, which translates into a global ocean yield of ∼308–771 million tons of hydrocarbons annually. We also demonstrate that both obligate and facultative marine hydrocarbon-degrading bacteria can consume cyanobacterial alkanes, which likely prevents these hydrocarbons from accumulating in the environment. Our findings implicate cyanobacteria and hydrocarbon degraders as key players in a notable internal hydrocarbon cycle within the upper ocean, where alkanes are continually produced and subsequently consumed within days. Furthermore we show that cyanobacterial alkane production is likely sufficient to sustain populations of hydrocarbon-degrading bacteria, whose abundances can rapidly expand upon localized release of crude oil from natural seepage and human activities.Hydrocarbons are ubiquitous in the oceans, where natural seepage and human activities are estimated to release between 0.4 and 4.0 million tons of crude oil into the ocean ecosystem annually (1). Even in minimally polluted marine surface waters, alkanes such as pentadecane and heptadecane have been found at concentrations ranging from 2 to 130 pg/mL (2, 3), although their sources remain unclear. A small proportion of alkanes, from 1 to 60 fg/mL, is associated with particulate matter >0.7 µm in diameter (4). Larger amounts may be associated with particulate matter <0.7 µm in diameter, because ocean concentrations are higher than the solubility of pentadecane and heptadecane, which is ∼10 pg/mL and 1 pg/mL, respectively (2). Populations of hydrocarbon-degrading bacteria, referred to as hydrocarbonoclastic bacteria, including many species that cannot use other carbon sources, are present in marine systems and play an important role in turnover of these compounds (5–9). Because obligate hydrocarbon-degrading bacteria are found in waters without significant levels of crude oil pollution, these organisms must use an alternate hydrocarbon source (9–11).Here, we investigate the extent to which cyanobacteria may contribute to these marine hydrocarbon pools. Cyanobacteria (oxygenic photosynthetic bacteria) can synthesize C15 to C19 hydrocarbons via two separate pathways. The first produces alkanes, predominantly pentadecane, heptadecane, and methyl-heptadecane, in addition to smaller amounts of alkenes, via acyl-ACP reductase (FAR) and aldehyde deformylating oxygenase (FAD) enzymes (12). The second pathway generates alkenes, primarily nonadecene and 1,14-nonadecadiene, via a polyketide synthase enzyme (Ols) (13). The abundance and ubiquity of cyanobacteria in the marine environment suggests hydrocarbon production in the oceans could be considerable and broadly distributed geographically (14, 15).We focused our studies on the two most abundant marine cyanobacteria, Prochlorococcus and Synechococcus (16). These genera have estimated global population sizes of 2.9 ± 0.1 × 10²⁷ and 7.0 ± 0.3 × 10²⁶ cells, respectively (14), and are together responsible for approximately a quarter of marine net primary production (14). These are also the only cyanobacterial genera for which global population size estimates have been compiled (14). Although the distribution patterns of both genera overlap (14, 17), Prochlorococcus cells dominate low-nutrient open-ocean areas between 40°N and 40°S and can be found at depths of up to 200 m (16, 18). Synechococcus are more numerous in coastal and temperate regions where conditions and nutrient levels are more variable (14, 16) but are still widely distributed in high abundance.     

Structural insights from a P450 Carrier Protein complex reveal how specificity is achieved in the P450(BioI) ACP complex

Cytochrome P450_BioI (CYP107H1) from the biotin operon of Bacillus subtilis forms a seven-carbon diacid through a multistep oxidative cleavage of a fatty acid linked to acyl carrier protein (ACP). Crystal structures of P450_BioI in complex with three different length fatty acyl-ACP (Escherichia coli) ligands show that P450_BioI binds the fatty acid such as to force the carbon chain into a U-shape above the active site heme. This positions the C7 and C8 carbons for oxidation, with a large additional cavity extending beyond the heme to accommodate the methyl termini of fatty acids beyond the site of cleavage. The structures explain the experimentally observed lack of stereo- and regiospecificity in the hydroxylation and cleavage of free fatty acids. The P450_BioI-ACP complexes represent the only structurally characterized P450-carrier protein complexes to date, which has allowed the generation of a model of the interaction of the vancomycin biosynthetic P450 OxyB with its proposed carrier protein bound substrate.     

Community factors associated with malaria prevention by mosquito nets: an exploratory study in rural Burkina Faso

Malaria-related knowledge, attitudes and practices (KAP) were examined in a rural and partly urban multiethnic population of Kossi province in north-western Burkina Faso prior to the establishment of a local insecticide-treated bednet (ITN) programme. Various individual and group interviews were conducted, and a structured questionnaire was administered to a random sample of 210 heads of households in selected villages and the provincial capital of Nouna. Soumaya, the local illness concept closest to the biomedical term malaria, covers a broad range of recognized signs and symptoms. Aetiologically, soumaya is associated with mosquito bites but also with a number of other perceived causes. The disease entity is perceived as a major burden to the community and is usually treated by both traditional and western methods. Malaria preventive practices are restricted to limited chloroquine prophylaxis in pregnant women. Protective measures against mosquitoes are, however, widespread through the use of mosquito nets, mosquito coils, insecticide sprays and traditional repellents. Mosquito nets are mainly used during the rainy season and most of the existing nets are used by adults, particularly heads of households. Mosquito nets treated with insecticide (ITN) are known to the population through various information channels. People are willing to treat existing nets and to buy ITNs, but only if such services would be offered at reduced prices and in closer proximity to the households. These findings have practical implications for the design of ITN programmes in rural areas of sub-Saharan Africa (SSA).     

Genetic polymorphisms of cytochrome P450 in patients with hepatitis C virus-associated hepatocellular carcinoma

BACKGROUND: The carcinogenic process can be modulated by exposure to endogenous or environmental substance(s) acting as carcinogens or protocarcinogens. Polymorphic enzymes of cytochrome P450 (CYP) that play a role in detoxication/toxication of such substances via metabolization may account for the interpatient variability of clinical course in cancers such as hepatocellular carcinoma (HCC). Many CYP genetic polymorphisms, which may change enzyme activity, are known to exist in Japanese. The aim of the present study was to compare the frequencies of CYP polymorphisms between hepatitis C virus (HCV)-related HCC patients and healthy subjects. METHODS: Seven mutant alleles and related genotypes of CYP in 44 HCV-positive HCC patients were chosen as follows: *1C heterozygous, *1C homozygous and *1F homozygous for CYP1A2, *4A homozygous for CYP2A6, *2A or *3 heterozygous, *2A or *3 homozygous and *2A and *3 heterozygous for CYP2C19, and *10/*5 homozygous for CYP2D6. These mutant alleles have been reported to change the CYP enzyme activity in Japanese. The frequencies of the mutant alleles and genotypes were then compared with those reported in healthy Japanese. RESULTS AND CONCLUSION: There is no statistically significant difference in genetic mutant alleles between the two groups, except for the genotype of CYP2A6*4A homozygous. The frequency of this genotype in the HCC patients (0.144) is significantly higher than that in healthy Japanese (0.034; P < 0.05; odds ratio 3.36). The clinical significance related to HCC is unknown. Further evaluation of CYP2A6*4A (deletion type) in HCV-related HCC patients is required.