Association of A313 G polymorphism (GSTP1*B) in the glutathione-S-transferase P1 gene with sporadic Parkinson's disease.

Genetic predisposition, environmental toxins and aging contribute to Parkinson's disease (PD) multifactorial etiology. Weak environmental neurotoxic factors may accumulate over time increasing the disease risk in genetically predisposed subjects. Polymorphic genes encoding drug-metabolizing-enzymes (DMEs) are considered to account for PD susceptibility by determining individual toxic response variability. In this work, the allelic distributions and genotype associations of three major brain-expressed DMEs were characterized, in sporadic PD cases and controls. No significant association was found between CYP2D6 genotype and PD, but subjects with extensive metabolizer (EM) CYP2D6 phenotype, and the variant GSTP1*B genotype were at significantly higher PD risk than the corresponding poor or intermediary metabolizers (CYP2D6 poor metabolizer phenotype+intermediary metabolizers). A significant association was observed between the GSTP1*B allele and zygosity with PD (GSTP1*A/*B- 51.58%/34.37%, odds ratio (OR) = 2.29; 95% confidence interval (95% CI) = 1.25-4.18; *B/*B- 6.32%/1.05%, OR = 10.67; 95% CI = 1.19-94.79). This association was particularly strong in the elder patients group (> or =69 year) who showed double PD risk for GSTP1*B heterozygous, whilst GSTP1*B/*B homozygous were exclusively found amongst patients. An interaction between GSTM1 and GSTP1 was observed in this late onset PD group. The present results suggest that native GSTP1 encoding the fully active transferase variant should play a relevant role in dopaminergic neuroprotection.

Interaction between smoking, GSTM1 deletion and colorectal cancer: results from the GSEC study.

Cigarette smoking has inconsistently been associated with an increased risk of colorectal cancer. One of the enzymes responsible for the detoxification of the carcinogenic compounds present in tobacco smoke is glutathione S-transferase-mu (GST-mu). The gene that codes for this enzyme is GSTM1. In this study, we evaluated the associations and interaction between GSTM1 deletion, smoking behaviour and the development of colorectal cancer. We performed a pooled analysis within the International Collaborative Study on Genetic Susceptibility to Environmental Carcinogens (GSEC). We selected six studies on colorectal cancer, including 1130 cases and 2519 controls, and restricted our analyses to Caucasians because the number of patients from other races was too limited. In addition we performed a meta-analysis including the studies from the GSEC database and other studies identified on MEDLINE on the same subject. The prevalence of the GSTM1 null genotype was within the range reported in other studies: 51.8% of the cases had the GSTM1 null genotype versus 56.6% of the controls. No significant association between the GSTM1 null genotype and colorectal cancer was found (odds ratio 0.92, 95% confidence interval 0.73-1.14). Our results suggest a possible positive association between lack of the GST-mu enzyme and colorectal cancer for non-smoking women (odds ratio 1.47, 95% confidence interval 0.80-2.70). There was no interaction between the effects of smoking and GSTM1 genotype on colorectal cancer risk in men and women (chi2=0.007, p=0.97). Our findings do not support an association between the GSTM1 null genotype and colorectal cancer. In addition, we did not find any modification of the smoking-induced colorectal cancer risk by GSTM1 genotype

Metabolic gene polymorphism frequencies in control populations.

Using the International Project on Genetic Susceptibility to Environmental Carcinogens (GSEC) database containing information on over 15,000 control (noncancer) subjects, the allele and genotype frequencies for many of the more commonly studied metabolic genes (CYP1A1, CYP2E1, CYP2D6, GSTM1, GSTT1, NAT2, GSTP, and EPHX) in the human population were determined. Major and significant differences in these frequencies were observed between Caucasians (n = 12,525), Asians (n = 2,136), and Africans and African Americans (n = 996), and some, but much less, heterogeneity was observed within Caucasian populations from different countries. No differences in allele frequencies were seen by age, sex, or type of controls (hospital patients versus population controls). No examples of linkage disequilibrium between the different loci were detected based on comparison of observed and expected frequencies for combinations of specific alleles.

Glycerol increases the yield and activity of human phenylalanine hydroxylase mutant enzymes produced in a prokaryotic expression system.

Chemical chaperones are low molecular weight compounds known to stabilize proteins in vitro. Recently it was shown that, in transfected cells, these molecules can also correct the defective folding of some mutant proteins. Hyperphenylalaninemia (HPA) has been proposed to be classified as a "conformational disease," since it has been shown that the majority of the PAH mutations affect protein folding, thereby causing an increasing tendency toward aggregation and proteolytic degradation. Based on these observations, the effect of glycerol as a stabilizer agent of recombinant mutant forms of human phenylalanine hydroxylase enzymes (hPAH) produced in a prokaryotic expression system was investigated. The wild-type and two mutant forms of the hPAH protein (R270K and V388M) were expressed in the presence of glycerol in the culture medium. The yield, specific enzymatic activities, and kinetic properties of the recombinant proteins were determined and compared with the data obtained under normal growth conditions. The results obtained demonstrate that glycerol not only improved the yield of the soluble hPAH proteins (2- to 3-fold depending on the mutant enzyme) produced but also increased the specific activity of the purified recombinant enzymes. We speculate that correction of protein folding abnormalities by chemical chaperones may be a possible therapeutic approach to correct conformational diseases.

Stereotactic breast biopsy of nonpalpable lesions: determinants of ductal carcinoma in situ underestimation rates.

PURPOSE: To measure the effect of biopsy device, probe size, mammographic lesion type, lesion size, and number of samples obtained per lesion on the ductal carcinoma in situ (DCIS) underestimation rate. MATERIALS AND METHODS: Nonpalpable breast lesions at 16 institutions received a histologic diagnosis of DCIS after 14-gauge automated large-core biopsy in 373 lesions and after 14- or 11-gauge directional vacuum-assisted biopsy in 953 lesions. The presence of histopathologic invasive carcinoma was noted at subsequent surgical biopsy. RESULTS: By performing the chi(2) test, independent significant DCIS underestimation rates by biopsy device were 20.4% (76 of 373) of lesions diagnosed at large-core biopsy and 11.2% (107 of 953) of lesions diagnosed at vacuum-assisted biopsy (P <.001); by lesion type, 24.3% (35 of 144) of masses and 12.5% (148 of 1,182) of microcalcifications (P <.001); and by number of specimens per lesion, 17.5% (88 of 502) with 10 or fewer specimens and 11.5% (92 of 799) with greater than 10 (P <.02). DCIS underestimations increased with lesion size. CONCLUSION: DCIS underestimations were 1.9 times more frequent with masses than with calcifications, 1.8 times more frequent with large-core biopsy than with vacuum-assisted biopsy, and 1.5 times more frequent with 10 or fewer specimens per lesion than with more than 10 specimens per lesion.

The correlation of genotype and phenotype in Portuguese hyperphenylalaninemic patients.

To understand the basis for the clinical heterogeneity of phenylalanine hydroxylase deficiency among Portuguese hyperphenylalaninemic patients, genotype-phenotype correlations were established. A group of 61 patients was completely genotyped, leading to the identification of 20 different mutant alleles in 36 different genotypic combinations, including a mutant allele not reported previously. The severity of those mutations found within this hyperphenylalaninemic population, which have not been previously expressed in vitro, were assessed. The results obtained by the present study exhibit a strong correlation between the predicted residual enzyme activity, as deduced from the genotype of the patients, and the biochemical phenotype represented by the diagnostic parameters (phenylalanine levels before the beginning of treatment and the dietary phenylalanine tolerance). It was observed that only a judicious follow-up and compliance with the appropriate diet permits the correct assessment of the clinical phenotype of the patients. Additionally, based upon the correlation observed between genotypes and diagnostic parameters, it was possible to predict the potential residual enzyme activity of those mutations (identified in our patients) which have not yet been studied in vitro.

The V388M mutation results in a kinetic variant form of phenylalanine hydroxylase.

The molecular mechanism underlying the metabolic defect in phenylketonuria (PKU) patients carrying the V388M missense mutation of the phenylalanine hydroxylase (PAH) gene has been characterized. An in vitro prokaryotic expression system has been used to produce both the wild-type and the mutant form of the human PAH (hPAH) protein. The recombinant enzymes, obtained as fusion proteins, were purified by immobilized metal affinity chromatography and recovered in high yields. The wild-type hPAH possessed a high specific activity and its kinetic properties were the same as those reported for the enzyme isolated from human liver and other recombinant wild-type hPAH enzymes. The recombinant V388M mutant form exhibited a reduced specific activity equivalent to 30% of the wild-type hPAH enzyme when assayed using the synthetic cofactor (6-methyltetrahydropterin). Lower values were obtained (23 and 19%) when the mutant enzyme was assayed with the natural cofactor ((6R)-tetrahydrobiopterin) and different concentrations of l-phenylalanine. The enzyme kinetic studies of the V388M mutant protein revealed that this enzyme was a kinetic variant form of hPAH with a reduced affinity for l-phenylalanine and for the natural cofactor ((6R)-tetrahydrobiopterin). The residual activities determined for the V388M form of hPAH were compatible with the phenotype presented by the PKU patients harboring the V388M mutation in the PAH gene.

Cerebral hemorrhage and apoE.

The epsilon4 allele of apolipoprotein E (apoE) is found more commonly among patients with Alzheimer's disease (AD) than in the normal population. ApoE is associated with brain amyloid, a component of cerebral amyloid angiopathy (CAA), which is both a pathological feature of AD and a frequent cause of lobar intracerebral hemorrhage (ICH). We hypothesized that the frequency of epsilon4 allele is higher in patients with CAA-related ICH than in hypertensive ICH and in the normal population. To test this hypothesis we compared the frequency of apoE alleles in four populations: 24 patients with lobar ICH, 24 matched patients with hypertensive ICH, 24 matched normal controls, and 173 population controls. Although there was a tendency to a higher frequency of apoE epsilon4 in lobar ICH patients, we found no significant differences in the frequency of this allele between the four studied populations. In addition we did not confirm the finding of some authors of a higher frequency of apoE epsilon2 in patients with lobar ICH than in the normal population. Previous studies on the subject are discussed. The relationship between apoE polymorphism and lobar CAA-related ICH remains to be clearly defined.

N-acetyltransferase (NAT2) genotype and susceptibility of sporadic Alzheimer's disease.

The importance of environmental aggression and individual susceptibility to develop Alzheimer's Disease (AD) has been suggested by epidemiological studies on both typical familial and sporadic AD cases. In order to elucidate functions that can influence the susceptibility to AD pathogenesis, we genotyped a group of 53 sporadic late-onset AD patients, matched control individuals and a larger randomly selected non-demented population for the N-acetyltransferase (NAT2). We determined the relative frequencies of individual allele combinations that define a broad range of acetylator phenotypes. Inter-individual variability in the cytotoxic and genotoxic responses to a wide diversity of environmental chemicals is known to result from the polymorphism of NAT2 as well as other drug-metabolizing-enzyme genes. The results presented are the first to demonstrate a significant difference in the NAT2 genotype profiles of sporadic AD patients compared with the healthy population. A lower frequency of the recessive alleles NAT2*6 (chi-squared 1 d.f. = 12.56, P < 0.0004) and NAT2*5B (chi-squared 1 d.f. = 6.72, P < 0.01) was found among the AD population compared with control individuals, which was concomitant with a significantly higher number of NAT2*4 fully active allele homozygotes and heterozygotes (chi-squared 1 d.f. = 5.69, P = 0.017). The most notable observation was the absence of NAT2*5B/NAT2*6 heterozygotes among cases while being present in 22.5% of control individuals (chi-squared 1 d.f. = 13.08, P = 0.0003). These observations indicate that NAT2 is a potential low-penetrance gene in AD pathogenesis, determining an individual susceptibility trait predisposing to this degenerative disease.

P450-catalyzed in-chain desaturation of valproic acid: isoform selectivity and mechanism of formation of Delta 3-valproic acid generated by baculovirus-expressed CYP3A1.

The mechanism of formation of the in-chain, unsaturated fatty acid metabolite, Delta3-valproic acid (Delta3-VPA) by rat liver microsomes was examined. Microsomal rates of formation of Delta3-VPA were below quantifiable limits in reactions catalyzed by control female rat liver microsomes, but were induced more than 20-fold following pretreatment with triacetyloleandomycin and pregnenolone-16alpha-carbonitrile. Microsomal incubations conducted with 3-hydroxy-VPA or [2-2H1]VPA demonstrated that Delta3-VPA did not arise by dehydration of preformed alcohol nor was it reversibly isomerized to Delta2-VPA. CYP3A1 expression was optimized in the baculovirus expression vector system, and infected insect cell membranes which were supplemented with P450 reductase catalyzed formation of 3-OH-, 4-OH-, 5-OH-, Delta3-, and Delta4-VPA in ratios of 160:35:6:3:1. Intramolecular deuterium isotope effects on metabolite formation, determined with cDNA-expressed CYP3A1 and either [3,3-2H2]VPA or [4,4-2H2]VPA, yielded kH/kD values for Delta3-VPA of 2.00 +/- 0.06 and 2.36 +/- 0.08, respectively. These values were significantly lower than the isotope effects observed in the same incubations for 3-OH-VPA formation from 3,3-D2-VPA (kH/kD = 6.04 +/- 0.08), or for 4-OH- and Delta4-VPA formation from 4, 4-D2-VPA (kH/kD > 5). Collectively, these data demonstrate the existence of a microsomal P450-dependent in-chain fatty acid desaturase system distinct from the well-documented cytochrome b5-linked CoA desaturases and suggest further that CYP3A1-dependent formation of Delta3-VPA arises via nonselective, initial hydrogen atom abstraction from either the C-3 or the C-4 position.

Absence of stimulation of poly(ADP-ribose) polymerase activity in patients predisposed to colon cancer.

Poly(ADP-ribose)polymerase (PARP) has been implicated in DNA repair mechanisms and the associated activity shown to markedly increase after DNA damage in carcinogen-treated cells. A defective DNA repair has been associated to the aetiology of human cancers. In order to assess the potential role of this enzyme in cellular response to DNA damage by gamma-radiation, we studied the activity of PARP in patients with familial adenomatous polyposis (FAP). We compared poly(ADP-ribose)polymerase activity by the rate of incorporation of radioactivity from [3H]adenine-NAD+ into acid-insoluble material in permeabilized leucocytes from FAP patients and healthy volunteers. Concomitantly, the intracellular levels of NAD+--the substrate for the PARP--and the reduced counterpart NADH were determined using an enzymatic cycling assay 30 min after [60Co] gamma-ray cells irradiation. Our results demonstrate that a marked stimulation of PARP activity is produced upon radiation of the cells from healthy subjects but not in the FAP leucocytes, which concomitantly show a marked decrease in total NAD-/NADH content. Our observations point to a role of PARP in the repair of the gamma-radiation-induced DNA lesions through a mechanism that is impaired in the cells from FAP patients genetically predisposed to colon cancer. The differences observed in PARP activation by gamma-radiation in patients and healthy individuals could reflect the importance of PARP activity dependent on treatment with gamma-rays. The absence of this response in FAP patients would seem to suggest a possible defect in the role of PARP in radiation-induced DNA repair in this cancer-prone disease.

Population genetics of hyperphenylalaninaemia resulting from phenylalanine hydroxylase deficiency in Portugal.

In order to elucidate the molecular basis of phenylketonuria (PKU) in Portugal, a detailed study of the Portuguese mutant phenylalanine hydroxylase (PAH) genes was performed. A total of 222 mutant alleles from 111 PKU families were analysed for 26 mutations and restriction fragment length polymorphismlvariable number tandem repeat (RFLP/VNTR) haplotypes. It was possible to characterise 55% of the mutant alleles, in which 14 different mutations (R261Q, V388M, IVS10nt-11, I65T, P281L, R252W, R158Q, L348V, Y414C, L311P, Y198fsdel22bp, R408W, R270K, and R261X) and three polymorphisms (Q232Q, V245V, and L385L) were identified. A total of 14 different haplotypes were observed, with a high prevalence of haplotype 1 among mutant and normal alleles. The results reported in this study show considerable genetic heterogeneity in the Portuguese PKU population, as has also been described for other southern European populations.

Increased frequency of wild-type arylamine-N-acetyltransferase allele NAT2*4 homozygotes in Portuguese patients with colorectal cancer.

Here we report that colorectal cancer patients show a markedly higher frequency (3-fold) of wild-type NAT2*4 allele homozygotes than the control population. However, a marked difference in NAT2*4/NAT2*4 genotype frequency associated with the patients gender was observed pointing to a male-specific effect of this genotype as a risk factor in colon cancer. The arylamine-N-acetyltransferase (E.C. 2.3.1.5.) NAT2, a phase II detoxification enzyme, has been implicated in procarcinogen activation, namely from food contained arylamines, cigarette smoking, as well as environmental amines of various types. NAT2 is encoded by a polymorphic gene presenting several allelic variants encoding partially inactive enzymes expressed in human liver and colon. Epidemiological studies based on phenotype determination have long indicated the importance of the NAT2 active phenotype as a susceptibility factor in colorectal cancer. In the present study we investigated the NAT2 allelic frequencies and genotype distribution in a group of 114 unrelated colorectal cancer patients, in parallel with 201 healthy Portuguese subjects. We first demonstrate that the frequency of the wild-type NAT2*4 allele in the Portuguese sample population (23.4%) does not significantly differ from the values described for other Europeans. Besides the 3-fold higher frequency of NAT2*4 homozygotes found in colorectal cancer subjects, the NAT2*4/NAT2*5A compound genotype, known to determine a faster acetylator phenotype than other heterozygotic combinations, also increased by the same order of magnitude. These two genotypes represent 32% of the patients population versus 11% of the healthy controls. Taken together, our results strongly indicate that NAT2 genotype, particularly NAT2*4 allele zygosity, constitutes an individual susceptibility trait associated with sporadic colorectal cancer development, probably due to the local dietary habits in Portugal.

Identification of a functional glucocorticoid response element in the CYP3A1/IGC2 gene.

The rat CYP3A subfamily of cytochrome P450 consists of steroid- and drug-metabolizing enzymes inducible by pregnenolone 16alpha-carbonitrile and by supra-physiological doses of dexamethasone. The induction of CYP3A by dexamethasone has been proposed to be mediated by a mechanism distinct from the glucocorticoid receptor mediated response. However, a synergistic induction of CYP3A has been observed with physiological doses of glucocorticoids and other CYP3A inducers. We have identified the presence of a glucocorticoid-responsive element in the CYP3A1/IGC2 gene that mediates the induction with physiological doses of glucocorticoids. A 219-bp dexamethasone responsive fragment of the CYP3A1/IGC2 gene localized at -2100/-1882 bp upstream of the transcription initiation site was identified in transfection experiments with HepG2 cells. Maximum induction was achieved with 50-100 nM dexamethasone. DNase I footprinting analysis revealed two glucocorticoid receptor-protected sequences in the 5' flank of the CYP3A1/IGC2 gene. Point mutations in footprint I (-1982/-1960-bp) completely abolished binding and transcription activation whereas a mutation in footprint II (-2001/-1986-bp) only decreased the binding and had no effect on transcription activation. These results led to the conclusion that the glucocorticoid response element present in footprint I mediated the dexamethasone response in transfection experiments with HepG2 cells. Pregnenolone 16alpha-carbonitrile failed to induce any transcriptional effect mediated by this response element in the HepG2 cells.

Developmental changes in the constitutive and inducible expression of cytochrome P450 3A2.

Using a CYP3A2-specific oligonucleotide and an antipeptide antibody raised against the C terminus of CYP3A2 (VINGA) it is demonstrated that metyrapone administration to adult (12 weeks old) but not immature (3 weeks old) male Sprague Dawley rats induces the hepatic expression of CYP3A2 mRNA and protein. The constitutively expressed level of CYP3A2 protein in adult male rats is markedly lower than the levels expressed in immature rats as determined using the anti-VINGA antibody, in contrast to previous reports using antibodies that do not discriminate between CYP3A forms. Hepatic microsomal CYP3A2 protein expression, examined between 3 and 15 weeks of age, is extinguished between 9 and 12 weeks of age in contrast to immunoreactive CYP3A protein (determined using a nonselective antibody) and CYP3A-dependent androstenedione 6beta-hydroxylase activity. These data suggest that the regulation of the induction of CYP3A2 is developmentally controlled and that the major expressed adult form(s) of constitutively expressed CYP3A is not CYP3A2.

Atypical ductal hyperplasia diagnosed at stereotactic breast biopsy: improved reliability with 14-gauge, directional, vacuum-assisted biopsy.

PURPOSE: To compare histologic findings of atypical ductal hyperplasia (ADH) at 14-gauge, directional, vacuum-assisted breast biopsy (hereafter, vacuum-assisted biopsy) and at 14-gauge, automated, large-core breast biopsy (hereafter, large-core biopsy) with findings at histologic examination after surgical biopsy. MATERIALS AND METHODS: Nonpalpable breast lesions were diagnosed as ADH at histologic examination after vacuum-assisted biopsy in 88 lesions in seven institutions and after large-core biopsy in 55 previously reported lesions. Histologic findings at subsequent surgical biopsy were compared for the presence of carcinoma. RESULTS: On the basis of histologic findings of carcinoma at surgical biopsy, the diagnosis of ADH was not correct in 26 (48%) of 54 lesions sampled at large-core biopsy and in 13 (18%) of 74 lesions sampled at vacuum-assisted biopsy (Fisher exact test, P < .0004). More tissue specimens were obtained at vacuum-assisted biopsy (mean, 15.8 specimens) than at large-core biopsy (mean, 9.7 specimens). Individual specimens were twice as large at vacuum-assisted biopsy (mean, 34 mg) as at large-core biopsy (mean, 17 mg) (previously reported). CONCLUSION: ADH was diagnosed 2.7 times more reliably at vacuum-assisted biopsy than at large-core biopsy (with no increase in complications) with most of the improvement as a result of acquisition of more than 10 specimens per lesion, but carcinoma was sufficiently underestimated with both methods to necessitate surgical biopsy.

Glucocorticoid receptor-independent transcriptional induction of cytochrome P450 3A1 by metyrapone and its potentiation by glucocorticoid.

Metyrapone administration to 21- and 90-day-old male rats causes a transcriptional induction of the hepatic glucocorticoid-inducible CYP3A1 gene within an hour as determined by nuclear run-on experiments. Analyses performed 24 hr after metyrapone administration in both ages of rat demonstrate that the transcriptional induction of CYP3A1 gene expression is followed by significant increases in CYP3A1 mRNA, CYP3A-immunoreactive microsomal protein and total microsomal cytochrome P450 (CYP). In 21-day-old rats, there is a significant increase in microsomal CYP3A dependent steroid 6 beta-hydroxylase activity but not in 90-day-old rats, possibly because of a slower clearance of this drug, which inhibits CYP activities. In hepatocytes cultured in serum- and glucocorticoid hormone-free medium, metyrapone alone induces CYP3A1 mRNA expression, which demonstrates that metyrapone transcriptionally induces hepatic CYP3A1 by a direct interaction with the liver. Metyrapone does not compete with the binding of the synthetic glucocorticoid and potent transcriptional CYP3A1 inducer dexamethasone to the glucocorticoid receptor (GR) in soluble fractions from liver. This suggests that metyrapone is not a ligand for the GR and induces CYP3A1 by a mechanism independent of the GR. Addition of glucocorticoid to cultured hepatocytes at levels that induce GR-dependent genes potentiate CYP3A1 mRNA induction by metyrapone without inducing CYP3A1 mRNA alone. A GR-dependent mechanism may therefore mediate the potentiation of CYP3A1 transcriptional induction by metyrapone. The CYP3A1 transcriptional inducer and glucocorticoid antagonist pregnenolone 16 alpha-carbonitrile at 100 microM blocks dexamethasone binding to the GR in 21-day-old rat liver soluble fractions but is less effective in 90-day-old rat liver soluble fractions in contrast with 10 microM glucocorticoid antagonist RU486, which is equally effective at blocking dexamethasone binding to the GR. The inability of pregnenolone 16 alpha-carbonitrile to fully compete with dexamethasone for cytosolic binding in adult animals suggests that there may exist variant receptors with different affinities for dexamethasone and pregnenolone 16 alpha-carbonitrile and may explain the mechanism by which low concentrations of dexamethasone potentiate the transcriptional induction of CYP3A1 mediated by high concentrations of pregnenolone 16 alpha-carbonitrile [J. Biol, Chem. 270:28917-28923 (1995)]. Examination of membrane-bound dexamethasone binding activity, with which other steroidal and nonsteroidal CYP3A inducers have been shown to compete, indicates that binding activity is detectable in 90- but not 21-day-old rat liver microsomes. The absence of membrane-bound glucocorticoid binding site activity and the presence of a functional CYP3A1 transcriptional response in 21-day-old rats suggest that membrane-bound glucocorticoid binding site activity is not involved in the transcriptional activation of CYP3A1 expression. These data suggest that both glucocorticoids and nonsteroidal compounds may trigger the transcriptional induction of CYP3A1 by a GR-independent mechanism that may be potentiated by a GR-dependent mechanism.