Concentration-QTcF Modeling of Icenticaftor from a Randomized, Placebo- and Positive-Controlled Thorough QT Study in Healthy Participants.

Icenticaftor (QBW251) is a potentiator of the cystic fibrosis transmembrane receptor. Based on its mechanism of action, icenticaftor is expected to provide benefits in patients with chronic obstructive pulmonary disease by restoring mucociliary clearance, which would eventually lead to a reduction of bacterial colonization and related inflammatory cascade. A placebo- and positive-controlled, 4-way crossover thorough QT study was conducted in 46 healthy participants with the objective to assess the effect of therapeutic (300 mg twice daily for 6 days) and supratherapeutic (750 mg twice daily for 6 days) oral doses of icenticaftor on electrocardiogram parameters, including concentration-corrected QT (QTc) analysis. Moxifloxacin (400 mg, oral) was used as a positive control. In the concentration-QTc analysis performed on pooled data from Day 1 and Day 6 (steady state), the estimated population slope was shallow and slightly negative: -0.0012 ms/ng/mL. The effect on the Fridericia corrected QT (QTcF) interval (∆ΔQTcF) was predicted to be -1.3 milliseconds at the icenticaftor 300-mg twice-daily peak concentration (geometric mean was 1094 ng/mL) and -5.5 milliseconds at the 750-mg twice-daily peak concentration (geometric mean Cmax was 4529 ng/mL) indicated a mild shortening effect of icenticaftor on QTcF interval length. The results of the by-time-point analysis indicated least squares placebo corrected mean ∆∆QTcF across time points ranged from -7.9 to 0.1 milliseconds at 1 and 24 hours after dosing both on Day 6 in the 750-mg dose group compared with -3.7 to 1.6 milliseconds at 1.5 and 24 hours after dosing on Day 1 in the 300-mg dose group. Assay sensitivity was demonstrated with moxifloxacin. The large accumulation of exposures, especially the 4.3-fold increase in peak plasma concentration observed at the icenticaftor 750-mg twice-daily dosage compared with Icenticaftor 300 mg twice daily (2.3-fold) on Day 6 provided a large concentration range (up to 9540 ng/mL) to evaluate the effect of icenticaftor on ΔΔQTcF. Based on the concentration-QTc analysis, an effect on ΔΔQTcF exceeding 10 milliseconds can be excluded within the full observed ranges of plasma concentrations on icenticaftor, up to approximately 9540 ng/mL. Icenticaftor at the studied doses demonstrated a mild shortening in QTcF, which is unlikely to be of clinical relevance in a therapeutic setting.

Effects of triclabendazole and its metabolite exposure on the heart-rate-corrected QT intervals: A randomized, placebo- and positive-controlled thorough QT study in healthy individuals.

Triclabendazole is an effective and well-tolerated treatment for human fascioliasis. A placebo- and positive-controlled, four-sequence by four-period crossover study was conducted in 45 healthy participants to assess the effect of therapeutic (10 mg/kg twice daily [b.i.d.] for 1 day) and supratherapeutic (10 mg/kg b.i.d. for 3 days) oral doses of triclabendazole on corrected QT (QTc) interval prolongation. Moxifloxacin (400 mg, oral) was used as a positive control. The highest mean placebo-corrected change from baseline in QTcF (ΔΔQTcF) on day 4 with triclabendazole was 9.2 at therapeutic dose ms and 21.7 ms at supratherapeutic dose, at 4 h postdose. The upper limit of the two-sided 90% confidence interval exceeded 10 ms across all timepoints, except at predose timepoint on day 4 in the therapeutic group indicating that an effect of triclabendazole on cardiac repolarization could not be excluded. However, triclabendazole had no clinically significant effects on heart rate and cardiac conduction at the studied doses. In the moxifloxacin group, the mean ΔΔQTcF peak value was 13.7 ms at 3 h on day 4. The assay sensitivity was confirmed. Maximum plasma concentration of triclabendazole, sulfoxide metabolite, and sulfone metabolite occurred at ~3-, 4-, and 6-h postdose, respectively. No deaths, serious adverse events, study discontinuations due to treatment-emergent adverse events, or clinically relevant abnormalities in laboratory evaluations and vital sign values were observed. This study showed that triclabendazole had no clinically relevant effects on heart rate and cardiac conduction; however, an effect on cardiac repolarization (ΔΔQTcF >10 ms) could not be excluded.

Development and validation of an accurate smartphone application for measuring waist-to-hip circumference ratio.

Waist-to-hip circumference ratio (WHR) is now recognized as among the strongest shape biometrics linked with health outcomes, although use of this phenotypic marker remains limited due to the inaccuracies in and inconvenient nature of flexible tape measurements when made in clinical and home settings. Here we report that accurate and reliable WHR estimation in adults is possible with a smartphone application based on novel computer vision algorithms. The developed application runs a convolutional neural network model referred to as MeasureNet that predicts a person's body circumferences and WHR using front, side, and back color images. MeasureNet bridges the gap between measurements conducted by trained professionals in clinical environments, which can be inconvenient, and self-measurements performed by users at home, which can be unreliable. MeasureNet's accuracy and reliability is evaluated using 1200 participants, measured by a trained staff member. The developed smartphone application, which is a part of Amazon Halo, is a major advance in digital anthropometry, filling a long-existing gap in convenient, accurate WHR measurement capabilities.

Evaluation of a Low-Fat Low-Calorie Meal on the Relative Bioavailability of Trametinib and Dabrafenib: Results From a Randomized, Open-Label, 2-Part Study in Healthy Participants.

In this randomized, open-label, 2-part, 2 × 2 crossover, phase 1 study, the effect of a low-fat low-calorie (LFLC) meal on the relative bioavailability of a trametinib 2-mg tablet or dabrafenib 150-mg capsule was evaluated in healthy participants. Trametinib adjusted geometric mean ratios (90%CI) of fed : fasted for area under the concentration-time curve (AUC) from time 0 to the last quantifiable concentration and AUC from time 0 extrapolated to infinity were 0.76 (0.71-0.82) and 0.82 (0.77-0.88), respectively. For dabrafenib, the adjusted geometric mean ratios of AUC from time 0 to the last quantifiable concentration and AUC from time 0 extrapolated to infinity (90%CI) for fed:fasted were 0.85 (0.79-0.91) and 0.86 (0.80-0.92), respectively. Consumption of an LFLC meal delayed trametinib and dabrafenib absorption, with an increase in time to maximum concentration of ≈15 and ≈30 minutes, respectively, compared to the fasted state. These findings indicate that consumption of an LFLC meal reduced the bioavailability and delayed the absorption of trametinib and dabrafenib, supporting current recommendations to administer both drugs in the fasting state; however, an occasional LFLC meal is unlikely to affect the pharmacokinetics of the drugs once steady state is reached and, by consequence, not likely to alter the overall intended efficacy.

Discovery and Optimization of Pyrazole Amides as Inhibitors of ELOVL1.

Accumulation of very long chain fatty acids (VLCFAs) due to defects in ATP binding cassette protein D1 (ABCD1) is thought to underlie the pathologies observed in adrenoleukodystrophy (ALD). Pursuing a substrate reduction approach based on the inhibition of elongation of very long chain fatty acid 1 enzyme (ELOVL1), we explored a series of thiazole amides that evolved into compound 27─a highly potent, central nervous system (CNS)-penetrant compound with favorable in vivo pharmacokinetics. Compound 27 selectively inhibits ELOVL1, reducing C26:0 VLCFA synthesis in ALD patient fibroblasts, lymphocytes, and microglia. In mouse models of ALD, compound 27 treatment reduced C26:0 VLCFA concentrations to near-wild-type levels in blood and up to 65% in the brain, a disease-relevant tissue. Preclinical safety findings in the skin, eye, and CNS precluded progression; the origin and relevance of these findings require further study. ELOVL1 inhibition is an effective approach for normalizing VLCFAs in models of ALD.

Models and Approaches Describing the Metabolism, Transport, and Toxicity of Drugs Administered by the Ocular Route.

The eye is a complex organ with a series of anatomic barriers that provide protection from physical and chemical injury while maintaining homeostasis and function. The physiology of the eye is multifaceted, with dynamic flows and clearance mechanisms. This review highlights that in vitro ocular transport and metabolism models are confined by the availability of clinically relevant absorption, distribution, metabolism, and excretion (ADME) data. In vitro ocular transport models used for pharmacology and toxicity poorly predict ocular exposure. Although ocular cell lines cannot replicate in vivo conditions, these models can help rank-order new chemical entities in discovery. Historic ocular metabolism of small molecules was assumed to be inconsequential or assessed using authentic standards. While various in vitro models have been cited, no single system is perfect, and many must be used in combination. Several studies document the use of laboratory animals for the prediction of ocular pharmacokinetics in humans. This review focuses on the use of human-relevant and human-derived models which can be utilized in discovery and development to understand ocular disposition of new chemical entities. The benefits and caveats of each model are discussed. Furthermore, ADME case studies are summarized retrospectively and capture the ADME data collected for health authorities in the absence of definitive guidelines. Finally, we discuss the novel technologies and a hypothesis-driven ocular drug classification system to provide a holistic perspective on the ADME properties of drugs administered by the ocular route.

A Containerized Software System for Generation, Management, and Exploration of Features from Whole Slide Tissue Images.

Well-curated sets of pathology image features will be critical to clinical studies that aim to evaluate and predict treatment responses. Researchers require information synthesized across multiple biological scales, from the patient to the molecular scale, to more effectively study cancer. This article describes a suite of services and web applications that allow users to select regions of interest in whole slide tissue images, run a segmentation pipeline on the selected regions to extract nuclei and compute shape, size, intensity, and texture features, store and index images and analysis results, and visualize and explore images and computed features. All the services are deployed as containers and the user-facing interfaces as web-based applications. The set of containers and web applications presented in this article is used in cancer research studies of morphologic characteristics of tumor tissues. The software is free and open source. Cancer Res; 77(21); e79-82. ©2017 AACR.

Pharmacokinetics and safety of olopatadine hydrochloride 0.77% in healthy subjects with asymptomatic eyes: data from 2 independent clinical studies.

PURPOSE: To assess the pharmacokinetics and safety of hydrochloride ophthalmic solution 0.77% olopatadine from 2 independent (Phase I and Phase III, respectively) clinical studies in healthy subjects. MATERIALS AND METHODS: The Phase I, multicenter, randomized (2:1), vehicle-controlled study was conducted in subjects ≥18 years old (N=36) to assess the systemic pharmacokinetics of olopatadine 0.77% following single- and multiple-dose exposures. The Phase III, multicenter, randomized (2:1), vehicle-controlled study was conducted in subjects ≥2 years old (N=499) to evaluate long-term ocular safety of olopatadine 0.77%. Subjects received olopatadine 0.77% or vehicle once daily bilaterally for 7 days in the pharmacokinetic study and 6 weeks in the safety study. RESULTS: In the pharmacokinetic study, olopatadine 0.77% was absorbed slowly and reached a peak plasma concentration (Cmax) of 1.65 ng/mL following single-dose and 1.45 ng/mL following multiple-dose exposures in 2 hours (time to reach maximum plasma concentration [Tmax]). After reaching peak concentrations, olopatadine showed a similar mono-exponential decay following single and multiple doses with mean elimination half-life ranging from 2.90 to 3.40 hours. No accumulation in olopatadine exposure (Cmax and area under the plasma concentration-time curve from 0 to 12 hours) was evident after multiple doses when compared to single dose. In the safety study, treatment-emergent adverse events were reported in 26.7% and 31.4% of subjects with olopatadine 0.77% and vehicle, respectively. Blurred vision was the most frequent ocular treatment-emergent adverse event in both treatment groups (olopatadine 0.77% vs vehicle, 4.8% vs 4.1%). No deaths or serious adverse events were reported during the study. CONCLUSION: Olopatadine 0.77% had minimal systemic exposure or accumulation in healthy subjects and was well tolerated in both adult and pediatric subjects.

Discovery of Novel Thiophene-Based, Thumb Pocket 2 Allosteric Inhibitors of the Hepatitis C NS5B Polymerase with Improved Potency and Physicochemical Profiles.

The hepatitis C viral proteins NS3/4A protease, NS5B polymerase, and NS5A are clinically validated targets for direct-acting antiviral therapies. The NS5B polymerase may be inhibited directly through the action of nucleosides or nucleotide analogues or allosterically at a number of well-defined sites. Herein we describe the further development of a series of thiophene carboxylate allosteric inhibitors of NS5B polymerase that act at the thumb pocket 2 site. Lomibuvir (1) is an allosteric HCV NS5B inhibitor that has demonstrated excellent antiviral activity and potential clinical utility in combination with other direct acting antiviral agents. Efforts to further explore and develop this series led to compound 23, a compound with comparable potency and improved physicochemical properties.

Ocular pharmacokinetics comparison between 0.2% olopatadine and 0.77% olopatadine hydrochloride ophthalmic solutions administered to male New Zealand white rabbits.

PURPOSE: The primary objective of this study was to compare uptake and distribution of the commercially available formulation of 0.2% olopatadine and the newly developed 0.77% olopatadine hydrochloride ophthalmic solution formulation with improved solubility following a single (30 µL), bilateral topical ocular dose in male New Zealand white rabbits. METHODS: Each animal received a single 30-µL topical ocular dose (0.2% olopatadine or 0.77% olopatadine hydrochloride ophthalmic solution) to the right (OD) eye followed by the left (OS) eye for a total dose of 60 µL. Olopatadine concentrations were measured in ocular tissues (cornea, bulbar, conjunctiva, choroid, iris-ciliary body, whole lens, retina), aqueous humor, and plasma at prespecified time points over 24 h using a qualified liquid chromatography coupled with mass spectrometry (LC-MS/MS) analytical method. RESULTS: Olopatadine was absorbed into the eye and reached maximal levels (Cmax) within 30 min (0.5 h) to 2 h (Tmax) in ocular tissues and plasma for both treatment groups, except for the lens in which the Tmax was 4 h in the 0.2% olopatadine group and 8 h in the 0.77% olopatadine hydrochloride group, respectively. Tissues associated with the site of dosing, that is, the conjunctiva and cornea, had the highest concentrations of olopatadine in both the 0.2% olopatadine (609 and 720 ng/g) and 0.77% olopatadine hydrochloride (3,000 and 2,230 ng/g) dose groups. The greatest differences between 0.2% olopatadine and 0.77% olopatadine hydrochloride were associated with the overall duration and level of ocular exposures. CONCLUSIONS: The newly developed 0.77% olopatadine hydrochloride ophthalmic solution formulation resulted in a higher and more prolonged olopatadine concentration in the target tissue, that is, conjunctiva compared to the commercial formulation of 0.2% olopatadine ophthalmic solution.

A Novel Study Using Accelerated Mass Spectrometry to Evaluate the Pharmacokinetics of Total (14)C AL-8309 (Tandospirone) Following Topical Ocular Administration in Healthy Male Subjects.

The primary objective of this study is to characterize the pharmacokinetics of total (14)C concentrations following bilateral, topical ocular drops of (14)C-AL-8309B labeled either at the pyrimidyl ring (cohort A) position or at the imido-carbonyl ring (cohort B) position twice daily from day 1 through day 6 and once in the morning of day 7 in 16 healthy male subjects (8 per cohort). Each drop (approximately 24 µL) of (14)C-AL-8309B 1.75% ophthalmic solution (equivalent to 420 µg-equiv AL-8309) contained approximately 500 nCi of (14)C-AL-8309. AL-8309 systemic absorption was relatively slow; the time of maximum observed plasma concentrations ranged from 0.25 to 3 hours. Moderate accumulation (1.48- to 1.86-fold) was observed in the mean systemic total (14)C plasma concentrations at steady state (day 7) compared with single dose (day 1). The mean total (14)C eliminated was 3.5-fold and 3.7-fold greater in the urine than the feces for cohort A and cohort B, indicating that (14)C-AL-8309 is primarily excreted through renal elimination. Single and multiple topical doses of AL-8309B were found to be safe and well-tolerated in healthy subjects. This is the first reported use of accelerator mass spectrometry technology with a topically applied ophthalmic product.

Reduced surface area chromatography for flow-through purification of viruses and virus like particles.

A method for flow-through purification of viruses and virus like nano-particles using a combination of binding and size-exclusion chromatography was developed. This technique relies on minimizing the external surface area per unit volume available for virus binding by increasing the mean diameter of the beads used in the column. At the same time the impurity binding capacity of the column is maximized by utilizing beads with multiple functionalities of the optimum size. Purification of different types of viruses and virus-like-particles could be achieved using this technique. Flow-through purification of influenza virus using this technique yielded virus recoveries greater than 70-80% coupled with impurity removal greater than 80%. Finally an approach to optimize and facilitate process development using this technology is presented. Since the impurity binding occurs via a non-specific mechanism and virus recovery is achieved through reduced surface area, the technique is not limited to specific types of viruses and offers the potential as a universal purification tool.

Global consequences of activation loop phosphorylation on protein kinase A.

Phosphorylation of the activation loop is one of the most common mechanisms for regulating protein kinase activity. The catalytic subunit of cAMP-dependent protein kinase autophosphorylates Thr(197) in the activation loop when expressed in Escherichia coli. Although mutation of Arg(194) to Ala prevents autophosphorylation, phosphorylation of Thr(197) can still be achieved by a heterologous protein kinase, phosphoinositide-dependent protein kinase (PDK1), in vitro. In this study, we examined the structural and functional consequences of adding a single phosphate to the activation loop of cAMP-dependent protein kinase by comparing the wild type C-subunit to the R194A mutant either in the presence or the absence of activation loop phosphorylation. Phosphorylation of Thr(197) decreased the K(m) by approximately 15- and 7-fold for kemptide and ATP, respectively, increased the stability of the enzyme as measured by fluorescence and circular dichroism, and enhanced the binding between the C-subunit and IP20, a protein kinase inhibitor peptide. Additionally, deuterium exchange coupled to mass spectrometry was used to compare the structural dynamics of these proteins. All of the regions of the C-subunit analyzed underwent amide hydrogen exchange at a higher or equal rate in the unphosphorylated enzyme compared with the phosphorylated enzyme. The largest changes occurred at the C terminus of the activation segment in the p + 1 loop/APE regions and the alphaH-alphaI loop motifs and leads to the prediction of a coordinated phosphorylation-induced salt bridge between two conserved residues, Glu(208) and Arg(280).

Effects of PRX-00023, a novel, selective serotonin 1A receptor agonist on measures of anxiety and depression in generalized anxiety disorder: results of a double-blind, placebo-controlled trial.

PRX-00023, a serotonin 1A receptor agonist, was designed to provide high potency and selectivity for its target. To assess the possible therapeutic utility in anxiety, a randomized, double-blind, placebo-controlled trial was conducted in 311 subjects who met the criteria of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, for generalized anxiety disorder. All subjects underwent a 1-week placebo run-in and were randomized to receive once-daily capsules containing either PRX-00023 (80 mg/d) or placebo for an additional 8 weeks. The primary outcome measure was the Hamilton Anxiety Scale (HAM-A). The Montgomery-Asberg Depression Rating Scale was used as a secondary endpoint to measure depressive symptoms. Statistical testing was performed with analysis of covariance, between baseline and week 8, with baseline values as a covariate. The anxiolytic effect of PRX-00023, compared with placebo, showed trends across all anxiolytic measures but failed to reach significance on the primary endpoint (HAM-A total score). Among the components of the HAM-A total score, the anxious mood item was significantly different from placebo in the PRX-00023-treated group (-1.015 vs -0.748; P = 0.02). The scores of the Montgomery-Asberg Depression Rating Scale were significantly improved compared with placebo at week 8 (-4.5 vs -1.6; P = 0.0094 in the last observation carried forward analysis). PRX-00023 was well tolerated; of note, there were no drug-related serious adverse events, and more patients discontinued due to adverse events in the placebo group (2.9%) than in the PRX-00023 group (1.4%). The most common adverse event was headache, observed in 15.7% and 10.9% of PRX-00023- and placebo-treated patients, respectively. Furthermore, there was no evidence of impaired sexual function, as measured by the Massachusetts General Hospital Sexual Function Scale. Collectively, these results support further clinical investigation of higher doses of PRX-00023 in anxiety and depression.

Staurosporine-based binding assay for testing the affinity of compounds to protein kinases.

Staurosporine is a broad-spectrum inhibitor of both tyrosine and serine/threonine protein kinases. Excitation of staurosporine and its analogues at 296 nm results in major emission bands centered at 378 and 396 nm. The intensity of the emission bands is enhanced on binding to the adenosine triphosphate (ATP) site of many protein kinases. This property was used to develop a competitive displacement assay for evaluating the binding affinity of small molecules to protein kinases. The assay was validated in both cuvette and plate formats for several phosphorylated and non-phosphorylated protein kinases. The throughput of the assay is high enough to be used in drug discovery for screening as well as lead optimization.

Tolerability, pharmacokinetics, and neuroendocrine effects of PRX-00023, a novel 5-HT1A agonist, in healthy subjects.

PRX-00023 is a novel, nonazapirone 5-HT1A agonist in clinical development for treatment of affective disorders. The objectives of the initial clinical phase I studies (a single ascending dose study and multiple dose-ascending and high-dose titration studies) were to measure the pharmacokinetics, pharmacodynamic (neuroendocrine) effects, and tolerability of PRX-00023 in healthy subjects. The studies evaluated 10-mg to 150-mg doses of PRX-00023 in up to 112 healthy male and female subjects aged 18 to 54 years. Single and multiple oral doses of PRX-00023 were found to be safe and well tolerated in healthy subjects. PRX-00023 was absorbed relatively rapidly, with a tmax of 0.5 to 2 hours, and eliminated with a half-life of approximately 12 hours. PRX-00023 treatment transiently increased blood prolactin levels 2 to 3 hours after administration, consistent with its mechanism as a 5-HT1A agonist.

Catalytic independent functions of a protein kinase as revealed by a kinase-dead mutant: study of the Lys72His mutant of cAMP-dependent kinase.

A highly conserved lysine in subdomain II is required for high catalytic activity among the protein kinases. This lysine interacts directly with ATP and mutation of this residue leads to a classical "kinase-dead" mutant. This study describes the biophysical and functional properties of a kinase-dead mutant of cAMP-dependent kinase where Lys72 was replaced with His. Although the mutant protein is less stable than the wild-type catalytic subunit, it is fully capable of binding ATP. The results highlight the effect of the mutation on stability and overall organization of the protein, especially the small lobe. Phosphorylation of the activation loop by a heterologous kinase, 3-phosphoinositide-dependent protein kinase-1 (PDK-1) also contributes dramatically to the global organization of the entire active site region. Deuterium-exchange mass spectrometry (DXMS) indicates a concerted stabilization of the entire active site following the addition of this single phosphate to the activation loop. Furthermore the mutant C-subunit is capable of binding both the type I and II regulatory subunits, but only after phosphorylation of the activation loop. This highlights the role of the large lobe as a scaffold for the regulatory subunits independent of catalytic competency and suggests that kinase dead members of the protein kinase superfamily may still have other important biological roles although they lack catalytic activity.

Consequences of lysine 72 mutation on the phosphorylation and activation state of cAMP-dependent kinase.

General strategies to obtain inactive kinases have utilized mutation of key conserved residues in the kinase core, and the equivalent Lys72 in cAMP-dependent kinase has often been used to generate a "dead" kinase. Here, we have analyzed the consequences of this mutation on kinase structure and function. Mutation of Lys72 to histidine (K72H) generated an inactive enzyme, which was unphosphorylated. Treatment with an exogenous kinase (PDK-1) resulted in a mutant that was phosphorylated only at Thr197 and remained inactive but nevertheless capable of binding ATP. Ser338 in K72H cannot be autophosphorylated, nor can it be phosphorylated in an intermolecular process by active wild type C-subunit. The Lys72 mutant, once phosphorylated on Thr197, can bind with high affinity to the RIalpha subunits. Thus a dead kinase can still act as a scaffold for binding substrates and inhibitors; it is only phosphoryl transfer that is defective. Using a potent inhibitor of C-subunit activity, H-89, Escherichia coli-expressed C-subunit was also obtained in its unphosphorylated state. This protein is able to mature into its active form in the presence of PDK-1 and is able to undergo secondary autophosphorylation on Ser338. Unlike the H-89-treated wild type protein, the mutant protein (K72H) cannot undergo the subsequent cis autophosphorylation following phosphorylation at Thr197. Using these two substrates and mammalian-expressed PDK-1, we can elucidate a possible two-step process for the activation of the C-subunit: initial phosphorylation on the activation loop at Thr197 by PDK-1, or a PDK-1-like enzyme, followed by second cis autophosphorylation step at Ser338.

The major lipid peroxidation product, trans-4-hydroxy-2-nonenal, preferentially forms DNA adducts at codon 249 of human p53 gene, a unique mutational hotspot in hepatocellular carcinoma.

Trans-4-hydroxy-2-nonenal (4-HNE), a major electrophilic by-product of lipid peroxidation, is able to interact with DNA to form exocyclic guanine adducts. 4-HNE is a mutagen and a significant amount of 4-HNE-guanine adduct has been detected in normal cells. Recently, it has been reported that exposure of the wild-type p53 human lymphoblastoid cell line to 4-HNE causes a high frequency of G to T transversion mutations at the third base of codon 249 (-AGG*-) in the p53 gene, a mutational hotspot in human cancers, particularly hepatocellular carcinoma. These findings raise a possibility that 4-HNE could be an important etiological agent for human cancers that have a mutation at codon 249 of the p53 gene. However, to date, the sequence specificity of 4-HNE-DNA binding remains unclear due to the lack of methodology. To address this question, we have developed a method, using UvrABC nuclease, a nucleotide excision repair enzyme complex isolated from Escherichia coli, to map the distribution of 4-HNE-DNA adducts in human p53 gene at the nucleotide sequence level. We found that 4-HNE-DNA adducts are preferentially formed at the third base of codon 249 in the p53 gene. The preferential binding of 4-HNE was also observed at codon 174, which has the same sequence and the same nearest neighbor sequences (-GAGG*C-) as codon 249. These results suggest that 4-HNE may be an important etiological agent for human cancers that have a mutation at codon 249 of the p53 gene.