Predictive models for carcinogenicity and mutagenicity: frameworks, state-of-the-art, and perspectives.

Mutagenicity and carcinogenicity are endpoints of major environmental and regulatory concern. These endpoints are also important targets for development of alternative methods for screening and prediction due to the large number of chemicals of potential concern and the tremendous cost (in time, money, animals) of rodent carcinogenicity bioassays. Both mutagenicity and carcinogenicity involve complex, cellular processes that are only partially understood. Advances in technologies and generation of new data will permit a much deeper understanding. In silico methods for predicting mutagenicity and rodent carcinogenicity based on chemical structural features, along with current mutagenicity and carcinogenicity data sets, have performed well for local prediction (i.e., within specific chemical classes), but are less successful for global prediction (i.e., for a broad range of chemicals). The predictivity of in silico methods can be improved by improving the quality of the data base and endpoints used for modelling. In particular, in vitro assays for clastogenicity need to be improved to reduce false positives (relative to rodent carcinogenicity) and to detect compounds that do not interact directly with DNA or have epigenetic activities. New assays emerging to complement or replace some of the standard assays include Vitotox, GreenScreenGC, and RadarScreen. The needs of industry and regulators to assess thousands of compounds necessitate the development of high-throughput assays combined with innovative data-mining and in silico methods. Various initiatives in this regard have begun, including CAESAR, OSIRIS, CHEMOMENTUM, CHEMPREDICT, OpenTox, EPAA, and ToxCast. In silico methods can be used for priority setting, mechanistic studies, and to estimate potency. Ultimately, such efforts should lead to improvements in application of in silico methods for predicting carcinogenicity to assist industry and regulators and to enhance protection of public health.

An assessment of the carcinogenic potential of ezetimibe using nonclinical data in a weight-of-evidence approach.

Ezetimibe blocks intestinal absorption of sterols via interaction with the Neimann-Pick C1-Like 1 (NPC1L1) transporter and is approved for use in the treatment of primary hyperlipidemia (heterozygous familial and non-familial), homozygous familial hypercholesterolemia, and homozygous sitosterolemia. A recently completed randomized clinical trial [simvastatin and ezetimibe in aortic stenosis (SEAS)] testing the effectiveness of Vytorin (a combination of simvastatin and ezetimibe) in patients with aortic stenosis reported an unexpected safety finding: an increase in overall cancer incidence and cancer-associated mortality (all types) in the treated groups relative to the placebo control. A subsequent meta-analysis utilizing a much larger database from two ongoing clinical trials indicated that the observed findings in the SEAS trial were likely due to chance and not a true drug-induced effect. Nonetheless, it has been suggested by various commentators on the SEAS trial that ezetimibe may be carcinogenic. The extensive nonclinical database for ezetimibe was used to test the hypothesis that ezetimibe may be a direct or indirect carcinogen. Using two different in silico approaches, ezetimibe showed no structural alerts for genetic toxicity or carcinogenicity. Ezetimibe was not genotoxic in two reverse mutation assays, one in vitro clastogenicity assay, and two mouse micronucleus assays. No evidence of proliferative lesions was observed in three species in studies of 1-12 months in duration. Ezetimibe was not carcinogenic in standard 2-year bioassays in mice and rats. Additionally, in these 2-year bioassays, no drug-related non-neoplastic lesions were noted. The absence of drug-induced non-neoplastic or proliferative lesions in these studies indicates that ezetimibe treatment was not associated with findings characteristic of carcinogens (i.e., DNA reactivity or cell proliferation) Administration of pharmacologic doses of ezetimibe to mice did not alter hepatic expression patterns of genes associated with apoptosis, cell proliferation, or epithelial-mesenchymal transition. No evidence of drug-induced tumors was observed in mice in which the molecular target of ezetimibe (NPC 1L1) was knocked out over the life span of the animal. In conclusion, the nonclinical data do not support the proposed hypothesis based on the single observation from the SEAS trial and, rather, support the conclusion that ezetimibe does not represent a carcinogenic hazard to humans using this drug in a therapeutic setting.

Information from the Internet: attitudes of Australian oncology patients.

BACKGROUND: Patients require accurate information about their illness to make informed decisions. Many sources of information exist, although reliability is variable. Our objective was to investigate information seeking behaviour and attitudes toward health-related information from the Internet in a sample of Australian oncology patients. METHOD: During their outpatient attendance, 109 patients completed a self-administered paper-pen format questionnaire. They were required to have a recent cancer diagnosis (<6 months ago) adequate English and no cognitive impairment. RESULTS: Seventy-four per cent of questionnaires were returned. The majority of patients (78%) wanted as much information about their cancer diagnosis as possible and 90% reported receiving adequate information from their treating team. Despite this, more than half actively searched for additional information, with 77% using the Internet. Patients were trusting of information obtained from the Internet. More than half of information searchers discussed information obtained in their search with a health professional. The majority of patients did not believe that information searching adversely affected the doctor-patient relationship. CONCLUSION: Information searching is common in ambulatory Australian oncology patients, with the Internet being a frequently used resource. To ensure patients find reliable and relevant information and to minimize the risk of harm, health professionals involved in treating oncology patients should provide guidance in finding information sources and assistance in interpreting the information obtained.

Further evidence that the radioprotective aminothiol, WR-1065, catalytically inactivates mammalian topoisomerase II.

It has recently been proposed that the thiol form of the cytoprotective drug amifostine that is designated WR-1065 [2-((aminopropyl)amino)ethanethiol] exerts its cytoprotective effects in part via a catalytic inhibition of DNA topoisomerase II (topo II)alpha. This in turn leads to the subsequent accumulation of cells in G2 phase and a prolongation of the cell cycle. We have used a Chinese hamster V79 cell-based micronucleus assay to further evaluate this hypothesis. It is demonstrated that WR-1065 strongly inhibits the clastogenesis of the topo II poisons etoposide and clinafloxacin at clinically attained exposure levels while having no effect on clastogenesis induced by topo II-noninteractive chemicals. These findings are consistent with the hypothesis that WR-1065 is a catalytic inhibitor of topo II in mammalian cells. These studies also suggest that WR-1065 might be expected to reduce the toxicity and clastogenicity in clinical applications of etoposide or quinolone antibiotics in dose-limiting normal tissues.

In vivo administration of dichloroacetic acid suppresses spontaneous apoptosis in murine hepatocytes.

Spontaneous apoptosis in hepatocytes of male B6C3F1 mice that received dichloroacetic acid (DCA) in their drinking water for 5-30 days (28-58 days of life) was examined as part of ongoing studies to determine the molecular basis of the hepatocarcinogenicity of this nongenotoxic water chlorination by-product. DCA at 0.5 and 5.0 g/liter, significantly reduced apoptosis relative to untreated controls in a dose-dependent fashion. Regression analysis indicated that apoptosis declined over the 30-day period in the livers of control, age-paired animals receiving no drug. Animals receiving low-dose DCA exhibited a similar, although quantitatively depressed, trend line, whereas animals receiving high-dose DCA showed maximal depression of apoptosis at 5 days, which was sustained throughout the course of the 30-day period. These studies suggest that DCA has the ability to down-regulate apoptosis in murine liver. When taken together with previous data demonstrating DCA-dependent decrease in labeling index in these same livers, these data further support the hypothesis that the carcinogenic mechanism of DCA may involve suppression of the ability of the liver to remove initiated cells by apoptosis rather than by induction of selective proliferation of initiated cells.

Differential responses of log and stationary phase human fibroblasts to inhibition of DNA repair by aphidicolin.

The tetracyclic diterpenoid, aphidicolin, is an effective inhibitor of DNA repair in human cells following ultraviolet irradiation. This inhibition is very efficient in confluent resting cells but not in rapidly cycling cells as measured by (1) analysis of DNA single-strand breaks by alkaline sucrose sedimentation, (2) chromatographic analysis of pyrimidine-dimer removal, and (3) repair replication using CsCl density centrifugation. The inhibition is reversed by deoxycytidine or thymidine but not by deoxyadenosine or deoxyguanosine during the repair period. The data suggest that differences in deoxynucleoside triphosphate pools between cycling and confluent resting cells determine the different efficacies of the agent in these two situations.

Apparent inhibition of apoptosis by polyamines and aminothiols in DNA fragmentation assays is artifactual.

We report that, in commonly used DNA fragmentation assays, polyamines and the radioprotective aminothiol WR1065 artifactually depress the degree of spontaneous or induced cellular apoptosis in two distinct ways. Firstly, in assays utilizing Hoechst 33258 dye to measure apoptotic DNA, both amines quench the fluorescence of low affinity dye/DNA binding resulting in preferential underestimation of DNA in the apoptotic DNA fraction and a resultant underestimation of the extent of DNA fragmentation. Secondly, these amines can cause aggregation and condensation of apoptotic DNA, causing anomalous sedimentation under conditions universally employed to separate apoptotic from intact DNA in cell lysates. This anomalous sedimentation of apoptotic DNA leads to underestimation of fragmentation in fluorescence assays as well as in agarose gel assays. We demonstrate that manipulation of the ionic strength of the lysis buffer or lowering the dye concentration ameliorates the effects of dye quenching in the Hoechst assay. Alternatively, this effect is alleviated by substituting DAPI for Hoechst in this assay. Inclusion of a polyanion to the lysis buffer antagonizes the condensation and anomalous sedimentation of apoptotic DNA observed regardless of which dye is used in the assay. These studies call into question the validity of previously reported studies suggesting that polyamines and the radioprotective aminothiol, WR1065, inherently suppress the apoptotic process and underline the need to consider alternative endpoints of apoptosis such as morphology in order to assess effects on cellular apoptosis of exogenously added agents, particularly di- or polycations.

Suppressors of mutations in the rII gene of bacteriophage T4 affect promoter utilization.

Homyk, Rodriguez and Weil (1976) have described T4 mutants, called sip, that partially suppress the inability of T4rII mutants to grow in lambda lysogens. We have found that mutants sip1 and sip2 are resistant to folate analogs and overproduce FH2 reductase. The results of recombination and complementation studies indicate that sip mutations are in the mot gene. Like other mot mutations (Mattson, Richardson and Goodin 1974; Chace and Hall 1975; Sauerbier, Hercules and Hall 1976), the sip2 mutation affects the expression of many genes and appears to affect promoter utilization. The mot gene function is not required for T4 growth on most hosts, but we have found that it is required for good growth on E. coli CTr5X. Homyk, Rodriguez and Weil (1976) also described L mutations that reverse the effects of sip mutations. L2 decreases the folate analog resistant and the inability of sip2 to grow on CTr5X. L2 itself is partially resistant to a folate analog, and appears to reverse the effects of sip2 on gene expression. These results suggest that L2 affects another regulatory gene related to the mot gene.

Identification of a second locus in Drosophila melanogaster required for excision repair.

The mus(2)201 locus in Drosophila is defined by two mutant alleles that render homozygous larvae hypersensitive to mutagens. Both alleles confer strong in vivo somatic sensitivity to treatment by methyl methanesulfonate, nitrogen mustard and ultraviolet radiation but only weak hypersensitivity to X-irradiation. Unlike the excision-defective mei-9 mutants identified in previous studies, the mus(2)201 mutants do not affect female fertility and do not appear to influence recombination proficiency or chromosome segregation in female meiocytes.--Three independent biochemical assays reveal that cell cultures derived from embryos homozygous for the mus(2)D1 allele are devoid of detectable excision repair. 1. Such cells quantitatively retain pyrimidine dimers in their DNA for 24 hr following UV exposure. 2. No measurable unscheduled DNA synthesis is induced in mutant cultures by UV treatment. 3. Single-strand DNA breaks, which are associated with normal excision repair after treatment with either UV or N-acetoxy-N-acetyl-2-aminofluorene, are much reduced in these cultures. Mutant cells possess a normal capacity for postreplication repair and the repair of single-strand breaks induced by X-rays.

The influence of N-dialkyl and other cationic substituents on DNA intercalation and genotoxicity.

DNA intercalation by small chemical molecules can result in frameshift mutagenesis and chromosomal breakage. With evidence mounting that broadly diverse structures are capable of intercalating between DNA base pairs, it becomes important to better define those structural features that enhance intercalation strength and those that confer genotoxicity particularly among those intercalators that do not have the classical planar tricyclic fused ring structure. A chemical substituent that is present on many pharmaceutical and other biologically active molecules is the N-dialkyl group. In the present study, we investigate if and how the presence of an aromatic N-dialkyl or other cationic group affects the genotoxicity and DNA intercalation ability of 26 selected acridines, phenothiazines, benzophenones, triphenylethylenes and other classes of molecules. The data were obtained from the literature, from experiments using a cell-based DNA intercalation assay, and from modeling studies using a three-dimensional computational DNA docking program. It is demonstrated that cationic substitution can enhance both genotoxicity and electrostatic interactions within a chemical/DNA intercalation complex.

The Melbourne Family Grief Study, II: Psychosocial morbidity and grief in bereaved families.

OBJECTIVE: The aim of this study was to describe the intensity of grief, the psychosocial morbidity, and the coping patterns in members of families classified according to a typology of family functioning comprising supportive, conflict-resolving, intermediate, sullen, and hostile classes. METHOD: One hundred fifteen families were assessed longitudinally 6 weeks (time 1), 6 months (time 2), and 13 months (time 3) after the death of a parent (constituting 670 individual responses) on measures of grief intensity, psychological state, social adjustment, and family coping. A previously described typology of perceptions of family functioning was applied. Repeated measures multivariate analysis of variance based on both individuals and families and post hoc comparisons of significant results were undertaken. RESULTS: Sullen families displayed the most intense grief and the most severe psychosocial morbidity. Well-functioning families (supportive and conflict-resolving) resolved their grief and adjusted more adaptively than their dysfunctional counterparts (intermediate, sullen, and hostile families). There were no cluster-by-time interactions. The clusters accounted for 15.7% of the variance in depression (Beck Depression Inventory) and 27.9% of the variance in social functioning (Social Adjustment Scale). Well-functioning families used more family coping strategies (Family Crisis Oriented Personal Evaluation Scales). CONCLUSIONS: More intense grief and greater psychosocial morbidity are found in sullen, hostile, and intermediate bereaved families than in the more adaptive supportive and conflict-resolving types. At-risk families are identifiable and could be treated preventively to reduce morbidity.

The Melbourne Family Grief Study, I: Perceptions of family functioning in bereavement.

OBJECTIVE: The aim of this study was to identify patterns of family functioning in adult families after the death of a parent. METHOD: One hundred fifteen families completed measures of family functioning, grief, psychological state, and social adjustment 6 weeks (time 1), 6 months (time 2), and 13 months (time 3) after the death of a parent (a total of 670 individual responses). Cluster analytic methods were applied to develop a typology of perceptions of family functioning during bereavement. RESULTS: Five types of families emerged from dimensions of cohesiveness, conflict, and expressiveness on the Family Environment Scale. Thirty-six percent of the families were considered supportive because of their high cohesiveness, and another 23% resolved conflict effectively. Two types were dysfunctional: hostile families, distinguished by high conflict, low cohesiveness, and poor expressiveness, and sullen families, who had more moderate limitations in these three areas; they declined in frequency from 30% at time 1 to 15% at time 3. The remaining type (26%), termed intermediate, exhibited midrange cohesiveness, low control, and low achievement orientation. The typology at time 1 predicted typologies at time 2 and time 3. There were no age or gender differences among the family types, but offspring, as compared with spouses, were overrepresented in the hostile families. CONCLUSIONS: Family types can be identified, allowing at-risk families to be helped to prevent complications of grief. Screening with the family relationship index of the Family Environment Scale would facilitate such a family-centered approach.

Late EEG findings and clinical status after organic mercury poisoning.

The EEGs of four siblings with organic mercury poisoning were recorded. The series of EEGs spanned two to eight years. Additional EEGs were obtained from an asymptomatic family member (the mother) who initially had elevated mercury levels. Various types of abnormalities were noted in the tracings of the siblings, including epileptiform features and disturbances of background rhythms. The mother's EEGs were normal. The degree of EEG change reflected the clinical state. In the two cases in which seizures were present, epileptiform activity was seen. Both clinical severity and EEG abnormalities may correlate with age.

Drug trial of superoxide dismutase in Duchenne's muscular dystrophy.

A multicenter, randomized, double-blind, placebo-controlled drug trial in Duchenne's muscular dystrophy, evaluating a superoxide dismutase in 51 ambulatory patients for 18 months was conducted. Fourteen aspects of muscle strength and five of functional ability, as well as serum creatine phosphokinase (CPK) level were studied. The total change in strength, function, and CPK level did not differ significantly in the two groups. The testing method used was reliable in assessing the natural history of Duchenne's dystrophy and would, therefore, be useful in future multicenter drug trials.

Möbius syndrome and transposition of the great vessels.

A case of Möbius syndrome was associated with transposition of the aorta and pulmonary artery, as well as acheiria. This combination of anomalies supports the hypothesis that Möbius syndrome is caused by an intrapartum insult during the fourth to seventh week of gestation and is consistent with the vascular theory of embryopathogenesis.

Neuropathy in Navajo children: clinical and epidemiologic features.

We describe a rare and apparently unique neuropathic syndrome among Navajo children living on the Navajo Reservation. Clinical features include sensorimotor neuropathy, corneal ulcerations, acral mutilation, poor weight gain, short stature, sexual infantilism, serious systemic infections, and liver derangement including Reye's syndrome-like episodes. Progressive CNS white matter lesions were diagnosed through magnetic resonance imaging. We identified 20 definite and 4 probable cases occurring between 1959 and 1986. Mean age at the time of 1st recognized symptom was 13 months (range, 1 month to 4 years 6 months). Ten individuals have died; 6 of the deaths occurred before 5 years of age. The incidence of this syndrome on the western Navajo reservation is 5 times higher than that on the eastern reservation (38 compared with 7 cases per 100,000 births). Although the etiology is unknown, this syndrome is consistent with an inborn error of metabolism, inherited in an autosomal recessive manner.

Adrenoleukodystrophy and adrenomyeloneuropathy associated with partial adrenal insufficiency in three generations of a kindred.

Four cases of adrenoleukodystrophy (ALD) and one case of adrenomyeloneuropathy (AMN) have developed in a kindred over three generations demonstrating that AMN is a clinical variant of ALD. Pituitary-adrenal function studies were performed in 10 family members, including two affected males and four females identified as carriers of ALD/AMN. No pituitary-adrenal abnormality was found in the carriers. However, basal morning plasma adrenocorticotropic hormone (ACTH) levels were markedly elevated in the two males with ALD and AMN, despite the fact that they had no clinical signs of adrenal insufficiency and that morning plasma cortisol levels and their response to maximal exogenous ACTH stimulation appeared to be normal. In addition, the integrated 24-hour response to the administration were also subnormal in these two cases. Thus, people with ALD and AMN may have subclinical partial adrenocrotical insufficiency. No other endocrinologic dysfunction was identified.

Synthesis and DNA-binding properties of polyamine analogues.

The synthesis of a series of novel polyamine analogues is reported. The DNA binding of these compounds and a variety of other polyamines were compared with their IC50 values against HeLa cell. There seemed to be no apparent correlation between the DNA binding and toxicity against HeLa cells.

The right not to read.

Skill in reading is desirable. However, the importance of reading may be overemphasized in schools. Reading skills are determined relatively and not absolutely. Thus, relatively poor readers will persist. Schools cannot eradicate individual differences. Biological makeup and societal pressures are the important factors in determining reading skill. Present methods of reading remediation are of questionable efficacy and are traumatic to some children. Time with its associated normal development succeeds in remediating the majority of children with dyslexia. Most poor readers eventually attain reading levels that enable them to comprehend the types of printed materials commonly encountered. If a child finds reading difficult or distasteful, that child should be encouraged to read but should have the right not to be forced to read.

Effects of sodium selenite on DNA and carcinogen-induced DNA repair in human diploid fibroblasts.

Sodium selenite induces substantial DNA damage in human fibroblasts. This damage appears to consist of true DNA breaks rather than alkali-labile sites and to not arise via free oxygen radical production. Cloning efficiency and DNA strand breakage show dramatically enhanced sensitivity to selenite if the treatments are carried out in the presence of reduced glutathione or, to a lesser degree, serum, supporting the notion that a glutathione-selenite conjugant is required for activation to a genotoxic form. In addition, the notion that selenium anticarcinogenicity involves enhancement of cellular DNA repair, has been examined. No evidence for enhancement (or inhibition) of repair of methyl methanesulfonate (MMS)-, UV- or bleomycin-induced DNA damage was observed in human fibroblasts treated with selenite.