Correlation of population mortality of COVID-19 and testing coverage: a comparison among 36 OECD countries.

Although testing is widely regarded as critical to fighting the COVID-19 pandemic, what measure and level of testing best reflects successful infection control remains unresolved. Our aim was to compare the sensitivity of two testing metrics - population testing number and testing coverage - to population mortality outcomes and identify a benchmark for testing adequacy. We aggregated publicly available data through 12 April on testing and outcomes related to COVID-19 across 36 OECD (Organization for Economic Development) countries and Taiwan. Spearman correlation coefficients were calculated between the aforementioned metrics and following outcome measures: deaths per 1 million people, case fatality rate and case proportion of critical illness. Fractional polynomials were used to generate scatter plots to model the relationship between the testing metrics and outcomes. We found that testing coverage, but not population testing number, was highly correlated with population mortality (rs = -0.79, P = 5.975 × 10-9vs. rs = -0.3, P = 0.05) and case fatality rate (rs = -0.67, P = 9.067 × 10-6vs. rs = -0.21, P = 0.20). A testing coverage threshold of 15-45 signified adequate testing: below 15, testing coverage was associated with exponentially increasing population mortality; above 45, increased testing did not yield significant incremental mortality benefit. Taken together, testing coverage was better than population testing number in explaining country performance and can serve as an early and sensitive indicator of testing adequacy and disease burden.

Preadmission statin use improves the outcome of less severe sepsis patients - a population-based propensity score matched cohort study.

BACKGROUND: Randomized controlled trials on the post-admission use of statins in sepsis patients have not shown a survival benefit. Whether preadmission use of statins would confer any beneficial effects in sepsis patients has not been well studied. METHODS: We conducted a population-based cohort study on a national health insurance claims database between 1999 and 2011. Sepsis patients were identified by ICD-9 codes compatible with the third International consensus definitions for sepsis. Use of statin was defined as the cumulative use of any statin for more than 30 days before the indexed sepsis admission. We determined the association between statin use and sepsis outcome by multivariate-adjusted Cox proportional hazard models and propensity score matched analysis. To minimize baseline imbalance between statin users and non-statin users, we matched/adjusted for social economic status, comorbidities, proxies for healthy lifestyle, health care facility utilization, and use of medications. RESULTS: We identified 52 737 sepsis patients, of which 3599 received statin treatment. Statins use was associated with a reduced 30-day mortality after multivariable adjustment (HR 0.86, 95% CI, 0.78-0.94) and propensity score matching (HR, 0.88; 95% CI, 0.78-0.99). On subgroup analysis, the beneficial effects of statins were not significant in patients receiving ventilator support or requiring ICU admission. CONCLUSIONS: In this national cohort study, preadmission statin therapy before sepsis development was associated with a 12% reduction in mortality when compared with patients who never received a statin. There were no consistent beneficial effects of statins in all patient subgroups.

High-voltage thin-film GaN LEDs fabricated on ceramic substrates: the alleviated droop effect at 670 W/cm(2).

High-voltage thin-film GaN LEDs with the emission wavelength of 455 nm were fabricated on ceramic substrates (230 W/m · K). The high-voltage operation was achieved by three cascaded sub-LEDs with dielectric passivation and metal bridges conformally deposited on the side walls. Under the driving power of 670 W/cm(2), the high-voltage LEDs exhibit much alleviated efficiency droop and the operative temperature below 80 °C. The excellent performances were attributed to the improved current spreading within each sub-LED and the superior heat sinking of the ceramic substrate.

The association of psychosocial factors and smoking with periodontal health in a community population.

BACKGROUND AND OBJECTIVE: The association between psychosocial factors and periodontal disease has been widely reported and might be modified by smoking status. This study investigated the association of periodontal status with psychosocial factors and smoking in a community population. MATERIAL AND METHODS: A structured questionnaire was administered to a total of 1,764 civilian noninstitutional (general population excluding from nursing homes, sanitariums and hospitals) Taiwanese individuals to assess the presence and severity of psychosocial factors [using the 12-item Chinese health questionnaire (CHQ-12)], smoking habits and other related factors. Periodontal status was established using the community periodontal index and by measuring clinical loss of attachment. RESULTS: Psychological factors and smoking were significantly associated with loss of attachment (odds ratio = 1.69, 95% confidence interval = 1.01-2.77, comparing the CHQ-12 score of >or= 6 with the CHQ-12 score of 0-2 and p = 0.032 for linear trend; odds ratio = 2.21, 95% confidence interval = 1.45-3.37, comparing smokers with nonsmokers) but not with community periodontal index. The association was found to be stronger among smokers than among nonsmokers. Smokers with a CHQ-12 score of >or= 6 had a higher odds ratio of loss of attachment (odds ratio = 2.49, 95% confidence interval = 0.91-6.49) than nonsmokers (odds ratio = 1.43, 95% confidence interval = 0.76-2.58). For periodontal health measured using the community periodontal index, married and divorced/widowed subjects tended to have poorer periodontal health (odds ratio = 3.38, 95% confidence interval = 1.26-10.81 and odds ratio = 3.83, 95% confidence interval = 1.21-13.83, respectively) than single subjects among nonsmokers but not among smokers. CONCLUSION: Poor mental health had a stronger association with periodontal disease among smokers than among nonsmokers, especially in accumulative attachment loss. Our findings suggest that mental health and smoking might have a synergistic effect on the risk of developing periodontal disease.

Locations of 18S and 28S ribosomal genes on the chromosomes of the Indian muntjac.

The locations of genes coding for 18S and 28S ribosomal RNA have been mapped on metaphase chromosomes of the Indian muntjac M. muntjak by in situ hybridization with (3H)rRNA from the toad X. laevis. The results show that, in the muntjac, rDNA clusters are associated with the prominent secondary constrictions on the X and the Y1 chromos. In addition a cluster of rDNA is found near the tip of one arm on the longest pair of autosomes. The autosomal cluster of rDNAs usually does not express as a secondary constriction at metaphase.

The possible role of histones in the mechanism of chromosomal G banding.

Cytochemical data are presented to show that the histone fractions f1 and f2a are involved in the induction of chromosomal G bands, whereas the f2b and f3 fractions are not involved. Removal of the f1 and f2a fractions probably occurs during fixation and is necessary for the induction of G bands.

Effect of chlorhexidine bathing on colonization or infection with Acinetobacter baumannii: a systematic review and meta-analysis.

Healthcare-associated infections (HAIs) caused by multi-drug-resistant Gram-negative bacteria (MDRGNB) have increased prevalence in intensive care units (ICUs). A common strategy to prevent HAIs is bathing patients with chlorhexidine gluconate (CHG). However, the effectiveness of CHG bathing against multidrug-resistant Acinetobacter baumannii (MDRAB) is still controversial. The aim of this study was to perform a systematic review and meta-analysis of the effectiveness of CHG bathing on Acinetobacter baumannii colonization and infection in the ICU setting. A systematic literature search of PubMed, EMBASE, Web of Science and CINAHL was performed from inception through to June 2018. Randomized controlled trials (RCTs), pre-post studies, or interrupted time series (ITS) studies were included. The numbers of patients with/without colonization or infection of A. baumannii in the experimental or control groups were extracted from each study. Quality assessment was performed by the related instruments of National Institute of Health. Pooled risk ratios (RRs) were calculated using the random-effects model. One RCT and 12 pre-post or ITS studies comprising 18,217 patients were included, of which 8069 were in the CHG bathing arm and 9051 in the control arm. CHG bathing was associated with a reduced colonization of A. baumannii (RR, 0.66; 95% confidence interval: 0.57-0.77; P<0.001). Chlorhexidine at 4% showed a better effect than 2% chlorhexidine (meta-regression P=0.044). CHG bathing was associated with a non-significant reduction of infection (pooled RR 0.41, 95% CI: 0.13-1.25). This study suggests that CHG bathing significantly reduces colonization of A. baumannii in the ICU setting. However, more trials are needed to confirm whether CHG bathing can reduce infections with A. baumannii.

Multiplex PCR system for the rapid diagnosis of respiratory virus infection: systematic review and meta-analysis.

OBJECTIVES: To provide a summary of evidence for the diagnostic accuracies of three multiplex PCR systems (mPCRs)-BioFire FilmArray RP (FilmArray), Nanosphere Verigene RV+ test (Verigene RV+) and Hologic Gen-Probe Prodesse assays-on the detection of viral respiratory infections. METHODS: A comprehensive search up to 1 July 2017 was conducted on Medline and Embase for studies that utilized FilmArray, Verigene RV+ and Prodesse for diagnosis of viral respiratory infections. A summary of diagnostic accuracies for the following five viruses were calculated: influenza A virus (FluA), influenza B virus, respiratory syncytial virus, human metapneumovirus and adenovirus. Hierarchical summary receiver operating curves were used for estimating the viral detection performance per assay. RESULTS: Twenty studies of 5510 patient samples were eligible for analysis. Multiplex PCRs demonstrated high diagnostic accuracy, with area under the receiver operating characteristic curve (AUROC) equal to or more than 0.98 for all the above viruses except for adenovirus (AUROC 0.89). FilmArray, Verigene RV+ and ProFlu+ (the only Prodesse assay with enough data) demonstrated a summary sensitivity for FluA of 0.911 (95% confidence interval, 0.848-0.949), 0.949 (95% confidence interval, 0.882-0.979) and 0.954 (95% confidence interval, 0.871-0.985), respectively. The three mPCRs were comparable in terms of detection of FluA. CONCLUSIONS: Point estimates calculated from eligible studies showed that the three mPCRs (FilmArray, Verigene RV+ and ProFlu+) are highly accurate and may provide important diagnostic information for early identification of respiratory virus infections. In patients with low pretest probability for FluA, these three mPCRs can predict a low possibility of infection and may justify withholding empirical antiviral treatments.

Double minutes in human carcinoma cell lines, with special reference to breast tumors.

Small DNA-containing particles called double minutes (dm) were observed in metaphases during a survey of human tumor cell lines. Detection of dm in uncultured malignant effusions, in a series of 14 breast carcinoma cell lines, and in a cervical carcinoma cell line, and a literature survey indicated that dm may be more common among human malignant cells than previously suspected. Some of the human breast carcinoma cell lines showed a high incidence of dm, which permitted a series of cytochemical studies. The dm stained identically with euchromatic regions of human chromosomes. Unlike typical chromsomes, dm contained neither C-bands nor Cd bands indicative of paracentromeric heterochromatin and centromeres, respectively. The dm were observed to cluster at the ends of chromosomes, and individual dm adhered to chromosomes. This clustering behavior allows dm to pass through cell division in the absence of centromeric regions. These results should alert tumor cytogeneticists to the possibility that their material may contain a low incidence of undetected dm.

Clonal origin of metastasis in B16 murine melanoma: a cytogenetic study.

A cell line isolated from the B16 melanoma and carried in continuous culture for 8 years (the parent line) exhibited great heterogeneity in terms of marker chromosome content. A lung metastasis from a C57BL/6 mouse inoculated im with cells of this line showed karyotypic homogeneity. Inoculation iv of cells from the parent line produced numerous tumor foci in various organs. Cytogenetic analyses of 18 such lesions led to the following conclusions: Cells from each metastatic colony exhibited relatively homogeneous karyotypic characteristics, indicating that metastases are of clonal origin; many parental cells with different marker chromosomes had metastatic potential; and some genomes maintained homogeneity longer than others.

Mutagen sensitivity in patients with head and neck cancers: a biologic marker for risk of multiple primary malignancies.

Eighty-four patients with head and neck cancers were evaluated for in vitro sensitivity to mutagens and then followed longitudinally for development of multiple primary malignancies. We assessed mutagen sensitivity by exposing lymphocytes to bleomycin in vitro and quantitating the bleomycin-induced chromosomal breaks per cell. The mutagen-hypersensitive patients, ie, those who expressed greater than 1.0 break per cell, were significantly more likely to develop multiple primary cancers than were patients who were less sensitive (less than or equal to 1.0 break per cell) (relative risk = 4.4; 95% confidence limits = 1.2, 15.8). This relationship was independent of age, sex, site, and treatment of first primary cancer and tobacco or alcohol exposures. Sensitivity to bleomycin-induced chromosomal damage serves as an indicator of genetic susceptibility to multiple primary malignancies in patients with head and neck cancers.

A human breast adenocarcinoma with chromosome and isoenzyme markers similar to those of the HeLa line.

Pleural effusion was obtained from a 51-year-old black woman who had breast adenocarcinoma and had received chemotherapy and radiation therapy after a radical mastectomy. Cytogenetic and isoenzymic analyses of the cells were performed within a few hours of obtaining the sample. Similar analyses were also done with a cell line established from this effusion. The stemline chromosome number was 35, one of the lowest in human neoplasms. In addition to a marker chromosome involving 1q, which is common in human breast tumors, we found several other marker chromosomes whose G-banding patterns were similar to some of the typical HeLa markers. Genetic signature analysis of 15 isoenzyme loci revealed that 13 were identical to those of HeLa. Both HeLa and the cell line described here express glucose-6-phosphate dehydrogenase type a, yet they were derived from heterozygotic individuals (ab). Our data indicate the necessity to extensive cytogenetic and biochemical analysis before conclusions are made that cell lines are actually intercell-line contaminants.

Mutagen sensitivity as a risk factor for second malignant tumors following malignancies of the upper aerodigestive tract.

BACKGROUND: Second malignant tumors in patients successfully treated for an initial cancer of the upper aerodigestive tract are an important cause of morbidity and mortality. Biologic markers capable of identifying high-risk subgroups of patients who could be targeted for intensive clinical surveillance, therefore, have immense therapeutic and prognostic relevance. We previously demonstrated in a pilot study of 84 patients with cancers of the upper aerodigestive tract that mutagen sensitivity was a significant predictor of risk of developing second malignant tumors. PURPOSE: We extended the study to include 278 patients diagnosed with previously untreated cancers of the upper aerodigestive tract from 1987 to August 1993. METHODS: For each patient, base-line (pretreatment) mutagen sensitivity was measured in vitro in 50 metaphases established from peripheral lymphocyte cultures. Patients with an average of more than 1 chromosomal break/cell were deemed mutagen hypersensitive. Cox proportional hazards analysis was used to predict the risk of developing second malignant tumors associated with mutagen sensitivity. RESULTS: Overall, 44% of the case group exhibited mutagen hypersensitivity. There were no differences in the distribution of mutagen hypersensitivity by site, sex, stage of disease, or smoking status. There were 17 synchronous and 11 metachronous cancers, of which 15 (54%) were smoking-related malignancies. Sixteen (13.1%) of the mutagen-sensitive patients developed second malignant tumors, compared with 12 (7.7%) of the nonsensitive patients. The mean break/cell value (+/- SD) for patients developing second malignant tumors was 1.17 (+/- 0.54), compared with 0.98 (+/- 0.44) for patients with only one cancer (P = .04). Mutagen hypersensitivity conferred a relative risk of 2.67 (95% confidence interval = 1.22-5.79) of developing second malignant tumors. CONCLUSIONS: Mutagen hypersensitivity increases the risk of developing second malignant tumors. IMPLICATIONS: Future research should focus on the molecular mechanisms underlying mutagen sensitivity.

Genetic susceptibility to head and neck squamous cell carcinoma.

BACKGROUND: In addition to influences of exposure to carcinogenic compounds, the development of cancer may depend on an individual intrinsic cancer susceptibility. Biomarkers for cancer susceptibility can be powerful additions to epidemiologic analyses. PURPOSE: This multicenter, case-control analysis combines previously published data and new data to substantiate the value of mutagen sensitivity as a biomarker of susceptibility to head and neck squamous cell carcinoma and, more importantly, to gain insight into the interaction between susceptibility and exposure to carcinogens. METHODS: Mutagen sensitivity (mean number of chromatid breaks per cell of cultured lymphocytes treated with bleomycin in the late S-G2 phase of the cell cycle) was determined in 313 patients with head and neck cancer and in 334 control subjects at two major U.S. medical institutions and one European institution, yielding a unique study population. The ages of the case and control subjects, as well as their history of use of tobacco and alcohol, were also recorded. The relationships between variables were analyzed by use of Student's t tests, Spearman's rank correlations, and multiple linear regression. For estimation of cancer risk, crude odds rations (ORs) were measured and multiple logistic regression was performed. All P values were based on two-sided tests. RESULTS: There were no differences across institutions in the distribution of mutagen sensitivity (Kruskal-Wallis test) for both case subjects and control subjects. Values for case subjects were consistently and significantly (P<.0001) higher than values for control subjects in the overall analyses. Age and tobacco or alcohol use did not influence the outcome in terms of mutagen-sensitivity values for either the case or the control subjects. A mean number of breaks per cell dichotomized at 1.0 was found to be the best predictor of a hypersensitive phenotype. For nonsensitive, heavy smokers, the OR was 11.5 (95% confidence interval [CI] = 5.0-26.6). This risk increased dramatically in mutagen-hypersensitive, heavy smokers to 44.5 (95% CI = 17.4-114.0). Multiple logistic regression analysis confirmed these results, and a significant trend was found (P<.01) for the dose-dependent increase in cancer risk by smoking. The consumption of alcohol potentiated the effects of smoking, resulting in an OR of 57.5 (95% CI = 17.5-188.0) in hypersensitive persons. CONCLUSIONS: Mutagen sensitivity was found to be a biomarker of cancer susceptibility. This study underscores the importance of utilizing both susceptibility markers and the exposure data for the identification of persons at high risk of developing cancer. IMPLICATIONS: More accurate risk estimation can define susceptible subgroups who might be targeted for intensive behavioral interventions, surveillance through screening, and enrollment in chemoprevention programs.

Rate of generation of major karyotypic abnormalities in relationship to the metastatic potential of B16 murine melanoma.

To test the hypothesis that genetic instability correlates with malignant potential, we compared the rate of generation of marker chromosomal abnormalities in clones of B16 F1 and B16 F10 murine melanoma. These rates were estimated through an adaptation of fluctuation analysis of Luria and Delbruck (S. E. Luria and M. Delbruck, Genetics, 28: 491-511, 1943). The highly metastatic F10 line showed the same degree of marker chromosomal instability as the poorly metastatic F1 line (0.01 variants/cell/generation). When subclones of a karyotypically unstable F10 clone were compared with those of a more stable F10 clone, both groups caused the same number of pulmonary metastases, thus demonstrating a further lack of correlation of malignant potential with the level of genomic instability. Since measurements based on marker chromosomes may not truly reflect all of the changes detectable by G-banding, we also analyzed the G-banded karyotypes of the cell lines and their clones (chromatid or chromosomal breaks were not considered in this study). The F10 clones possessed an additional copy of chromosome 1 and also a significantly higher prevalence of the translocation t(9,12) when compared with the F1 clones. Rather than general rates of major karyotypic change determining tumor progression, we suggest the importance of other genetic or epigenetic mechanisms, particularly subtle nonrandom genetic or molecular changes, as the determining factors for malignant potential.

Modulator inhibits nuclear translocation of the glucocorticoid receptor and inhibits glucocorticoid-induced apoptosis in the human leukemic cell line CEM C-7.

Modulator is an endogenous low-molecular-weight regulator of both glucocorticoid and mineralocorticoid receptors as well as protein kinase C. Structural analysis of modulator purified to apparent homogeneity suggests that it is a novel ether aminophosphoglyceride. In this report, we show that modulator inhibits cytosolic human glucocorticoid receptor (GR) complex activation as measured by DNA-cellulose binding. In addition, modulator blocks glucocorticoid-induced nuclear translocation of the GR in intact human leukemic (CEM C-7) cells, as illustrated by immunocytochemical localization. Furthermore, we demonstrate that modulator, by blocking the activation and subsequent translocation of GR, inhibits glucocorticoid-mediated apoptosis, characterized by chromatin condensation, internucleosomal DNA fragmentation, and cell death in glucocorticoid-sensitive CEM C-7 cells. Modulator inhibits glucocorticoid-induced c-myc gene repression and glucocorticoid receptor gene up-regulation. These data suggest that modulator functions to regulate the GR in intact cells as well as in cytosolic preparations. In addition, the inhibition of glucocorticoid-induced programmed cell death by modulator sheds light on the cellular function of modulator as well as on the mechanism by which apoptosis occurs in CEM C-7 cells.

A case-control study of nonrandom distribution of bleomycin-induced chromatid breaks in lymphocytes of lung cancer cases.

We used a case-control study design to determine the association between bleomycin-induced chromatid breaks and the risk of lung cancer in general and by specific histopathological types. Lymphocytes from primary blood cultures of 78 controls and 75 cases with 4 histopathological types of lung cancer were treated with 0.03 unit/ml bleomycin for 5 h, and the frequency of induced chromatid breakage and the locations of the breaks were determined in Q-banded preparations. After adjustment for their length, the larger chromosomes had more breaks than the smaller chromosomes in both cases and controls. The cases had significantly more breaks on chromosomes 4 and 5 than the controls did, with odds ratios (ORs) of 4.9 [95% confidence limits (CL), 2.0, 11.7] and 3.9 (95% CL, 1.6, 9.3), respectively. When the lung cancers were classified by histopathological type, adenocarcinomas had significantly more breaks on chromosomes 4 and 5, with ORs of 3.0 (95% CL, 1.0, 8.7) and 3.5 (95% CL, 1.2, 10.7), respectively. For squamous cell carcinoma, the ORs were significantly elevated for breaks on chromosomes 2, 4, and 5 with ORs of 3.5 (95% CL, 1.0, 11.7), 10.2 (95% CL, 2.5, 41.9), and 7.9 (95% CL, 1.9, 32.8). For small cell carcinoma, breaks on chromosomes 2 and 4 showed significantly increased ORs of 33.2 (95% CL, 2.2, 513.3) and 20.4 (95% CL, 1.7, 250.1), respectively. However, no specific chromatid breaks were detected in cases with large cell carcinoma. When the frequency of chromatid breaks at specific regions was calculated, breaks at 4p14, 4q27, 4q31, 5q21-q22, 5q31, and 5q33 were significantly more common in lung cancer cases than in controls. Lung cancer risk had a dose-response relationship with breaks on chromosomes 4 and 5. Cigarette smoking had a strong interaction with breaks on chromosomes 2, 4, and 5. The findings suggest that the susceptibility of particular chromosome loci to mutagenic damage may be a risk factor for specific types of lung cancer.

Chromosome sensitivity to bleomycin-induced mutagenesis, an independent risk factor for upper aerodigestive tract cancers.

Defective DNA repair capability, measured by enumerating mutagen-induced chromosomal lesions, might explain variable host susceptibility to the action of environmental carcinogens. We compared sensitivity to bleomycin-induced chromosome damage in 75 patients (53 men and 22 women) with previously untreated upper aerodigestive tract malignancies with that in 62 healthy control subjects. Data on tobacco and alcohol use were derived from a detailed, self-administered cancer risk factor questionnaire. Forty-five patients and 13 controls were sensitive to bleomycin-induced mutagenesis (average breaks/cell greater than 0.8). Differential susceptibility was detected in patients categorized by primary tumor location. Odds ratios for chromosome sensitivity were significantly elevated for all sites (odds ratio = 10.3 for pharyngeal cancers, 8.0 for laryngeal cancers, and 3.8 for oral cavity cancers). On logistic regression analysis, chromosome sensitivity remained a strong and independent risk factor after adjustment for potential confounding from age, sex, and tobacco and alcohol use (odds ratio = 4.3, 95% confidence limits = 2.0, 10.2). Despite the small study size and design constraints, the strength of the association with chromosome sensitivity even after adjustment for potential confounders is impressive and suggests a promising avenue for further research. The preventive implications of a valid marker for carcinogen sensitivity are manifold.

Transformation nonresponsive cells owe their resistance to lack of p65/nuclear factor-kappaB activation.

Clonal variants of mouse epidermal JB6 cells that are genetically susceptible (P+) or resistant (P-) to tumor promoter-induced neoplastic transformation exhibit differential activator protein-1 (AP-1) response. Transactivation of AP-1 appears to be necessary but not sufficient to promote transformation in JB6 cells. Inhibition of AP-1 is invariably accompanied by inhibition of nuclear factor-kappaB (NF-kappaB) when transformation is suppressed, suggesting that NF-kappaB may also play a role in neoplastic transformation. We report here that transactivation of NF-kappaB is inducible by tumor promoters in P+ but not in P- JB6 cells. Inhibition of NF-kappaB using a nondegradable mutant of IkappaBalpha suppressed inducible anchorage-independent transformation of P+ JB6 cells, suggesting that NF-kappaB activation is required for tumor promotion. Induced degradation of IkappaBalpha occurred in both P+ and P- JB6 cells, indicating that failure to activate NF-kappaB in P- JB6 cells cannot be attributed to failure to degrade IkappaBalpha. Slightly higher levels of nuclear p65 were seen in P+ than in P- JB6 cells. The p65-specific DNA binding activity was also higher in P+ cells upon induction by tumor necrosis factor-alpha, suggesting that differential NF-kappaB activation may be attributable to changes in p65 activity. Transactivation of p65 protein was substantially higher in P+ than in P- JB6 cells, as determined by assay of Gal4-p65 fusion constructs. Thus activated, p65 may be a limiting factor for NF-kappaB activation and transformation responses. Stable expression of p65 in P- JB6 cells conferred not only inducible NF-kappaB and AP-1 activation but also transformation response to tumor promoters. Therefore, p65/NF-kappaB appears to be not only necessary for but also sufficient to confer tumor promotion response. Although stable expression of p65 in P- cells produced p65 increases in whole cell extracts, only the transfectants exhibiting increased nuclear p65 showed transformation response. Thus, elevation of nuclear p65 appears to be a necessary step for a transformation response. The P-/p65 transfectants showing acquired transformation response also showed elevated p65-specific transactivation response, thus recapitulating the NF-kappaB phenotypes seen in P+ cells. Expression of a transactivation-deficient mutant of Jun or dominant-negative extracellular signal-regulated kinase suppressed both AP-1 activation and p65-specific transactivation in JB6 cells, suggesting that AP-1 activity is needed for p65 transactivation and consequently for NF-kappaB activation. Thus, the transformation nonresponsive P- JB6 cells owe their resistance to lack of NF-kappaB activation and p65 transactivation that appears in turn to be attributable to insufficient AP-1 activation.

Mutagen-induced chromatid breakage as a marker of cancer risk.

Risk assessment is now recognized as a multidisciplinary process, extending beyond the scope of traditional epidemiologic methodology to include biological evaluation of interindividual differences in carcinogenic susceptibility. Modulation of environmental exposures by host genetic factors may explain much of the observed interindividual variation in susceptibility to carcinogenesis. These genetic factors include, but are not limited to, carcinogen metabolism and DNA repair capacity. This chapter describes a standardized method for the functional assessment of mutagen sensitivity. This in vitro assay measures the frequency of mutagen-induced breaks in peripheral lymphocytes. Mutagen sensitivity assessed by this method has been shown to be a significant risk factor for tobacco-related malignancies, especially those of the upper aerodigestive tract. Mutagen sensitivity may therefore be a useful member of a panel of susceptibility markers for defining high-risk subgroups for chemoprevention trials. This chapter describes methods for and discusses results from studies of mutagen sensitivity as measured by quantifying chromatid breaks induced by chromosome breaking agents, such as the gamma-radiation radiomimetic DNA crosslinking agent bleomycin and chemicals that form so-called bulky DNA adducts, such as 4-NQO and the tobacco smoke constituent, benzo[a]pyrene, in short-term cultured peripheral blood lymphocytes.