A BAYESIAN APPROACH TO DOSE-RESPONSE ASSESSMENT AND DRUG-DRUG INTERACTION ANALYSIS: APPLICATION TO IN VITRO STUDIES

The considerable search for synergistic agents in cancer research is motivated by the therapeutic benefits achieved by combining anti-cancer agents. Synergistic agents make it possible to reduce dosage while maintaining or enhancing a desired effect. Other favorable outcomes of synergistic agents include reduction in toxicity and minimizing or delaying drug resistance. Dose-response assessment and drug-drug interaction analysis play an important part in the drug discovery process, however analysis are often poorly done. This dissertation is an effort to notably improve dose-response assessment and drug-drug interaction analysis. The most commonly used method in published analysis is the Median-Effect Principle/Combination Index method (Chou and Talalay, 1984). The Median-Effect Principle/Combination Index method leads to inefficiency by ignoring important sources of variation inherent in dose-response data and discarding data points that do not fit the Median-Effect Principle. Previous work has shown that the conventional method yields a high rate of false positives (Boik, Boik, Newman, 2008; Hennessey, Rosner, Bast, Chen, 2010) and, in some cases, low power to detect synergy. There is a great need for improving the current methodology. We developed a Bayesian framework for dose-response modeling and drug-drug interaction analysis. First, we developed a hierarchical meta-regression dose-response model that accounts for various sources of variation and uncertainty and allows one to incorporate knowledge from prior studies into the current analysis, thus offering a more efficient and reliable inference. Second, in the case that parametric dose-response models do not fit the data, we developed a practical and flexible nonparametric regression method for meta-analysis of independently repeated dose-response experiments. Third, and lastly, we developed a method, based on Loewe additivity that allows one to quantitatively assess interaction between two agents combined at a fixed dose ratio. The proposed method makes a comprehensive and honest account of uncertainty within drug interaction assessment. Extensive simulation studies show that the novel methodology improves the screening process of effective/synergistic agents and reduces the incidence of type I error. We consider an ovarian cancer cell line study that investigates the combined effect of DNA methylation inhibitors and histone deacetylation inhibitors in human ovarian cancer cell lines. The hypothesis is that the combination of DNA methylation inhibitors and histone deacetylation inhibitors will enhance antiproliferative activity in human ovarian cancer cell lines compared to treatment with each inhibitor alone. By applying the proposed Bayesian methodology, in vitro synergy was declared for DNA methylation inhibitor, 5-AZA-2'-deoxycytidine combined with one histone deacetylation inhibitor, suberoylanilide hydroxamic acid or trichostatin A in the cell lines HEY and SKOV3. This suggests potential new epigenetic therapies in cell growth inhibition of ovarian cancer cells.

Metabolism and action of 9-$\beta$-D-arabinofuranosyl-2-fluoroadenine

9-$\beta$-D-arabinofuranosyl-2-fluoroadenine (F-ara-A) is an analogue of adenosine and 2$\sp\prime$-deoxyadenosine with potent antitumor activity both in vitro and in vivo. The mechanism of action of F-ara-A was evaluated both in whole cells and in experimental systems with purified enzymes. F-ara-A was converted to its 5$\sp\prime$-triphosphate F-ara-ATP in cells and then incorporated into DNA in a self-limiting manner. About 98% of the incorporated F-ara-AMP residues were located at the 3$\sp\prime$-termini of DNA strands, suggesting a chain termination property of this compound. DNA synthesis in CEM cells was inhibited by F-ara-A treatment with an IC$\sb{50}$ value of 1 $\mu$M. Cells were not able to restore the normal level of DNA synthesis even after being cultured in drug-free medium for 40 h. A DNA primer extension assay with M13mp18(+) single-stranded DNA template using purified human DNA polymerases $\alpha$ and further revealed that F-ara-ATP competed with dATP for incorporation into the A sites of the elongating DNA strands. The incorporation of F-ara-AMP into DNA resulted in a termination of DNA synthesis at the incorporated A sites. Pol $\alpha$ and $\delta$ were not able to efficiently extend the DNA primer with F-ara-AMP at its 3$\sp\prime$-end. Furthermore, the presence of F-ara-AMP at the 3$\sp\prime$-end of an oligodeoxyribonucleotide impaired its ligation with an adjacent DNA fragment by human and T4 ligases. Human DNA polymerase $\alpha$ incorporated more F-ara-AMP into DNA than polymerase $\delta$ and was more sensitive to the inhibition by F-ara-ATP, suggesting that polymerase $\alpha$ may be a preferred target for this analogue. On the other hand, DNA-dependent nucleotide turnover experiments and sequencing gel analysis demonstrated that DNA polymerase $\delta$ was able to remove the incorporated F-ara-AMP residue from the 3$\sp\prime$-end of the DNA strand with its 3$\sp\prime$-5$\sp\prime$ exonuclease activity in vitro, subsequently permitting further elongation of the DNA strand.^ The incorporation of F-ara-AMP into DNA was linearly correlated both with the inhibition of DNA synthesis and with the loss of clonogenicity. Termination of DNA synthesis and deletion of genetic material resulted from F-ara-AMP incorporation may be the mechanism responsible for cytotoxicity of F-ara-A. (Abstract shortened with permission of author.) ^

A longitudinal comparison of cardiovascular disease risk factors among children and adolescents in the U.S. and Japan: Project HeartBeat!

Blood cholesterol and blood pressure development in childhood and adolescence have important impact on the future adult level of cholesterol and blood pressure, and on increased risk of cardiovascular diseases. The U.S. has higher mortality rates of coronary heart diseases than Japan. A longitudinal comparison in children of risk factor development in the two countries provides more understanding about the causes of cardiovascular disease and its prevention. Such comparisons have not been reported in the past. ^ In Project HeartBeat!, 506 non-Hispanic white, 136 black and 369 Japanese children participated in the study in the U.S. and Japan from 1991 to 1995. A synthetic cohort of ages 8 to 18 years was composed by three cohorts with starting ages at 8, 11, and 14. A multilevel regression model was used for data analysis. ^ The study revealed that the Japanese children had significantly higher slopes of mean total cholesterol (TC) and high density lipoprotein (HDL) cholesterol levels than the U.S. children after adjusting for age and sex. The mean TC level of Japanese children was not significantly different from white and black children. The mean HDL level of Japanese children was significantly higher than white and black children after adjusting for age and sex. The ratio of HDL/TC in Japanese children was significantly higher than in U.S. whites, but not significantly different from the black children. The Japanese group had significantly lower mean diastolic blood pressure phase IV (DBP4) and phase V (DBP5) than the two U.S. groups. The Japanese group also showed significantly higher slopes in systolic blood pressure, DBP5 and DBP4 during the study period than both U.S. groups. The differences were independent from height and body mass index. ^ The study provided the first longitudinal comparison of blood cholesterol and blood pressure between the U.S. and Japanese children and adolescents. It revealed the dynamic process of these factors in the three ethnic groups. ^

Household health assessment and associated water sample analysis in the Miches watershed of the Dominican Republic

Background. Diarrhea and malnutrition are the leading causes of mortality for children age one to four in the Dominican Republic. Communities within the Miches watershed lack sanitation infrastructure and water purification systems, which increases the risk of exposure to water-borne pathogens. The purpose of this cross-sectional study was to analyze health information gathered through household interviews and to test water samples for the presence of diarrheagenic pathogens and antibiotic-resistant bacteria within the Miches watershed. Methods. Frequency counts and thematic analysis were used to investigate Human Health Survey responses and Fisher's exact test was used to determine correlation between water source and reported illness. Bacteria cultured from water samples were analyzed by Gram stain, real-time PCR, API® 20E biochemical identification, and for antibiotic resistance. Results. Community members reported concerns about water sources with respect to water quality, availability, and environmental contamination. Pathogenic strains of E. coli were present in the water samples. Drinking aquifer water was positively-correlated with reported stomach aches (p=0.04) while drinking from rivers or creeks was associated with the reported absence of “gripe” (cold or flu) (p=0.01). The lack of association between reported illnesses and water source for the majority of variables suggested that there were multiple vehicles of disease transmission. Antibiotic resistant bacteria were isolated from the water samples tested. Conclusions. The presence of pathogenic E. coli in water samples suggested that water is at least one route of transmission for diarrheagenic pathogens in the Miches watershed. The presence of antibiotic-resistant bacteria in the water samples may indicate the proliferation of resistance plasmids in the environment as a result of antibiotic overuse in human and animal populations and a lack of sanitation infrastructure. An intervention that targets areas of hygiene, sanitation, and water purification is recommended to limit human exposure to diarrheagenic pathogens and antibiotic-resistant organisms. ^

A STUDY OF THE RELATIONSHIP BETWEEN SELF-ASSESSMENT AND CLINICAL EVALUATION OF HEARING STATUS

The relationship was explored between a subjective measure of hearing status, derived from a functional self-assessment expressed in terms of ability to hear and understand spoken words, and a comparable objective measure of hearing status, obtained from a speech reception test. The Augmentation Survey of the Health and Nutrition Examination Survey of the National Center for Health Statistics provided the necessary data for a sample of 3059 adults. Using chi-square tests for the subsample with the highest level of objectively assessed hearing status, favorable subjective assessments were found to be significantly associated with higher income, lower age group, higher level of educational attainment, greater psychological adjustment, fewer symptoms of depression, and higher self-ratings of overall health. In a linear regression with self-assessment of hearing status as the dependent variable, less than one-quarter of the variation could be explained by objective status and the six explanatory variables.^

INTAKE VARIABLES AS PREDICTORS OF ASSESSMENT AND REFERRAL PROCEDURE OUTCOMES IN EMPLOYEE ASSISTANCE PROGRAMS

While reported prevalence rates of troubled employees vary considerably, even conservative estimates indicate a major public health problem. For example, alcohol and drug related problems alone cost U.S. industry more than 45 billion dollars annually.^ Of the alternatives available to deal with these problems, e.g., dismissal or disciplinary actions, the most viable and cost effective are employee assistance programs (EAP), designed to provide professional assistance to employees experiencing alcohol, drug, emotional or personal crisis.^ The principal component of an EAP is that of assessment and referral, and this study was developed to determine which EAP client intake variables are the most efficacious predictors of assessment and referral procedures.^ Although, specific client intake variables were statistically significant the discriminant classification analysis was demonstrably inadequate. Nevertheless, the identification of A/R procedure phases which were not efficacious, as well as EAP client populations for whom services were not effective, were extremely valuable discernments. Identifying the less efficacious components of the A/R process provided an opportunity to recommend alternatives to current program procedures and practices, which may ameliorate program effectiveness. ^

Critical indicators associated with negative performance in a selectively manned unit

Introduction. Selectively manned units have a long, international history, both military and civilian. Some examples include SWAT teams, firefighters, the FBI, the DEA, the CIA, and military Special Operations. These special duty operators are individuals who perform a highly skilled and dangerous job in a unique environment. A significant amount of money is spent by the Department of Defense (DoD) and other federal agencies to recruit, select, train, equip and support these operators. When a critical incident or significant life event occurs, that jeopardizes an operator's performance; there can be heavy losses in terms of training, time, money, and potentially, lives. In order to limit the number of critical incidents, selection processes have been developed over time to “select out” those individuals most likely to perform below desired performance standards under pressure or stress and to "select in" those with the "right stuff". This study is part of a larger program evaluation to assess markers that identify whether a person will fail under the stresses in a selectively manned unit. The primary question of the study is whether there are indicators in the selection process that signify potential negative performance at a later date. ^ Methods. The population being studied included applicants to a selectively manned DoD organization between 1993 and 2001 as part of a unit assessment and selection process (A&S). Approximately 1900 A&S records were included in the analysis. Over this nine year period, seventy-two individuals were determined to have had a critical incident. A critical incident can come in the form of problems with the law, personal, behavioral or family problems, integrity issues, and skills deficit. Of the seventy-two individuals, fifty-four of these had full assessment data and subsequent supervisor performance ratings which assessed how an individual performed while on the job. This group was compared across a variety of variables including demographics and psychometric testing with a group of 178 individuals who did not have a critical incident and had been determined to be good performers with positive ratings by their supervisors.^ Results. In approximately 2004, an online pre-screen survey was developed in the hopes of preselecting out those individuals with items that would potentially make them ineligible for selection to this organization. This survey has aided the organization to increase its selection rates and save resources in the process. (Patterson, Howard Smith, & Fisher, Unit Assessment and Selection Project, 2008) When the same prescreen was used on the critical incident individuals, it was found that over 60% of the individuals would have been flagged as unacceptable. This would have saved the organization valuable resources and heartache.^ There were some subtle demographic differences between the two groups (i.e. those with critical incidents were almost twice as likely to be divorced compared with the positive performers). Upon comparison of Psychometric testing several items were noted to be different. The two groups were similar when their IQ levels were compared using the Multidimensional Aptitude Battery (MAB). When looking at the Minnesota Multiphasic Personality Inventory (MMPI), there appeared to be a difference on the MMPI Social Introversion; the Critical Incidence group scored somewhat higher. When analysis was done, the number of MMPI Critical Items between the two groups was similar as well. When scores on the NEO Personality Inventory (NEO) were compared, the critical incident individuals tended to score higher on Openness and on its subscales (Ideas, Actions, and Feelings). There was a positive correlation between Total Neuroticism T Score and number of MMPI critical items.^ Conclusions. This study shows that the current pre-screening process is working and would have saved the organization significant resources. ^ If one was to develop a profile of a candidate who potentially could suffer a critical incident and subsequently jeopardize the unit, mission and the safety of the public they would look like the following: either divorced or never married, score high on the MMPI in Social Introversion, score low on MMPI with an "excessive" amount of MMPI critical items; and finally scores high on the NEO Openness and subscales Ideas, Feelings, and Actions.^ Based on the results gleaned from the analysis in this study there seems to be several factors, within psychometric testing, that when taken together, will aid the evaluators in selecting only the highest quality operators in order to save resources and to help protect the public from unfortunate critical incidents which may adversely affect our health and safety.^

The utility of rapid participatory appraisal for community assessment, diagnosis, and policy development

The selection of a model to guide the understanding and resolution of community problems is an important issue relating to the foundation of public health practice: assessment, policy development, and assurance. Many assessment models produce a diagnosis of community weaknesses, but fail to promote planning and interventions. Rapid Participatory Appraisal (RPA) is a participatory action research model which regards assessment as the first step in the problem solving process, and claims to achieve assessment and policy development within limited resources of time and money. Literature documenting the fulfillment of these claims, and thereby supporting the utility of the model, is relatively sparse and difficult to obtain. Very few articles discuss the changes resulting from RPA assessments in urban areas, and those that do describe studies conducted outside the U.S.A. ^ This study examines the utility of the RPA model and its underlying theories: systems theory, grounded theory, and principles of participatory change, as illustrated by the case study of a community assessment conducted for the Texas Diabetes Institute (TDI), San Antonio, Texas, and subsequent outcomes. Diabetes has a high prevalence and is a major issue in San Antonio. Faculty and students conducted the assessment by informal collaboration between two nursing and public health assessment courses, providing practical student experiences. The study area was large, and the flexibility of the model tested by its use in contiguous sub-regions, reanalyzing aggregated results for the study area. Official TDI reports, and a mail survey of agency employees, described policy development resulting from community diagnoses revealed by the assessment. ^ The RPA model met the criteria for utility from the perspectives of merit, worth, efficiency, and effectiveness. The RPA model best met the agencies' criteria (merit), met the data needs of TDI in this particular situation (worth), provided valid results within budget, time, and personnel constraints (efficiency), and stimulated policy development by TDI (effectiveness). ^ The RPA model appears to have utility for community assessment, diagnosis, and policy development in circumstances similar to the TDI diabetes study. ^

A qualitative assessment of multi-level nutrition strategies for reducing racial and ethnic disparities in diabetes

The purpose of this study is to examine the stages of program realization of the interventions that the Bronx Health REACH program initiated at various levels to improve nutrition as a means for reducing racial and ethnic disparities in diabetes. This study was based on secondary analyses of qualitative data collected through the Bronx Health REACH Nutrition Project, a project conducted under the auspices of the Institute on Urban Family Health, with support from the Centers for Disease Control and Prevention (CDC). Local human subjects' review and approval through the Institute on Urban Family Health was required and obtained in order to conduct the Bronx Health REACH Nutrition Project. ^ The study drew from two theoretical models—Glanz and colleagues' nutrition environments model and Shediac-Rizkallah and Bone's sustainability model. The specific study objectives were two-fold: (1) to categorize each nutrition activity to a specific dimension (i.e. consumer, organizational or community nutrition environment); and (2) to evaluate the stage at which the program has been realized (i.e. development, implementation or sustainability). ^ A case study approach was applied and a constant comparative method was used to analyze the data. Triangulation of data based was also conducted. Qualitative data from this study revealed the following principal findings: (1) communities of color are disproportionately experiencing numerous individual and environmental factors contributing to the disparities in diabetes; (2) multi-level strategies that targeted the individual, organizational and community nutrition environments can appropriately address these contributing factors; (3) the nutrition strategies greatly varied in their ability to appropriately meet criteria for the three program stages; and (4) those nutrition strategies most likely to succeed (a) conveyed consistent and culturally relevant messages, (b) had continued involvement from program staff and partners, (c) were able to adapt over time or setting, (d) had a program champion and a training component, (e) were integrated into partnering organizations, and (f) were perceived to be successful by program staff and partners in their efforts to create individual, organizational and community/policy change. As a result of the criteria-based assessment and qualitative findings, an ecological framework elaborating on Glanz and colleagues model was developed. The qualitative findings and the resulting ecological framework developed from this study will help public health professionals and community leaders to develop and implement sustainable multi-level nutrition strategies for addressing racial and ethnic disparities in diabetes. ^