A trilocus sequence typing scheme for hospital epidemiology and subspecies differentiation of an important nosocomial pathogen, Enterococcus faecalis.

In this study, we present a trilocus sequence typing (TLST) scheme based on intragenic regions of two antigenic genes, ace and salA (encoding a collagen/laminin adhesin and a cell wall-associated antigen, respectively), and a gene associated with antibiotic resistance, lsa (encoding a putative ABC transporter), for subspecies differentiation of Enterococcus faecalis. Each of the alleles was analyzed using 50 E. faecalis isolates representing 42 diverse multilocus sequence types (ST(M); based on seven housekeeping genes) and four groups of clonally linked (by pulsed-field gel electrophoresis [PFGE]) isolates. The allelic profiles and/or concatenated sequences of the three genes agreed with multilocus sequence typing (MLST) results for typing of 49 of the 50 isolates; in addition to the one exception, two isolates were found to have identical TLST types but were single-locus variants (differing by a single nucleotide) by MLST and were therefore also classified as clonally related by MLST. TLST was also comparable to PFGE for establishing short-term epidemiological relationships, typing all isolates classified as clonally related by PFGE with the same type. TLST was then applied to representative isolates (of each PFGE subtype and isolation year) of a collection of 48 hospital isolates and demonstrated the same relationships between isolates of an outbreak strain as those found by MLST and PFGE. In conclusion, the TLST scheme described here was shown to be successful for investigating short-term epidemiology in a hospital setting and may provide an alternative to MLST for discriminating isolates.

UNDERSTANDING NANOG'S ROLE IN CANCER BIOLOGY

Understanding Nanog’s Role in Cancer Biology Mark Daniel Badeaux Supervisory Professor Dean Tang, PhD The cancer stem cell model holds that tumor heterogeneity and population-level immortality are driven by a subset of cells within the tumor, termed cancer stem cells. Like embryonic or somatic stem cells, cancer stem cells are believed to possess self-renewal capacity and the ability to give rise to a multitude of varieties of daughter cell. Because of cancer’s implied connections to authentic stem cells, we screened a variety of prostate cancer cell lines and primary tumors in order to determine if any notable ‘stemness’ genes were expressed in malignant growths. We found a promising lead in Nanog, a central figure in maintaining embryonic stem cell pluripotency, and through a variety of experiments in which we diminished Nanog expression, found that it may play a significant role in prostate cancer development. We then created a transgenic mouse model in which we targeted Nanog expression to keratin 14-expressing in order to assess its potential contribution to tumorigenesis. We found a variety of developmental abnormalities and altered differentiation patterns in our model , but much to our chagrin we observed neither spontaneous tumor formation nor premalignant changes in these mice, but instead surprisingly found that high levels of Nanog expression inhibited tumor formation in a two-stage skin carcinogenesis model. We also noted a depletion of skin stem cell populations, which underlies the wound-healing defect our mice harbor as well. Gene expression analysis shows a reduction in c-Jun and Bmp5, two genes whose loss inhibits skin tumor development and reduces stem cell counts respectively. As we further explored Nanog’s activity in prostate cancer, it became apparent that the protein oftentimes was not expressed. Emboldened by the competing endogenous RNA (ceRNA) hypothesis, we identified the Nanog 3’UTR as a regulator of the tumor suppressive microRNA 128a (miR-128a), which includes known oncogenes such as Bmi1 among its authentic targets. Future work will necessarily involve discerning instances in which Nanog mRNA is the biologically relevant molecule, as well as identifying additional mRNA species which may serve solely as a molecular sink for miR-128a.

The biology and mechanism of chemoresistance of brain metastases

Primary brain neoplasms and metastases to the brain are generally resistant to systemic chemotherapy. The purpose of theses studies was to determine the mechanism(s) for this resistance. We have developed a model to study the biology of brain metastasis by injecting metastatic K1735 melanoma cells into the carotid artery of syngeneic C3H/HeN or nude mice. The resulting brain lesions are produced in the parenchyma of the brain. Mice with subcutaneous or brain melanoma lesions were treated intravenously with doxorubicin (DXR) (7 mg/kg). The s.c. lesions regressed in most of the mice whereas no therapeutic benefits were produced in mice with brain metastases. The intravenous injection of sodium fluorescine revealed that the blood-brain barrier (BBB) is intact in and around brain metastases smaller than 0.2 mm$\sp2$ but not in larger lesions, implying that the BBB is not a major obstacle for chemotherapy of brain metastases.^ Western blot and FACS analyses revealed that K1735 melanoma brain metastases expressed high levels of P-glycoprotein (P-gp) as compared to s.c. tumors or in vitro cultures. Similarly, K1735 cells from brain metastases expressed higher levels of mdrl mRNA. This increased expression of mdrl was due to adaptation to the local brain environment. We base this conclusion on the results of two studies. First, K1735 cells from brain metastases cultured for 7 days lost the high mdrl expression. Second, in crossover experiments K1735 cells from s.c. tumors (low mdrl expression) implanted into the brain exhibited high levels of mdrl expression whereas cells from brain metastases implanted s.c. lost the high level mdrl expression.^ To investigate the mechanism by which the brain environment upregulates mdrl expression of the K1735 cells we first studied the regulation of P-gp in brain endothelial cells. Since astrocytes are closely linked with the BBB we cocultured brain endothelial cells for 3 days with astrocytes. These endothelial cells expressed high levels of mdrl mRNA and protein whereas endothelial cells cocultured with endothelial cells or fibroblasts did not. We next cocultured K1735 melanoma cells with astrocytes. Here again, astrocytes (but not fibroblasts or tumor cells) uprelated the mdrl expression in K1735 tumor cells. This upregulation inversely correlated with intracellular drug accumulation and sensitivity to DXR.^ The data conclude that the resistance of melanoma brain metastases to chemotherapy is not due to an intact BBB but to the upregulation of the mdrl gene by the organ microenvironment, i.e., the astrocytes. This epigenetic mediated resistance to chemotherapy has wide implications for the therapy of brain metastases. ^

The epidemiology of chronic fatigue in San Francisco

Chronic fatigue syndrome (CFS) is a recently defined condition characterized by severe disabling fatigue that persists for a minimum of six months, and a host of somatic and neurocognitive symptoms. Although conditions similar to CFS have been described in the medical literature for over 100 years, little is known about the epidemiology of CFS or of chronic fatigue generally. The San Francisco Fatigue Study was undertaken to describe the prevalence and characteristics of self-reported chronic fatigue and associated conditions in a diverse urban community. The study utilized a cross-sectional telephone survey of a random sample of households in San Francisco, followed by case/control interviews of fatigued and nonfatigued subjects. Respondents were classified as chronically fatigued (CF) if they reported severe fatigue lasting six months or longer, then further classified as having CFS-like illness if, based on self-reported information, their condition appeared to meet CFS case definition criteria. Subjects who reported idiopathic chronic fatigue that did not meet CFS criteria were classified as having ICF-like illness.^ 8004 households were screened, yielding fatigue and demographic information on 16970 residents. CF was reported by 635 persons, 3.7% of the study population. CFS-like illness was identified in 34 subjects (0.2%), and ICF-like illness in 259 subjects (1.6%). Logistic regression analysis indicated that prevalence odds ratios for CFS-like illness were significantly elevated for females compared to males (OR = 2.9), and in Blacks (OR = 2.9) and Native Americans (OR = 13.2) relative to Whites, but significantly lower in Asians (OR = 0.12). Above-average household income was protective for all categories of CF. CFS-like subjects reported more symptoms and were more severely disabled than ICF-like subjects, but the pattern of symptoms experienced by both groups was similar. In conclusion, unexplained chronic fatigue, including CFS-like illness, occurs in all sociodemographic groups, but may be most prevalent among persons with lower incomes and in some racial minorities. Future studies that include clinical evaluation of incident cases of CFS and ICF are required to further clarify the epidemiology of unexplained chronic fatigue in the population. ^

Content of prenatal care and spontaneous preterm birth: Findings from the 1988 National Maternal and Infant Health Survey

The purposes of this study were to examine (1) the relationship between selected components of the content of prenatal care and spontaneous preterm birth; and (2) the degree of comparability between maternal and caregivers' responses regarding the number of prenatal care visits, selected components of the content of prenatal care, and gestational age, based on analyses of the 1988 National Maternal and Infant Health Survey conducted by the National Centers for Health Statistics. Spontaneous preterm birth was subcategorized into very preterm and moderately preterm births, with term birth as the controls. The study population was limited to non-Hispanic Anglo- and African-American mothers. The racial differences in terms of birth outcomes were also compared.^ This study concluded that: (1) there was not a high degree of comparability (less than 80%) between maternal and prenatal care provider's responses regarding the number of prenatal care visits and the content of prenatal care; (2) there was a low degree of comparability (less than 50%) between maternal and infant's hospital of delivery responses regarding gestational age at birth; (3) there were differences in selected components of the content of prenatal care between the cases and controls, overall and stratified by ethnicity (i.e., hemoglobin/hematocrit test, weight measurement, and breast-feeding counseling), but they were confounded with missing values and associated preterm delivery bias; (4) there were differences in selected components of the content of prenatal care between Anglo- and African-American cases (i.e., vitamin/mineral supplement advice, weight measurement, smoking cessation and drug abuse counseling), but they, too, were difficult to interpret definitively due to item nonresponse and preterm delivery biases; (5) no significant predictive association between selected components of the content of prenatal care and spontaneous preterm birth was found; and (6) inadequate/intermediate prenatal care and birth out of wedlock were found to be associated with moderately preterm birth.^ Future research is needed to examine the validity of maternal and prenatal care providers' responses and identify the sources of disagreement between their responses. In addition, further studies are needed to examine the relationship between the quality of prenatal care and preterm birth. Finally, the completeness and quality of patient and provider data on the utilization and content of prenatal care needs to be strengthened in subsequent studies. ^

Genetic predisposition to prostate cancer

Prostate cancer (PC) is a significant economic and health burden in the U.S. and Europe but its causes are largely unknown. The most significant risk factors (after gender) are age and family history of the disease. A gene with high penetrance but low frequency on chromosome 1q, HPC 1, has been suggested to cause a proportion of the familial aggregation of PC but other more common genes, conferring less risk, are also thought to contribute to disease predisposition. We have pursued a strategy to study both types of genetic risk in PC. To identify high penetrance genes, affected men from thirteen families have been genotyped for genetic linkage analysis at six microsatellite markers spanning 45 cM of 1q24-25. Both LOD score and non-parametric statistics provide no significant support for HPC1 in this genomic region, although 3 of the families did combine to produce a LOD score of 0.9. These families will be included in a genome wide search for other PC predisposition genes as part of a multinational collaboration.^ For study of common genetic factors in PC development, leukocyte DNA samples from an unselected series of 55 patients and 67 controls have been examined for genetic differences in two other candidate genes, the androgen receptor gene, hAR, at Xq11-12, and the vitamin D receptor gene, hVDR, at 12q12-14. hAR was typed for two trinucleotide repeat length polymorphisms, (CAG)$\rm\sb{n}$ and (GGC)$\rm\sb{n},$ encoding polyglutamine and polyglycine tracts, respectively, which have been implicated in PC susceptibility. These data, combined with similarly processed patients and controls from the U.K. show no consistent association of allele length with PC risk. A novel finding, however, has been a significant association between the number of GGC repeats and the length of time between diagnosis and relapse in stage T1-T4 Caucasian patients irrespective of therapy and age of the patient. Of 49 patients who relapsed out of 108 entering the study, those with 16 or fewer GGC repeats had an average relapse-free-period of 101 (+/$-$7.7) months while for those with more than 16 repeats the period averaged 48 (+/$-$2.9) months, a difference of 2.1 fold or 4.4 years.^ The second gene, hVDR, was genotyped at two polymorphisms, a synonymous C/T substitution in exon 9 identified by differential TaqI enzymatic digestion and a variable length polyA tract in the 3$\sp\prime$ UTR. Although these polymorphisms are in strong linkage disequilibrium only the polyA region showed a possible association with PC risk. Men homozygous for alleles with fewer than 18 A's had an increased risk (OR = 3.0, p = 0.0578) compared to controls. This result is opposite to the findings of others and may either indicate off-setting random errors which together balance out to no significant overall effect or reflect more complex genetic and/or environmental associations.^ Overall, this research suggests that single gene familial predisposition may be less prominent in PC than in other cancers and that the characteristics of PC pathology may be useful in identifying the effects of common genetic factors. ^

Epidemiology of secondary leukemia with reference to chromosomal abnormalities

Secondary acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) have been recognized as one of the most feared long-term complications of cancer therapy. The aim of this case-control study was to determine the prevalence of chromosomal abnormalities and family history of cancer among secondary AML/MDS cases and de novo AML/MDS controls. Study population were 332 MD Anderson Cancer Center patients who were registered between 1986 and 1994. Cases were patients who had a prior invasive cancer before diagnoses of AML/MDS and controls were de novo AML/MDS. Cases (166) and controls (166) were frequency matched on age $\pm$5 years, sex and year of diagnosis of leukemia. Cytogenetic data were obtained from the leukemia clinic database of MD Anderson Cancer Center and data on family history of cancer and other risk factors were abstracted from the patients' medical record. The distribution of AML and MDS among cases was 58% and 42% respectively and among controls 67% and 33% respectively. Prevalence of chromosomal abnormalities were observed more frequently among cases than controls. Reporting of family history of cancer were similar among both groups. Univariate analysis revealed an odds ratio (OR) of 2.8 (95% CI 1.5-5.4) for deletion of chromosome 7, 1.9 (95% CI 0.9-3.8) for deletion of chromosome 5, 2.3 (95% CI 0.8-6.2) for deletion of 5q, 2.0 (95% CI 1.0-4.2) for trisomy 8, 1.3 (95% CI 0.8-2.1) for chromosomal abnormalities other than chromosome 5 or 7 and 1.3 (95% CI 0.8-2.0) for family history of cancer in a first degree relative. The OR remained significant for deletion of chromosome 7 (2.3, 95% CI 1.1-4.8) after adjustment for age, alcohol, smoking, occupation related to chemical exposure and family history of cancer in a first degree relative. Of the 166 secondary AML/MDS patients 70% had a prior solid tumor and 30% experienced hematological cancers. The most frequent cancers were breast (21.1%), non-Hodgkin lymphoma (13.3%), Hodgkin's disease (10.2%), prostate (7.2%), colon (6%), multiple myeloma (3.6%) and testes (3.0%). The majority of these cancer patients were treated with chemotherapy or radiotherapy or both. Abnormalities of chromosome 5 or 7 were found to be more frequent in secondary AML/MDS patients with prior hematological cancer than patients with prior solid tumors. Median time to develop secondary AML/MDS was 5 years. However, secondary AML/MDS among patients who received chemotherapy and had a family history of cancer in a first degree relative occurred earlier (median 2.25 $\pm$ 0.9 years) than among patients without such family history (median 5.50 $\pm$ 0.18 years) (p $<$.03). The implication of exposure to chemotherapy among patients with a family history of cancer needs to be further investigated. ^

The relationship of maternal low birthweight and infant low birthweight among African-American women at term delivery: Findings from the 1988 National Maternal and Infant Health Survey

A cohort study study design was used to study the relationship of maternal low birthweight and infant low birthweight among African American women delivering full term infants. The cohort consisted of 3,157 mother-infant pairs drawn from the 1988 National Maternal and Infant Health Survey conducted by the National Center for Health Statistics. The objectives of the study were (1) to determine if low birthweight, African American mothers delivering term infants experienced higher rates of infant low birthweight and (2) to examine the role of selected contributory variables in the relationship of maternal low birthweight and infant low birthweight. Contributory risk factors examined included maternal marital status, maternal age, maternal education, maternal height, maternal prepregnant weight, birth order, history of a prior low birthweight delivery, timing of prenatal care, number of prenatal visits, gestational length, infant gender, and behavioral factors of smoking, alcohol, and illicit drug use during pregnancy.^ Using logistic regression analysis, risk of infant low birthweight among maternal low birthweight mothers increased after controlling for less than a high school education, less than 20 years of age, prepregnant weight less than 100 lbs, history of a prior low birthweight delivery, birth order, smoking during pregnancy, and use of alcohol and illicit drugs during pregnancy, but was not statistically significant. Loss of statistical significance was attributed to a large reduction in cases available for analysis after including illicit drug use in the model.^ This study demonstrated a consistent pattern of increased rates of infant low birthweight among low birthweight mothers. The force of history remains, hence women with this trait should be carefully monitored and advised during pregnancy to decrease risk of a low birthweight infant, in order to decrease the chain of events leading to future generations of low birthweight mothers. ^

Statistical characterization and development of summary measures of non-normal distributions of nuclear morphometry data from prostate cancer cells for use as prognostic indicators

Nuclear morphometry (NM) uses image analysis to measure features of the cell nucleus which are classified as: bulk properties, shape or form, and DNA distribution. Studies have used these measurements as diagnostic and prognostic indicators of disease with inconclusive results. The distributional properties of these variables have not been systematically investigated although much of the medical data exhibit nonnormal distributions. Measurements are done on several hundred cells per patient so summary measurements reflecting the underlying distribution are needed.^ Distributional characteristics of 34 NM variables from prostate cancer cells were investigated using graphical and analytical techniques. Cells per sample ranged from 52 to 458. A small sample of patients with benign prostatic hyperplasia (BPH), representing non-cancer cells, was used for general comparison with the cancer cells.^ Data transformations such as log, square root and 1/x did not yield normality as measured by the Shapiro-Wilks test for normality. A modulus transformation, used for distributions having abnormal kurtosis values, also did not produce normality.^ Kernel density histograms of the 34 variables exhibited non-normality and 18 variables also exhibited bimodality. A bimodality coefficient was calculated and 3 variables: DNA concentration, shape and elongation, showed the strongest evidence of bimodality and were studied further.^ Two analytical approaches were used to obtain a summary measure for each variable for each patient: cluster analysis to determine significant clusters and a mixture model analysis using a two component model having a Gaussian distribution with equal variances. The mixture component parameters were used to bootstrap the log likelihood ratio to determine the significant number of components, 1 or 2. These summary measures were used as predictors of disease severity in several proportional odds logistic regression models. The disease severity scale had 5 levels and was constructed of 3 components: extracapsulary penetration (ECP), lymph node involvement (LN+) and seminal vesicle involvement (SV+) which represent surrogate measures of prognosis. The summary measures were not strong predictors of disease severity. There was some indication from the mixture model results that there were changes in mean levels and proportions of the components in the lower severity levels. ^

A comparison of Markov and generalized linear models of hospital mortality

This paper reports a comparison of three modeling strategies for the analysis of hospital mortality in a sample of general medicine inpatients in a Department of Veterans Affairs medical center. Logistic regression, a Markov chain model, and longitudinal logistic regression were evaluated on predictive performance as measured by the c-index and on accuracy of expected numbers of deaths compared to observed. The logistic regression used patient information collected at admission; the Markov model was comprised of two absorbing states for discharge and death and three transient states reflecting increasing severity of illness as measured by laboratory data collected during the hospital stay; longitudinal regression employed Generalized Estimating Equations (GEE) to model covariance structure for the repeated binary outcome. Results showed that the logistic regression predicted hospital mortality as well as the alternative methods but was limited in scope of application. The Markov chain provides insights into how day to day changes of illness severity lead to discharge or death. The longitudinal logistic regression showed that increasing illness trajectory is associated with hospital mortality. The conclusion is reached that for standard applications in modeling hospital mortality, logistic regression is adequate, but for new challenges facing health services research today, alternative methods are equally predictive, practical, and can provide new insights. ^

Design and implementation of a multicriteria medical decision support system for diagnosis and treatment

Health care providers face the problem of trying to make decisions with inadequate information and also with an overload of (often contradictory) information. Physicians often choose treatment long before they know which disease is present. Indeed, uncertainty is intrinsic to the practice of medicine. Decision analysis can help physicians structure and work through a medical decision problem, and can provide reassurance that decisions are rational and consistent with the beliefs and preferences of other physicians and patients. ^ The primary purpose of this research project is to develop the theory, methods, techniques and tools necessary for designing and implementing a system to support solving medical decision problems. A case study involving “abdominal pain” serves as a prototype for implementing the system. The research, however, focuses on a generic class of problems and aims at covering theoretical as well as practical aspects of the system developed. ^ The main contributions of this research are: (1) bridging the gap between the statistical approach and the knowledge-based (expert) approach to medical decision making; (2) linking a collection of methods, techniques and tools together to allow for the design of a medical decision support system, based on a framework that involves the Analytic Network Process (ANP), the generalization of the Analytic Hierarchy Process (AHP) to dependence and feedback, for problems involving diagnosis and treatment; (3) enhancing the representation and manipulation of uncertainty in the ANP framework by incorporating group consensus weights; and (4) developing a computer program to assist in the implementation of the system. ^

Relationship between enterotoxigenic Escherichia coli and travelers' diarrhea in Mexico, from 1992 to 1997

The purpose of this study was to examine the relationship between enterotoxigenic ETEC and travelers' diarrhea over a period of five years in Guadalajara, Mexico. Specifically, this study identified and characterized ETEC from travelers with diarrhea. The objectives were to study the colonization factor antigens, toxins and antibiotic sensitivity patterns in ETEC from 1992 to 1997 and to study the molecular epidemiology of ETEC by plasmid content and DNA restriction fragment patterns. ^ In this survey of travelers' diarrhea in Guadalajara, Mexico, 928 travelers with diarrhea were screened for enteric pathogens between 1992 and 1997. ETEC were isolated in 195 (19.9%) of the patients, representing the most frequent enteric pathogen identified. ^ A total of 31 antimicrobial susceptibility patterns were identified among ETEC isolates over the five-year period. ^ The 195 ETEC isolates contained two to six plasmids each, which ranged in size from 2.0 to 23 kbp. ^ Three different reproducible rRNA gene restriction patterns (ribotypes R-1 to R-3) were obtained among the 195 isolates with the enzyme, HindIII. ^ Colonization factor antigens (CFAs) were identified in 99 (51%) of the 195 ETEC strains studied. ^ Cluster analysis of the observations seen in the four assays all confirmed the five distinct groups of study-year strains of ETEC. Each group had a >95% similarity level of strains within the group and <60% similarity level between the groups. In addition, discriminant analysis of assay variables used in predicting the ETEC strains, reveal a >80% relationship between both the plasmid and rRNA content of ETEC strains and study-year. ^ These findings, based on laboratory observations of the differences in biochemical, antimicrobial susceptibility, plasmid and ribotype content, suggest complex epidemiology for ETEC strains in a population with travelers' diarrhea. The findings of this study may have implications for our understanding of the epidemiology, transmission, treatment, control and prevention of the disease. It has been suggested that an ETEC vaccine for humans should contain the most prevalent CFAs. Therefore, it is important to know the prevalence of these factors in ETEC in various geographical areas. ^ CFAs described in this dissertation may be used in different epidemiological studies in which the prevalence of CFAs and other properties on ETEC will be evaluated. Furthermore, in spite of an intense search in near 200 ETEC isolates for strains that may have clonal relationship, we failed to identify such strains. However, further studies are in progress to construct suitable live vaccine strains and to introduce several of CFAs in the same host organism by recombinant DNA techniques (Dr. Ann-Mari Svennerholm's lab). (Abstract shortened by UMI.)^

Effect of nonnormal random components on level and power in group-randomized trials

The use of group-randomized trials is particularly widespread in the evaluation of health care, educational, and screening strategies. Group-randomized trials represent a subset of a larger class of designs often labeled nested, hierarchical, or multilevel and are characterized by the randomization of intact social units or groups, rather than individuals. The application of random effects models to group-randomized trials requires the specification of fixed and random components of the model. The underlying assumption is usually that these random components are normally distributed. This research is intended to determine if the Type I error rate and power are affected when the assumption of normality for the random component representing the group effect is violated. ^ In this study, simulated data are used to examine the Type I error rate, power, bias and mean squared error of the estimates of the fixed effect and the observed intraclass correlation coefficient (ICC) when the random component representing the group effect possess distributions with non-normal characteristics, such as heavy tails or severe skewness. The simulated data are generated with various characteristics (e.g. number of schools per condition, number of students per school, and several within school ICCs) observed in most small, school-based, group-randomized trials. The analysis is carried out using SAS PROC MIXED, Version 6.12, with random effects specified in a random statement and restricted maximum likelihood (REML) estimation specified. The results from the non-normally distributed data are compared to the results obtained from the analysis of data with similar design characteristics but normally distributed random effects. ^ The results suggest that the violation of the normality assumption for the group component by a skewed or heavy-tailed distribution does not appear to influence the estimation of the fixed effect, Type I error, and power. Negative biases were detected when estimating the sample ICC and dramatically increased in magnitude as the true ICC increased. These biases were not as pronounced when the true ICC was within the range observed in most group-randomized trials (i.e. 0.00 to 0.05). The normally distributed group effect also resulted in bias ICC estimates when the true ICC was greater than 0.05. However, this may be a result of higher correlation within the data. ^

EMPLOYMENT AND EXPOSURES IN THE PETROLEUM REFINING AND PETROCHEMICAL INDUSTRIES AND THE RISK OF LUNG CANCER (EPIDEMIOLOGY, ASSESSMENT)

This dissertation addresses the risk of lung cancer associated with occupational exposures in the petroleum refining and petrochemical industries. Earlier epidemiologic studies of this association did not adjust for cigarette smoking or have specific exposure classifications. The Texas EXposure Assessment System (TEXAS) was developed with data from a population-based, case-comparison study conducted in five southeast Texas counties between 1976 and 1980. The Texas Exposure Assessment System uses job and process categories developed by the American Petroleum Institute, as well as time-oriented variables to identify high risk groups.^ An industry-wide, increased risk for lung cancer was associated with jobs having low-level hydrocarbon exposure that also include other occupational inhalation exposures (OR = 2.0--adjusted for smoking and latency effects). The prohibition of cigarette smoking for jobs with high-level hydrocarbon exposure might explain part of the increased risk for jobs with low-level hydrocarbon exposures. Asbestos exposure comprises a large part of the risk associated with jobs having other inhalation exposures besides hydrocarbons. Workers in petroleum refineries were not shown to have an increased, occupational risk for lung cancer. The increased risk for lung cancer among petrochemical workers (OR = 3.1--smoking and latency adjusted) is associated with all jobs that involve other inhalation exposure characteristics (not only low-level hydrocarbon exposures). Findings for contract workers and workers exposed to specific chemicals were inconclusive although some hypotheses for future research were identified.^ The study results demonstrate that the predominant risk for lung cancer is due to cigarette smoking (OR = 9.8). Cigarette smoking accounts for 86.5% of the incident lung cancer cases within the study area. Workers in the petroleum industry smoke significantly less than persons employed in other industries (p << 0.001). Only 2.2% of the incident lung cancer cases may be attributed to petroleum industry jobs; lifestyle factors (e.g., nutrition) may be associated with the balance of the cases. The results from this study also suggest possible high risk time periods (OR = 3.9--smoking and occupation adjusted). Artifacts in time-oriented findings may result because of the latency interval for lung cancer, secular peaks in age-, sex-specific incidence rates, or periods of hazardous exposures in the petroleum industry. ^

Ovarian cancer angiogenesis, biology and therapy

The progressive growth of epithelial ovarian cancer tumor is regulated by proangiogenic molecules and growth factors released by tumor cells and the microenvironment. Previous studies showed that the expression of interleukin-8 (IL-8) directly correlates with the progression of human ovarian carcinomas implanted into the peritoneal cavity of nude mice. We examined the expression level of IL-8 in archival specimens of primary human ovarian carcinoma from patients undergoing curative surgery by in situ mRNA hybridization technique. The expression of IL-8 was significantly higher in patients with stage III disease than in patients with stage I disease. To investigate the role of IL-8 in the progressive growth of ovarian cancer, we isolated high- and low-IL-8 producing clones from parental Hey-A8 human ovarian cancer cells, and compared their proliferative activity and tumorigenicity in nude mice. The effect of exogenous IL-8 and IL-8 neutralizing antibody on ovarian cancer cell proliferation was investigated. Finally, we studied the modulation of IL-8 expression in ovarian cancer cells by sense and antisense IL-8 expression vector transfection and its effect on proliferation and tumorigenicity. We concluded that IL-8 has a direct growth potentiating activity in human ovarian cancer cells. ^ The expression level of IL-8 directly correlates with disease progression of human ovarian cancer, but the mechanism of induction is unknown. Since hypoxia and acidic pH are common features in solid tumors, we determined whether hypoxic and acidic conditions could regulate the expression of IL-8. Culturing the human ovarian cancer cells in hypoxic or acidic medium led to a significant increase in IL-8 mRNA and protein. Hypoxic- and acidosis-mediated transient increase in IL-8 expression involved both transcriptional activation of the IL-8 gene and enhanced stability of the IL-8 mRNA. Furthermore, we showed that IL-8 transcription activation by hypoxia or acidosis required the cooperation of NF-κB and AP-1 binding sites. ^ Finally, we studied novel therapies against human ovarian cancer. First, we determined whether inhibition of the catalytic tyrosine kinase activity of the receptors for vascular endothelial growth factor/vascular permeability factor (VEGF/VPF) inhibits the formation of malignant ascites and the progressive growth of human ovarian carcinoma cells implanted into the peritoneal cavity of nude mice. Our results suggest that blockade of the VEGF/VPF receptor may be an efficient strategy to inhibit formation of malignant ascites and growth of VEGF/VPF-dependent human ovarian carcinomas. Secondly, we determined whether local sustained production of murine interferon-β could inhibit the growth of human ovarian cancer cells in the peritoneal cavity of nude mice. Our results showed that local production of IFN-β could inhibit the in vivo growth of human ovarian cancer cells by upregulating the expression of the inducible nitric oxide synthase (NOS) in host macrophages. ^