Polymorphisms of the DNA repair gene MGMT and risk and progression of head and neck cancer.

Methylating agents are involved in carcinogenesis, and the DNA repair protein O(6)-methylguanine-DNA methyltransferase (MGMT) removes methyl group from O(6)-methylguanine. Genetic variation in DNA repair genes has been shown to contribute to susceptibility to squamous cell carcinoma of the head and neck (SCCHN). We hypothesize that MGMT polymorphisms are associated with risk of SCCHN. In a hospital-based case-control study of 721 patients with SCCHN and 1234 cancer-free controls frequency-matched by age, sex and ethnicity, we genotyped four MGMT polymorphisms, two in exon 3, 16195C>T and 16286C>T and two in the promoter region, 45996G>T and 46346C>A. We found that none of these polymorphisms alone had a significant effect on risk of SCCHN. However, when these four polymorphisms were evaluated together by the number of putative risk genotypes (i.e. 16195CC, 16286CC, 45996GT+TT, and 46346CA+AA), a statistically significantly increased risk of SCCHN was associated with the combined genotypes with three to four risk genotypes, compared with those with zero to two risk genotypes (adjusted odds ratio (OR)=1.27; 95% confidence interval (CI)=1.05-1.53). This increased risk was also more pronounced among young subjects (OR=1.81; 95% CI=1.11-2.96), men (OR=1.24; 95% CI=1.00-1.55), ever smokers (OR=1.25; 95%=1.01-1.56), ever drinkers (OR=1.29; 95% CI=1.04-1.60), patients with oropharyngeal cancer (OR=1.45; 95% CI=1.12-1.87), and oropharyngeal cancer with regional lymph node metastasis (OR=1.52; 95% CI=1.16-1.89). In conclusion, our results suggest that any one of MGMT variants may not have a substantial effect on SCCHN risk, but a joint effect of several MGMT variants may contribute to risk and progression of SCCHN, particularly for oropharyngeal cancer, in non-Hispanic whites.

Human mutations that confer paclitaxel resistance.

The involvement of tubulin mutations as a cause of clinical drug resistance has been intensely debated in recent years. In the studies described here, we used transfection to test whether beta1-tubulin mutations and polymorphisms found in cancer patients are able to confer resistance to drugs that target microtubules. Three of four mutations (A185T, A248V, R306C, but not G437S) that we tested caused paclitaxel resistance, as indicated by the following observations: (a) essentially 100% of cells selected in paclitaxel contained transfected mutant tubulin; (b) paclitaxel resistance could be turned off using tetracycline to turn off transgene expression; (c) paclitaxel resistance increased as mutant tubulin production increased. All the paclitaxel resistance mutations disrupted microtubule assembly, conferred increased sensitivity to microtubule-disruptive drugs, and produced defects in mitosis. The results are consistent with a mechanism in which tubulin mutations alter microtubule stability in a way that counteracts drug action. These studies show that human tumor cells can acquire spontaneous mutations in beta1-tubulin that cause resistance to paclitaxel, and suggest that patients with some polymorphisms in beta1-tubulin may require higher drug concentrations for effective therapy.

Characterization of the beta-lactamase gene from {\it Enterococcus faecalis\/} strain HH22

The plasmid-encoded, constitutively produced $\beta$-lactamase gene from Enterococcus faecalis strain HH22 was genetically characterized. A restriction endonuclease map of the 5.1 kb EcoRI fragment encoding the enterococcal $\beta$-lactamase was prepared and compared with the restriction map of a cloned staphylococcal $\beta$-lactamase gene (from the naturally-occurring staphylococcal $\beta$-lactamase plasmid pI258). Comparison and hybridization studies showed that there were identical restriction sites in the region of the $\beta$-lactamase structural gene but not in the region surrounding this gene. Also the enterococcal $\beta$-lactamase plasmid did not encode resistance to mercury or cadmium which is encoded by the small, transducible staphylococcal $\beta$-lactamase plasmids. The nucleotide sequence of the enterococcal gene was shown to be identical to the published sequences of three of four staphylococcal type A $\beta$-lactamase genes; more differences were seen with the genes for staphylococcal type C and D enzymes. One hundred-forty nucleotides upstream of the $\beta$-lactamase start codon were also determined for the inducible staphylococcal $\beta$-lactamase gene on pI258; this sequence was identical to that of the constitutively expressed enterococcal gene indicating that the changes resulting in constitutive expression are not due to changes in the promoter or operator region. Moreover, complementation studies indicated that production of the enterococcal enzyme could be repressed. The gene for the enterococcal $\beta$-lactamase and an inducible staphylococcal $\beta$-lactamase were each cloned into a shuttle vector and then transformed into enterococcal and staphylococcal recipients. The major difference between the two host backgrounds was that more enzyme was produced by the staphylococcal host, regardless of the source of the gene but no qualitative difference was seen between the two genera. Also a difference in the level of resistance to ampicillin was seen between the two backgrounds with the cloned enzymes by MIC and time-kill studies. The location of the enzyme was found to be host dependent since each cloned gene generated extracellular (free) enzyme in the staphylococcus and cell bound enzyme in the enterococcus. Based on the identity of the enterococcal $\beta$-lactamase and several staphylococcal $\beta$-lactamases, these data suggest recent spread of $\beta$-lactamase to enterococci and also suggest loss of a functional repressor. ^

Nonviolent factors: Variables associated with ethnic violence, and factors which are associated with nonviolent response to grievances toward members of other ethnic groups

Ethnic violence appears to be the major source of violence in the world. Ethnic hostilities are potentially all-pervasive because most countries in the world are multi-ethnic. Public health's focus on violence documents its increasing role in this issue.^ The present study is based on a secondary analysis of a dataset of responses by 272 individuals from four ethnic groups (Anglo, African, Mexican, and Vietnamese Americans) who answered questions regarding variables related to ethnic violence from a general questionnaire which was distributed to ethnically diverse purposive, nonprobability, self-selected groups of individuals in Houston, Texas, in 1993.^ One goal was psychometric: learning about issues in analysis of datasets with modest numbers, comparison of two approaches to dealing with missing observations not missing at random (conducting analysis on two datasets), transformation analysis of continuous variables for logistic regression, and logistic regression diagnostics.^ Regarding the psychometric goal, it was concluded that measurement model analysis was not possible with a relatively small dataset with nonnormal variables, such as Likert-scaled variables; therefore, exploratory factor analysis was used. The two approaches to dealing with missing values resulted in comparable findings. Transformation analysis suggested that the continuous variables were in the correct scale, and diagnostics that the model fit was adequate.^ The substantive portion of the analysis included the testing of four hypotheses. Hypothesis One proposed that attitudes/efficacy regarding alternative approaches to resolving grievances from the general questionnaire represented underlying factors: nonpunitive social norms and strategies for addressing grievances--using the political system, organizing protests, using the system to punish offenders, and personal mediation. Evidence was found to support all but one factor, nonpunitive social norms.^ Hypothesis Two proposed that the factor variables and the other independent variables--jail, grievance, male, young, and membership in a particular ethnic group--were associated with (non)violence. Jail, grievance, and not using the political system to address grievances were associated with a greater likelihood of intergroup violence.^ No evidence was found to support Hypotheses Three and Four, which proposed that grievance and ethnic group membership would interact with other variables (i.e., age, gender, etc.) to produce variant levels of subgroup (non)violence.^ The generalizability of the results of this study are constrained by the purposive self-selected nature of the sample and small sample size (n = 272).^ Suggestions for future research include incorporating other possible variables or factors predictive of intergroup violence in models of the kind tested here, and the development and evaluation of interventions that promote electoral and nonelectoral political participation as means of reducing interethnic conflict. ^

Factors related to employment among chronically mentally ill patients

A descriptive study of demographic and psychosocial factors believed to be associated with employment was carried out through face-to-face interviews with 417 chronically mentally-ill patients. Subjects had been hospitalized a minimum of two times for psychiatric treatment, had been discharged from at least one of these hospitalizations in the two years prior to the study, and were currently residing within a specific community mental health center catchment area in Texas. The study group ranged in age from 16 to 68 years and over one-half had chart diagnoses of schizophrenia.^ A structured interview was developed which addressed current employment status, length of current employment, job title of current or last job, and detailed work history for the prior five years. Four measures of social support were included in the interview. Each subject was asked to identify one recent work and one recent non-work situation which had been stressful or very demanding. A coping questionnaire was verbally administered to measure the ways in which subjects had coped with these specific stressful situations.^ Analysis of results revealed that 27 percent of the sample was gainfully employed at time of interview. Differences between the employed and unemployed groups were analyzed by t-test an chi square. The employed demonstrated significantly more weeks of employment in the prior five years than the unemployed. The current jobs of the employed required a significantly higher relationship to "things" or inanimate objects than the last jobs of the unemployed. Subjects diagnosed as schizophrenic were significantly less likely to be employed than subjects with other diagnoses.^ Employed subjects scored significantly higher on three of four measures of social support than unemployed subjects, including reported frequency of social group attendance and/or meetings with mental health professionals. Problem-focused coping was used significantly more by the employed than by the unemployed to deal with stressful situations in the work, but not the non-work, context. ^

Regulation of squamous cell differentiation in human head and neck carcinoma cells by retinoids

Retinoids have been found to be effective in the prevention of premalignant lesions and second primary cancers in the upper aerodigestive tract. Further development of retinoids for prevention and therapy of head and neck squamous cell carcinoma (HNSCC) requires a better understanding of their mechanism of action on the growth and differentiation of such cells. I have chosen to employ cultured HNSCC cell lines as a model system for investigating the mechanism underlying the effects of retinoids. These cells are useful because all-trans retinoic acid (ATRA) inhibits their proliferation. Furthermore, two HNSCC cell lines were found to express three squamous differentiation (SqD) markers characteristic of normal keratinocytes and ATRA suppressed the expression of these markers as reported for normal keratinocytes. It is thought that nuclear retinoic acid receptors (RARs and RXRs), which act as DNA-binding transcription modulating factors, mediate the effects of retinoids on the growth and differentiation of normal and tumor cells. I found that all four cell lines examined expressed RAR-$\alpha ,$ RAR-$\tau ,$ and RXR-$\alpha$ and three of four expressed RAR-$\beta .$ ATRA treatment increased the level of RAR-$\alpha ,$ -$\beta ,$ and -$\tau$ in four cell lines. Two HNSCC cell lines that exhibited a progressive increase in the expression of SqD markers during growth in culture also showed a concurrent decrease in RAR-$\beta$ level. Moreover, increasing concentrations of RA suppressed the SqD marker while inducing RAR-$\beta$ mRNA. Several synthetic retinoids which exhibit a preference for binding to specific nuclear RARs showed a differential ability to inhibit cell proliferation, transactivate transcription of the reporter genes (CAT and luciferase) from the RA response element (RARE) of the RAR-$\beta$ gene, and induce RAR-$\beta$ expression. Those retinoids that were effective inducers of RAR-$\beta$ also suppressed SqD effectively, indicating an inverse relationship exists between the expression of RAR-$\beta$ and SqD. This inverse relationship suggests a role for RAR-$\beta$ in the suppression of SqD. ^

MEETING THE NEEDS OF HANDICAPPED CHILDREN: A STUDY OF EDUCATIONAL AND HEALTH CARE SERVICES PROVIDED TO PRE-KINDERGARTEN CHILDREN IN THE HOUSTON INDEPENDENT SCHOOL DISTRICT EARLY CHILDHOOD PROGRAM FOR THE HANDICAPPED (PARENT SATISFACTION, FUNCTIONAL STATUS, PSYCHOSOCIAL DEVELOPMENT)

The Education for All Handicapped Children Act of 1975, P.L. 94-142, created a new challenge for the nation's public school systems. During 1982-1983, a national study, called the "Collaborative Study of Children with Special Needs", was conducted in 5 metropolitan school districts to evaluate the effectiveness of education and health care services of children in kindergarten to 6th grade being provided under P.L. 94-142 programs. This dissertation (the Substudy) was undertaken to augment the findings of the Collaborative Study. The purpose of this study was to develop a database to provide descriptive information on the demographic, service and health characteristics of a small group of 3 and 4 year old handicapped children served by the Houston Independent School District (HISD) during 1982-1983.^ The study involved a stratified sample of 105 three and four year old children divided into 3 groups according to type of handicapping condition.^ The results of the study gave a clearer picture of the demographic characteristics of these Pre-K children. Specifically, sex ratio was approximately one, lower than the national norm. Family and socioeconomic characteristics were assessed.^ The study used an independence/dependence index composed of 11 items on the parent questionnaire to assess the level of functional independence of each child. An association was found between index scores and parent-reported effects of the child on family activity. Parents who said that their child's condition had affected the family's job situation, housing accomodations, vacation plans, marriage, choice of friends and social activities were also more likely to report less independence in the child. In addition, many of the Substudy children had extensive care-taking needs reflected in specific components of the index such as dressing, feeding, toileting or moving about the house.^ In general the results of the Pre-K Substudy indicate that at the early childhood level, the HISD special education program is functioning well in most areas and that parents are very satisfied with the program. (Abstract shortened with permission of author.)^