Human papillomavirus (HPV) is the sexually-transmitted etiologic agent of cervical cancer. Despite screening programs, cervical cancer remains too common, particularly in developing countries. Various correlates of prevalent infections have been identified. However, the determinants of incident infections have never been studied. / Data were collected during a prospective cohort study conducted in Brazil. Incidence density rates of infection were calculated and determinants of incident infection were identified using Cox regression models. Analyses were done for HPV types classified into low-risk and high-risk depending on their association with cervical neoplasia. / The incidence density rates were 9.3 and 7.6 per 1000 women-months respectively for low-risk and high-risk HPV infection. Independent positive associations were found between the time of first occurrence of low-risk infection and age, number of sexual partners in the past 5 years, education level and use of non-commercial hygienic absorbents. The first occurrence of high-risk infection was independently predicted by age, age at first sexual intercourse, condom use (negative associations) and by the number of sexual partners in the past year (positive association). Elucidation of the dynamics of infection is a first step towards implementation of public health programs for reducing the risk of cervical cancer.

Breast and ovarian cancers are among the most common tumours affecting Canadian women. A proportion of these tumours was thought to be due to family history and the breast cancer susceptibility gene and are more likely to occur before the age of 50. It is hypothesized that women who have both primary tumours of the breast and ovary are more likely to have a mutation in this gene. The main objective of this study is to examine the role of family history in those women with breast cancer that subsequently develop ovarian cancer. The role of chemotherapy and radiotherapy in the treatment of breast cancer, as a risk factor for future development of ovarian cancer, was also assessed. / This was a case-control study. The cases studied were women with multiple primary breast and ovarian cancers and were identified from the Quebec Tumour Registry and a database at Sunnybrook Hospital in Toronto.

The p16/MTS1 (multiple tumor suppressor 1), p15/MTS2 and H19 genes have been recently proposed as candidate tumor suppressor genes. In this study, we determined the mutation status of these three genes in 82 Wilms' tumors by the polymerase chain reaction and single-strand conformation polymorphism (PCR-SSCP) analysis. The results suggested that p16/MTS1 and p15/MTS2 genes are not involved in Wilms' tumor, and that the H19 gene may be altered at a low frequency in Wilms' tumorigenesis. / We also analyzed the involvement of the WT1-3$ sp prime$untranslated region (UTR) in the translational regulation of the WT1 gene expression. The data revealed that the WT1-3$ sp prime$UTR does not affect WT1 gene expression at the translational level in vitro. / These studies contribute to the molecular genetic understanding of Wilms' tumorigenesis.

Previous studies of nitrogen mustard drug resistance in B-cell chronic lymphocytic leukemia (B-CLL) indicated that resistance was a result of enhanced DNA repair associated with increased expression of two DNA repair genes, ERCC-1 and alkyl-N-purine DNA glycosylase. The aim of this thesis was to expand upon these observations and solidify the link between DNA repair and nitrogen mustard drug resistance. Contrary to our expectations, overexpression of ERCC-1 in CHO cells produced increased sensitivity to melphalan and cisplatin. No correlation was found between ERCC-1 expression and nitrogen mustard resistance in B-CLL, when analyzed in a larger cohort by both Northern and western blots, nor was there evidence of altered expression of a second nucleotide excision repair gene (NER), ERCC-2. Overexpression of alkyl-N-purine DNA glycosylase in CHO cells failed to produce melphalan resistance. Nitrogen mustard resistant B-CLL lymphocytes displayed cross-resistance to the bifunctional agents, mitomycin C and cisplatin, but not to UV or methyl methanesulfonate, supporting a role for enhanced crosslink repair in the resistant phenotype. Poly(ADP-ribose) polymerase (PARP) has been identified as a binding protein which can recognize melphalan damaged DNA. This binding appears to result from nicks induced by the melphalan treatment and can be inhibited if the DNA is alkylated with melphalan in the presence of methoxyamine. PARP expression was the same in both sensitive and resistant lymphocytes. When 3-aminobenzamide was used to inhibit PARP, synergy with melphalan was found in 4 of 7 samples we studied. When the DNA synthesis inhibitors, aphidicolin and ara-C, were used to modulate chlorambucil toxicity, synergy was found in both sensitive and resistant populations. There was also evidence for cross-resistance between chlorambucil and ara-C. / Thus, our studies indicate that nitrogen mustard resistance in B-CLL correlates with enhanced activity of a crosslink specific repair process. The observation that nitrogen mustard resistance in B-CLL is associated with cross-resistance to mitomycin C, cisplatin and ara-C, through a mechanism other than P-glycoprotein or glutathione, suggests that this model may represent a novel multi-drug resistant phenotype.

In the present population-based, case-control study of incident, postmenopausal breast cancer, we obtained an extensive history of alcohol consumption. Indices reflecting age-specific exposure, duration and cumulative exposure of alcohol were developed for specific types of alcoholic beverages as well as the combination of these beverages. Unconditional logistic regression, within the context of the Generalized Additive Models, was used to estimate adjusted odds ratios (OR) and 95% confidence intervals (CI). Case subjects included all new histologically-confirmed cases of malignant breast cancer among postmenopausal women, age 51--75 years, diagnosed or treated in 1996 and 1997 in all major hospitals in Montreal. Control subjects were selected randomly from other histologically-confirmed sites of cancer from the same hospitals as the cases. The response rate was 82% for cases and 75% for controls. Current drinkers of any kind of alcohol were at an increased risk of breast cancer (OR = 1.47; 95%CI: 1.01--2.15). In particular, the risk of breast cancer was increased by 1.6-fold among weekly and current exclusive drinkers of wine. Other factors suggestive of an increased risk of breast cancer include early-age at first consumption of alcohol (≤30 years old) and increased number of years (>15 years) of consuming wine among women who only drank wine. We did not find, however, monotonically increasing risks with levels of consumption. Although, the associations found were relatively weak, our findings provide further support for a positive association between the risk of breast cancer and alcohol consumption, particularly wine.

Introduction. Radon gas is a naturally occurring, radioactive contaminant of indoor air. Based on extrapolations from occupational epidemiologic studies in underground miners, as many as 10--14% of lung cancer deaths may be attributable to radon exposure. Such extrapolations involve many sources of uncertainty. The individual results of the eight major completed studies investigating residential exposures have been equivocal. Inadequate statistical power is a substantial problem in their interpretation. To mitigate this problem, an analysis of the combined primary data from the three completed North American studies has been undertaken. / Methods. Individual-level data were received from Winnipeg, Canada, and New Jersey and Missouri, USA and compiled into a common format. Radon exposure was expressed both in cumulative working level months (WLM) and as average intensity in Becquerels per cubic metre. Parallel logistic regression analyses were undertaken to identify a common model for the prediction of lung cancer rate ratio which would adjust for all matching variables and risk factors (including potential confounders) determined to be important in at least one site. Next, a combined analysis utilized a random-effects model to obtain the most realistic assessment to date of the rate ratio of lung cancer as a function of residential radon exposure. Sensitivity of the results to exposure time window definition and statistical model form (exponential logistic versus additive excess relative risk) was also investigated. / Results. Estimated arithmetic mean (standard error) cumulative exposures among population controls for the period 5 to 50 years prior to subject ascertainment were 4.6 (2.6), 10.2 (6.3), and 16.7 (9.9) weighted WLMs in New Jersey, Missouri, and Winnipeg, respectively. During this same exposure period, the estimated rate ratio [and 95% confidence interval] was 0.94 [0.52, 1.72] per increment of 10 weighted WLMs radon exposure, and 0.98 [0.84, 1.14] per increment of 100 Bq/m3 weighted average radon concentration. No or negligible differences were observed in the estimated radon effect between sites. / Conclusions. At the observed levels of radon exposure, the log-linear and linear excess relative risk models provided indistinguishable fits to the data. Modification of the weighting factors did not affect radon effect estimates. Statistical and other sources of uncertainty preclude a definitive conclusion with respect to the magnitude of effect of residential radon on lung cancer. (Abstract shortened by UMI.)

Epithelial (E)-cadherin is a calcium-dependent cell adhesion molecule. As a crucial component of epithelial cell adherens junctions, E-cadherin is responsible for the establishment of cell polarity and the maintenance of tissue integrity. Appropriately regulated E-cadherin expression is essential for morphogenesis and its misregulation is an important factor in the progression of cancer. / The regulation of E-cadherin expression by 17beta-estradiol was analyzed in human breast carcinoma MCF-7 cells. These cells are well-differentiated and display many epithelial characteristics. MCF-7 cell E-cadherin mRNA and protein levels were increased in response to 17beta-estradiol, but levels of the E-cadherin associated cytoplasmic proteins alpha-catenin, beta-catenin and plakoglobin were unchanged. Culture of MCF-7 cells in estrogen-deprived conditions, or in the presence of anti-estrogens led to an altered morphology, reminiscent of a decreased polarization. This was evidenced by changes in the subcellular localization of E-cadherin, beta-catenin and plakoglobin, as well as rearrangement of the actin-based cytoskeleton. Futhermore, the packing of the MCF-7 monolayer was less ordered under these conditions. The cells reverted to a well organized phenotype upon treatment with 17beta-estradiol. These data show that E-cadherin expression in a mammary epithelial-derived cell line is estrogen-responsive, and that changes in the estrogenic environment have consequences upon cell shape and monolayer packing. These findings suggest a novel role for estrogens in the regulation of mammary gland cadherins which has not previously been appreciated. / The mechanism of E-cadherin gene regulation by 17beta-estradiol was studied using promoter-reporter assays and electrophoretic mobility shift assays. A 380 by fragment of the E-cadherin gene promoter was found to be sufficient to drive estrogen-responsive expression in MCF-7 cells. Mutagenesis studies revealed a non-consensus estrogen response element (ERE) within this fragment to be important for regulation by estrogen. Furthermore, the E-cadherin ERE specifically interacted with purified recombinant estrogen receptor (ER) alpha and beta in vitro, supporting the hypothesis that regulation of E-cadherin gene expression by estrogen occurs by direct interaction of the ER and the incomplete ERE in the gene promoter. The involvement of the ER in E-cadherin gene expression provides a functional explanation for the concomitant loss of both ER and E-cadherin expression manifested in aggressive breast cancers. / The activity of the 380 by fragment of the E-cadherin promoter and its stimulation by 17beta-estradiol were compromised by overexpression of ErbB2 tyrosine kinase receptor in MCF-7 cells. The ErbB2 receptor is frequently overexpressed in advanced stage breast cancer, and signalling via this tyrosine kinase is implicated in the progression of the disease. The suppression of 17beta-estradiol's effect on E-cadherin promoter activity by ErbB2 may represent a functional intersection between the ErbB2 and estrogen-dependent signalling pathways. / In summary, these studies demonstrate that alterations in estrogen levels can have profound consequences on E-cadherin expression and cell morphology. Furthermore, the expression of E-cadherin appears to be under the direct control of estrogens by virtue of the presence of a non-consensus ERE in the gene promoter.

Background. For stage I and II breast cancer, the standard treatment is partial mastectomy followed by radiation treatment. The risk of local recurrence ranges from 6 to 9%. A controversy exists as to whether there is an increased risk of local recurrence as a result of excessive delay between surgery and radiation treatment. A natural experiment associated with a prolonged waiting time in our institution provided an opportunity to evaluate the impact of waiting times for radiation treatment of breast cancer on the risk of local recurrence. / Methods. Between January 1988 and December 1989, 486 patients with stage I or II breast cancer from McGill hospitals were treated with radiotherapy. Their charts were reviewed, and information with regard to prognostic factors, such as age, tumor size, histological grade, number of positive lymph nodes, and margins of resection, was abstracted. The interval between the date of surgery and the date of initial radiation treatment, and events, such as local recurrence, metastases and death, were noted. / Results. At five years, the local recurrence rate was 8%, the metastatic rate 13%, and the disease-free survival rate 89%. In the univariate analysis, the risk of local recurrence was associated with younger age, higher histological grade, and time to radiation treatment. In the multivariate Cox proportional hazard models, higher histological grade and time to radiation treatment were significant. Using recursive partitioning, the risk of local recurrence was almost five times higher for patients who waited in excess of 79 days for radiation treatment. / Conclusion. Delay in radiation treatment is associated with an increased risk of local recurrence of breast cancer.

Multiple myeloma (MM) is a plasma cell malignancy with a high mortality rate. The current treatment options may prolong survival but none of them are curative. Allogeneic gene therapy is a novel vaccine strategy that can augment anti-tumor immune responses and cause remission in some non-hematologic cancers. Immunogene transfer has been successfully performed in human and murine myeloma cells using viral vectors. We used immuno-magnetic negative selection to purify myeloma cells from bone marrow (BM) specimens. We investigated the possibility of in vitro culture of bone marrow mononuclear cells (BMMC) and myeloma cell enrichments. We used liposomal and adenoviral vectors to transduce myeloma cell lines. We cloned the allogene HLA-B7 into a recombinant adenoviral transfer plasmid and, subsequently, produced a recombinant, HLA-B7-positive, adenoviral vector. We evaluated allogene expression by the adenoviral vector in myeloma cell lines. In three of four BM samples tested, 95--99% purification of primary myeloma cells was achieved. Poor expansion and considerable variability (6--22 days) in the duration of culture of BMMC (two samples) and purified myeloma cells (four samples) was observed. Adenoviral vectors expressing green fluorescent protein (GFP) were highly efficient (70--94%) for transduction of myeloma cell lines. Using the HLA-B7-adenoviral vector, a small population (13%) of HLA-B7-positive myeloma cells (RPMI-8226 cell line) was identified. These observations support the feasibility of creating a myeloma vaccine by transduction of primary human myeloma cells with an allogene.

The glutathione-S-transferases (GSTs) are a multigene family of enzymes that catalyze the conjugation of glutathione (GSH) with toxic endogenous and xenobiotic compounds including anticancer drugs, as part of detoxification pathways. Our laboratory previously isolated a melphalan resistant rat mammary carcinoma cell-line (MLNr MatB). The in vitro and in vivo studies demonstrated increased GST activity, especially elevated GST alpha class in MLNr cells. At the outset of my work, I examined the nature of the increased GST form in MLNr cells. I cloned the GSTA3 cDNA which is overexpressed in MLNr cells and found that it is identical to the previously described GSTA3 mRNA, suggesting that there is no additional GST alpha gene induced by melphalan. To study the role of the rat GSTA3 gene in chemotherapy resistance, and understand the mechanism of its overexpression in drug resistant tumors, I isolated the entire rGSTA3 subunit gene, including its regulatory regions, from a genomic library and characterized it. The rGSTA3 gene is approximately 15 kb in length and consists of seven exons interrupted by introns of different lengths. The functional activity of its promoter was shown by its ability to drive the expression of a CAT reporter gene in MatB cells, and its activity was greater in melphalan resistant cells. I also presented evidence that rGSTA3 subunit evolved as a duplication of the rGSTA5 subunit gene, increasing the diversification and functional benefits. In addition to drug resistance, I have been examining the implications of GST to carcinogenesis. Epidemiological studies have shown an association between Hepatitis B Virus (HBV) infection and exposure to chemical carcinogens in the incidence of hepatocellular carcinoma (HCC). The exact mechanism of these interactions is not known, but reduced GST activity could increase cellular sensitivity to chemical carcinogens. Semiquantitative RT-PCR revealed that HBV infected cells contain a significant decrease in th