The Molecular Epidemiologic Investigation In Association Among Chromosome Instability, Breast Cancer Suscetability And Prognostic Factors

Part1The Association Between Bleomycin-induced Mutagen Sensitivity and the Risk of Breast Cancer:A Case-Control StudyObjective It is well recognized that genetic variation as well as environmental factors modulate breast cancer risk. Deficiencies in DNA repair capacity are thought to associate with breast cancer risk. The main aim of this study was to use the mutagen sensitivity assay (MSA) as an indirect measure of DNA repair capacity to assess breast cancer risk, and the relationship between passive smoking and breast cancer risk among women in China.Methods We carried out a case-control study, involving196Chinese patients with breast cancer and211controls without the disease and with no history of cancer. We investigated the association between mutagen sensitivity and breast cancer risk using bleomycin as the mutagen. Mutagen sensitivity was measured by quantifying the chromatid breaks induced by mutagens in short-term cultures of peripheral blood lymphocytes. Non-parametric tests and the Fisher’s exact test were used to determine the statistical significance of the crude case-control comparisons, followed by logistic regression to adjust for important covariates.Results The mean number of bleomycin-induced breaks per cell was0.81for cases compared with0.73for the controls (P=0.016). A greater number of bleomycin-induced chromosomal breaks per cell was associated with an increased risk of breast cancer (adjusted odds ratio of1.82, P trend <0.01). The association between bleomycin sensitivity and breast cancer risk was greater for women who were premenopausal and exposed to tobacco smoke (passive smokers). The combination of bleomycin sensitivity and exposure to tobacco smoke increased risk further; women passive smokers with high sensitivity to bleomycin had a2.77-fold increased risk of breast cancer. Of these women, those who were exposed to tobacco smoke for>20hour-year had a5.02-fold increased risk of breast cancer.Conclusions Our data indicate that increased bleomycin-induced mutagen sensitivity is significantly associated with an increased risk of breast cancer among Chinese women. Exposure to passive smoke is also associated with increased breast cancer risk, and the correlation is even greater for women with both longer passive exposure to tobacco smoke and high sensitivity to bleomycin. Part2The case-control study of relationship between telomere length from blood cells and the risk of breat cancerObjective Telomere dysfunction, which leads to genomic instability, maybe played an important role in the development of breast cancer. Although the telomere in tumors was considered to be a potential promising biomarker for early diagnosis and indicator for prognostic judgment in breast cancer, current results in the research of the peripheral leukocyte telomere length are not consistent in breast cancer risk assessment. Thus, we examined telomere length in peripheral leukocyte DNA in breasts cancer patients and explore the association among telomere length and breast cancer risk as well as clinicopathological features such as tumor stage, grade of differential status.Method In this case-control study of breast cancer conducted in a Chinese population, we measured telomere length of peripheral leukocyte DNA in213breast cancer cases and230age-matched controls using telomere specific quantitative real-time PCR. The Fisher’s exact test, multivariate Logstic regression and linear trend test were used to analysis the association between telomere length and breast cancer risk.Result It is showen that shorter telomere length in breast cancer cases (mean telomere length,8.47Kb) when compared with controls (9.02Kb; P=0.06). With the telomere length became shorter, the breast cancer risk increased (P for trend <0.01). Especially in premenopausal women, the adjusted OR was1.95(95%CI:1.02-3.73). There also showed a dose-dependent (adjusted OR was3.41,95%CI:1.29-9.05, P for treand<0.01). There is an association between telomere length and clinicopathological features such as tumor stage, grade of differential status. The letomere length in advanced TNM stage and higher tumor grade were shorter than those in earlier TNM stage and lower tumor grade respectively. Among advanced TNM stage and higher tumor grade, their adjusted OR was1.72(95%CI:1.00-2.96) and1.65(95%CI:1.17-2.57), respectively. Our data does not show that telomere length change in peripheral leukocyte DNA was associated with hormone receptors status.Conclusion Our results suggest that telomere length in peripheral leukocyte DNA was associated with breast cancer risk. Shortened telomeres not only increased breast cancer risk in Chinese women, but also are closely associated with clinicopathological features such as tumor stage, grade of differential status in cases. The peripheral leukocyte telomere length shorten could be an important screening marker for early diagnosis and indicator for prognosis in breast cancer. Part3The study of the relationship among telomere length, telomere attrition from tumor tissue and the risk and prognosis in breast cancerObjective Maintenance of telomere length is critical in tumorigenesis of breast cancer. Shortness of telomere attrition is frequently presented in the process of pre-cancer development of breast cancer from ductal hyperplasia to carcinoma in situ. Examination of telomere length can be used as bio-marker of tumorigenesis and provide pivotal prognostics in clinic. In this study, telomere length of multiple cell types from primary breast cancer samples of213from219patients, which were have clinicopathological data and tumor tissue slides, were examined and telomere length of different cell type was analyzed to correlate them with breast cancer risk factors and prognosis. Therefore, this study will provide evidence to finding reliable bio-markers for clinical prognosis.Methods A modified protocol for quantitative telomere-specific fluorescent-in-situ-hybridization (FISH) was used in this study. Image J was employed to quantify the data. Telomere length of multiple cell types from primary breast cancer samples of213patients was examined.213of219samples have complete clinical pathology data as well as slides.Results The average telomere attrition of tumor cells (0.54±0.43) is significantly shorter than that of tumor infiltrated lymphatic cells (1.34±0.96, P<0.001) and adjacent normal epithelial cells (0.88±0.56, P<0.001). The correlation analysis of tumor relative telomere length and breast cancer risk factors suggests that active smoker, long-term drinker, and females with no family history of breast cancer are highly related to the shortness of telomere. OR scores (95%CI) are1.83(0.52-6.11),1.02(0.39-2.48), and1.23(0.26-5.43), respectively. There is no statistically significant difference.The relationship between telomere attrition of tumor cells and breast cancer clinical pathological characteristics:telomere attrition of tumors larger than1.5cm (0.43±0.41) is significantly shorter than that of tumors smaller than1.5cm (0.56±0.34, P=0.019). Telomere attrition of tumors at stage Ⅲ and Ⅳ (0.45±0.52) is significantly shorter than that of tumors at stage I and II (0.59±0.56, P=0.05). Telomere attrition of tumors graded as Ⅲ (0.39±0.52) is significantly shorter than that of tumors graded as Ⅰ and Ⅱ (0.48±0.57, P=0.043). Logistic analysis shows that telomere attrition of tumor cells is closely related to tumor size, clinical tumor stage, and pathological tumor grade. The adjusted OR (95%CI) are1.71(1.12-2.79),1.97(1.06-3.25), and2.06(1.17-3.45), respectively. There is no significant correlation between telomere attrition of tumor cells and tumor histology type, ER and PR status.Conclusions The telomere attrition of tumor cells is significantly shorter than that of tumor stroma cells and adjacent normal epithelial cells. It is closely related to the size, clinical stage, and pathological grade of tumors. Tumors have large size, higher clinical stage, and pathological grade tend to have shorter telomeres. Both telomere length and telomere attrition are potential bio-markers for breast cancer prognosis.