Genetic polymorphisms, the metabolism of estrogens and breast cancer: a review.

Breast cancer is the most common female cancer and the second cause of cancer death in women. Despite recent breakthroughs, much of the etiology of this disease is unknown and the most important risk factor, i.e., exposure to endogenous and exogenous estrogen throughout life cannot explain the heterogeneity of prognosis nor clinical features of patients. Recently, many gene polymorphisms in the metabolism of breast cancer have been described as possible neoplasm etiologic factors. This review is an attempt to summarize the current knowledge about these polymorphisms and to determine new target genes for diagnosis and treatment of the disease. Polymorphisms in the genes CYP17, CYP19, CYP1A1, CYP1A2, CYP1B1, UGT1A1, SULT1A1, 17-hydroxysteroid-dehydrogenase, COMT, GST, ESR1, and ESR2 are described.

Chromosome aberrations as a predictor of clinical outcome for smoking associated lung cancer.

The ability to identify individuals at greatest risk of developing lung cancer can significantly enhance the efficacy of intervention modalities. One strategy for identifying these individuals is through biomarkers that reflect the severity of their cancer. In the present study, we evaluated 22 lung cancer patients and 35 controls to determine whether the frequency of chromosome aberrations was significantly associated with specific clinical variables such as the histological type, grade and stage of the tumors. Chromosome aberrations (expressed as total breaks) were investigated on chromosome 1 in interphase nuclei obtained from blood lymphocytes of the study participants using the fluorescence in situ hybridization (FISH) chromosome aberration assay. Our results indicate a significant linear increase (P=0.01) in the level of breaks with respect to the grade of the carcinoma. The poorly differentiated tumors had a significantly higher level of chromosome breaks mean+/-SD (1.7+/-0.46) as compared to the well differentiated tumors (0.98+/-0.23, P<0.05). These results indicate that chromosome aberrations, as determined by the FISH assay, can be used as a biomarker for identifying individuals with aggressive types of lung cancer and potentially, as a predictor for prognostic outcome of the disease.

Genetic polymorphism and their contribution to cancer susceptibility.

Since the majority of chemical carcinogens are not capable of causing hazardous effects per se, the metabolism of these compounds is a crucial part of the initial host response to the environmental exposure. Disturbances in the balance between activation and detoxification may thus explain the individual variations in responses to exposures to carcinogens. The amount of the ultimate carcinogen produced depends on the action of competing activation and detoxification pathways involving cytochrome P450 and glutathione-S-transferases enzymes.

Predisposing genes and increased chromosome aberrations in lung cancer cigarette smokers.

Genotoxic effects linking cigarette smoking with lung cancer have not been consistently demonstrated, therefore claims for the cause-effect relationships are vigorously contested. Using matched populations of 22 lung cancer patients who have been cigarette smokers (LCP), 22 non-cancerous cigarette smokers (SC) and 13 non-smokers (NSC), we have applied the fluorescence in situ hybridization (FISH) tanden probe assay to elucidate the frequency of chromosome breakage among the participants. Two probes were used, a classical satellite probe which hybridizes to the large heterochromatin region of chromosome 1, and an alpha-satellite probe which targets a small region adjacent to the heterochromatin probe. The highest frequency of structural aberrations was observed in LCP (1.4 +/- 0.1) followed by SC (1.25 +/- 0.1) and NSC (0.4 +/- 0.1). Aberration frequencies were not significantly different between LCP and SC (p > 0.05), however, a statistically significant difference was detected between the smoker populations combined (LCP and SC) and the NSC (p < 0.001). The breakage frequencies showed a positive correlation with duration of smoking for LCP (r = 0.5; p < 0.01), but not for SC (P > 0.05). In addition, the aberration frequencies were influences by the inheritance of polymorphic glutathione S-transferase (GST) genes. LCPs missing one or the other GST (GSTM1 or GSTT1) genes were found to have significantly higher chromosome breaks compared to LCPs with both genes present (p < 0.05). Our data indicate that genetic predisposition and chromosome aberrations may be mechanistically related to the initiation of lung carcinogenesis; therefore, they may be useful biomarkers for lung cancer among cigarette smokers.

Interactions between genetic predisposition and environmental toxicants for development of lung cancer.

Significant interindividual variations in health outcome may be caused by the inheritance of variant polymorphic genes, such as CYP2D6 and CYP2E1 for activation, and GSTM1 and GSTT1 for detoxification of chemicals. However, mechanistic studies linking the inheritance of predisposing genes with genotoxic effects towards cancer have yet to be systematically conducted. We have studied 54 lung cancer patients and 50 matched normal controls, who have been cigarette smokers, to elucidate the role of polymorphic genes in cancer. Our data indicates that the inheritance of unfavorable CYP2D6, CYP2E1, and GSTT1 genes in strongly correlated with the smoking-related lung cancer. For heavy cigarette smokers (> 30 pack-years), the smoking habit is the strongest predictor of lung cancer risk irrespective of the inheritance of unfavorable metabolizing genes. For moderate to light smokers (< 30 pack-years), the genetic predisposition plays an important role for the risk (odds ratio = 3.46; 95% Cl = 0.46-40.2). Using a subgroup of the study population, we observed that cigarette smokers having the defective GST genes have significantly more chromosome aberrations as determined by the fluorescence-in-situ-hybridization (FISH) technique than smokers with the normal GST genes (P < 0.001). In conclusion, our study provides data to indicate that individuals who have inherited unfavorable metabolizing genes have increased body burden of toxicants to cause increased genetic damage and to have increased risk for cancer. Studies like ours can be used to understand the basis for interindividual variations in cancer outcome, to identify high risk individuals and to assess health risk.