Influence of nitric oxide signaling mechanisms in cancer.

Nitric oxide (NO) is a molecule with multiple biological functions that is involved in various pathophysiological processes such as neurotransmission and blood vessel relaxation as well as the endocrine system, immune system, growth factors, and cancer. However, in the carcinogenesis process, it has a dual behavior; at low doses, NO regulates homeostatic functions, while at high concentrations, it promotes tissue damage or acts as an agent for immune defense against microorganisms. Thus, its participation in the carcinogenic process is controversial. Cancer is a multifactorial disease that presents complex behavior. A better understanding of the molecular mechanisms associated with the initiation, promotion, and progression of neoplastic processes is required. Some hypotheses have been proposed regarding the influence of NO in activating oncogenic pathways that trigger carcinogenic processes, because NO might regulate some signaling pathways thought to promote cancer development and more aggressive tumor growth. Additionally, NO inhibits apoptosis of tumor cells, together with the deregulation of proteins that are involved in tissue homeostasis, promoting spreading to other organs and initiating metastatic processes. This paper describes the signaling pathways that are associated with cancer, and how the concentration of NO can serve a beneficial or pathological function in the initiation and promotion of neoplastic events.

Association of the GSTM1 null polymorphism with breast cancer in a Mexican population.

The glutathione S transferase (GST) family plays an important role in the processing of carcinogens. Data on the null GSTM1 genotype has revealed associations with cancer, and has been suggested to affect carcinogen metabolism and to contribute to tumor promotion in the mammary gland. We examined the role of the null GSTM1 genotype by comparing the genotypes of 276 healthy Mexican women with those of 558 Mexican women with breast cancer (BC). The genotype frequencies observed in the controls and patients with BC were 38 and 45% for the null GSTM1 genotype, respectively. The obtained odds ratio (OR) was 1.36, with a 95% confidence interval (95%CI) of 1.02-1.8, P = 0.04. The protective association was also evident upon analysis of the distributions of the null GSTM1 genotype in patients with positive chemotherapy response who had high plasma levels of glucose (OR 0.56, 95%CI = 0.33-0.94, P = 0.03). This study suggested that the null GSTM1 genotype is associated with BC susceptibility in the Mexican population analyzed.

Association of the C677T polymorphism in the methylenetetrahydrofolate reductase gene with breast cancer in a Mexican population.

The methylenetetrahydrofolate reductase (MTHFR) gene plays an important role in the steps involved in the processing of amino acids. The analysis of polymorphisms in the MTHFR gene has revealed associations with cancer; in particular the C677T polymorphism, which has been suggested to affect folate metabolism, DNA methylation, synthesis, and repair, and to contribute to tumor promotion in the mammary gland. We examined the role of the C677T polymorphism in the MTHFR gene by comparing the C677T genotypes of 339 healthy Mexican women with those of 497 Mexican women with breast cancer (BC). The genotype frequencies observed in the controls and patients with BC were 10 and 21% for 677TT; 41 and 36% for 677CT; and 49 and 43% for 677CC, respectively. The odds ratio (OR) for the 677TT genotype was 2.5, with a 95% confidence interval (95%CI) of 1.6-3.8; P = 0.0001. The positive association was also evident when the distributions of the 677TT genotype in control and patients affected within the following two categories were compared to alcohol consumption (OR = 0.41; 95%CI = 0.19-0.86; P = 0.018); and high level glutamate-oxaloacetate transaminase (SGOT) (OR = 0.36; 95%CI = 0.15-0.83, P = 0.017). These results suggest that the 677TT genotype of the C677T polymorphism in the MTHFR gene is associated with BC susceptibility in the Mexican population.

Association of the tumor necrosis factor-alpha -308G>A polymorphism with breast cancer in Mexican women.

The tumor necrosis factor-alpha (TNF-α) gene plays an important role in cell proliferation, differentiation, apoptosis, lipid metabolism, coagulation, insulin resistance, and endothelial function. Polymorphisms of TNF-α have been associated with cancer. We examined the role of the -308G>A polymorphism in this gene by comparing the genotypes of 294 healthy Mexican women with those of 465 Mexican women with breast cancer. The observed genotype frequencies for controls and breast cancer patients were 1 and 14% for AA, 13 and 21% for GA, and 86 and 65% for GG, respectively. We found that the odds ratio (OR) for AA genotype was 2.4, with a 95% confidence interval (95%CI) of 5.9-101.1 (P = 0.0001). The association was also evident when comparing the distribution of the AA-GA genotype in patients in the following categories: 1) premenopause and obesity I (OR = 3.5, 95%CI = 1.3-9.3, P = 0.008), 2) Her-2 neu and tumor stage I-II (OR = 2.5, 95%CI = 1.31-4.8, P = 0.004), 3) premenopause and tumor stage III-IV (OR = 1.7, 95%CI = 1.0-2.9, P = 0.034), 4) chemotherapy non-response and abnormal hematocrit (OR = 2.4, 95%CI = 1.2-4.8, P = 0.015), 5) body mass index and Her-2 neu and III-IV tumor stage (OR = 2.8, 95%CI = 1.2- 6.6, P = 0.016), and 6) nodule metastasis and K-I67 (OR = 4.0, 95%CI = 1.01-15.7, P = 0.038). We concluded that the genotypes AA-GA of the -308G>A polymorphism in TNF-α significantly contribute to breast cancer susceptibility in the analyzed sample from the Mexican population.