Association of endothelial nitric oxide synthase gene polymorphisms with endometrial carcinoma: a preliminary study

Variances in the Level of COX-2 and iNOS in Different Grades of Endometrial Cancer

BACKGROUND

Many experimental studies have demonstrated the importance of COX-2 in the tumor angiogenesis. Inducible iNOS is responsible for a high and stable level of nitric oxide and is expressed in response to pro-inflammatory factors.

OBJECTIVE

The aim of this study was to evaluate the expression of COX-2 and iNOS at the protein level and to assess their potential prognostic significance in patients with endometrial cancer.

METHODS

The study group consisted of 45 women with endometrial cancer divided according to the degree of histological differentiation i.e. G1, 17; G2, 15; G3, 13. The control group consisted of 15 women without neoplastic changes. The expression of studied proteins was determined immunohistochemically with specific polyclonal antibodies.

RESULTS

Analysis of the COX-2 expression showed that the optical density of the reaction product in G1 reached 186% in the control group, while the values in G2 and G3 reached 243% and 293%, respectively. In the case of iNOS, the optical density of the reaction product reached the following percentages in the control group: 147% in G1, 243% in G2, and 241% in G3.

CONCLUSION

Our findings suggest that changes in the expression of COX-2 and iNOS may be potentially useful in predicting the progression of endometrial cancer and treatment effectiveness.

Nitric oxide and pH modulation in gynaecological cancer

Nitric oxide plays several roles in cellular physiology, including control of the vascular tone and defence against pathogen infection. Neuronal, inducible and endothelial nitric oxide synthase (NOS) isoforms synthesize nitric oxide. Cells generate acid and base equivalents, whose physiological intracellular concentrations are kept due to membrane transport systems, including Na⁺/H⁺ exchangers and Na⁺/HCO₃⁻ transporters, thus maintaining a physiological pH at the intracellular (~7.0) and extracellular (~7.4) medium. In several pathologies, including cancer, cells are exposed to an extracellular acidic microenvironment, and the role for these membrane transport mechanisms in this phenomenon is likely. As altered NOS expression and activity is seen in cancer cells and because this gas promotes a glycolytic phenotype leading to extracellular acidosis in gynaecological cancer cells, a pro‐inflammatory microenvironment increasing inducible NOS expression in this cell type is feasible. However, whether abnormal control of intracellular and extracellular pH by cancer cells regards with their ability to synthesize or respond to nitric oxide is unknown. We, here, discuss a potential link between pH alterations, pH controlling membrane transport systems and NOS function. We propose a potential association between inducible NOS induction and Na⁺/H⁺ exchanger expression and activity in human ovary cancer. A potentiation between nitric oxide generation and the maintenance of a low extracellular pH (i.e. acidic) is proposed to establish a sequence of events in ovarian cancer cells, thus preserving a pro‐proliferative acidic tumour extracellular microenvironment. We suggest that pharmacological therapeutic targeting of Na⁺/H⁺ exchangers and inducible NOS may have benefits in human epithelial ovarian cancer.

The Potential Role of Nitric Oxide in Halting Cancer Progression Through Chemoprevention

Nitric oxide (NO) in general plays a beneficial physiological role as a vasorelaxant and the role of NO is decided by its concentration present in physiological environments. NO either facilitates cancer-promoting characters or act as an anti-cancer agent. The dilemma in this regard still remains unanswered. This review summarizes the recent information on NO and its role in carcinogenesis and tumor progression, as well as dietary chemopreventive agents which have NO-modulating properties with safe cytotoxic profile. Understanding the molecular mechanisms and cross-talk modulating NO effect by these chemopreventive agents can allow us to develop better therapeutic strategies for cancer treatment.

eNOS Genetic Polymorphisms and Cancer Risk: A Meta-Analysis and a Case-Control Study of Breast Cancer

The association between endothelial nitric oxide synthase (eNOS) polymorphisms (intron 4a/b, -786T>C and 894G>T) and cancer risk remains elusive. In addition, no studies focused on their associations with the risk of breast cancer in Chinese Han population. Thus, a meta-analysis was conducted to determine the relationship between eNOS polymorphisms and cancer risk, and then a case-control study in Chinese Han population was performed to assess their associations with breast cancer susceptibility.Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of association. The pooled analysis indicated that eNOS intron 4a/b and -786T>C polymorphisms were significantly associated with an increased risk of overall cancer. In subgroup analyses based on cancer type, the significant association was found between eNOS intron 4a/b polymorphism and prostate cancer risk, eNOS -786T>C polymorphism and risk of prostate, bladder and breast cancers, and eNOS 894G>T polymorphism and breast cancer risk. In subgroup analyses based on ethnicity, eNOS intron 4a/b and -786T>C polymorphisms were associated with an increased risk of cancer in Caucasians. In consistent with our meta-analysis results, a case-control study in Chinese Han population showed significant associations of eNOS -786T>C and 894G>T polymorphisms with the increased risk of breast cancer. In addition, stratified analyses based on pathological type showed that eNOS 894G>T polymorphism was only associated with the risk of infiltrative ductal carcinoma. Stratified analyses by tumor stage showed that eNOS -786T>C polymorphism was only associated with the risk of tumor stage III and IV.In conclusion, our meta-analysis and case-control study suggest that eNOS -786T>C and 894G>T polymorphisms are associated with the increased risk of breast cancer.