Abstract
PURPOSE: Nitric oxide, a messenger molecule has been reported as having various antineoplastic properties. The activation of insulin-activated nitric oxide synthase (IANOS) was found to be related to the production of NO as a result of the binding of insulin to its receptor through the activation of tyrosine kinase in erythrocyte membrane. As nitric oxide is reported to be a systemic anticancer agent, studies were carried out to determine the role of insulin receptor binding that lead to the activation of tyrosine kinase and IANOS in erythrocytes in breast cancer. METHODS: Blood samples were collected from female breast cancer patients who, at the time of participation in the study, had not undergone any therapeutic intervention but had opted for surgery. The binding of insulin to its receptor in erythrocyte membrane and the activation of both receptor tyrosine kinase and IANOS due to the hormone binding were determined and compared with the appropriate control. RESULTS: It was found that the impaired NO synthesis in erythrocyte membrane in breast cancer was related to the marked decrease of insulin binding sites of the high-affinity hormone receptor population. This impaired insulin binding to high-affinity receptors resulted in the impairment of both reaction velocity (Vmax) of the IANOS and receptor tyrosine kinase activation. CONCLUSION: These results indicated that the impairment of interaction between insulin and its high-affinity receptors in erythrocyte membrane might be a critical pathophysiological event in the development of breast cancer.