The “Cross Talk” between the Receptors of Insulin, Estrogen and Progesterone in Neutrophils in the Synthesis of Maspin through Nitric Oxide in Breast Cancer

PURPOSE The binding of either insulin, or estrogen or progesterone to their specific receptors on neutrophils has been reported to stimulate nitric oxide (NO) induced maspin synthesis in these cells. Experiments were carried out to determine the role of insulin receptor interaction in the nitric oxide induced maspin synthesis in neutrophils that was effected by estrogen or progesterone. METHODS Estrogen receptor positive (ER+) and progesterone receptor positive (PR+) neutrophils were isolated from the blood cancer subjects. Maspin was determined by enzyme linked immunosorbent assay after in vitro translation of maspin mRNA. NO was determined by methemoglobin method. RESULTS It was found that pre incubation of normal neutrophils with insulin to reach equilibrium binding decreased both ER and PR numbers by ≈50% without changing the dissociation constants of the steroids binding. The reduction of ER or PR numbers on neutrophils due to the pretreatment with insulin resulted in the decreased NO induced maspin synthesis from 2.383 ± 0.014 nM to 1.454 ± 0.004 nM in the case of estrogen and in the decrease of maspin synthesis from 2.329 ± 0.012 nM to 1.410 ± 0.002 nM in the case of progesterone. The incubation of ER+ neutrophils or PR+ neutrophils with insulin further decreased the maspin synthesis from 1.422 ± 0.029 nM to 0.790 ± 0.004 nM in the case of estrogen, and from 1.138 ± 0.024 nM to 0.555 ± 0.003 nM maspin in the case of progesterone respectively compared to normal control. CONCLUSION These results suggested that a "cross-talk" between the insulin receptors and the steroid receptors down regulated maspin synthesis in normal and in breast cancer neutrophils.