The Role of Neutrophil Estrogen Receptor Status on Maspin Synthesis via Nitric Oxide Production in Human Breast Cancer

Purpose: Estrogen, through its binding to nuclear estrogen receptor (ER), has been implicated in the development of human breast cancer. The presence or absence of ER in breast lesions has been used to classify breast cancer into ER+ or ER- type. Maspin, an anti-breast cancer protein produced in normal mammary cells, has also been reported to control the condition. Studies have been conducted to determine the role of ER+ and ER- status in neutrophils in the synthesis of maspin in human breast cancer. Methods: Maspin presence was determined by enzyme linked immunosorbent assay, while nitric oxide (NO) level was determined using the methemoglobin method. Results: Scatchard plots of the equilibrium binding of estrogen demonstrated the presence of 4.18 x 10(7) receptors per normal neutrophil and 2.46 x 10(7) receptors per ER+ neutrophil with a similar dissociation constant (0.926 nM). The ER- type showed non-specific estrogen binding only. At 0.6 nM estrogen, NO synthesis was maximally increased to 1.829 and 0.887 mu M NO/10(9) cells at 4 hours in normal and ER+ neutrophils respectively, with synthesis of 2.383 and 1.422 nM maspin in normal and ER+ neutrophils respectively. Estrogen failed to produce these effects in ER- neutrophils. Conclusion: ER status in neutrophils determined maspin synthesis in breast cancer through the stimulation of NO synthesis. Neutrophils with ER- status which do not produce any maspin when treated with estrogen, might imply a worse prognostic outcome in ER- breast cancer due to the lack of anti-breast cancer protein synthesis.