Abstract
Abstract Background: Cyclooxygenase-2 (COX-2) over expression has been observed in different cancers. Till date, COX-2 expression in breast cancer has been studied using RT-PCR and immunohistochemistry. The aim of this study was to use surface plasmon resonance (SPR) technology for determining the expression levels of COX-2 in breast cancer and design peptide inhibitors to evaluate their enzyme inhibition in vitro. Patients and methods: This case-controlled study was performed on 84 biopsy proven breast cancer patients having invasive ductal carcinoma and 40 age, sex and ethnicity matched healthy subjects. Blood and tissue samples were collected and serum and tissue lysate was prepared. Serum and tissue levels of COX-2 were evaluated using SPR where samples were allowed to flow over anti-COX-2 antibody immobilized sensor chip to obtain the respective RUs. Similarly, standard curve of COX-2 was prepared from cloned, expressed and purified protein to deduce the concentrations in different samples. To evaluate enzyme inhibition, fifteen peptides were synthesized using the solid and solution-phase peptide synthesis based on the active site structure of COX-2 and enzyme activity was evaluated spectrophotometrically. Results: A significant increase in COX-2 levels in breast cancer patients 11.23-30.77μg/ml (Mean±SD=14.55±5.74) as compared to normal controls 2.13-5.16µg/ml (Mean±SD=3.71±0.86) (P>0.0001) was observed. Serum COX-2 levels were significantly higher (P<0.0061) in patients with lymph node involvement. More than 65% patients showed significantly (P<0.0025) reduced COX-2 levels after chemotherapy. This was confirmed by western blot to check tissue level expression and spectrophotometrically to determine the activity of COX-2 at different stages. In addition, the peptides showed significant in vitro enzyme inhibition, and had a KD ranging from 1 X 10-8 to 1X10-10. Conclusion: SPR is a useful proteomic technique for early detection and monitoring progession of breast cancer and peptides are a novel class of COX-2 inhibitors that can be further developed for anti-tumor therapy. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P4-08-11.
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