Antitumor activity of a novel glyco-nitric oxide conjugate in ovarian carcinoma

Abstract

Several studies have shown that nitric oxide (NO)-releasing agents can kill tumor cells. Unfortunately, currently available NO delivery molecules do not target tumor cells preferentially. To exploit the overexpression of glucose transport proteins and the high level of glucose transport characteristics of tumor cells, glucose was conjugated to S-nitroso-N-acetyl-penicillamine (2-gluSNAP) and evaluated for cytotoxicity in human ovarian carcinoma cells. The cytotoxicity of 2-gluSNAP and SNAP was assessed by clonogenic cell survival assays performed in A2780S (cisplatin sensitive) and A2780cP (cisplatin-resistant) ovarian carcinoma cells in vitro. Immunoblotting and immunohistochemistry were used to assess the expression of Glut-1 hexose transport protein in the cell lines as well as in paraffin blocks from 28 surgical specimens of epithelial ovarian carcinoma. Apoptosis was assessed by an end-labeling assay. The ovarian carcinoma cell lines consistently were more sensitive to 2-gluSNAP than SNAP alone. The median effective doses (MEDs) for 2-gluSNAP and SNAP in the A2780s cell line were 0.0042 microM and 20.4 microM, respectively. Therefore, 2-GluSNAP was nearly 5000-fold more potent than the NO-donating moiety (SNAP) alone. In the A2780cP cells, the MED for 2-gluSNAP (0.38 microM) was 250-fold lower than that for SNAP alone (100 microM). Immunoblotting and immunohistochemistry studies showed overexpression of Glut-1 in the cell lines and in 23 of 28 epithelial ovarian carcinoma specimens. The novel glyco-NO conjugate 2-gluSNAP exhibits a much greater cytotoxicity than the parent NO donor without the hexose moiety. These agents have the potential to target tumor cells preferentially, that overexpress Glut-1. This transporter is expressed highly in epithelial ovarian carcinoma.