Abstract 2267: Inhibition of extracellular sulfatase 2 as a possible mechanism to partially explain the anticancer activity of the nitrone OKN007

Abstract

Abstract Sulfatase 2 (Sulf2) is an extracellular enzyme that has endosulfatase activity and catalyzes the removal of 6-O-sulfate groups on glucosamine from subregions of the glycosaminoglycans heparin sulfate. The action of Sulf2 has been shown to alter the binding of protein ligands to heparin which is involved in the binding of growth factors such as VEGF, FGF-2 and TGF to cellular receptors. Studies in experimental models have shown that fully active Sulf2 is important in the development of breast cancer and pancreatic cancer. Several tumors have been shown to be enriched in Sulf2 in comparison to the normal tissues where its level is either absent or present at very low levels. Sulf2 acts as a potentiator for the Wnt signaling and this is considered important in cancer stem cell growth. We have shown that PBN (alpha-phenyl-tert-butylnitrone) has anti-cancer activity in three experimental models, A) the choline deficiency induced liver cancer model, B) the APCmin model of colon cancer and C) the rat C6 glioma model. We have also shown that 2,4-disulfonyl-alpha-phenyl-tert-butylnitrone (OKN007) has potent anti-cancer activity in the rat C6 glioma model. We considered based on the presence of phenyl sulfonyl groups that the nitrone 2,4-disulfonyl-alpha-phenyl-tert-butylnitrone (OKN007) may act as a competitive inhibitor of Sulf2. We have found that Sulf2 is secreted into the media of Sulf2 transfected Hek-293 cells as well as several cancer cells, including from the highest to lower levels; MCF-7 breast cancer cells, Hek-293 cells, C6 glioma cells and BxPc-3 pancreatic cancer cells. Utilizing the concentrated media of these cells we have shown that Sulf2 has aryl sulfatase activity against the sulfate ester of 4-methylumbelliferone. We have shown that phenyl sulfonyl compounds suppress Sulf2 activity in an apparent competitive action. For instance, we found that the polysulfonated compound suramin potently suppressed the Sulf2 aryl sulfatase activity and that 2,4-disulfonylphenyl-tert-butylnitrone inhibited Sulf2 activity but less so than suramin. Utilizing concentrated extracellular media of several human cancer cell lines we have shown that Sulf2 activity is decreased by incubation with H2O2. Our results suggest that the anti-cancer activity of OKN007 may in part be explained by its inhibitory action against Sulf1. Research to test this concept is now underway. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2267.