Glutathione S-Transferase π-Activatable O2-(Sulfonylethyl Derived) Diazeniumdiolates Potently Suppress Melanoma in Vitro and in Vivo

A group of glutathione S-transferase pi (GST pi) activatable O-2-(sulfonylethyl derived) diazeniumdiolates 5-12 were designed and synthesized. These compounds could be activated by GST pi to initiate the beta-elimination reaction, liberating an active vinyl sulfone-based GSH derivative and a diazeniumdiolate anion which subsequently releases NO in situ. The most active compound 6 released relatively high levels of NO and inhibited proliferation of melanoma B16 cells, superior to a diazeniumdiolate-based anticancer agent JS-K (1). Importantly, 6 had 8-fold less inhibitory activity against normal epithelial JB6 Cl 30-7b cells. The inhibitory activity of 6 could be diminished by an NO scavenger or GST pi inhibitor. Furthermore, 6 induced nitration of mitochondrial tyrosine in B16 cells and inoculated B16 tumors in mice, which might be responsible for oxidation of protein leading to tumor suppression. Finally, 6 significantly retarded the B16 cells growth in a mouse xenograft model. These findings suggest that 6 may have a potential to treat melanoma.